Homocysteine, an amino acid, is a usually harmless. Your body regulates it by using B vitamins to convert it to other substances. A lack of B vitamins allows homocysteine levels to rise, which can cause vascular toxicity and thus increase the risk of cardiovascular disease. Cardiovascular disease is the leading cause of death in the U.S. As of 2006, the American Heart Association estimates over 81 million people in the U.S have one or more forms of cardiovascular disease.
Discovery
According to the July 1999 issue of the journal "Nutrition Science News," Kilmer McCully, M.D., made the first connection between homocysteine levels and cardiovascular disease in 1969 when investigating the case of a 9-year-old girl with homocystinuria, a genetic defect in homocysteine conversion. Upon investigation, he learned that her 9-year-old uncle died of the condition. The first clue appeared when a pathologist mentioned the boy had arteriosclerosis, a cardiovascular disease characterized by hardening of the arteries, which is not common for a person this age.
The B Vitamin Connection
The study of another case of homocystinuria provided more answers when tests revealed urine concentrations of homocysteine and cystathionine, indicating a deficiency of an enzyme requiring B-12 and folic acid, another B vitamin. Both B vitamins, along with B-6, are necessary to regulate homocysteine levels. This discovery linked elevated homocysteine levels with B vitamin deficiency and began to paint a clearer picture between the relationship of B vitamins, elevated homocysteine and cardiovascular disease.
From Theory to Reality
McCully theorized that elevated homocysteine levels, caused by B vitamin deficiency, elevated cholesterol levels, leading to an accumulation and hardening of plaque in arteries. Though the medical community did not initially support McCully's theory, subsequent studies provided further indication and he went on to win numerous awards for his research, including the 1998 Linus Pauling Functional Medicine Award.
Modern Times
Modern medicine is now aware of the connection between B vitamin deficiency and homocysteine levels, thanks to McCully. In fact, treatment for homocystinuria includes B-6 and folic acid, which according to the National Institutes of Health, many people respond to. Because of the increased risk for cardiovascular disease, Individuals who have high homocysteine levels, not in relation to a genetic condition, but rather due to B vitamin deficiency, are commonly treated with Metanx, a medical vitamin combination of the active forms of B-6, B-12 and folic acid, along with dietary changes to increase intake.
Metabolic Regulation
The conversion of homocysteine is important for reducing vascular toxicity. Your body uses vitamins B-6, B-12 and folic acid to regulate homocysteine levels by converting it to other chemicals. It is first converted by the enzyme cystathionine b-synthase, to cystathionine, then to cysteine, an amino acid that protects cells by acting as an antioxidant. A failure in this conversion, either by B vitamin deficiency or genetic defect leads to elevated homocysteine, which the medical community now understands damages arteries, increasing the risk of cardiovascular disease.
Clinical Data and Prevalence
According to the American Academy of Family Physicians, elevated homocysteine is highly prevalent in the general population. This may be connected to a finding from a study on U.S plasma levels of B-12 published in the June 2004 journal "Nutrition Reviews," which found 40 percent of individuals had deficient or marginal B-12 blood levels. Current studies hope to answer more questions about this connection, but the medical community agrees that elevated homocysteine found in the general population is associated with an increased risk of fatal and nonfatal cardiovascular disease, independent of classic cardiovascular risk factors.
References
- "Nutrition Reviews"; Folate and Vitamin B12 Status in the Americas; Lindsay H. Allen; June 2004
- "Nutrition Science News" Kilmer Mccully, M.D., Connects Homocysteine and Heart Disease; Gloria Bucco; July 1999
- Pubmed Health: Homocystinuria
- Drugs.com: Metanx
- Linus Pauling Institute: the Vascular Toxicity of Homocysteine and How to Control it; Mark F. McCarty et al.; November 1999
- Aafp.org: Homocysteine Levels and Cardiovascular Disease
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