Got Soy?

September 24, 2003

Heather Heilman
Phone: (504) 865-5714

Karen Paret checks the blood pressure of a security guard at the New Orleans Centre during a recent screening What if preventing or controlling high blood pressure was as easy as consuming more soy protein? Some small studies have suggested this could be the case.

Now Tulane is one of two sites participating in a large randomized, double-blinded trial comparing the effects of soy protein, milk protein and a placebo on blood pressure.

Jiang He, the newly appointed chair of epidemiology, is principal investigator of the study, which is sponsored by the National Heart, Lung and Blood Institute. The other site is in Jackson, Miss. Kristi Reynolds, a doctoral candidate in epidemiology, is supervising recruitment for both sites.

Researchers are hoping to recruit people with pre-hypertension and moderate hypertension.

With that goal in mind, they've been offering free blood pressure screenings at farmers' markets around town, and large workplaces such as the main branch of the Post Office, City Hall and New Orleans Centre. They've also sent out a mass mailing about the study.

"We've gotten a great response," said Lisa Harewood, the study coordinator. "People are very interested in the idea that they can start to address the problem before getting to the point where they have to take medication."

In New Orleans, 140 volunteers are needed and recruitment will be ongoing through the end of 2004. Levels of blood pressure that used to be considered "high normal" are now thought of as pre-hypertension, a change which is meant to convey that people in that category are at risk for developing hypertension. Hypertension is one of the biggest, and most modifiable, risk factors for heart disease, stroke and kidney disease.

The effects of sodium, potassium and alcohol on blood pressure have been well-studied, but the effects of protein and other macro-nutrients have not. Researchers hope to find out whether or not protein helps lower blood pressure, and if so whether soy protein is more effective than animal protein, as some small studies have suggested. They're not sure of the mechanism by which protein might have a beneficial effect, though it might be related to the amino acid arginine, which the body transforms into nitric oxide.

Soy contains more arginine than cows' milk. Each participant will take, in random order, a soy supplement, a milk protein supplement and a complex carbohydrate placebo two times a day for eight weeks each, with a three-week washout period in between. Along the way, changes in blood pressure and in levels of insulin, glucose, leptin, homocysteine and serum lipids in the blood will be measured. The supplements come in powder form and may be mixed with liquid or even used in baking.

Deborah Bujnowski, a registered dietitian, teaches participants about acceptable ways to use the supplement. "People have been very inventive about the way they've used it," said Harewood. Volunteers will get free information about their blood pressure and levels of cholesterol, blood sugar and insulin. Those who complete the 32-week study will receive $200. For information about participating in the study, call 988-4390.

Heather Heilman can be reached at

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Tulane University, New Orleans, LA 70118 504-865-5000