Vegan nutrition refers to the nutritional and human health aspects of vegan diets. A well-planned, balanced vegan diet is suitable to meet all recommendations for nutrients in every stage of human life. Vegan diets tend to be higher in dietary fiber, magnesium, folic acid, vitamin C, vitamin E, iron, and phytochemicals; and lower in calories, saturated fat, cholesterol, long-chain omega-3 fatty acids, vitamin D, calcium, zinc, and vitamin B12.
Researchers agree that those on a vegan diet should take a vitamin B12 dietary supplement.
The American Academy of Nutrition and Dietetics and Dietitians of Canada state that properly planned vegan diets are appropriate for all life stages, including pregnancy, lactation, infancy, childhood, and adolescence. They indicate that vegetarian diets may be more common among adolescents with eating disorders, but that its adoption may serve to camouflage a disorder rather than cause one. The Australian National Health and Medical Research Council similarly recognizes a well-planned vegan diet as viable for any age, as does the New Zealand Ministry of Health, British National Health Service, British Nutrition Foundation, Dietitians Association of Australia, United States Department of Agriculture, Mayo Clinic, Canadian Pediatric Society, and Heart and Stroke Foundation of Canada. The British National Health Service's Eatwell Plate allows for an entirely plant-based diet, as does the United States Department of Agriculture's (USDA) MyPlate. The USDA allows tofu to replace meat in the National School Lunch Program. The American Academy of Nutrition and Dietetics adds that well-planned vegan diets are also appropriate for older adults and athletes.
The German Society for Nutrition does not recommend a vegan diet for babies, children and adolescents, or for pregnancy or breastfeeding, citing insufficient data for these subpopulations.
Further information: Nutrition and pregnancy
The Academy of Nutrition and Dietetics and Dietitians of Canada consider well-planned vegetarian and vegan diets "appropriate for individuals during all stages of the lifecycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes". The German Society for Nutrition cautioned against a vegan diet for babies, children, and adolescents, and during pregnancy and breastfeeding, due to insufficient data. The position of the Canadian Pediatric Society is that "well-planned vegetarian and vegan diets with appropriate attention to specific nutrient components can provide a healthy alternative lifestyle at all stages of fetal, infant, child and adolescent growth. It is recommended that attention should be given to nutrient intake, particularly protein, vitamins B12 and D, essential fatty acids, iron, zinc, and calcium.
According to a 2015 systematic review, there was little evidence available about vegetarian and vegan diets during pregnancy, and a lack of randomized studies meant that the effects of diet could not be distinguished from confounding factors. It concluded: "Within these limits, vegan-vegetarian diets may be considered safe in pregnancy, provided that attention is paid to vitamin and trace element requirements." A daily source of vitamin B12 is important for pregnant and lactating vegans, as is vitamin D if there are concerns about low sun exposure. A different review found that pregnant vegetarians consumed less zinc than pregnant non-vegetarians, with both groups' intake below recommended levels; however, the review found no significant difference between groups in actual zinc levels in bodily tissues, nor any effect on gestation period or birth weight.
Researchers have reported cases of vitamin B12 deficiency in lactating vegetarian mothers that were linked to deficiencies and neurological disorders in their children. It is recommended that a doctor or registered dietitian should be consulted about taking supplements during pregnancy.
Vegan diets have attracted negative attention from the media because of cases of nutritional deficiencies that have come to the attention of the courts, including the death of a baby in New Zealand in 2002 due to hypocobalaminemia, i.e. vitamin B12 deficiency.
The American Academy of Nutrition and Dietetics states that special attention may be necessary to ensure that a vegan diet will provide adequate amounts of vitamin B12, omega-3 fatty acids, vitamin D, calcium, iodine, iron, and zinc. These nutrients are available in plant foods, with the exception of vitamin B12, which can be obtained only from B12-fortified vegan foods or supplements. Iodine may also require supplementation, such as using iodized salt.
Further information: Vitamin B12 deficiency
Vitamin B12 is not made by plants or animals, but by bacteria that grow in soil, feces, dirty water, the intestines of animals or laboratories, so plant foods are not reliable sources of B12. It is synthesized by some gut bacteria in humans and other animals, but humans cannot absorb the B12 made in their guts, as it is made in the colon which is too far from the small intestine, where absorption of B12 occurs. Ruminants, such as cows and sheep, absorb B12 produced by bacteria in their guts.
