- FRIDAY, Aug. 8 (HealthDay News) — Eating foods with soy protein
has been promoted as a way to lower cholesterol, but a new study finds it
has no significant effect on cholesterol levels.

The findings “do not support the current health claims for soy protein
in a general population,” said study author Peter R.C. Howe, director of
the Nutritional Physiology Research Centre at the Sansom Institute for
Health Research at the University of South Australia in Adelaide.

He's referring to the health claims approved for soy foods in both the
United States and the United Kingdom that link daily consumption of 25
grams of soy protein to a reduction in heart disease risk through a
lowering of LDL, or “bad,” cholesterol.

Howe's team studied 35 men and 58 women, average age 52, who had
mildly high cholesterol levels. He assigned each participant to rotate
through one of three diets for six weeks each. Each diet had varying
amounts of soy protein and isoflavones, substances in soy that some
experts say may have cholesterol-lowering powers.

One diet contributed 24 grams of soy protein and 71 milligrams of
isoflavone equivalents, one had 12 grams of dairy protein and 12 of soy
protein, with 76 milligrams of isoflavones. The dairy diet, which served
as the control, had 24 grams of dairy protein without isoflavones.

Howe's team measured each person's blood cholesterol — LDL, HDL and
trigylcerides — at the start of the study and after each six-week
diet.

They found no significant effect of the diets with either 24 grams or
12 grams of soy protein on LDL levels.

In his research, Howe also looked closely at whether a person's ability
to maximize the body's response to soy protein had a better
cholesterol-lowering effect. These people are termed “equol producers”
because of their above-average ability to make equol, a substance produced
in the intestines as a metabolite of a potent soy isoflavone called
daidzen. Equol is thought to inhibit LDL.

When Howe compared the cholesterol-lowering effects of those who were
equol producers with those who were not, he found no differences.

Howe's study was confined to those with mildly high cholesterol; he
said it may have an effect on those with higher cholesterol levels. And
the soy diets did lower triglycerides, a blood fat, by 4 percent.

The findings were published in the August issue of The American
Journal of Clinical Nutrition.

Even though the study found no effect of the soy protein on LDL
cholesterol, Dr. Frank Sacks, a professor of nutrition at Harvard School
of Public Health, called the research interesting. One facet he finds
especially intriguing, he said, is the finding that equol producers have
no benefit either.

After a series of studies on soy and its effect on cholesterol, the
American Heart Association's Nutrition Committee, of which Sacks is
vice-chairman, reviewed the evidence and issued an advisory, saying there
is “nothing special” about soy or isoflavones for improving cholesterol
and that the heart association doesn't recommend isoflavone
supplements.

However, “there are other benefits to soy foods,” Sacks said. They are
healthy due to high levels of polyunsaturated fats, fiber, vitamins and
minerals. But, he added, “forget soy protein for lowering LDL.”

More information

To learn more about LDL cholesterol, visit the American Heart Association.