A vegan diet can be deficient in many essential vitamins and nutrients, especially in those vegans who are not lacto-ovo. Deficiencies can lead to all sorts of health problems, some of which may not be distinguishable from other common diseases. It is generally recommended that vegans take at least some supplements, and the ones most commonly deficient in vegans include vitamin B12, iron, omega 3 fatty acids, and calcium.
Cobalamin, known as vitamin B12, is necessary for many cellular processes involving the blood and the heart. Deficiencies in this vitamin are rare in the Western world, but when it happens it is generally in vegans and especially vegan children, as they have higher needs and less ability to store it for lengths of time. Vitamin B12 deficiency symptoms include memory problems, depression, fatigue, and a host of other problems.
Most vegans generally get enough iron from vegetable sources, but the type found in these sources are not as easily digestible as from animal sources. However, vitamin C supplementation can help with iron absorption and so a vitamin C supplement may be a good choice.
A diet that has too high a ratio of omega 6 fatty acids to omega 3 can increase the risk of cardiovascular illness such as heart disease. Omega 6 is common in most vegetable sources, including nuts, and so supplementation with omega 3 is wise. Flaxseed is the most common way to get omega 3. However, th is version is not efficiently absorbed by the body and may still lead to deficiencies. Fish oil is the best way to get omega 3 that can be more readily used by the body. Other fish oil benefits include anti-cancer and lower blood pressure.
Vegans can also be deficient in calcium due to inadequate vegetable sources. One way to increase calcium intake is to take a supplement and also drink fortified soy milk. Vitamin D is also a good supplemental addition to most soy milk, and is also highly recommended if not enough sunlight is absorbed by the body.