Animals store vitamin B12 in liver and muscle and some pass the vitamin into their eggs and milk; meat, liver, eggs and milk are therefore sources of B12.
The UK Vegan Society, the Vegetarian Resource Group, and the Physicians Committee for Responsible Medicine, among others, recommend that every vegan consume adequate B12 either from fortified foods or by taking a supplement.
Vitamin B12 deficiency is potentially extremely serious, leading to megaloblastic anemia (an undersupply of oxygen due to malformed red blood cells), nerve degeneration and irreversible neurological damage. Cases of severe vitamin B12 deficiency have been reported in vegan adults, children infants and toddlers.
Because B12 is stored in large amounts in the liver, deficiency in adults may begin only years after adoption of a diet lacking B12. For infants and young children who have not built up these stores, onset of B12 deficiency can be faster and supplementation for vegan children is thus crucial.
Evidence shows that vegans who are not taking vitamin B12 supplements do not consume sufficient B12 and often have abnormally low blood concentrations of vitamin B12. This is because, unless fortified, plant foods do not contain reliable amounts of active vitamin B12. Vegans are advised to adopt one of the following dietary options:
B12 is more efficiently absorbed in small regular doses, which explains why the quantity required rises so quickly as frequency goes down.
The US National Institutes of Health recommends B12 intake in a range from 0.4 micrograms a day for infants, to 2.4 micrograms for adults, and up to 2.8 micrograms for nursing mothers.  The European Food Safety Authority set the Adequate Intake at 1.5 micrograms for infants, 4 micrograms for children and adults, and 4.5 and 5 micrograms during pregnancy and nursing. These amounts can be obtained by eating B12 fortified foods, which include some common breakfast cereals, plant milks, and meat analogues, as well as from common multivitamins such as One-A-Day. Some of the fortified foods require only a single serving to provide the recommended B12 amounts. 
It has been suggested that nori (an edible seaweed), tempeh (a fermented soybean food), and nutritional yeast may be sources of vitamin B12. In 2016, the Academy of Nutrition and Dietetics stated that nori, fermented foods (such as tempeh), spirulina, chlorella algae, and unfortified nutritional yeast are not adequate sources of vitamin B12 and that vegans need to consume regularly fortified foods or supplements containing B12. Otherwise, vitamin B12 deficiency may develop, as has been demonstrated in case studies of vegan infants, children, and adults.
Vitamin B12 is mostly manufactured by industrial fermentation of various kinds of bacteria, which make forms of cyanocobalamin, which are further processed to generate the ingredient included in supplements and fortified foods. A Pseudomonas denitrificans strain was most commonly used as of 2017[update]. It is grown in a medium containing sucrose, yeast extract, and several metallic salts. To increase vitamin production, it is supplemented with sugar beet molasses, or, less frequently, with choline. Certain brands of B12 supplements are certified vegan.
Humans require iodine for the production of thyroid hormones that enable normal thyroid function. Iodine supplementation may be necessary for vegans in countries where salt is not typically iodized, where it is iodized at low levels, or where, as in Britain and Ireland, dairy products are relied upon for iodine delivery because of low levels in the soil. Iodine can be obtained from most vegan multivitamins or regular consumption of seaweeds, such as kelp.
One study reported a "potential danger of iodine deficiency disorders due to strict forms of vegetarian nutrition, especially when fruits and vegetables grown in soils with low [iodine] levels are ingested." A study in Germany showed that iodine status of vegans is a concern.
Vegan diets typically require special attention for iodine, for which the only substantial and reliable vegan sources are sea vegetables, iodized salt and supplements. The iodine content of sea vegetables varies widely and may provide more than the recommended upper limit of iodine intake.
Proteins are composed of amino acids. Vegans obtain all their protein from plants, omnivores usually a third, and ovo-lacto vegetarians half. Sources of plant protein include legumes such as soy beans (consumed as tofu, tempeh, textured vegetable protein, soy milk, and edamame), peas, peanuts, black beans, and chickpeas (the latter often eaten as hummus); grains such as quinoa, brown rice, corn, barley, bulgur, and wheat (the latter eaten as bread and seitan); and nuts and seeds. Combinations that contain high amounts of all the essential amino acids include rice and beans, corn and beans, and hummus and whole-wheat pita. In 2012, the United States Department of Agriculture stated that soy protein (tofu) may replace meat protein in the National School Lunch Program.
