“Eat food. Not too much. Mostly plants.” That’s food writer Michael Pollan’s famous and intentionally terse and provocative saying about the confusion surrounding contemporary strategies of nutrition. After decades of faddish diets coming and going from the nutrition news cycle, Pollan recommends a common-sense approach. To rephrase: You must eat, but you shouldn’t eat too much, and fruits and vegetables should make up a large part of what you do eat.
A 2013 poll found that 13 percent of Americans consider themselves to be either vegetarian or vegan; that works out to roughly 41 million people. If you're one of the millions who have decided not to eat meat or not to partake of or use any animal products, that's great. But you need to be aware that even with all the health advantages gained by plant-based diets, there is some danger of nutritional deficiency. So what essential vitamins and nutrients are missing from vegan and vegetarian diets?
Arguably the most important deficiency for vegetarians to be aware of and to avoid is Vitamin B-12. Unlike most other vitamins, B-12 is not found in any plant. Also called cobalamin, it is the largest vitamin and is very complex. Its roles include cellular metabolism (including DNA synthesis), blood formation, and helping to regulate nervous system functions.
Vitamin B-12 deficiencies have been linked to a variety of nervous system disorders, from depression and fatigue to irreversible brain damage resulting in memory loss and mania. New research is exploring a suspected link between low B-12 levels and Alzheimer’s disease. Vitamin B-12 also helps prevent megaloblastic anemia, which induces fatigue and weakness. Worryingly, a study in the Annals of Nutritional Metabolism found that depressed B-12 levels were found in 92 percent of vegans, 47 percent of ovo-lacto vegetarians (meaning those who consume milk and eggs), and 20 percent of semi-vegetarians.1
Ovo-lacto vegetarians can find B-12 in eggs and milk but, as noted above, they may not find the vitamin in sufficient quantities. B-12 is readily available in supplement form, either on its own or as a multi-vitamin combined with other nutrients. The recommended daily dose for an adult is 2.4 micrograms.2
Vitamin D is another nutrient that is often missing in vegan and vegetarian diets. Vitamin D's interaction with calcium is essential for bone health, which makes it particularly important for aging people. But it is found primarily in meat and the rays of the sun, which is good news for those who don't consume meat; they can still get it from other natural sources.
Sure, sun worship works to increase Vitamin D levels, but skin cancer is no fun. Although 5 to 10 minutes in the sun (sans sunscreen) can help boost your levels and is probably safe, your best bet if you have insufficient Vitamin D is supplements. The recommended dosage is 600 international units (IU) daily for those under the age of 70, and 800 IU for those older than 70.
The importance of a protein-rich diet cannot be overstated, and some sources believe protein should make up at least 30 percent of your daily caloric intake. Protein is instrumental in maintaining mass (both muscle and bone), keeping energy levels up and keeping the immune system strong. The problem for vegetarians is that protein is most easily ingested through meat, poultry and fish.
There are alternatives to these traditional sources of protein, although getting enough may take some dedication. According to Jack Norris and Ginny Messina, authors of Vegan for Life, the essential protein for vegans to focus on is the amino acid “lysine.” Meeting lysine requirements, the authors say, usually ensures that you will have also met the protein requirements. A very helpful guide to requirements for vegan lysine, protein, and US RDA can be found on Dr. Norris’s website “Vegan Health.” 3 The best sources of lysine are legumes (beans, lentils, etc.) and wheat gluten. Soybean products, such as tofu and so many of those “mock-meat” products, are also high in lysine and other proteins.
But what if you are allergic or somehow adverse to gluten and/or soy? Some nuts (especially pistachios) and seeds (especially pumpkin) are high in healthy protein. But your best bet is quinoa, a tasty superfood that is also considered a “complete protein” because it contains all of the essential amino acids as well as 18 grams of protein per cup! A fun website containing great quinoa recipes is Queen of Quinoa.
When you think iron, think muscles. Iron is a mineral that is an essential component in blood cells that transfer oxygen to tissues and muscles, bolsters metabolism and cellular function, and is necessary for the synthesis of some hormones and connective tissues. There are two main forms of iron, both of which are necessary and only one of which is available in plants. Non-meat eaters can get their iron through oatmeal, baked potatoes, peanut butter and broccoli, particularly when these foods are combined with Vitamin C (Vitamin C helps the body absorb the iron found in those foods). Or vegetarians and vegans can fulfill their iron requirements through oral supplements.
Related to iron is creatine, an acid that supplies energy to cells and increases ATP, the prime mover in cellular energy exchange.4 It is well-known in the world of strength training, both for its contributions to muscle mass and its effects on maintaining energy levels. While creatine is produced naturally in the body, it is also found in red meat and in a variety of fish, including tuna and salmon. It appears that the body does not produce creatine in sufficient quantities, especially for active individuals, and therefore relies on gaining some of its creatine through a meat and fish diet. Vegetarians and very physically active people—especially athletes who need to sustain bursts of energy—might want to consider creatine as a supplement. Many already do: Creatine is one of the top-selling muscle-building supplements worldwide.
Whatever reason you choose to follow a plant-based diet—to protect animals, to protect the environment or to promote your personal health—the above precautions should be taken seriously. Our ancestors were omnivores, surviving on whatever they could successfully metabolize, and our bodies’ needs developed accordingly. Many vegetarians and vegans say their diets are the "next step in evolution," but our bodies aren't quite there yet and still need many vitamins and nutrients that can't be found in plant-based diets. Vegetarianism and veganism can be done, but those who choose to do it must pay extra attention to their bodies' needs.
- Dong A. Scott S.C. Serum Vitamin B12 and Blood Cell Values in Vegetarians. Ann Nutr Metab 1982;26:209–216
- NIH Office of Dietary supplements. Vitamin B12 dietary supplement fact sheet. http://ods.od.nih.gov/factsheets/Vitaminb12-Consumer
- Vegan Health. Protein. http://www.veganhealth.org/articles/protein.
- Burke DG, Chilibeck PD, Parise G, Candow DG, Mahoney D, Tarnopolsky M. Effect of creatine and weight training on muscle creatine and performance in vegetarians. Med Sci Sports Exerc. 2003 Nov;35(11):1946-55