Long-Term Issues With a Vegan Diet

by Michelle Kerns, Demand Media

A vegan diet can lower your risk of Type 2 diabetes, obesity, cancer, heart disease and high blood pressure, but it needs to be carefully planned, says the American Dietetic Association. Without any animal-based foods in their diet, long-term vegans may have trouble getting enough of certain nutrients, including vitamin B-12, vitamin D, zinc, iodine and omega-3 fatty acids. If you're concerned about your health as a vegan, talk to your doctor or a nutritionist.

Vitamin B-12

Vitamin B-12 is naturally found only in animal-based foods such as seafood, poultry, meat, milk and eggs. Vegans who become deficient in vitamin B-12 over time may develop nervous system damage, anemia, heart disease and neurological disorders such as Alzheimer's disease or depression. A woman who follows a strictly vegan diet during her pregnancy may have a higher risk of having a child with neural tube defects. To prevent these problems, the Vegan Society recommends that all vegans should have two or three servings of foods fortified with vitamin B-12 daily, including breakfast cereal, soy products or plant milks like almond milk. Alternatively, vegans can regularly take a vitamin B-12 supplement.

Vitamin D

Vitamin D helps build strong bones and is linked to a decreased risk of arthritis, heart disease and certain types of cancer. Adults need about 200 International Units of vitamin D each day. Although your skin synthesizes vitamin D when it's exposed to ultraviolet light from the sun, you need to have a steady source of the nutrient in your diet to get enough. For most people, those sources are fortified cow's milk, eggs and fatty fish like salmon. Registered dietitian Reed Mangels says that a vegan can fail to get enough vitamin D unless she includes fortified products like soy milk, almond milk or hemp milk in her diet, or takes a supplement. Mangels cautions that juices, cereals and margarine spreads fortified with vitamin D often use vitamin D-3, a form derived from sheep's wool.


Whole grains, nuts and legumes all contain zinc that is bound by phytate compounds. These phytates significantly lower the amount of zinc that your body can absorb compared to the amount available from animal products such as meat, dairy products, seafood or poultry. Long-term vegans may consume enough zinc-containing foods, but still have low blood zinc levels. Not getting enough zinc may impair your immune system and cause pregnancy complications in women. To ensure that you're consuming adequate zinc, the Vegetarian Nutrition Dietetic Practice Group says vegans should take zinc supplements and eat yeasted whole-grain breads and fermented soy products, which have a larger amount of bioavailable zinc. Vegans should also soak dried beans before cooking them and look for zinc-fortified cereals.


Most vegan diets contain a large amount of soy products and brassica vegetables like cabbage, broccoli, cauliflower and Brussels sprouts. These foods contain goitrogens, compounds that inhibit the function of iodine. In addition, vegans who aren't getting enough zinc will have a greater propensity to become deficient in iodine. Not having enough iodine in your diet can cause hypothyroidism. Infants whose mothers lacked iodine during pregnancy may be more likely to suffer from motor problems or brain damage. Seaweed is a source of iodine, but some types contain too much and vegans who eat them often may develop iodine toxicity. VeganHealth.org advises vegans to take an iodine supplement that provides 75 to 150 micrograms of the mineral every one to two days.

Omega-3 Fatty Acids

A diet rich in the omega-3 fatty acids docosahexaenoic acid, or DHA, and eicosapentaenoic acid, or EPA, may help prevent heart disease. Fatty fish like salmon, albacore tuna and mackerel are the best sources of these fats, though Harvard professor Dr. Frank Sacks says that vegans can get them from foods rich in alpha-linolenic acid, or AHA, which the body partially converts to DHA and EPA. AHA is contained in foods like walnuts, flaxseeds and soybean oil. Vegans should aim to include 1 tablespoon of ground flaxseed or 2 tablespoons of rapeseed or soybean oil in their diets daily. There are also vegan-friendly AHA supplements available.

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