Best Organ Supplements and Beef Liver Capsules in 2026: Complete Evidence-Based Guide

Why Organ Supplements Are Making a Comeback

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There is a reason your great-grandmother insisted that liver was good for you. For hundreds of thousands of years, organ meats were the most prized parts of the animal. Hunter-gatherer societies across every continent consumed heart, liver, kidney, and other offal preferentially, often reserving these nutrient-dense cuts for pregnant women, children, and the sick. The muscle meat we overwhelmingly favor today was historically considered secondary.

Modern nutritional science has vindicated what ancestral cultures understood instinctively. A single 100-gram serving of beef liver delivers more vitamin A, vitamin B12, folate, riboflavin, copper, and heme iron than virtually any other food on earth. Beef heart is the richest natural dietary source of Coenzyme Q10 (CoQ10). Kidney tissue provides diamine oxidase (DAO), the enzyme responsible for breaking down histamine in the gut. Spleen is extraordinarily concentrated in heme iron and the immune-activating peptide tuftsin.

The problem is that most people living in the modern world simply will not eat organ meats. The taste, texture, and cultural unfamiliarity create an insurmountable barrier for the vast majority of people. This is exactly where organ supplements – freeze-dried or desiccated capsules of grass-fed beef organs – fill a legitimate and meaningful gap. They deliver the nutritional payload of organ meats without the sensory challenges of preparing and eating them fresh.

But the market has exploded. Dozens of brands now sell beef liver capsules, multi-organ complexes, and single-organ supplements, and they vary enormously in sourcing, processing, potency, and quality. Some preserve heat-sensitive nutrients through careful freeze-drying. Others use high-temperature desiccation that can degrade enzymes and vitamins. Some source exclusively from grass-fed, pasture-raised animals in New Zealand or Australia. Others are vague about their supply chain.

This guide cuts through the noise. We will examine what the published research actually says about organ meat nutrition and supplementation, break down the differences between individual organs, explain how processing methods affect nutrient retention, address safety concerns including vitamin A toxicity, and provide specific product recommendations with honest assessments of their strengths and limitations.

Whether you are dealing with iron deficiency, looking for a whole-food alternative to synthetic multivitamins, managing histamine intolerance, or simply trying to increase your nutrient density, this guide will help you make an informed decision.

Watch Our Video Review

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The Science Behind Organ Meat Nutrition: Why Organs Are Nature’s Multivitamin

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Nutrient Density Per Calorie: How Organs Compare

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The concept of nutrient density – the amount of essential vitamins and minerals per calorie – is where organ meats truly distinguish themselves from every other food category. A landmark 2024 study published in Translational Animal Science conducted a comprehensive nutrient analysis of raw United States beef offal items including liver, kidney, tongue, honeycomb tripe, oxtail, marrow bones, and blood. The researchers found that each of these offal items qualified for at least one “Good Source” or “Excellent Source” nutrient labeling claim per USDA standards (1).

Beef liver is the standout performer. Per 100-gram serving (roughly 3.5 ounces), beef liver provides:

• Vitamin B12: 59.3 mcg (2,471% of the Daily Value)
• Vitamin A (retinol): 4,968 mcg RAE (552% DV)
• Riboflavin (B2): 2.76 mg (212% DV)
• Folate: 290 mcg (73% DV)
• Copper: 9.76 mg (1,085% DV)
• Iron (heme): 4.9 mg (27% DV)
• Selenium: 39.7 mcg (72% DV)
• Zinc: 4.0 mg (36% DV)
• Choline: 333 mg (61% DV)
• Niacin (B3): 13.2 mg (82% DV)

No synthetic multivitamin comes close to replicating this profile in its whole-food matrix form. The nutrients in liver exist alongside cofactors, enzymes, and peptides that research suggests may enhance absorption and utilization in ways that isolated synthetic vitamins cannot fully replicate (2).

The Whole-Food Matrix Advantage

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A 2021 review published in PeerJ examined how food-sourced vitamins compare to synthetic forms at the molecular level. The researchers found that vitamins within their natural food matrix are accompanied by cofactors, enzymes, and binding proteins that can influence absorption kinetics and tissue utilization. For example, the folate in liver exists primarily as 5-methyltetrahydrofolate (5-MTHF) – the bioactive form that bypasses the MTHFR enzyme pathway that up to 40% of the population has genetic variants in (3).

The iron in organ meats is predominantly heme iron, which follows a completely different absorption pathway than the non-heme iron found in plant foods and most supplements. A 2024 systematic review and meta-analysis of 13 randomized controlled trials comparing heme iron to non-heme iron administration found that heme iron demonstrates absorption rates of 25-30%, compared to just 3-5% for non-heme iron. Critically, heme iron absorption is largely unaffected by dietary inhibitors like phytates, polyphenols, and calcium that dramatically reduce non-heme iron uptake (4).

This has enormous practical implications. A person with iron deficiency taking ferrous sulfate tablets may absorb only a fraction of the stated dose, and the unabsorbed iron sitting in the gut frequently causes constipation, nausea, and dark stools. Heme iron from liver supplements rarely produces these side effects because a much higher percentage is actually absorbed.

The Evolutionary Argument: How Organ Meats Shaped Human Development

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The relationship between organ meat consumption and human evolution is not speculative – it is supported by substantial paleontological and nutritional evidence. Research published in The International Journal of Primatology and Annual Review of Nutrition has established that the emergence of Homo erectus approximately 1.8 million years ago coincided with a dramatic dietary shift toward nutrient-dense animal foods, including organ meats (5).

The human brain, which constitutes only about 2% of body mass but consumes roughly 20% of resting metabolic energy, required an extraordinarily nutrient-dense diet to develop and maintain. A gram of brain tissue requires 20 times more energy to grow and maintain than a gram of tissue from the kidney, heart, or liver. The “Expensive Tissue Hypothesis” proposed by Aiello and Wheeler suggests that as early humans increased their consumption of nutrient-dense animal foods, particularly organs, the gut shortened (requiring less energy to operate), and that freed-up metabolic energy was redirected to brain growth (6).

Organ meats are particularly rich sources of vitamins A and D, iron, zinc, folate, selenium, choline, and vitamin B12 – several of which are either obtained exclusively from animal-sourced foods or are substantially more bioavailable in animal versus plant form. These nutrients are considered critical for neurodevelopment, myelination, and cognitive function (7).

Clues Your Body Tells You: Signs You May Benefit From Organ Supplements

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Your body communicates nutrient deficiencies through a constellation of symptoms that many people dismiss as “normal” aging, stress, or just how they feel. Many of these symptoms point directly to deficiencies in nutrients that organ supplements are exceptionally well-suited to address.

