A vegan diet is a strict vegetarian diet without any eggs or dairy products. A well-balanced vegan diet provides all the essential nutrients you require and has the same overall health advantages as a vegetarian diet. Nutritional guidelines for vegans are essentially similar to those for vegetarians, although vegans lack the option of gaining certain nutrients from dairy products and eggs. Being more restricted than the more common lacto-ovo vegetarian diet, vegan eating plans need to ensure adequate intake of certain nutrients by consuming adequate quantities of appropriate plant-foods.
Vegetarians who consume a variety of legumes and nuts will probably meet their zinc requirement, but otherwise a vegetarian diet may be inadequate in zinc. Since the zinc from plant sources is absorbed less readily, this increases the concern about zinc status in vegetarians who do not consume legumes and nuts.
Although vegans tend not to consume tough/rubbery meats or high-fat foods, they do (like everyone else after bariatric surgery) also need to avoid fried foods, sugary foods, junk food, and sticky foods. Vegans need to be especially careful to consume sufficient protein and avoid crunchy foods such as raw fruits & vegetables, and nuts.
Sub-clinical hypothyroidism, with raised thyroid stimulating hormone (TSH) levels but mild or absent overt symptoms, has been found to be more common among vegans than the general population. Most vegans have low iodine intakes but a significant minority consume excessive amounts of iodine from seaweed, particularly kelp. Both low and excessively high iodine intakes in vegans have been linked to elevated TSH levels. The optimal range for TSH appears to be 1-2 mIU/l with values below 0.5 suggesting hyperthyroidism and values above 5 suggesting hypothyroidism.
Various theories have been proposed to explain reduced fertility among vegetarians and vegans: possible vitamin deficiencies (such as vitamin B12); increased use of soy (contains phyto-oestrogens); increased pesticide consumption through a diet high in fruits and vegetables.
For longer-term vegans who have not been too careful about consuming enough B12 (in the form of supplements or fortified foods), it would be wise to have B12 levels assessed and to commence dietary supplementation immediately. Some 80% of people who have been vegan for over 2 years have a functional B12 deficiency, meaning their homocysteine is too high.
Vegans who don't eat sea vegetables or use iodized salt should consider supplementing their diet with iodine. Using excess salt is not good for the bones, but if you do use table salt, use iodized salt.
Vegetarians may need as much as 50% more zinc than non-vegetarians because of the lower absorption of zinc from plant foods, so it is very important for vegetarians to include good sources of zinc in their diet.