Potential Vitamin and Mineral Deficiency Risks on a Vegan Diet

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

The Vegan Diet as a Neglected Cause of Psychosis: A tragic story of a 47-year-old woman with a five-year history of psychosis treated with antipsychotics, after years of hallucinations. Finally, her mother revealed that the patient was following a strict vegan diet for seven years, and was not supplementing with vitamin B12. They started giving her B12 supplements and eventually her psychiatric symptoms went away. But she spent five years of her life in a psychotic haze, because she wasn’t getting a regular reliable source of vitamin B12. B12 supplements, or sufficient intake of B12-fortified foods, is mandatory for vegans and effective––but only if you do it. Like in the largest study of vegans in history, the Adventist Health Study-2, the prevalence of low vitamin B12 status was the same between vegans, vegetarians, and meat-eaters. Why? Presumably because they were eating fortified food and supplements. The researchers concluded: the encouragement of vitamin B12 supplementation cannot be overemphasized.

Vitamins B12 and D are the only two vitamins not made by plants. Vitamin B12 is made by microbes, and vitamin D is made by animals such as ourselves when we walk outside; it’s the sunshine vitamin. Some other nutrients are only found concentrated in certain plants, though, and you can become deficient if you don’t eat them. For example, this case of a 10-year-old girl with night blindness. She couldn’t see well at night. Vitamin A deficiency was the doctor’s first thought, but the kid was vegetarian and so getting whopping doses of beta carotene in all the vegetables she ate, which your body turns into vitamin A. Almost as an afterthought as they were leaving the office, the doctor just asked the mother, “I assume she is getting plenty of vegetables, right?” But no, she does not like vegetables and only eats, I don’t know, Ritz crackers or something. So, with something like vitamin A, it’s easy to get enough eating greens or any of the orange fruits and vegetables, like mangos, sweet potatoes, carrots, or cantaloupe, but you actually have to eat fruits and vegetables. A vegan living off a diet of fast food is at a greater risk for vitamin A deficiency than a meat-eater living on fast food, because at least the cow ate some greens and passed it along.

Iodine is a similar situation. Cow’s milk is a primary source of dietary iodine in the United States. Not because cows somehow synthesize iodine, or any other element. Iodine in milk comes from the leaching of iodine-containing disinfectants used to clean contaminated udders and milking equipment into the milk, or from supplements fed to cattle. Regardless, those not drinking milk  or eating seaweed, which is even a better source, may be at an increased risk for iodine deficiency.

A study of vegans in the UK suggested as many as 90 percent aren’t getting enough in their diet––though this is likely an overestimate since their food frequency questionnaire didn’t include seaweed or iodized salt, two of the ways some may be getting it. Are there reports of it actually causing problems? Yes indeed: “Veganism as a cause of iodine deficient hypothyroidism.” A 23-month-old boy was breastfed until 16 months of age, and then weaned on a strictly plant-based diet without iodized salt. Mom was fine, presumably because of the iodine in the prenatal vitamins she continued to take, which spilled over into her breastmilk. The American Thyroid Association is very clear about recommending that pregnant and breastfeeding women take a prenatal with 150 micrograms of iodine a day. Most kids in the US transition from breast milk to cow’s milk, but those who don’t need to get their iodine from somewhere. Thankfully, after an iodine-containing multivitamin, his deficiency cleared. That’s one way––taking supplements like the cows do, but sea vegetables are the healthiest source of iodine.

A half teaspoon of mild seaweeds like arame or dulse should get you all the iodine you need for the day. You can just have a shaker of dulse flakes at the kitchen table. Or two nori sheets of seaweed—that’s my favorite method, because you can just eat them like a snack. In fact, it’s probably the healthiest snack there is, since you’re snacking on dark green leafy vegetables.

There was also a recent report of severe iron-deficiency anemia attributed to a plant-based diet and menorrhagia, which means excess blood loss during menstruation. A 21-year-old woman presented with reduced vision in one of her eyes because a vein clotted off, which can happen when you get really anemic. Thankfully, her vision resolved after taking iron supplements. Now, according to the American Dietetic Association, the incidence of iron-deficiency anemia among vegetarians is no worse than that of nonvegetarians; so, it may just have been her excess monthly blood loss. But a more recent review questioned the official position that iron deficiency anemia appears to be no more prevalent among vegetarian women than among nonvegetarian women. The updated review claimed to find four studies where this wasn’t the case, where vegetarians had significantly higher rates. Yet, here are the four studies (and as always, I’ll put links to them in the sources cited section beneath this video on NutritionFacts.org so you can read them yourself, like I do for every study I cite in my video) and…not a single one backed up that statement.

