Potential Nutrient Deficiencies
Poorly planned vegetarian diets can be relatively low in protein, iron, zinc, vitamin B12, calcium, omega-3 fatty acids, retinol (vitamin A), vitamin D, riboflavin (vitamin B2) and iodine. Vegans may have particularly low intakes of vitamin B12 and calcium. Nonetheless, well-balanced vegetarian and vegan diets can meet all these nutrient requirements and are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence.
The typical vegetarian gets adequate protein as long as caloric intake is adequate and a variety of foods is eaten. Vegetarian diets are usually relatively low in protein, which may be beneficial.
Main article: Protein combining
” Virtually all plant foods have all of the essential amino acids; and not only are the amino acids there, they are present in more than enough quantity to meet the needs of normal adults, if you are on a calorically adequate diet.” – Keith Akers
Despite a widespread belief that vegetarians must eat grains and beans within a few hours of each other in order to make a ‘complete’ protein which contains all 9 “essential amino acids”, this has never been substantiated by research. The protein-combining theory was brought to popular attention in Frances Moore Lappé’s 1971 bestseller Diet for a Small Planet. In later editions of the book, as early as 1981, Lappé withdrew her contention that protein ‘combining’ is necessary.
Meat, fish and poultry are the only sources of heme iron; plants contain only non-heme iron, which is absorbed less efficiently by the human body. However, cereals, eggs, legumes (including peas, beans, chickpeas, lentils and soy foods) and nuts are significant sources of iron, so a well planned vegetarian diet should not lead to iron deficiency.
A study in the Journal of the American Dietetic Association found that while iron-deficiency anemia is not more common among vegetarians, “vegetarian children had … reduced levels of haemoglobin and iron compared to omnivores” due “to the absence of animal iron sources with high utilizability”.
Western vegetarians and vegans have not been found to suffer from overt zinc deficiencies any more than meat-eaters. However, phytates in many whole-grains and fiber in many foods may interfere with zinc absorption and marginal zinc intake has poorly understood effects.
Vitamin B12 deficiency is potentially extremely serious, leading to pernicious anemia, nerve degeneration and irreversible neurological damage. A regular source of vitamin B12 is particularly important for those over the age of 50 years, and pregnant and lactating women (and for breastfed infants if the mother’s diet is not supplemented).
Evidence suggests that vegetarians and vegans who are not taking vitamin B12 supplements or B12-fortified foods do not consume sufficient servings of B12 and often have abnormally low blood concentrations of vitamin B12. This is because, unless fortified, plant foods do not contain significant amounts of active vitamin B12.
It is essential, therefore, that vegetarians consume adequate amounts of dairy products, eggs, dietary supplements or foods that have been fortified with B12 (such as certain yeast extracts, vegetable stock, veggie burger mixes, textured vegetable protein, soy milks, vegetable and sunflower margarines, and breakfast cereals).
nori(Seaweed) contains B12 very abundantly. However, plant sources of B12 (or analogues) have not yet been shown to benefit humans. There is a patent for a cultivation method of a mycelium’s enriching vitamin B12 of the vegetable.
Omega-3 fatty acids
Vegetarian sources of omega-3 fatty acids include flaxseeds and flaxseed oil, olive oil, walnuts, canola (rapeseed) oil, avocado, and eggs.
Vegetarian sources of omega-3 fatty acids are primarily the short chain variety and likely to have lower concentrations of the particular essential fatty acids (EFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The body can synthesize small quantities of EPA and DHA from other omega-3 fatty acids, such as alpha-linolenic acids, which are present in vegetarian sources of omega-3 fatty acids. The human body can also convert DHA into EPA. DHA supplements derived from DHA-rich microalgae are available. Whilst the human body can in theory do this conversion, in practice modern diets and lifestyles reduce the effectiveness of the conversion systems. Roughly ten times more of the short chain omega-3s must be consumed to have the same effect as the long chain form from fish oil.
While there is no scientific consensus on the role of omega-3 fatty acids, it is generally believed that they may reduce the risk of coronary heart disease, lower triglycerides, stabilize mood and help prevent depression, help reduce symptoms of ADD, reduce joint pain and other rheumatoid problems and reduce the risk of dementia in older age.
The human body can synthesize Vitamin D when skin is exposed to ultraviolet radiation from the sun. Vegans who do not eat foods or pills fortified with synthetic vitamin D and with little exposure to the sun’s ultraviolet radiation (e.g., those who don’t expose their extremities for at least 15-30 minutes per day or those living at latitudes close to the poles) are vulnerable to Vitamin D deficiencies.
Vitamin D acts as a hormone, sending a message to the intestines to increase the absorption of calcium and phosphorus, which produces strong bones. Vitamin D also works in concert with a number of other vitamins, minerals, and hormones to promote bone mineralization. Research also suggests that vitamin D may help maintain a healthy immune system and help regulate cell growth and differentiation.
According the British Journal of Nutrition there is a “potential danger of [Iodine] deficiency disorders due to strict forms of vegetarian nutrition, especially when fruits and vegetables grown in soils with low [Iodine] levels are ingested.” Iodine, however, is usually supplied by iodized salt and other sources in first world countries. Additionally, it should be noted that any iodine found in animal products is sourced from plant life (see: Iodine: Sources).
According to the American Dietetic Association, “Some studies have shown vegans to have lower intakes of riboflavin, compared with nonvegetarians; however, clinical riboflavin deficiency has not been observed.”
– via Wikipedia