Choline, B12, zinc, copper: animal micronutrients
The bioavailability story usually focuses on the headline nutrients, iron, protein, vitamin A. But four quieter nutrients deserve their own article, because they are concentrated in animal foods, easy to run short on without them, and individually consequential for the brain, blood, immune system, and metabolism. They are the strongest part of the nutrient-density case.
Vitamin B12: an absence, not a shortfall
B12 is the clearest case in all of nutrition. It is synthesized by microorganisms and accumulates almost exclusively in animal and fermented foods; unfortified plant foods contain essentially none.[3] This isn't a bioavailability nuance, it's an absence. A literature review found B12 deficiency in a substantial share of vegetarians and an even higher share of vegans, reaching well over half of adults in some unsupplemented populations.[4] Because deficiency can cause irreversible neurological damage, B12 supplementation on a vegan diet is non-negotiable.
Choline: the nutrient almost no one gets enough of
Choline is essential for the liver, cell membranes, the neurotransmitter acetylcholine, and fetal brain development. It is richest in eggs and liver, and chronically under-consumed: only about 11% of Americans meet the Adequate Intake, and egg consumers are far more likely to get there than non-consumers.[1][2] Plant sources exist (soy, cruciferous vegetables) but are less concentrated, so a low-animal-food diet makes the already-common shortfall harder to close.
Zinc: present in plants, but locked up
Plants do contain zinc, the problem is absorption. The same phytate that limits iron binds zinc, so zinc from a high-phytate plant diet is far less bioavailable. Vegetarians may need meaningfully more zinc to compensate, and absorption improves when phytate is reduced by soaking, sprouting, fermenting, and leavening.[5][6] Animal foods (meat, shellfish) deliver zinc without the phytate penalty. Zinc matters for immunity, wound healing, testosterone, and taste, a quiet deficiency with broad effects.
Copper: the under-recognized one
Copper rounds out the set. It is essential for iron metabolism, connective tissue, and the nervous system, and it is concentrated in liver and shellfish, liver being the single richest common source.[7] Copper status gets little attention, but it interacts tightly with zinc (high zinc intake can suppress copper), which is exactly why getting these minerals from food, in their natural ratios, is more forgiving than mega-dosing one in isolation.
The honest counterpoint
None of this makes a plant-based diet unworkable, it makes it a planning problem. Every one of these nutrients can be obtained without meat:
- B12 via supplements or fortified foods (mandatory, not optional).[4]
- Choline via soy, cruciferous vegetables, and supplements if needed.[1]
- Zinc via legumes and seeds, prepared to reduce phytate, at higher total intake.[5]
- Copper via nuts, seeds, and legumes.
The point is not "you must eat meat." It's that these four nutrients are the part of the nutrient-density thesis that holds up most strongly, animal foods supply them by default, and a plant-based diet has to supply them on purpose.
The practical protocol
- If you avoid animal foods, supplement B12, reliably, for life.[3][4]
- Eat eggs (or supplement choline), most people fall short regardless of diet.[1]
- For plant zinc, raise total intake and cut phytate with preparation.[5]
- Don't mega-dose zinc without copper, get both from food in natural ratios.[7]
- A small amount of liver or shellfish covers copper, B12, and more in one move.[2]
FAQ
Hardest nutrients without animal foods? B12 (essentially absent from unfortified plants), plus choline, bioavailable zinc, and copper.
Do vegans need B12 supplements? Yes, non-negotiable; deficiency is common without it and can cause irreversible harm.
Isn't there zinc in plants? Yes, but phytate limits absorption; vegetarians may need more, and preparation helps.
References
- 1.Wallace TC, Fulgoni VL (2016). Assessment of total choline intakes in the United States. Journal of the American College of Nutrition 35(2):108–112. PMID: 26886842. Link
- 2.National Institutes of Health, Office of Dietary Supplements (2026). Choline, Health Professional Fact Sheet. NIH ODS. Link
- 3.National Institutes of Health, Office of Dietary Supplements (2026). Vitamin B12, Health Professional Fact Sheet. NIH ODS. Link
- 4.Pawlak R, et al. (2014). The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature. European Journal of Clinical Nutrition 68(5):541–548. PMID: 24667752. Link
- 5.Lönnerdal B (2000). Dietary factors influencing zinc absorption. Journal of Nutrition 130(5):1378S–1383S. DOI: 10.1093/jn/130.5.1378S. Link
- 6.National Institutes of Health, Office of Dietary Supplements (2026). Zinc, Health Professional Fact Sheet (phytate and vegetarian bioavailability). NIH ODS. Link
- 7.National Institutes of Health, Office of Dietary Supplements (2026). Copper, Health Professional Fact Sheet (liver and shellfish as top sources). NIH ODS. Link
This article is for educational purposes only and is not medical advice. It is not a substitute for professional diagnosis, treatment, or the guidance of a qualified clinician. Always consult your physician before changing your diet, starting a fast, taking supplements, or beginning a new training or heat/cold protocol, especially if you are pregnant, breastfeeding, managing a medical condition, or taking medication.