Diet high in B vitamins lowers heart risks in Japanese study

"Japanese people need more dietary intake of folate and vitamin B-6, which may lead to the prevention of heart disease," said Hiroyasu Iso, M.D., professor of public health at Osaka University.

The findings on the value of B vitamins were consistent with studies in Europe and North America, although the dietary consumption of vitamin B-6 is generally lower in Japan than in the United States.

Researchers analyzed data from 23,119 men and 35,611 women (ages 40-79) who completed food frequency questionnaires as part of the large Japan Collaborative Cohort (JACC) Study. During a median 14 years of follow-up, 986 died from stroke, 424 from heart disease and 2,087 from all diseases related to the cardiovascular system.

Investigators divided participants into five groups based on their intake of folate, vitamin B-6 and vitamin B-12. Comparing those with the diets lowest and highest for each nutrient, they found that higher consumption of folate and vitamin B-6 was associated with significantly fewer deaths from heart failure in men, and significantly fewer deaths from stroke, heart disease and total cardiovascular diseases in women. Vitamin B-12 intake was not associated with reduced mortality risk.

The protective effects of folate and vitamin B-6 didn't change when researchers adjusted for the presence of cardiovascular risk factors, nor when they eliminated supplement users from the analysis. Folate and vitamin B-6 may help guard against cardiovascular disease by lowering homocysteine levels, the investigators said. Homocysteine is an amino acid in the blood that's affected by diet and heredity. Folic acid and other B vitamins help break down homocysteine in the body.

A direct causal link hasn't been established, but evidence has shown that too much homocysteine may damage the inner lining of arteries and promote the formation of blood clots.

Sources of folate include vegetables and fruits, whole or enriched grains, fortified cereals, beans and legumes. Sources of vitamin B-6 include vegetables, fish, liver, meats, whole grains and fortified cereals.

Co-authors include: Renzhe Cui, M.D.; Chigusa Date, M.D.; Shogo Kikuchi, M.D.; Akiko Tamakoshi, M.D.; and the JACC study group. Author disclosures and funding sources are on the manuscript.