February 9/Los Angeles/States News Service -- In research using 2,657 participants in the Northern Manhattan Study (NOMAS), scientists found that high salt intake, independent of the hypertension it causes, was linked to a dramatically increased risk of ischemic strokes (when a blood vessel blockage cuts off blood flow to the brain).

In the study, people who consumed more than 4,000mg per day of sodium had more than double the risk of stroke compared to those consuming less than 1,500mg per day.

At the start of both studies, researchers assessed diet by a food frequency questionnaire.

NOMAS is a collaboration of investigators at Columbia University in New York and Miamis Miller School of Medicine, launched in 1993 to examine stroke incidence and risk factors in a multi-ethnic urban population. A total of 3,298 participants over 40 years old (average age 69) were enrolled through 2001 and continue to be followed. Some 63% were women; 21% were white, 24% black and 53% Hispanic.

In the sodium research, 187 ischemic strokes were reported during 9.7 years of follow-up. Stroke risk, independent of hypertension, increased 16% for every 500mg of sodium consumed a day, the scientists calculated. Those figures included adjustment for age, sex, race/ethnicity, education, alcohol use, exercise, daily caloric intake, smoking status, diabetes, high cholesterol, high blood pressure and previous heart disease.

Only a third of participants met the current U.S. Dietary Guidelines for Americans that recommend daily sodium intake fall below 2,300mg, or about a teaspoon of salt, Gardener said. Only 12% of subjects met the American Heart Associations recommendations to consume less than 1,500mg a day. Average intake was 3,031mg.

The take-home message is that high sodium intake is a risk factor for ischemic stroke among people with hypertension as well as among those without hypertension, underscoring the importance of limiting consumption of high sodium foods for stroke prevention, Gardener said.

Participants reporting their dietary behavior is a key limitation of the study, Gardener said.

Co-authors for the sodium study are: Rundek; Wright; Norbelina Disla, B.A.; Elkind; and Sacco.

Funding for the study was provided by a Javits award from The National Institute of Neurological Disorders and Stroke and the Evelyn F. McKnight Brain Institute.

From the February 21, 2011, Prepared Foods E-dition