Signs of Iron Deficiency (Liver and Spleen Support)

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Iron deficiency is the most common nutrient deficiency worldwide, affecting an estimated 1.6 billion people. It disproportionately impacts women of reproductive age, endurance athletes, vegetarians, and people with gastrointestinal conditions that impair absorption. Watch for these clues:

• Persistent fatigue that sleep does not fix – iron is essential for oxygen transport via hemoglobin, and when levels drop, every cell in your body receives less oxygen
• Pale skin, nail beds, and inner eyelids – reduced hemoglobin literally changes the color of your blood and the tissues it supplies
• Shortness of breath during moderate activity – your cardiovascular system compensates for lower oxygen-carrying capacity by increasing respiratory rate
• Restless legs, especially at night – iron deficiency is strongly linked to restless leg syndrome; studies show iron supplementation often resolves it
• Ice or non-food cravings (pica) – the craving to chew ice is so closely associated with iron deficiency that it has its own medical term: pagophagia
• Brittle, spoon-shaped nails – koilonychia (concave nails) is a classic clinical sign of iron deficiency
• Hair loss or thinning – iron is required for hair follicle cell proliferation; deficiency can trigger telogen effluvium

If you are experiencing three or more of these symptoms, especially if you are a menstruating woman, it is worth getting your serum ferritin tested. Ferritin below 30 ng/mL is considered suboptimal by many functional medicine practitioners, even though lab reference ranges often go as low as 12 ng/mL.

Beef liver and spleen supplements are particularly effective for iron deficiency because they provide heme iron, which is absorbed 5-8 times more efficiently than the non-heme iron in standard supplements like ferrous sulfate (4). For a deep dive into iron supplement forms, see our comparison of iron bisglycinate vs ferrous sulfate.

Signs of Vitamin B12 Deficiency (Liver Support)

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Vitamin B12 deficiency is far more common than many practitioners realize, affecting an estimated 6% of people under 60 and nearly 20% of those over 60 in the United States and United Kingdom. Vegans, vegetarians, people taking metformin or proton pump inhibitors, and those with pernicious anemia are at especially high risk. Your body may be telling you through:

• Numbness or tingling in hands and feet – B12 is essential for myelin sheath maintenance; deficiency causes peripheral neuropathy
• Brain fog, poor memory, and difficulty concentrating – B12 supports methylation pathways critical for neurotransmitter synthesis
• Depression or mood changes – B12 deficiency impairs the production of serotonin and dopamine
• A swollen, inflamed, or unusually smooth tongue – glossitis is a classic B12 deficiency sign
• Difficulty with balance and coordination – subacute combined degeneration of the spinal cord is a serious consequence of prolonged B12 deficiency
• Unexplained fatigue even with adequate sleep and iron levels – B12 is required for red blood cell formation; deficiency causes megaloblastic anemia

Beef liver contains 59.3 mcg of B12 per 100 grams – nearly 2,500% of the daily value. This is more than 10 times the B12 content of any other commonly eaten food. A standard dose of 3 grams of liver supplement (six 500mg capsules) provides approximately 1.8 mcg of B12, which is still meaningful as part of a comprehensive nutritional strategy. For more on B12 specifically, read our guide to vitamin B12 deficiency and the best B12 supplements.

Signs of CoQ10 Depletion (Heart Support)

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CoQ10 is essential for mitochondrial energy production in every cell, but concentrations are highest in the heart, kidneys, liver, and muscles – tissues with the highest energy demands. CoQ10 levels decline naturally with age, and statin medications dramatically accelerate this decline. Signs include:

• Muscle weakness or pain, especially if taking statins – CoQ10 depletion is the primary mechanism behind statin myopathy
• Exercise intolerance that seems disproportionate to your fitness level – CoQ10 is critical for ATP production in cardiac and skeletal muscle
• Heart palpitations or irregular heartbeat – the heart depends on CoQ10 more than any other tissue

• Chronic fatigue despite adequate sleep, B12, and iron levels – if you have ruled out other causes, CoQ10 depletion should be considered
• Gum disease and slow-healing mouth sores – gingival tissues have high CoQ10 requirements

Beef heart is the richest natural dietary source of CoQ10. CoQ10 was first isolated from beef heart mitochondria in 1957 by Dr. Frederick Crane at the University of Wisconsin (8). A heart supplement provides CoQ10 in its natural form within the mitochondrial matrix, along with taurine and B vitamins that support cardiac function. For more on CoQ10 forms, see our CoQ10 ubiquinol vs ubiquinone comparison.

Signs of Histamine Intolerance (Kidney DAO Support)

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Histamine intolerance is an increasingly recognized condition caused by insufficient activity of diamine oxidase (DAO), the primary enzyme responsible for degrading histamine in the gut. The kidney is the richest natural source of DAO enzyme activity. Symptoms include:

• Headaches or migraines after eating certain foods – particularly aged cheeses, fermented foods, wine, and cured meats
• Facial flushing, hives, or unexplained skin reactions – especially after meals
• Nasal congestion or runny nose unrelated to allergies or illness – histamine causes vasodilation and increased mucus production
• Digestive distress (bloating, diarrhea, cramping) after high-histamine meals
• Anxiety or heart palpitations after eating – histamine acts as a neurotransmitter and can trigger cardiovascular symptoms
• Worsening of symptoms during certain times of the menstrual cycle – estrogen inhibits DAO activity, which is why histamine intolerance disproportionately affects women

A 2019 clinical trial published in Food Science and Biotechnology found that oral DAO supplementation significantly improved all symptoms in patients with histamine intolerance. When supplementation was discontinued during the follow-up period, symptom scores increased again, confirming the causal relationship (9).

Breaking Down Each Organ: What You Get and Why It Matters

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Beef Liver: The Nutritional Powerhouse

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Beef liver is the single most nutrient-dense food available to humans. There is no close second. Its concentration of vitamin A (as preformed retinol), vitamin B12, folate, copper, riboflavin, niacin, and heme iron makes it effectively nature’s multivitamin. A 2022 study analyzing the polyunsaturated fatty acid composition of beef liver found that grass-fed liver also provides meaningful amounts of omega-3 fatty acids, with particularly favorable n-6 to n-3 ratios of 0.71 in pasture-raised animals (10).