The Academy of Nutrition and Dietetics said in 2009 that a variety of plant foods consumed over the course of a day can provide all the essential amino acids for healthy adults, which means that protein combining in the same meal is generally not necessary. The Dietitian's Guide to Vegetarian Diets writes that there is little reason to advise vegans to increase their protein intake; but erring on the side of caution, the authors recommend a 25 percent increase over the RDA for adults, to 1 g/kg (15gr/lb) of body weight.
Experts have not established recommended amounts for omega-3 fatty acids, except for ALA. The human body can use ALA to synthesize DHA and EPA. However, this only works efficiently if the ratio between omega 3 (mainly in flaxseed, chia seeds) to omega 6 (mainly in sunflower oil) does not exceed 1:5. This can sometimes be hard to accomplish as modern food includes a lot of omega 6.
Major vegan sources of the essential omega-3 fatty acid ALA include walnuts, flaxseeds and flaxseed oil, canola (rapeseed) oil, algae oil, hempseeds and hempseed oil, olive oil, and avocado.
While there is little evidence of adverse health or cognitive effects due to DHA deficiency in adult vegetarians or vegans, fetal and breast milk levels remain a concern.
DHA supplements derived from DHA-rich microalgae are available, and the human body can also convert DHA to EPA.
It is recommended that vegans eat three servings per day of a high-calcium food, such as fortified plant milks, green leafy vegetables, seeds, tofu, or other calcium-rich foods, and take a calcium supplement as necessary.
A 2009 study of bone density found the bone density of vegans was 94 percent that of omnivores, but deemed the difference clinically insignificant.
Calcium is one component of the most common type of human kidney stones, calcium oxalate. Some studies suggest that people who take supplemental calcium have a higher risk of developing kidney stones, and these findings have been used as the basis for setting the recommended daily intake (RDI) for calcium in adults.
Calcium intake through food sources is preferred over supplementation given inconclusive but growing evidence to suggest that supplementation carries no health benefit or might be harmful.
It is recommended for vegans to eat iron-rich foods and vitamin C daily. In several studies, vegans were not found to suffer from iron-deficiency any more than non-vegans. However, due to the low absorption rate on non-heme iron it is recommended to eat dark leafy greens (and other sources of iron) together with sources of Vitamin C. Iron supplementation should be taken at different times to other supplements with a 2+ valence (chemistry) such as calcium or magnesium, as they inhibit the absorption of iron.
Iron and the zinc levels of vegans may be of concern because of the limited bioavailability of these minerals. There are concerns about the bioavailability of iron from plant foods, assumed by some researchers to be 5–15 percent compared to 18 percent from a non-vegetarian diet. Iron-deficiency anemia is found as often in non-vegetarians as in vegetarians, and vegetarians' iron stores are lower.
Due to the lower bioavailability of iron from plant sources, the Food and Nutrition Board of the National Academy of Sciences established a separate RDA for vegetarians and vegans of 14 mg for vegetarian men and postmenopausal women, and 33 mg for premenopausal women not using oral contraceptives.
High-iron vegan foods include soybeans, blackstrap molasses, black beans, lentils, chickpeas, spinach, tempeh, tofu, and lima beans. Iron absorption can be enhanced by eating a source of vitamin C at the same time, such as half a cup of cauliflower or five fluid ounces of orange juice. Coffee and some herbal teas can inhibit iron absorption, as can spices that contain tannins such as turmeric, coriander, chiles, and tamarind.
The main function of vitamin D in the body is to enhance absorption of calcium for normal mineralization of bones and calcium-dependent tissues.
Sunlight, fortified foods, and dietary supplements are the main sources of vitamin D for vegans. Humans produce vitamin D naturally in response to sun exposure and ultraviolet light (UV) acting on skin to stimulate vitamin D synthesis. UV light penetrates the skin at wavelengths between 290 and 320 nanometers, where it is then converted into vitamin D3. Vitamin D2 can be obtained from fungi, such as mushrooms exposed to sun or industrial ultraviolet light, offering a vegan choice for dietary or supplemental vitamin D. Plant milks, such as from oat, soy, or almond, and breakfast cereals are commonly fortified with vitamin D.
