Bioavailability: Why animal-based nutrients are more effective than plant-based alternatives

Most people who are interested in dietary supplements sooner or later ask themselves the same question: Does the active ingredient really arrive where it is needed? The answer depends on a term that plays a central role in nutritional science, namely bioavailability. There is much more behind this than the mere amount of a nutrient in a food or capsule. It is about how much the body can actually absorb, transport, and use. And this is precisely where significant differences become apparent between animal, plant-based, and synthetic sources.

What exactly does bioavailability mean?

Bioavailability describes the proportion of an ingested nutrient that actually enters the bloodstream after digestion and becomes available to the tissues. A food can, on paper, be rich in a particular vitamin or mineral and still deliver very little of it to the body. The reasons for this are varied: antinutrients such as phytates and oxalates in plant foods bind minerals and prevent their absorption in the intestine. Synthetic forms of vitamins are often recognized less effectively than their naturally occurring counterparts. And isolated nutrients often lack the cofactors required for their activation and utilization in the body.

The example of iron: A clear contrast

Hardly any nutrient illustrates the differences in bioavailability as clearly as iron. Animal heme iron, as found in beef liver and other organ meats, is absorbed by the human intestine at a rate of around 15 to 35 percent. Non-heme iron from plant-based sources, on the other hand, is absorbed at only 2 to 20 percent, and this rate fluctuates greatly depending on the rest of the meal. Phytates from grains and legumes, polyphenols from tea and coffee, and calcium-rich foods can drastically inhibit the absorption of plant-based iron.

Heme iron is absorbed via its own transport mechanism in the intestinal mucosa, which functions largely independently of other dietary components. This makes it a reliable and efficient source, especially for people with increased needs such as women of childbearing age, pregnant women, or endurance and performance athletes. Freeze-dried beef liver, as found in Grass-Fed Beef Liver from N2T Nutrition, provides heme iron together with copper, which is essential for incorporating iron into hemoglobin. This combination is difficult to reproduce in synthetic iron supplements.

Vitamin A: Retinol and the limits of the plant-based precursor

A similar picture emerges with vitamin A. Plant-based sources such as carrots or spinach do not provide real vitamin A, but rather precursors such as beta-carotene, which the body must first convert into usable retinol. However, this conversion rate is highly variable and significantly limited in many people. Genetic polymorphisms in the BCMO1 enzyme, which is responsible for splitting beta-carotene into retinol, mean that a considerable proportion of the population obtains very little usable vitamin A from plant-based beta-carotene. Studies suggest that the actual conversion efficiency in affected individuals can be as high as a ratio of 28 to 1, meaning that up to 28 micrograms of beta-carotene may be required to produce a single microgram of retinol.

Retinol, as it naturally occurs in high concentrations in beef liver, is directly usable by the body. No conversion is required. The nutrient is immediately available for vision, immune defense, cell growth, and reproduction.

The principle of nutrient synergy

What fundamentally distinguishes animal foods, and especially organ meats, from synthetic dietary supplements is the principle of nutrient synergy. In a natural food, vitamins, minerals, enzymes, and cofactors occur in ratios that have developed over millions of years of evolutionary adaptation and are aligned with the biochemistry of the human body. Isolated supplements can hardly replicate this interaction.

A clear example is coenzyme Q10. The highest naturally occurring concentration of this mitochondrial enzyme is found in heart muscle. Beef heart, which is included in the Organ Complex from N2T Nutrition, provides CoQ10 together with a range of B vitamins, especially vitamins B2 and B3, which are partly responsible for the synthesis and regeneration of CoQ10 in human tissue. Synthetic CoQ10 capsules completely lack this biochemical context.

The same applies to the ratio of copper and iron in beef liver. Copper is necessary for proper iron metabolism, and both minerals occur in the liver in a naturally balanced ratio. Synthetic iron supplements without sufficient copper supply cannot reflect this synergism.

The pancreas as a natural enzyme source

A less well-known, but scientifically well-documented aspect is the benefit of digestive enzymes from the pancreas. Pancreatic tissue from pasture-raised animals contains proteases, lipases, and amylases, exactly the enzymes the human body itself produces to break down food. In the Organ Complex from N2T Nutrition, pancreas is included alongside liver, heart, spleen, kidney, and lung. This component supports digestive capacity in a natural way, without synthetic enzyme concentrates or excipients.

Marine sources and trace elements from the sea

Not only beef organ meats, but also marine sources are characterized by exceptional bioavailability. Oysters are considered one of the most concentrated natural sources of zinc, and in a form the body can absorb directly. Unlike plant-based zinc from legumes or seeds, whose absorption is inhibited by phytates, zinc in oysters is present as part of amino acid complexes that are efficiently transported. Oysters also contain organically bound iodine, selenium, taurine, and other marine micronutrients that are absent from plant-based diets or present only in marginal amounts.

In the Women's Complex from N2T Nutrition, freeze-dried oysters form the main ingredient. They provide this marine trace element combination in concentrated form, supplemented by spleen and colostrum with its natural immunoglobulins.

Freeze-drying: Preserving nutrients in their natural structure

The gentlest method for preserving biochemical nutrient complexes is freeze-drying. In this process, water is removed from the raw material through sublimation without exposing it to heat. Heat-sensitive enzymes, cofactors, and fat-soluble vitamins remain preserved in their natural structure. Unlike high-temperature processing, which many conventional supplement forms undergo, the biochemical profile of the original material remains almost identical to that of the fresh tissue.

All products from N2T Nutrition are made from freeze-dried tissue from Estonian pasture-raised cattle that have been fed exclusively on grass and have not been exposed to any hormones or pesticides. The resulting fatty acid composition, with a naturally more favorable omega-3 to omega-6 ratio compared with conventionally raised animals, is another quality aspect that goes far beyond individual micronutrients.

What this means for everyday practice

The science of bioavailability shows that nutrition and supplementation are not merely a question of nutrient quantities. How a nutrient is absorbed, which other compounds it interacts with, and in what form it is presented to the body determine whether it actually has an effect. Animal foods, and in particular organ meats such as liver, heart, kidney, and spleen, provide a biochemical profile that plant-based sources and isolated synthetic supplements do not achieve in many areas.

This is not an ideological argument, but the result of a growing number of nutritional science studies showing how strongly the origin and form of a nutrient determine its effect in the body. For anyone who wants to build their nutrient supply on a solid and scientifically grounded foundation, freeze-dried organ meats from pasture-raised cattle offer one of the most direct and efficient ways to do so.

References:

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Tang G. (2010). Bioconversion of dietary provitamin A carotenoids to vitamin A in humans. The American Journal of Clinical Nutrition. https://pubmed.ncbi.nlm.nih.gov/20200262/

Leung WC et al. (2009). Two common single nucleotide polymorphisms in the gene encoding beta-carotene 15,15'-monoxygenase alter beta-carotene metabolism in female volunteers. FASEB Journal. https://pubmed.ncbi.nlm.nih.gov/19010968/

EFSA Panel on Dietetic Products, Nutrition and Allergies. (2015). Scientific Opinion on Dietary Reference Values for iron. EFSA Journal. https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2015.4254

NIH Office of Dietary Supplements. (2024). Iron: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/

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German Nutrition Society (DGE). (2021). Reference Values for Nutrient Intake. https://www.dge.de/wissenschaft/referenzwerte/