Key nutrients and their functions:

• Vitamin A (retinol): Unlike beta-carotene from plants, retinol from liver is the preformed, bioactive version that requires no conversion. It is essential for immune function, vision, skin health, and gene expression. Liver is the richest natural source.
• Vitamin B12 (cobalamin): Critical for nerve function, DNA synthesis, red blood cell formation, and methylation. Liver provides approximately 60 mcg per 100 grams.
• Folate (as 5-MTHF): The natural, bioactive form of folate, crucial during pregnancy and for anyone with MTHFR gene variants who cannot efficiently convert synthetic folic acid.
• Heme iron: The most bioavailable form of dietary iron, absorbed at 25-30% efficiency regardless of other dietary factors.
• Copper: Essential for iron metabolism (you cannot properly use iron without adequate copper), connective tissue formation, and antioxidant enzyme function. Liver provides over 1,000% of the daily value per serving.
• Riboflavin (B2): A cofactor for hundreds of enzymatic reactions, including those involved in energy production, cellular function, and the metabolism of fats and drugs.
• Choline: Critical for liver function, brain development, nerve signaling, and muscle movement. Most people are deficient.

Who benefits most from liver supplements:

• Women with iron deficiency or heavy menstrual periods
• People with B12 deficiency (vegans transitioning back to animal foods, older adults, metformin users)
• Anyone seeking a whole-food multivitamin replacement
• Pregnant women (in appropriate doses – see vitamin A section below)
• Athletes with high nutrient turnover

Beef Heart: The CoQ10 Source

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The heart is one of the hardest-working organs in the body, beating roughly 100,000 times per day without rest. To sustain this workload, cardiac tissue is packed with mitochondria, and those mitochondria are concentrated with Coenzyme Q10. Beef heart is the richest natural dietary source of CoQ10 in existence.

CoQ10 exists in two forms: ubiquinone (the oxidized form) and ubiquinol (the reduced, active form). After absorption, approximately 95% of circulating CoQ10 in the body is in the ubiquinol form. Beef heart provides CoQ10 within its natural mitochondrial context, alongside supporting nutrients (8).

Key nutrients in beef heart:

• CoQ10: Beef heart contains approximately 11.3 mg of CoQ10 per 100 grams – the highest concentration of any common food
• Taurine: An amino acid critical for bile salt formation, heart rhythm regulation, and antioxidant defense. Heart tissue is one of the richest natural sources.
• B vitamins: Heart provides meaningful amounts of B12, B6, niacin, and riboflavin
• Collagen and elastin: Structural proteins that support connective tissue health
• Iron and zinc: Present in moderate amounts

Who benefits most from heart supplements:

• People taking statin medications (which deplete CoQ10)
• Those with cardiovascular concerns
• Athletes seeking mitochondrial support
• Anyone over 40 (CoQ10 production declines significantly with age)
• People experiencing chronic fatigue with adequate B12 and iron levels

Beef Kidney: The DAO and Selenium Specialist

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Kidney tissue has a unique nutritional profile that sets it apart from other organs. While it shares some nutrients with liver (B12, iron, selenium), its distinguishing feature is its concentration of diamine oxidase (DAO) – the primary enzyme responsible for breaking down histamine in the gastrointestinal tract.

The 2019 clinical trial on DAO supplementation used supplements derived from pig kidney protein, demonstrating that oral DAO taken before meals significantly reduced histamine intolerance symptoms. When supplementation was stopped, symptoms returned, establishing a clear dose-response relationship (9).

Key nutrients in beef kidney:

• Diamine oxidase (DAO): The enzyme responsible for histamine degradation in the gut
• Selenium: 141 mcg per 100 grams (256% DV) – one of the richest natural sources. Selenium is critical for thyroid function, antioxidant defense (via glutathione peroxidase), and immune function.
• Vitamin B12: 27.5 mcg per 100 grams (1,146% DV)
• Iron: 4.6 mg per 100 grams, predominantly heme iron
• Riboflavin: 2.84 mg per 100 grams (218% DV)

Who benefits most from kidney supplements:

• People with histamine intolerance (headaches, flushing, digestive issues after high-histamine foods)
• Those with mast cell activation syndrome (MCAS)
• People needing selenium for thyroid support (especially those with Hashimoto’s thyroiditis)
• Anyone seeking additional B12 and heme iron beyond what liver provides

Beef Spleen: The Iron and Immune Specialist

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Spleen is often overlooked in supplement formulations, but it has two remarkable characteristics: an extraordinarily high concentration of heme iron and the production of tuftsin, a tetrapeptide that powerfully stimulates phagocytic immune cells.

A foundational study on tuftsin published in Annals of the New York Academy of Sciences established that this peptide stimulates virtually all functions of phagocytic cells, including phagocytosis, pinocytosis, motility, immunogenic activity, bactericidal activity, and tumoricidal activity (11). Subsequent research confirmed that tuftsin and spleen extract demonstrated considerable enhancement of polymorphonuclear leukocyte activity compared to thymus preparations (12).

Key nutrients in beef spleen:

• Heme iron: Spleen contains approximately 44.4 mg of iron per 100 grams of dried weight – making it by far the most iron-dense organ, several times higher than liver
• Tuftsin: An immune-activating tetrapeptide (Thr-Lys-Pro-Arg) naturally produced by the spleen
• Splenin peptides: Immune-modulating peptides unique to spleen tissue
• Vitamin C: Spleen contains modest amounts of vitamin C, which further supports iron absorption

Who benefits most from spleen supplements:

• People with severe iron deficiency or iron deficiency anemia
• Those recovering from illness who want immune support
• People who have undergone splenectomy (spleen removal) – tuftsin production is lost after splenectomy
• Athletes with high iron turnover from endurance training

Beef Pancreas: The Digestive Enzyme Source

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The pancreas produces and secretes the digestive enzymes responsible for breaking down proteins (proteases), fats (lipases), and carbohydrates (amylases) in the small intestine. Pancreatic insufficiency – where the pancreas does not produce adequate enzymes – is more common than most people realize, particularly with aging, chronic stress, and in people with certain gastrointestinal conditions.

Key components in beef pancreas:

• Pancreatic enzymes: Lipase, protease, and amylase in their natural, whole-food form
• Insulin-like growth factors: Peptides that may support blood sugar regulation
• B vitamins: Moderate concentrations of B12 and other B vitamins

Who benefits most from pancreas supplements:

• People with digestive difficulties, especially fat malabsorption (pale, floating, or greasy stools)
• Those with exocrine pancreatic insufficiency
• Older adults with declining enzyme production
• Anyone experiencing bloating or indigestion after meals

For more on digestive enzymes and when they are actually necessary, see our guide: Best Digestive Enzyme Supplements: Who Actually Needs Them.

Multi-Organ Complexes vs. Single-Organ Supplements: Which Should You Choose?

