People who do not supplement and follow a vegan lifestyle - strict vegetarians who try to eat no meat or animal products of any kind - may increase their risk of developing blood clots and atherosclerosis or "hardening of the arteries," which are conditions that can lead to heart attacks and stroke, according to a new study.
Researchers come to the conclusion after a review of dozens of articles published on the biochemistry of vegetarianism during the past 30 years.
In the review, researcher Duo Li notes that meat eaters are known for having a significantly higher combination of cardiovascular risk factors than vegetarians.
Lower-risk vegans, however, may not be immune. Their diets tend to be lacking several key nutrients - including iron, zinc, vitamin B12, and omega-3 fatty acids, Li said.
Long-term studies are the key since B12 deficiency is a lengthy process and takes years to manifest. Vitamin B12 is stored in the liver, kidneys, and muscle tissue, and most B12 (65-75%) is reabsorbed by the body instead of excreted. A deficiency could take from 5 to 20 years of inadequate intake to develop and consequently, the deficiency is also found in a percentage of the population that has poor absorption of B12 such as those who smoke or inadequately nourished.
Omega-3 fatty acids include ALA, EPA and DHA. Alpha-linolenic acid (ALA) is found mainly in the oil of flaxseeds, hemp seeds, and walnuts. ALA reduces blood clotting, and is good for the heart. The body converts some of the ALA into two other essential omega-3 fats called EPA and DHA. These two are also found to a small degree in seaweeds, and there are vegan DHA supplements available made from micro-algae.
While a balanced vegetarian diet can provide enough protein, this isn't always the case when it comes to fat and fatty acids. A tablespoon of ground flaxseeds or a teaspoon of flax oil per day can meet the needs of most vegans, however many may not obtain the most adequate sources of EPA or DHA required for their metabolic needs without consuming the highest bioavailable foods in EFAs including those from krill, sardines and other marine life. As a result of poor supplementation, many vegans tend to have elevated blood levels of homocysteine and decreased levels of HDL, the "good" form of cholesterol. Both are risk factors for heart disease.
The study concludes that there is a strong scientific basis for vegetarians and vegans to increase their dietary omega-3 fatty acids and vitamin B12 to help contend with those risks.