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Higher Folic Acid Intake Related to Reduced Risk of Stroke

James Meschino DC, MS, ROHP

Men and women who consume, on average, 405 mcg per day of folic acid were shown to have a 20% lower risk of stroke and a 13% lower risk of all cardiovascular events, including heart attacks, compared to individuals consuming only 99 mcg of folic acid per day, on average.  These were the findings from the National Health and Examination Survey I Epidemiologic Follow-Up Study (NHANES I) published in Stroke: Journal ofthe American Heart Association.  Study participants included 9,764 U.S. men and women aged 25 to 74 years old, who were surveyed for dietary intake of folic acid at baseline using a 24-hour dietary recall method.  Over an average of 19 years of follow-up, 926 incident strokes events and 3758 incident cardiovascular disease events were documented in this population.  This study showed that higher folic acid intake was associated with a significant reduction in stroke and cardiovascular disease events.

The preventive role played by folic acid is considered to be through its involvement with homocysteine.  Within all body cells, folic acid is required as a methyl donor (CH3), to convert homocysteine to methionine.  Once formed, methionone acquires the adenosine ring from ATP to become S-adenosylmethionone (SAMe).  SAMe is the primary methyl donor for a multitude of important reactions that give rise to DNA bases (required to help prevent spinal birth defects in the fetus), creatine synthesis in the liver, the synthesis of many neurotransmitters in the brain, and through transmethylation participates in detoxification reactions in the liver and in intestinal epithelial cells.  Thus, the body has an ongoing need to convert homocysteine to methionine to ensure adequate concentrations of SAMe are in place for these vital biochemical reactions to occur each minute of our lives.  Once SAMe gives up its methyl group in the above noted reactions it is quickly converted back to homocysteine, awaiting a methyl group from folic acid to be once again reconverted back to methionine and SAMe.  If there is insufficient intake of folic acid, then less homocysteine is converted to methionine and this results in an intracellular build up of homocysteine.  As homocysteine builds up in the cell, it begins to leak through the cell membrane into the bloodstream.  Within the bloodstream, homocysteine causes denuding of the endothelial lining of arteries, oxidizes LDL-cholesterol, produces vasoconstriction and increases platelet coagulation.  All of these effects are associated with an increased risk of ischemic stroke, myocardial infarction and other cardiovascular events.

As such, many studies have shown that elevated homocysteine levels are associated with a significant increase in risk of cardiovascular disease and that approximately 10% of the attributable risk of heart disease is determined by homocysteine blood levels (it is advisable to have a blood level of homocysteine below 9 micromoles per liter).  Studies show that folic acid supplementation can reduce homocysteine levels in patients presenting with elevated homocysteine levels, which is considered to reduce risk of heart disease in these individuals.  The NHANES I Epidemiologic Follow-Up Study provides further evidence that folic acid is a vital nutrient in the prevention of the nation’s number one killer disease (CVD).  Unfortunately, cross-sectional nutrition surveys in the U.S. indicate that the average intake of folic acid among the adult population is only 190-210 mcg per day.  The body of evidence indicates that this is insufficient to prevent an undesirable build-up of homocysteine in the blood stream, prevent spinal birth defects in women who may become pregnant, and provide adequate folic acid concentrations necessary to prevent cancer and support health optimization.  It is very difficult to ingest 400-600 mcg of folic acid per day from food without relying heavily upon wheat germ, wheat bran, cooked spinach, broccoli, beans, and collard greens.  As a rule, North Americans do not consume these foods in high enough quantities to derive the optimum benefits available from folic acid.  This is yet another reason to educate patients on the principles of a healthy diet and to encourage them to use a high potency multiple vitamin and mineral each day.  The 400 mcg contained within a multiple vitamin may not appear to stand out when surrounded by antioxidants and other more high profile ingredients, but this seemingly modest daily contribution of folic acid can be the difference between life and death for many patients, family members and friends, who value your advice on matters of preventive health care.

Bazzano L.A et al, Dietary intake of folate and risk of stroke in US men and women: NHANES I Epidemiologic follow-up study.  Stroke.  2002; 33, 5: 1183

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