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This is one of the most common questions people ask when entering the organ supplement space, and the answer depends entirely on your goals and situation.

When to Choose a Single-Organ Supplement

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Choose beef liver alone if:

• Your primary goal is increasing iron, B12, vitamin A, or overall nutrient density
• You want the simplest, most researched organ supplement
• You are looking for a whole-food multivitamin replacement
• Budget is a concern (single-organ supplements are generally less expensive)

Choose beef heart alone if:

• You are specifically targeting CoQ10 for statin-related muscle pain, cardiac health, or mitochondrial function

• You want concentrated taurine support

Choose beef kidney alone if:

• Histamine intolerance is your primary concern
• You need targeted selenium for thyroid support

Choose beef spleen alone if:

• You have significant iron deficiency and need the most iron-dense organ option
• You want immune support via tuftsin after illness or splenectomy

When to Choose a Multi-Organ Complex

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Multi-organ complexes typically contain liver, heart, kidney, spleen, and pancreas in a single capsule formula. The rationale is that consuming a diversity of organs provides a broader spectrum of nutrients, enzymes, and peptides than any single organ alone.

Choose a multi-organ complex if:

• You want the broadest possible nutrient spectrum from organ supplementation
• You are following an ancestral or carnivore dietary approach and want to replicate the organ diversity our ancestors consumed
• You do not have a specific single-nutrient concern (like iron deficiency or histamine intolerance) that warrants a targeted single-organ approach
• You prefer the simplicity of one product rather than multiple bottles

The trade-off to understand: Because multi-organ formulas divide their capsule space among 5 organs, you get less of each individual organ per serving. A typical multi-organ product provides approximately 600 mg of liver per serving (versus 3,000 mg in a dedicated liver supplement). This means you get about one-fifth the liver-specific nutrients. If you have a pronounced B12 or iron deficiency, a liver-specific or spleen-specific supplement will deliver a higher therapeutic dose of those particular nutrients.

The combination approach: Many serious users take a liver-specific supplement as their foundation and add a multi-organ complex on top. This provides a concentrated liver dose plus the unique nutrients from heart, kidney, spleen, and pancreas.

Grass-Fed vs. Conventional: Does the Source Actually Matter?

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This is not just marketing – the differences between grass-fed and conventional organ supplements are meaningful and supported by published research.

Fatty Acid Profile Differences

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A comprehensive 2010 review published in the Nutrition Journal examining grass-fed versus grain-fed beef found significant differences in fatty acid composition. Grass-based diets enhanced total conjugated linoleic acid (CLA) isomers and trans-vaccenic acid (TVA), a precursor to CLA, as well as omega-3 fatty acids. The n-6 to n-3 fatty acid ratio in grass-fed beef was 0.71 compared to 4.8 in grain-fed animals – a nearly seven-fold difference (13).

For liver specifically, the 2011 study in Meat Science found that total fatty acid content of liver was comparable between grass-fed (3.5%) and grain-fed (3.7%) animals, but the composition was dramatically different. Grass-fed liver had a much more favorable omega-6 to omega-3 ratio and higher concentrations of long-chain omega-3 fatty acids like DHA and EPA (10).

Antioxidant and Vitamin Content

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Multiple studies demonstrate that grass-fed animals accumulate higher levels of fat-soluble vitamins and antioxidants. Grass-based diets elevate precursors for vitamin A and vitamin E, as well as antioxidant enzymes including glutathione (GT) and superoxide dismutase (SOD) compared to grain-fed animals (13). Since liver is the primary organ for vitamin storage and metabolism, these differences are concentrated in liver tissue.

Contaminant Concerns

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The liver functions as the body’s primary detoxification organ, filtering and metabolizing toxins from the bloodstream. This raises a legitimate question: does consuming liver mean consuming concentrated toxins?

The answer is nuanced. The liver metabolizes and exports toxins – it does not permanently store most of them in the way that fat tissue accumulates persistent organic pollutants. However, the quality of the animal’s feed and environment does influence residue levels. Animals raised on conventional feedlots with exposure to hormones, antibiotics, pesticide-treated grain, and crowded conditions will have different residue profiles than animals raised on open pasture eating their natural diet of grass.

For organ supplements specifically, the most reputable brands source from:

• New Zealand: Where cattle are raised 100% grass-fed year-round on open pasture, without added hormones or routine antibiotics. New Zealand also has strict BSE (mad cow disease) prevention protocols.
• Australia: Similar pasture-based farming standards with strict regulatory oversight.
• United States: Look for USDA Organic, 100% grass-fed certifications. “Grass-fed” alone without “grass-finished” may mean the animal was grain-finished in a feedlot.

Bottom line: For organ supplements, grass-fed sourcing from reputable origins is worth the modest price premium. You are specifically consuming the organ that processes everything the animal ate and was exposed to. Choose the cleanest source available.

Freeze-Dried vs. Heat-Processed Desiccated: Why Processing Matters

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Not all organ supplements are created equal, and the processing method is one of the most important quality differentiators.

Freeze-Drying: The Gold Standard

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Freeze-drying (lyophilization) works by first freezing the organ tissue to temperatures between -30 degrees C and -50 degrees C, then applying a vacuum that causes the frozen water to sublimate directly from ice to vapor – bypassing the liquid phase entirely. This happens at temperatures well below freezing throughout the entire process.

The result is remarkable nutrient preservation. Research on freeze-drying food matrices shows retention of up to 97% of vitamin C content (a particularly heat-sensitive nutrient), and overall micronutrient loss of less than 5%. Enzymes like DAO from kidney tissue remain active. Heat-sensitive cofactors and peptides are preserved in their native conformations.

Freeze-dried organ supplements typically:

• Retain the original color of the raw organ (deep red-brown for liver)
• Preserve enzyme activity (particularly important for kidney DAO and pancreatic enzymes)
• Maintain the full spectrum of heat-sensitive B vitamins
• Cost more due to the longer, more energy-intensive process

Heat-Processed Desiccation: The Budget Option

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Traditional desiccation uses heat (often 40-70 degrees C or higher) to evaporate moisture from organ tissue. While this is faster and less expensive than freeze-drying, the elevated temperatures can:

• Denature heat-sensitive enzymes (DAO, pancreatic lipase, protease, amylase)
• Reduce B vitamin content (particularly B12, folate, and riboflavin)
• Alter protein structures and reduce bioactive peptide activity
• Oxidize fatty acids, including the omega-3s and CLA in grass-fed organs

Desiccated liver tablets have been used by bodybuilders and athletes since the 1950s, and they do still provide meaningful nutrition – particularly the more heat-stable minerals like iron, copper, zinc, and selenium. But they are objectively inferior to freeze-dried products for preserving the full spectrum of organ nutrition.

