By
Christopher Theberge
Vegetarianism has become a popular alternative to the
traditional Western-style diet for many individuals. Rises in protests against
animal slaughtering and recognition of potential health benefits have led to
this trendy way of eating. A vegetarian diet is considered beneficial by many
because of the low intakes of saturated fat and cholesterol along with high
amounts of fruits and vegetables. Results from previous research have shown
that diets low in saturated fat and cholesterol are associated with a decreased
risk for heart disease. However, vegetarians, especially strict vegans, may be
at an ever-increasing risk for developing heart disease.
Studies
comparing vegetarian diets to omnivore (meat-eating) diets have shown that
vegetarians have increased homocysteine levels. Homocysteine is an amino acid formed in the body. Elevated homocysteine levels have shown to increase the risk of
heart disease because it leads to inflammation of arterial walls. The breakdown
of homocysteine requires vitamin B6, vitamin B12 and folate. So why vegetarians?
Vegetarian
diets are often low in vitamin B12 and vitamin B6. Plant sources lack B12 and
are very low in B6. The essential amino acid methionine
is another substance often very low in vegetarian diets. When a deficiency of
either folate or B12 occurs, the body cannot
efficiently metabolize homocysteine to form methionine. An alternative pathway exists for homocysteine metabolism, which requires vitamin B6. Normal homocysteine metabolism leads to production of methionine. Methionine is then
converted to a compound known as SAM, which is required for over 100 reactions
in the body. SAM regulates the rate at which the body breaks down homocysteine. When methionine
levels are low, so are SAM levels. Thus, a deficiency in vitamin B12, B6, or folate can affect the rate at which homocysteine
is metabolized and can lead to elevated concentrations in the body. Low methionine intakes can also exacerbate the problem.
Diets low in B12 are also low in vitamin B6, which are found
widely in animal food sources. Most of the heart disease risk among vegetarians
occurs because of the lack of vitamin B12. As noted above, a deficiency in the
vitamin can lead to a deficiency in other vitamins despite their presence in
the body.
If a deficiency
of vitamin B12 were to exist for too long, anemia could develop characterized
by overly large red blood cells. Folate deficiency
may occur indirectly because vitamin B12 is required for making it available to
aid in DNA synthesis. Food manufacturers have tried to prevent folate deficiency and folate-related
hyperhomocysteinemia by adding folic acid to foods.
This has been an effective strategy; however, this has not completely solved
the problem. Yperhomocysteinemia is now related to
B12 deficiency. Folic acid can mask B12 deficiency because impaired red blood
cell synthesis will not occur. Yet, homocysteine
levels will still be very high.
It is important
to understand that even though you follow a vegetarian diet, you may still be
at risk for developing heart disease. Vegans appear to be at the highest risk
because of total lack of animal sources in the diet, leading to very low, if
any, B12 consumption. Foods high in vitamin B12 are foods of animal origin,
like eggs, dairy products and meats. Becoming aware of this problem, food
manufacturers have begun to add vitamin B12 to a variety of foods. Vegetarian
diets have been shown to lower total and LDL cholesterol. Yet, a vitamin
deficiency resulting in elevated homocysteine levels
will negate any of the other potential benefits. Making sure that your diet is
adequate in all of the essential nutrients is crucial. Once this is achieved,
only then can you be sure that you will maintain a healthy body. Be Healthy!
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