There is an epic battle being waged over a common food that you and your children likely are exposed to every single day.
In one corner are those who proudly profess the almost miracle-like qualities of this food, with boastful claims about how it can do everything from curing cancer to preventing heart disease and even menopause.
In the other corner there is a persnickety bunch who retorts that this food is anything but a “miracle.” They claim it can lead to thyroid disease, actually CAUSE cancer, hamper your immune system, destroy your brain, make you infertile, and even turn males into females!
So what is this food that’s prompting two equally passionate groups to go to war?
It’s soy…and each side in this battle is going out of its way to convince you that soy is either the messiah of health or the devil itself.
So who’s right, how will this affect you and your children’s health and what should you do?
Laying Out the Soy Controversy
Adding to the murky waters of the soy controversy is that there are two opposing, titanic-sized industries that have a vested interest in each side.
For example, many of the pro-soy studies are funded, in part, by John Deere and other companies that have a vested interest in soy production.
On the flip side, some of the anti-soy studies are funded, in part, by the dairy lobby, which has an interest in the consumption of less soy and more dairy.
Given all this, the only thing to do is to look at the facts and review the studies on each side.
Soy advocates point to two key areas in which this controversial bean may show some benefits: decreasing cholesterol levels and relief from menopause symptoms.
Let’s first take a look at the cholesterol claims.
Can Soy Help Improve Your Cholesterol?
Advocates point out that more than 30 clinical studies have been performed since 1968, all showing that soy is highly effective for decreasing cholesterol levels. A meta-analysis from the New England Journal of Medicine(1) confirmed these findings.
After reviewing 38 placebo-controlled clinical trials, researchers concluded that individuals who consumed an average of 47 grams of soy protein per day had a 13 percent decrease in LDL cholesterol, a 10.5 percent decrease in triglycerides, and a 9 percent decrease in total cholesterol levels.
While this is clearly strong support in favor of soy’s ability to lower cholesterol levels, what it doesn’t lay out is the form of soy protein. Was it a powder, the actual soybean itself, tofu (soybean curd), or tempeh (fermented soy)? Or was it a textured, processed soy food?
As odd as it may sound, the form of soy really does matter…as you’ll soon see.
In another study(2), researchers gave 42 participants with high LDL cholesterol levels four different diets, fed in randomized order for six weeks at a time over the course of 24 weeks. The diets contained:
- At least 25 grams of animal protein a day
- At least 25 grams of isolated soy protein
- Either trace amounts or 50 mg of soy isoflavones
Researchers found that soy significantly reduced total and LDL cholesterol and triglyceride levels in participants with very high cholesterol levels. However, it had only a modest effect on those participants with elevated, but not severely high, cholesterol.
They concluded, “Although potentially helpful when used to displace products containing animal fat from the diet, the regular intake of relatively high levels of soy protein had only a modest effect on blood cholesterol levels and only in subjects with elevated LDL cholesterol levels. Soy-derived isoflavones had no significant effect.”
In other words, eating soy (but NOT taking a supplement) helps those people with elevated cholesterol, but doesn’t really help someone with moderately high cholesterol.
What the researchers fail to mention is that simply reducing the consumption of animal protein (particularly with no regard for the quality of that animal protein), regardless of the soy substitute, may have had the same effect. It would be interesting to see the results of that type of study.
A similar study from the November 2001 issue of Archives of Internal Medicine(3) followed more than 9,600 men and women for 19 years. They found that those who ate legumes (all legumes, not just soy) four times or more per week (compared to less than once a week) enjoyed a 22 percent lower risk of coronary heart disease and an 11 percent lower risk of cardiovascular disease.
Researchers concluded that increased legume intake may be an important part of a dietary approach to preventing cardiovascular heart disease.
What is interesting about this study is that it includes all legume consumption, not just soy. And since legumes (beans, peas, etc.) are high in fiber, it could be the legumes themselves, not the soy per se, that is responsible for the decreased risk of heart disease.
Still, it was these types of studies that, in 1999, led the FDA to authorize of the use of health claims on the labeling of foods containing soy protein.
The ruling was based on research that suggested such foods might reduce the risk of coronary heart disease by lowering blood cholesterol levels.
According to the FDA, foods must contain 6.25 grams per serving of soy protein in order to qualify for the claim. And a daily intake of 25 grams is recommended to achieve a significant cholesterol-lowering effect.