How to Tell the Difference on the Label

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• “Freeze-dried” – clearly indicates the superior processing method
• “Desiccated” – traditionally means heat-processed, though some brands now freeze-dry and still use this term
• “Raw” or “Gently dried” – marketing terms without standardized definitions; check the brand’s processing details
• “Cold-processed” – typically indicates freeze-drying, but verify with the manufacturer

Our recommendation: For organ supplements, freeze-dried products are worth the additional cost, particularly if you are taking kidney supplements for DAO activity or multi-organ complexes where enzyme preservation matters. The nutrient retention difference is substantial enough to affect real-world outcomes.

Vitamin A Toxicity: An Honest Risk Assessment

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Vitamin A toxicity (hypervitaminosis A) is the most frequently raised safety concern about liver supplements, and it deserves a thorough, evidence-based discussion rather than the dismissive hand-waving you see on many supplement company websites.

What the Research Actually Shows

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According to the NCBI StatPearls database and the National Institutes of Health, chronic vitamin A toxicity generally occurs with daily intakes exceeding 10,000 IU (3,000 mcg RAE) sustained over prolonged periods. The Tolerable Upper Intake Level (UL) established by the Institute of Medicine for all adults is 10,000 IU per day (14).

Acute toxicity typically requires ingestion of over 300,000 IU in a single dose in adults, or proportionally less in children. Symptoms of chronic toxicity include headaches, dizziness, nausea, skin changes (dry, peeling skin), hair loss, bone pain, and in severe cases, liver damage.

How This Translates to Liver Supplements

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A typical beef liver supplement provides 500 mg per capsule, with a standard serving of 6 capsules (3,000 mg or 3 grams). Raw beef liver contains approximately 16,899 IU of vitamin A per 100 grams. At 3 grams per serving, a standard liver supplement dose provides roughly 500 IU of vitamin A – well below any toxicity concern.

Even at the higher end, if you take double the recommended dose (6,000 mg), you would still only get approximately 1,000 IU – one-tenth of the established upper limit.

The realistic risk assessment:

• Standard liver supplement doses (3-6 grams per day) provide roughly 500-1,000 IU of vitamin A
• The established upper limit is 10,000 IU per day
• You would need to consume approximately 60-120 capsules per day – an absurd amount that no one would accidentally take – to approach vitamin A toxicity levels from liver supplements alone
• The real risk is combining liver supplements with high-dose vitamin A supplements (like cod liver oil at high doses) plus dietary liver consumption on the same day

Groups who should exercise extra caution:

• Pregnant women (high-dose vitamin A is teratogenic; however, moderate intake from food sources has a long safety history)
• People with liver disease (impaired vitamin A metabolism)
• People already taking high-dose vitamin A or cod liver oil supplements
• Children (lower body weight means lower absolute threshold)

Bottom line: For the vast majority of adults taking liver supplements at recommended doses, vitamin A toxicity is not a realistic concern. The fearmongering around this issue has likely caused more harm (by discouraging people from taking a genuinely beneficial supplement) than the actual risk of toxicity at standard doses. That said, more is not better – stick to label recommendations and do not combine multiple concentrated vitamin A sources without tracking your total intake.

Dosing Protocols and Timing: How to Take Organ Supplements

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Standard Dosing for Beef Liver Capsules

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Most liver supplements are formulated as 500 mg capsules with a recommended serving of 6 capsules per day (3,000 mg total). This is a reasonable and well-tolerated dose for most adults. Here is how to approach dosing based on your situation:

For general nutrient density and wellness:

• 3,000 mg per day (6 capsules) – standard maintenance dose
• Take with meals to maximize absorption of fat-soluble vitamins (A, D, E, K)
• Can be split into 2-3 doses throughout the day or taken all at once

For iron deficiency:

• 3,000-4,500 mg per day (6-9 capsules) – higher end for active repletion
• Consider pairing with a dedicated spleen supplement for maximum heme iron intake
• Take on an empty stomach or with a small amount of vitamin C-rich food for enhanced iron absorption
• Avoid taking within 2 hours of calcium supplements, coffee, or tea (though heme iron is less affected by these inhibitors than non-heme iron)
• Monitor ferritin levels every 8-12 weeks and adjust dose accordingly

For B12 deficiency:

• 3,000 mg per day minimum
• Note: If you have clinically significant B12 deficiency (below 200 pg/mL), liver supplements alone may not provide sufficient B12 for rapid repletion; consider pairing with a sublingual methylcobalamin supplement initially
• Liver supplements work well for maintenance and prevention of B12 deficiency once levels are restored

Standard Dosing for Multi-Organ Complexes

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Multi-organ products typically contain a blend of liver, heart, kidney, spleen, and pancreas. The standard dose is usually 6 capsules (3,000 mg total), with each organ comprising roughly 600 mg of the blend.

• Take with meals for optimal absorption
• Best taken with a meal containing dietary fat, which enhances absorption of fat-soluble nutrients

Standard Dosing for Heart (CoQ10 Support)

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• 3,000 mg per day (6 capsules) for general cardiovascular and mitochondrial support
• If you are taking statins, consider the higher end of the dosing range
• CoQ10 is fat-soluble, so always take heart supplements with a meal containing fat
• It may take 4-8 weeks to notice improvements in energy and reduction of statin-related muscle discomfort

Standard Dosing for Kidney (DAO/Histamine Support)

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• Timing is critical for histamine intolerance: Take kidney supplements 15-20 minutes BEFORE meals, particularly before meals that contain high-histamine foods

• 500-1,000 mg before each meal (1-2 capsules, up to 3 times daily)
• The DAO enzyme needs to be present in the gut before histamine-containing food arrives
• This is the one organ supplement where timing relative to food matters significantly

Standard Dosing for Spleen (Iron and Immune Support)

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• 3,000 mg per day for immune support
• For severe iron deficiency, some practitioners recommend up to 4,500 mg per day temporarily
• Can be taken with or between meals
• If combining with liver, start with lower doses of each and increase gradually

When to Take Organ Supplements: Morning vs. Evening

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• Morning or midday is generally preferred – the B vitamins and iron in organ supplements can be energizing and may interfere with sleep if taken late in the evening
• Exception: If you experience mild nausea from organ supplements (uncommon but possible), taking them with your largest meal of the day, regardless of timing, usually resolves this
• With food is always better than without – fat-soluble vitamins A, D, E, K require dietary fat for absorption

Starting Protocol for First-Time Users

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If you have never taken organ supplements before, start conservatively:

1. Week 1-2: Half the recommended dose (3 capsules per day for most products)
2. Week 3-4: Increase to the full recommended dose (6 capsules per day)
3. Week 5+: Assess how you feel and adjust. Some people benefit from higher doses; others find the standard dose optimal.

