Decrease Homocysteine With DASH

August 22, 2000

New York (MedscapeWire) Aug 22 — The DASH diet, which may lower blood pressure, also reduces levels of homocysteine, a possible independent risk factor for heart disease and stroke, researchers report in the August 22 issue of Circulation.

DASH refers to the Dietary Approaches to Stop Hypertension trial, a multicenter trial designed to assess how dietary patterns affect blood pressure. The DASH diet is a low-fat diet rich in fruits, vegetables, and low-fat dairy products.

"Our research points out that changes in diet have additional beneficial effects on heart disease beyond reductions in blood pressure and improvements in cholesterol levels," says Lawrence J. Appel, MD, MPH, associate professor of medicine at Johns Hopkins Medical Institutions in Baltimore, Maryland, and lead author of the study.

"Other studies have documented that high levels of homocysteine are associated with an increased risk of heart disease. Results from our study suggest that if people who are consuming a typical American diet adopt the more healthy DASH diet, the change in homocysteine levels alone would reduce their risk of heart disease by about 7 to 9 percent," he says. "This is on top of the benefits of reduced blood pressure and lower cholesterol as noted in the DASH trial."

Previous studies have shown an association between high blood levels of homocysteine — a by-product of protein metabolism — and increased rates of heart attack and stroke. In a study of adults younger than 60 years, those with a homocysteine level in the top 20% of the normal range were more than twice as likely to develop heart disease as those with homocysteine levels in the bottom 80%.

In healthy individuals, homocysteine levels are affected by the intake of folate, vitamin B12, and other nutrients. Studies have shown that taking large doses of folic acid, the vitamin supplement form of folate, may reduce homocysteine levels.

Folate is a B vitamin found in leafy green vegetables, meat, poultry, seafood, and legumes, as well as whole grain products. Because folate can help prevent birth defects of the brain and spinal cord, the government now requires fortification of cereals, bread and flour with folic acid. Vitamin B12 comes from animal products including milk and other dairy products.

Appel says his study focuses on the impact of whole dietary changes, rather than vitamin supplements, on homocysteine levels.

In this study, researchers controlled the diets of 118 subjects for 11 weeks. Appel says the participants were basically healthy except for elevated blood pressure, typically in the "high-normal" range (130-139/85-89 mm Hg) or stage 1 high blood pressure (140-159/90-99 mm Hg).

For the first 3 weeks, all of the volunteers ate the control diet: low in fruits, vegetables, and dairy products with 37 percent of its calories from fat — similar to the typical American diet. Study participants were then divided into 3 groups: the first stayed on the control diet, the second ate a diet rich in fruits and vegetables but otherwise similar to the control. The third group ate the DASH diet.

The researchers found that the control diet contained 168 micrograms of folate. The second diet averaged 314 micrograms of folate per day, and the DASH diet provided about 400 micrograms, which is the current USDA recommendation.

Individuals on the control diet had higher homocysteine levels at the end of the study than they had at the beginning. Individuals on the DASH diet had reduced homocysteine levels — their levels were an average of 0.8 micromoles/liter lower than that of the control group participants. Those on the control diet enriched with fruits and vegetables had an intermediate effect.

Appel says that because heart disease tends to develop over decades, the earlier someone starts a healthy diet, the better. "The public health message is: Eat right. Start early. There are multiple benefits."

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