Soy May Not Pack a Strong Antioxidant Punch

Wed Feb 2, 2:47 PM ET

By Amy Norton

NEW YORK (Reuters Health) - Soy may not be the antioxidant powerhouse that some research has suggested, according to a new study.

Researchers found that 6 weeks on a soy-rich diet did not seem to diminish "oxidative stress" among 42 middle-aged adults with borderline-high cholesterol and no effect was seen with a diet supplemented with soy-derived antioxidants called isoflavones.

Oxidative stress refers to the potentially cell-damaging effects of oxygen free radicals, molecules that are generated by normal metabolism. The oxidation of "bad" LDL cholesterol, for example, may contribute to the "hardening" and narrowing of arteries that can lead to heart attack and stroke.

LDL particles carry cholesterol to the arteries, and it's thought that the greater the number of particles that are oxidized, that is, interact with oxygen, the more likely they are to be deposited into artery-clogging plaques.

Antioxidants, which include various nutrients such as vitamins C and E, help absorb the oxygen free radicals roaming the body. Diets rich in soy products, such as tofu, have been linked to lower cholesterol levels and lower rates of heart disease and stroke, and some lab research has suggested that the reason may rest in the ability of soy isoflavones to fight oxidative stress.

The new study, however, found that neither soy nor isolated isoflavones had much of an impact on oxidative stress.

"There was some protection against oxidation, but nothing too striking," said Dr. Sonia Vega-Lopez, a researcher at the U.S. Department of Agriculture, Human Nutrition Research Center on Aging at Tufts University in Boston.

That doesn't mean it's time to swap your tofu for T-bone steak, though. Soy is a good source of low-fat, plant-based protein, Vega-Lopez noted in an interview.

"Soy might not be the magic bullet some have thought," she said, "but it's still a good food."

Vega-Lopez and her colleagues report their findings in the American Journal of Clinical Nutrition.

The study involved 42 men and women, age 50 or older, who had elevated LDL cholesterol levels. All participants followed each of four 6-week diets at some point in the study: one diet rich in soy, one containing soy with the isoflavones depleted, one with animal protein supplemented with isoflavones, and one based on animal protein and no added isoflavones.

During the last week of each diet, the researchers collected blood samples to look at several markers of oxidative stress, including the oxidation of LDL cholesterol.

They found that antioxidant activity in participants' blood was slightly higher on the soy-protein diet, regardless of the isoflavone content, and soy protein did seem to reduce one measure of oxidative stress. There were no effects on LDL oxidation or other markers of oxidative stress, however.

All of the diets, Vega-Lopez noted, contained healthy servings of fruits and vegetables, which are prime antioxidant sources. So it's possible that those effects masked some antioxidant benefits of the soy or isoflavones.

An editorial published with the report agrees that soy eaters should not give up on the food. More research is needed to determine the potential health benefits of soy, according to Penny M. Kris-Etherton and Sheila G. West of Pennsylvania State University in University Park.

"Until then," they write, "it remains prudent to recommend soy products in a heart healthy diet because of their nutritional value and as a healthy substitute for protein sources that are higher in saturated fat and cholesterol."

SOURCE: American Journal of Clinical Nutrition, January 2005.

http://story.news.yahoo.com/news?tm..._antioxidant_dc

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Isn't it amazing how no one can publish anything negative about soy without it being hedged around with comments reassuring us that it's really a good thing. Even the publication in a research journal has an editorial attached to it asking soy eaters to keep eating and others to keep recommending it. Science or commerce? Sad to see in AJCN.

I thought natural Soy products were fine, that it was only things that were supplemented with soy that weren't so good for you? (not trying to start an argument, I TRULY don't know, so this is more of a question)

Studies like this continue to convince me that nutrition is more about religion and belief.

Nutritionists have 'decided', for whatever personal reasons, that soy is wonderful, so they do research to 'prove' their pre-conceived notions. And when the research doesn't quite prove that, they editorialize and rationalize it away.

If low-carb researchers did that, they'd be skewered for conducting bad science.


Notice, at least in this article, that they DID NOT say that the diet with plenty of animal protein was worst. Hmm. Probably because they found it WAS NOT so bad in terms of oxidative stress. Ooops.

hi KoKo,

Check out the articles and studies listed at the Weston A. Price Foundation's website .. Soy Alert!. I think you might find some answers there.


Doreen

I think it comes from the "meat is murder" group and their influence. If they can prove that soy is just as good or better for you than meat, than there is no reason to eat meat and we can save all of those cuddly cows. So far, they haven't been able to.

I get physically ill when I eat something with "fake meat", made from soy, in it. Funny, but that doesn't happen with the real thing.

Another set of links and articles can be found here:

The Omnivore

arc, I think the soy industry is more likely to be the culprit. We are talking billions of dollars involved.

Wyv

Thanks Doreen, I'm checking them out now

The conclusion of the editorial was

So they basically conclude that soy has no proven benefits, and then they still recommend eating it instead of meat!