The gradual ramp-up is not because organ supplements are dangerous at full dose – it is because introducing a concentrated source of B vitamins, iron, and other nutrients can occasionally cause mild digestive adjustment, especially in people with sensitive guts.

Product Recommendations: What We Recommend and Why

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Best Overall Beef Liver Supplement: Ancestral Supplements Grass-Fed Beef Liver

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Ancestral Supplements has become the most recognized brand in the organ supplement space, and for good reason. Their beef liver product is sourced from grass-fed, pasture-raised cattle in New Zealand – one of the cleanest, most strictly regulated livestock environments in the world. The product is freeze-dried to preserve nutrient integrity, free of fillers, flow agents, and additives, and encapsulated in bovine gelatin capsules.

Serving size: 6 capsules (3,000 mg) Per serving: 3,000 mg grass-fed New Zealand beef liver Processing: Freeze-dried Third-party testing: Yes Notable: No hormones, no antibiotics, no GMOs, no pesticides. BSE-free sourcing.

Strengths:

• Gold-standard sourcing from New Zealand grass-fed cattle
• Freeze-dried processing preserves heat-sensitive nutrients and enzymes
• Clean label with no fillers, binders, or flow agents
• Extensively reviewed with a large user base providing real-world feedback
• Consistent dosing and quality across batches

Limitations:

• Premium pricing (approximately $40-48 for 180 capsules, a 30-day supply)
• Capsules are large, which some people find difficult to swallow
• Lower iron per capsule compared to dedicated spleen supplements

Best Multi-Organ Complex: Ancestral Supplements Grass-Fed Beef Organs

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For those seeking the broadest nutrient spectrum, the Ancestral Supplements multi-organ formula combines liver, heart, kidney, pancreas, and spleen in a single product. This mimics the diverse organ consumption of ancestral populations and provides nutrients unique to each organ – CoQ10 from heart, DAO from kidney, tuftsin from spleen, and digestive enzymes from pancreas – alongside the foundational nutrition from liver.

Serving size: 6 capsules (3,000 mg) Per serving: Proprietary blend of grass-fed liver, heart, kidney, pancreas, and spleen (600 mg each) Processing: Freeze-dried Third-party testing: Yes

Strengths:

• Five organs in one product for maximum nutrient diversity
• Same New Zealand grass-fed sourcing and freeze-dried processing as their liver product
• Convenient for people who want broad organ nutrition without taking multiple products
• Includes DAO from kidney and CoQ10 from heart alongside liver nutrition

Limitations:

• You get less of each individual organ per serving (600 mg each vs. 3,000 mg in a single-organ product)
• If you have a specific deficiency (iron, B12), a dedicated liver or spleen supplement will provide a higher targeted dose
• Premium pricing

Best Budget-Friendly Beef Liver Option

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For those who want the benefits of beef liver supplementation without the premium price of Ancestral Supplements, several brands offer quality grass-fed liver capsules at lower price points. When shopping for budget options, prioritize:

1. Grass-fed sourcing (non-negotiable)
2. Freeze-dried processing (preferred) or at minimum “cold-processed”
3. No fillers, flow agents, or artificial additives
4. Third-party testing for heavy metals and contaminants
5. Transparent sourcing (country of origin clearly stated)

Best for Histamine Intolerance: Dedicated Kidney DAO Supplement

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If histamine intolerance is your primary concern, a dedicated kidney supplement will provide a higher concentration of DAO enzyme per serving than a multi-organ complex. Look for:

• Kidney-specific products (not blended with other organs)
• Freeze-dried processing (critical for DAO enzyme preservation – heat destroys DAO activity)
• Dosing that allows you to take it 15-20 minutes before meals

Best for Severe Iron Deficiency: Dedicated Spleen Supplement

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Spleen contains dramatically more heme iron per gram than liver. If you are working with a healthcare provider to resolve iron deficiency anemia and want a whole-food approach, a spleen-specific supplement provides the highest available heme iron dosing in capsule form.

Comprehensive Multi-Organ Shopping

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Organ Supplements vs. Synthetic Multivitamins: A Direct Comparison

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One of the most compelling arguments for organ supplements is their potential superiority over conventional multivitamins. Let us compare them directly.

Nutrient Forms: Whole Food vs. Isolated Synthetics

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What Organ Supplements Do Better

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• Heme iron that is 5-8 times more bioavailable than the non-heme iron in standard multivitamins, with far fewer gastrointestinal side effects
• Folate as 5-MTHF rather than synthetic folic acid, which approximately 40% of the population cannot efficiently convert due to MTHFR variants
• B12 in its natural coenzyme forms rather than cyanocobalamin, which requires multiple conversion steps
• CoQ10 and DAO enzyme that are simply not present in conventional multivitamins
• Cofactors, peptides, and enzymes that exist within the whole-food matrix and may enhance nutrient utilization
• No artificial colors, flavors, binders, or fillers (in quality products)

What Synthetic Multivitamins Do Better

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To be fair, organ supplements are not a perfect multivitamin replacement in all respects:

• Vitamin D: Organ supplements provide minimal vitamin D. Most people need a separate vitamin D supplement, particularly in northern latitudes. See our vitamin D supplement guide.
• Vitamin C: Not present in meaningful amounts in organ supplements
• Vitamin E: Present but in small amounts
• Calcium and magnesium: Not present in significant amounts. See our guide to the best magnesium supplements.
• Specific therapeutic doses: If you need, say, 5,000 IU of vitamin D or 400 mg of magnesium, organ supplements will not provide those targeted doses

The practical recommendation: Use organ supplements as your nutritional foundation for B vitamins, iron, vitamin A, copper, selenium, and trace nutrients. Add individual supplements for vitamin D, magnesium, and omega-3s (if you are not eating fatty fish regularly). This approach gives you the whole-food matrix benefits of organs plus targeted doses of nutrients they do not adequately provide. For more on this approach, see our comparison of multivitamins vs. individual supplements.

Who Should NOT Take Organ Supplements

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While organ supplements are safe for the vast majority of adults, certain groups should exercise caution or avoid them:

People with Hemochromatosis (Iron Overload)

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Hemochromatosis is a genetic condition affecting approximately 1 in 200 people of Northern European descent. It causes excessive iron absorption and accumulation, leading to organ damage. People with hemochromatosis or known iron overload should avoid liver and especially spleen supplements due to their high heme iron content. If you have a family history of hemochromatosis, get your ferritin and transferrin saturation tested before starting organ supplements.