The recommended daily intake of vitamin D for adults is 600 IU (15 micrograms), and for adults over 70 years old, 800 IU (20 micrograms).
Vitamin D comes in two forms. Cholecalciferol (vitamin D3) is synthesized in the skin after exposure to the sun or consumed from food, usually from animal sources. Ergocalciferol (vitamin D2) is derived from ergosterol from UV-exposed mushrooms or yeast. When produced industrially as supplements, vitamin D3 is typically derived from lanolin in sheep wool. However, both provitamins and vitamins D2 and D3 have been discovered in various species of edible Cladina lichens (especially Cladina rangiferina). These edible lichen are harvested in the wild for producing vegan vitamin D3. Conflicting studies have suggested that the two forms of vitamin D may or may not be bioequivalent. According to 2011 research from the U. S. National Academy of Medicine (then called Institute of Medicine), the differences between vitamins D2 and D3 do not affect metabolism, both function as prohormones, and when activated, exhibit identical responses in the body. Although vitamin D3 is produced in small amounts by lichens or algae exposed to sunlight, industrial production in commercial quantities is limited, and there are few supplement products as of 2019.
Some news reports presented vegan diets as deficient in choline following an opinion piece in the BMJ by a nutritionist affiliated with the meat industry. Although many animal products, like liver and egg, contain high amounts of choline (355 mg/3 oz and 126 mg/large egg, respectively), wheat germ (172 mg/cup), Brussels sprouts (63 mg/cup), and broccoli (62 mg/cup) are also good sources of choline. Other sources are, among others, soybeans, mushrooms, tangerines and whole wheat pitta bread.
Due to lack of evidence, no country has published a Recommended Dietary Allowance (RDA) for choline, which is a vitamin-like essential nutrient. The Australian, New Zealand, and European Union national nutrition bodies note there have been no reports of choline deficiency in the general population. There are, however, Adequate Intakes such as the European Union's number of 400 mg/day for adults, and the US's number of 425 mg/day for adult non-pregnant women and 550 mg/day for adult men. An Adequate Intake is a level assumed to ensure nutritional adequacy, established when evidence is insufficient to develop an RDA (see Dietary Reference Intake).
Vegan diets are usually higher in dietary fiber, magnesium, folic acid, vitamins C and E, iron, and phytochemicals, and they tend to be lower in calories, saturated fat and cholesterol, long-chain n–3 (omega-3) fatty acids, vitamin D, calcium, zinc, and vitamin B-12. ... A vegan diet appears to be useful for increasing the intake of protective nutrients and phytochemicals and for minimizing the intake of dietary factors implicated in several chronic diseases.
The Nutrition Standards in the National School Lunch and School Breakfast Programs final rule was published on January 26, 2012. The final rule gives schools the option to offer commercially prepared tofu as a meat alternate in the National School Lunch Program (NSLP) and School Breakfast Program (SBP).
Because the available data remain insufficient, no satisfactory assessment can be made with regard to micronutrient intake and supply status or prevalence of nutrient deficiencies or other adverse health effects regarding a vegan diet in these special population groups.CS1 maint: DOI inactive as of October 2021 (link)
Caleb died in March last year from broncho-pneumonia associated with anaemia and brain damage caused by vitamin B12 deficiency.
Strict vegetarians and vegans are at greater risk than lacto-ovo vegetarians and nonvegetarians of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods.
High-risk groups such as vegetarians, adolescent girls and women athletes need to eat iron-rich foods each day (combined with foods that are high in vitamin C). ... Vegetarians who exclude all animal products from their diet may need almost twice as much dietary iron each day as non-vegetarians. Sources include dark green leafy vegetables—such as spinach—and raisins, nuts, seeds, beans, peas, and iron-fortified cereals, breads and pastas
The key role of ascorbic acid for the absorption of dietary nonheme iron is generally accepted. The reasons for its action are twofold: (1) the prevention of the formation of insoluble and unabsorbable iron compounds and (2) the reduction of ferric to ferrous iron, which seems to be a requirement for the uptake of iron into the mucosal cells.
Although choline is essential, there appear to have been no reports of deficiency in the general population. Deficiencies have been seen in experimental situations and also in total parenteral nutrition (Buchman et al. 1992, 1993, 1995, Chalwa et al. 1989, Shapira et al. 1986, Sheard et al. 1986).