But just because vegetarians don’t have worse anemia rates than nonvegetarians, that’s not saying much, since up to 1 in 20 menstruating women suffer from iron-deficiency anemia across the board. Having lower iron stores is actually advantageous, as I’ve done videos about, which is yet another reason to consume more plants and less meat. But if your blood count is dropping, if your hemoglobin is getting too low, then you can enhance iron absorption by eating vitamin C-rich foods with your meal—fresh fruit, bell peppers, broccoli, etc. And since especially tea, but also coffee, can inhibit iron absorption, you shouldn’t drink them with meals.

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• Bachmeyer C, Bourguiba R, Gkalea V, Papageorgiou L. Vegan Diet as a Neglected Cause of Severe Megaloblastic Anemia and Psychosis. Am J Med. 2019;132(12):e850-e851.
• Haddad EH, Jaceldo-Siegl K, Oda K, Fraser GE. Associations of Circulating Methylmalonic Acid and Vitamin B-12 Biomarkers Are Modified by Vegan Dietary Pattern in Adult and Elderly Participants of the Adventist Health Study 2 Calibration Study. Curr Dev Nutr. 2020;4(2):nzaa008.
• Marmor MF. Night Blindness in a Healthy Middle-Class Child. Ophthalmic Surg Lasers Imaging Retina. 2020;51(5):286-288.
• Yeliosof O, Silverman LA. Veganism as a cause of iodine deficient hypothyroidism. J Pediatr Endocrinol Metab. 2018;31(1):91-94.
• Leroy F, Barnard ND. Children and adults should avoid consuming animal products to reduce risk for chronic disease: NO. Am J Clin Nutr. 2020;112(4):931-936.
• Eveleigh ER, Coneyworth LJ, Avery A, Welham SJM. Vegans, Vegetarians, and Omnivores: How Does Dietary Choice Influence Iodine Intake? A Systematic Review. Nutrients. 2020;12(6):1606.
• Sobiecki JG, Appleby PN, Bradbury KE, Key TJ. High compliance with dietary recommendations in a cohort of meat eaters, fish eaters, vegetarians, and vegans: results from the European Prospective Investigation into Cancer and Nutrition-Oxford study. Nutr Res. 2016;36(5):464-477.
• Yang V, Turner LD, Imrie F. Central retinal vein occlusion secondary to severe iron-deficiency anaemia resulting from a plant-based diet and menorrhagia: a case presentation. BMC Ophthalmol. 2020;20(1):112.
• Craig WJ, Mangels AR; American Dietetic Association. Position of the American Dietetic Association: vegetarian diets. J Am Diet Assoc. 2009;109(7):1266-1282.
• Pawlak R, Berger J, Hines I. Iron Status of Vegetarian Adults: A Review of Literature. Am J Lifestyle Med. 2016;12(6):486-498.
• Recommendations to prevent and control iron deficiency in the United States. Centers for Disease Control and Prevention. MMWR Recomm Rep. 1998;47(RR-3):1-29.
• Haider LM, Schwingshackl L, Hoffmann G, Ekmekcioglu C. The effect of vegetarian diets on iron status in adults: A systematic review and meta-analysis. Crit Rev Food Sci Nutr. 2018;58(8):1359-1374.
• Lee Y, Krawinkel M. The nutritional status of iron, folate, and vitamin B-12 of Buddhist vegetarians. Asia Pac J Clin Nutr. 2011;20(1):42-49.
• Li D, Sinclair AJ, Mann NJ, Turner A, Ball MJ. Selected micronutrient intake and status in men with differing meat intakes, vegetarians and vegans. Asia Pac J Clin Nutr. 2000;9(1):18-23.
• Harman SK, Parnell WR. The nutritional health of New Zealand vegetarian and non-vegetarian Seventh-day Adventists: selected vitamin, mineral and lipid levels. N Z Med J. 1998;111(1062):91-94.
• Reddy S, Sanders TA. Haematological studies on pre-menopausal Indian and Caucasian vegetarians compared with Caucasian omnivores. Br J Nutr. 1990;64(2):331-338.

Motion graphics by Avo Media

• Adventist Health Studies
• anemia
• bell peppers
• beta carotene
• beverages
• breast milk
• breastfeeding
• broccoli
• carrots
• coffee
• dairy
• fruit
• greens
• iodine
• iron
• mango
• menstruation
• nori
• oranges
• Plant-Based Diets
• sea vegetables
• seaweed
• supplements
• sweet potatoes
• tea
• thyroid health
• vegans
• vegetables
• vegetarians
• vitamin A
• vitamin B12
• vitamin C
• vitamin D supplements
• vitamins
• women's health