People with Wilson’s Disease

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Wilson’s disease is a rare genetic disorder (affecting about 1 in 30,000 people) that causes copper accumulation in the body. Since beef liver is extremely rich in copper (over 1,000% of the daily value per 100 grams), people with Wilson’s disease should avoid liver supplements entirely.

People with Gout or Hyperuricemia

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Organ meats are high in purines, which are metabolized to uric acid. People with gout or significantly elevated uric acid levels should be cautious with organ supplements, particularly liver, and should consult their healthcare provider before starting.

Pregnant Women: A Nuanced Discussion

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This topic generates significant debate. Excessive preformed vitamin A (retinol) during pregnancy, particularly during the first trimester, is associated with birth defects. The concern applies to doses exceeding 10,000 IU per day from preformed sources.

However, as discussed in the vitamin A toxicity section above, standard doses of liver supplements provide roughly 500-1,000 IU of vitamin A – well below the 10,000 IU threshold. Many traditional cultures specifically fed liver to pregnant women for its iron, folate, and B12 content. The Weston A. Price Foundation and many ancestral health practitioners consider moderate liver consumption during pregnancy to be beneficial.

Our position: Pregnant women should discuss liver supplementation with their healthcare provider, ideally one who understands both the risks of excessive vitamin A and the benefits of whole-food nutrient sources. Standard supplement doses are very unlikely to pose a vitamin A risk, but this is a decision best made with professional guidance.

People Taking Blood Thinners (Warfarin)

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Liver contains vitamin K, which can interfere with warfarin (Coumadin) dosing. If you take warfarin, maintain a consistent intake of organ supplements rather than varying your dose, and inform your healthcare provider so your INR can be monitored appropriately.

Common Questions About Organ Supplements

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Can I Take Organ Supplements If I Am Vegetarian or Vegan?

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By definition, organ supplements are animal-derived and are not vegan or vegetarian. However, some people who follow plant-based diets for ethical rather than health reasons may make an exception for organ supplements, particularly to address B12 or iron deficiency. This is a personal decision. If you are firmly committed to avoiding all animal products, you will need to use synthetic or plant-derived alternatives for these nutrients.

Do Organ Supplements Interact With Medications?

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The primary interactions to be aware of:

• Warfarin: Vitamin K in liver can affect INR (discussed above)
• Thyroid medications (levothyroxine): Take organ supplements at least 4 hours apart from thyroid medication, as iron can interfere with absorption
• Metformin: No direct interaction, and metformin depletes B12, so liver supplements may actually be beneficial
• Proton pump inhibitors: No direct interaction, but PPIs reduce stomach acid which impairs B12 and iron absorption; organ supplements provide more bioavailable forms of both

How Long Should I Take Organ Supplements?

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Organ supplements can be taken indefinitely as part of a whole-food nutritional strategy. They are food in concentrated capsule form, not pharmaceutical drugs. Many users take them continuously for years. If you started them to address a specific deficiency (iron, B12), retest your levels after 8-12 weeks and discuss ongoing dosing with your healthcare provider.

Can I Open the Capsules and Add Them to Food?

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Yes. Freeze-dried organ powders can be mixed into smoothies, ground meat, sauces, or soups. The taste will be noticeable but can be masked with strongly flavored ingredients. This approach is common for children or people who cannot swallow capsules. Some brands sell organ powders specifically for this purpose.

Are There Any Side Effects?

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Most people tolerate organ supplements extremely well. Occasionally reported effects include:

• Mild nausea: Usually resolves by taking capsules with food; more common in the first week
• Changes in stool color: Iron-containing supplements can darken stool; this is normal and harmless
• Increased energy that feels uncomfortable: If you were significantly deficient in B12 or iron, the sudden improvement can feel strange initially; this normalizes within days
• Burping with slight liver taste: Uncommon with freeze-dried products but can occur; taking with food typically prevents this

Special Populations: Tailored Recommendations

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For Athletes and Active Individuals

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Athletes have significantly elevated requirements for iron (especially endurance athletes who lose iron through foot-strike hemolysis, sweat, and GI bleeding during intense exercise), B vitamins (increased energy metabolism), CoQ10 (mitochondrial energy production), and selenium (antioxidant defense against exercise-induced oxidative stress). A study published in Nutrients demonstrated that iron supplementation was beneficial for non-anemic endurance athletes to improve stress, mood states, subjective fatigue, and sweating conditions (15).

Recommended protocol for athletes:

• Beef liver: 3,000-4,500 mg daily (iron, B12, folate foundation)
• Beef heart: 1,500-3,000 mg daily (CoQ10, taurine for cardiac output and recovery)
• Consider adding spleen during periods of heavy training for additional heme iron

For Women of Reproductive Age

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Menstruation causes monthly iron loss that accumulates over years, making iron deficiency the most common nutrient deficiency among premenopausal women. The combination of heme iron from liver and spleen, folate and B12 from liver, and the whole-food matrix delivery makes organ supplements particularly well-suited for this population.

Recommended protocol for menstruating women:

• Beef liver: 3,000 mg daily (foundational – provides iron, B12, folate, vitamin A)
• Consider adding beef spleen during menstruation for additional heme iron
• Monitor ferritin every 6-12 months; target above 50 ng/mL for optimal energy and hair health

For Keto and Carnivore Dieters

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People following ketogenic or carnivore diets are already eating animal-based foods exclusively or predominantly, but many still neglect organ meats in favor of muscle meat. This can lead to subtle nutrient gaps, particularly in vitamin A, copper, folate, and certain B vitamins that are concentrated in organs rather than muscle tissue.

Recommended protocol for keto/carnivore dieters:

• Multi-organ complex: 3,000-6,000 mg daily to ensure organ diversity
• Or beef liver: 3,000 mg daily if you are already eating some organs
• Organ supplements complement a meat-heavy diet by filling the specific gaps that muscle meat leaves

For Older Adults (60+)

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Aging brings predictable declines in stomach acid production (reducing B12 and iron absorption), CoQ10 synthesis, DAO activity, and digestive enzyme output. These are precisely the nutrients and enzymes that organ supplements provide.

Recommended protocol for older adults:

• Multi-organ complex: 3,000 mg daily (provides broad-spectrum support)
• Consider additional beef heart for CoQ10, especially if taking statins
• Kidney supplement if experiencing new-onset food sensitivities (may indicate declining DAO)

For more on energy and fatigue in general, see our guide: Best Supplements for Energy and Fatigue: What Actually Works.

