Study Shows Eating Soy Protein Could Help Lower Cholesterol

Perhaps you read about the new study that shows eating soy protein - now found in products ranging from infant formula to meat extenders - will lower your cholesterol.

If you are among the 20 percent of Americans with elevated cholesterol, you should know a couple things before going oat-bran-crazy over soy protein.

First, the study, published in the Aug. 3 edition of the New England Journal of Medicine, found that the benefits of a diet high in soy protein were more pronounced in people with the highest initial cholesterol levels. Those with levels of 200 milligrams per deciliter or less exhibited only minor drops.

Second, not all sources of soy protein contain significant quantities of the phytoestrogen compounds that researchers believe cause the cholesterol changes, says Dr. James Anderson, professor of medicine and clinical nutrition at the University of Kentucky.

Anderson and university colleagues Dr. Bryan Johnstone and Margaret E. Cook-Newell conducted the study by combining experimental data from 38 individual studies of soy protein, then making adjustments for variations in methodology. The results, which are considered more significant and reliable than any of the separate studies taken alone, were published in the Aug. 3 edition of the New England Journal of Medicine.

The analysis showed that eating a daily average of 47 grams of soy protein (about the amount found in 3/4-pound of firm tofu) could lower cholesterol by 20 percent in people with levels greater than 335 milligrams per deciliter. People with lower cholesterol levels showed a more moderate but nonetheless significant reduction.

Based on other studies, mostly in animals, Anderson believes that the effect mostly is due to soy’s unique phytoestrogen compounds, called isoflavones. But most of these phytoestrogens are lost if the protein is made using alcohol extraction rather than water extraction, he says.

Unfortunately, many supermarket products with lots of soy protein - such as Green Giant’s popular Harvest Burgers, or meat substitutes such as vegetarian chili mix - use soy protein made by alcohol extraction, Anderson says.

More natural foods such as tofu and soy milk are sources of phytoestrogen-rich soy protein, but it is not as concentrated.

Most product labels don’t reveal which extraction method was used, something Anderson and others hope will change if soy protein catches on.

“It’s pretty exciting,” Anderson said in presenting his findings. “I think soy protein has more potential than oat bran.” (Anderson also was one of the researchers responsible for launching the oat-bran craze in the 1980s.)

“These isoflavones also may help reduce the risk of breast cancer and osteoporosis in women,” he said, referring to additional research not considered in his study.

Anderson believes reaction to soy protein could be similar to that of the oat-bran revelations.

“I think companies could start adding soy protein to foods, not because ‘It’s the right thing to do,’ as Wilfred Brimley says (in Quaker Oats commercials), but because of the bottom line,” he said.

Anderson suggests that men and women with cholesterol problems can “derive significant reductions in serum cholesterol levels” by drinking a cup of a soy beverage - which would provide about 8 to 20 grams of soy protein, depending on its composition - and eating an entree containing 15 to 20 grams of soy protein.

More important than just lowering total cholesterol, soy protein significantly reduced the LDL or “bad” cholesterol and triglycerides, both of which are primary heart disease risk factors. At the same time, the HDL or “good” cholesterol levels went up 2.4 percent. That’s positive, though it’s not considered statistically significant, Anderson says.

The American Heart Association’s position is that it is premature to endorse soy protein as a cholesterollowering agent for the American diet.

“The available evidence is that while use of soy protein sounds promising, it should lead to more and better studies,” said Dr. Neil Stone, former chairman of the AHA nutrition committee.

“If I had high cholesterol, I’d be eating it every day,” said Susan M. Potter, an associate professor of nutrition at the University of Illinois who ran two large studies that Anderson considered in the analysis.

“I hope we’ll be seeing soy protein in more products, such as baked goods,” she said. “People have a problem with the present soy foods. They say ‘Oh, tofu. Give me a break!’

“But isolated soy protein is different. With a little work it can fit into the basic American diet.”