How to Evaluate Organ Supplement Quality: A Checklist

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Before purchasing any organ supplement, run through this checklist:

Non-negotiable criteria:

1. Grass-fed, pasture-raised sourcing – ideally from New Zealand, Australia, or verified US grass-fed operations
2. Freeze-dried processing – especially important if you are buying kidney (for DAO) or multi-organ products
3. No fillers, flow agents, or additives – the only ingredients should be the organ powder and the capsule material
4. Country of origin clearly stated – brands that are vague about sourcing are a red flag
5. Third-party testing – at minimum for heavy metals (lead, mercury, cadmium, arsenic) and microbial contaminants

Additional quality indicators:

6. BSE-free certification or sourcing from BSE-free countries – New Zealand, Australia, and several South American countries have never had a case of BSE
7. Hormone-free and antibiotic-free declarations – standard in New Zealand and Australian sourcing; verify for US products
8. Capsule material – bovine gelatin capsules are preferred for ancestral consistency; some brands offer vegetable cellulose capsules for those who prefer them
9. Batch testing results available – the best brands make Certificate of Analysis (COA) results available upon request
10. Transparent company with responsive customer service – willingness to answer questions about sourcing and processing is a good quality signal

Where to Buy Quality Supplements

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Based on the research discussed in this article, here are some high-quality options:

• Vitamin D Supplement
• Vitamin C Supplement
• Vitamin B12 Supplement
• Omega-3 Supplement
• Magnesium Supplement

The Bottom Line: Is an Organ Supplement Worth Taking?

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Organ supplements are not a magic pill, and no single supplement is. But they occupy a genuinely unique position in the supplement landscape. They are not synthetic isolates manufactured in a lab. They are concentrated whole foods – the same organ meats that humans consumed for hundreds of thousands of years, delivered in a modern format that makes them practical for people who cannot or will not eat organs directly.

The evidence supports real, measurable benefits:

• Heme iron with 5-8 times the bioavailability of standard iron supplements and dramatically fewer side effects (4)
• Vitamin B12 in its natural coenzyme forms, critical for neurological function and blood cell formation
• Vitamin A as preformed retinol, the bioactive form that requires no conversion
• CoQ10 from heart tissue, supporting mitochondrial energy production and cardiac health (8)
• DAO from kidney tissue, clinically demonstrated to improve histamine intolerance symptoms (9)
• Tuftsin from spleen, a well-characterized immune-stimulating peptide (11)
• Natural digestive enzymes from pancreas, supporting fat, protein, and carbohydrate digestion

For the person dealing with iron deficiency who cannot tolerate ferrous sulfate, a grass-fed liver or spleen supplement may genuinely change their quality of life. For the person on statins experiencing muscle pain, adding a heart supplement for its natural CoQ10 content may provide relief that they have not found elsewhere. For the person with mysterious food reactions who discovers they have histamine intolerance, a kidney DAO supplement taken before meals may resolve symptoms that they have struggled with for years.

Choose grass-fed, freeze-dried products from transparent companies. Start with a standard dose and give it 4-8 weeks before evaluating results. Combine with appropriate individual supplements (vitamin D, magnesium, omega-3s) for nutrients that organ supplements do not adequately provide. And monitor your relevant lab values to objectively track your progress.

Your great-grandmother was right. Liver really is good for you. Now you just do not have to taste it.

Related Articles

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• Iron Bisglycinate vs. Ferrous Sulfate – Which form of iron supplement is best for absorption and tolerability?
• CoQ10 Ubiquinol vs. Ubiquinone – Understanding the two forms of CoQ10 and which one your body actually uses.
• Vitamin B12 Deficiency Symptoms and Best B12 Supplements – Complete guide to recognizing and resolving B12 deficiency.
• Best Supplements for Energy and Fatigue – Evidence-based options for fighting fatigue beyond caffeine.
• Multivitamin vs. Individual Supplements – When does a multivitamin make sense, and when should you target specific nutrients?

References

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1. Nutrient Analysis of Raw United States Beef Offal Items. Translational Animal Science. 2024. PMC11435426.

2. Venn BJ. Macronutrients and Human Health for the 21st Century. Nutrients. 2020;12(8):2363. PMID: 32785058.

3. Liu Y, et al. Revisiting food-sourced vitamins for consumer diet and health needs: a perspective review, from vitamin classification, metabolic functions, absorption, utilization, to balancing nutritional requirements. PeerJ. 2021;9:e11940. PMC8418216.

4. Blanco-Rojo R, Vaquero MP. A comparative analysis of heme vs non-heme iron administration: a systematic review and meta-analysis of randomized controlled trials. European Journal of Nutrition. 2024;64(1):46. PMID: 39708071.

5. Aiello LC, Wheeler P. The Expensive-Tissue Hypothesis: The Brain and the Digestive System in Human and Primate Evolution. Current Anthropology. 1995;36(2):199-221.

6. Mann N. Meat in the human diet: An anthropological perspective. Nutrition & Dietetics. 2007;64(Suppl 4):S102-S107.

7. Balehegn M, et al. The role of meat in the human diet: evolutionary aspects and nutritional value. Animal Frontiers. 2023;13(2):pmid: PMC10105836.

8. Crane FL. Biochemical Functions of Coenzyme Q10. Journal of the American College of Nutrition. 2001;20(6):591-598. PMID: 11771674.

9. Yacoub MR, et al. Diamine oxidase supplementation improves symptoms in patients with histamine intolerance. Food Science and Biotechnology. 2019;28(6):1779-1784. PMID: 31807350.

10. Howlett CM, et al. The polyunsaturated fatty acid composition of beef and lamb liver. Meat Science. 2012;91(1):76-83. PMID: 22060582.

11. Najjar VA. Tuftsin, a natural activator of phagocyte cells: an overview. Annals of the New York Academy of Sciences. 1983;419:1-11. PMID: 6370072.

12. Gruner S, et al. The effect of the calf spleen and calf thymus extracts, thymopentin and tuftsin, on the phagocytosis activity of neutrophilic granulocytes. Zeitschrift fur die gesamte innere Medizin und ihre Grenzgebiete. 1992;47(5):214-218. PMID: 1610426.

13. Daley CA, et al. A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef. Nutrition Journal. 2010;9:10. PMID: 20219103.

14. Vitamin A Toxicity. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. NBK532916.

15. Sim M, et al. Iron supplementation is beneficial for non-anemic endurance athletes. Nutrients. 2019;11(4):906. PMC6566869.