While the studies surrounding cholesterol and soy are compelling, there are several obvious questions that remain. Let’s see if the studies regarding soy and menopause symptoms can help answer those questions.
Can Soy Help Ease Menopause Symptoms?
Many studies show soy helps to alleviate menopause symptoms. In fact, its effects are similar to that of a drug…a somewhat shocking observation that we’ll have more to say about later.
In one double-blind, randomized, placebo-controlled study,(4) researchers divided 180 menopausal women into two groups. The first group received 80 mg soy isoflavones while the second received a placebo. At the end of 12 weeks, those taking the soy isoflavones reported a 41.2 percent reduction in hot flashes as compared to a 29.3 percent reduction in the placebo group.
Conclusion: soy appears to be more effective than placebo at reducing hot flashes.
This makes us question: How would soy stack up against something known to reduce hot flashes? Researchers at the State University of Campinas in Brazil wondered the same thing.
They performed a double-blind, randomized, placebo-controlled study on 60 healthy, postmenopausal women.(5) Their goal was to see if soy worked as well as conventional hormone therapy at relieving menopause symptoms.
Dividing the women into three groups, the first group received 90 mg of soy isoflavones, the second group received 1 mg estradiol and 0.5 mg of noresthisterone acetate, and the third group received a placebo.
At the end of 16 weeks, researchers found a statistically significant improvement in hot flashes, muscle pain and vaginal dryness in both the estrogen and soy groups. Also, there was no statistically significant difference between these groups.
Researchers concluded: “Dietary soy supplementation may constitute an effective alternative therapy for symptoms of menopause.”
So, here we have a “gold standard” study indicating that a fairly high dose of soy isoflavones worked as well as conventional hormone therapy at reducing some of the main complaints of menopause, namely hot flashes and vaginal dryness.
But, we have to ask the question: is a high dose of soy isoflavones safe? This is the key argument for those opposed to soy. Let’s see what they have to say.
The Argument Against Soy…
On February 19, 1999, two researchers from the Food and Drug Administration (FDA) signed a letter of protest against the FDA’s approval of soy6. They pointed to a number of animal studies showing a connection between soy consumption and many health problems, including cancer.
In their letter, they take issue with soy isoflavones’ estrogenic effects. They pointed out that soy isoflavones “demonstrate toxicity in estrogen sensitive tissues and in the found 31 dose-response curves for hormone-mimicking chemicals that also fail to show a threshold.”
They go on to say, “Our conclusions are that no dose is without risk; the extent of the risk is simply a function of dose.”
What does this scientific gobbledygook mean? It simply means that tissues that are estrogen sensitive (i.e. breast, uterus, cervix, ovaries, etc.) interpret soy as an estrogen mimic and as toxic, possibly even cancer-causing.
Moreover, there is no higher or lower dosage that indicates toxicity. No matter how much or how little you eat or take (if in supplement form), soy always poses a risk.
To put the issue of risk into context for you, it would be like swimming in shark-infested waters. Whether you just go in for a five-minute dip or splash around for an hour, you are at a risk of being bitten.
Your risk is less if you just jump in and out, but there is a real risk nonetheless.
When listing their reasons for asking the FDA to pull back on their blanket recommendation of soy without discussing the dark side, these concerned FDA researchers pointed to three specific areas of concern:
- the possible connection between soy and estrogen-dependent cancers,
- a possible link between soy and thyroid issues, and
- the use of soy to feed infants.
These are very serious allegations, so let’s take a look at each one briefly…
The Connection Between Soy and Cancer
On the cancer front, soy advocates point to the fact that the Japanese, who eat significantly more soy than Americans, have a lower incidence of breast, uterus, and prostate cancers(7).
However, what they fail to mention is that the Japanese population has higher rates of other cancers, such as esophageal, stomach, pancreatic, thyroid, and liver cancer(8, 9). This inconvenient fact is something you almost never hear about.
Also, in a study from the May 2002 issue of Cancer Research(10), researchers investigated the interactions between dietary genistein (the major isoflavone found in soy) and tamoxifen (an estrogen antagonist used in the treatment of estrogen-dependent breast cancer).
They implanted estrogen-dependent breast cancer cells in mice who had had their ovaries and thymus removed. This is important, because your ovaries and thymus produce estrogen. By removing these, researchers were trying to ensure that any estrogen effects were coming from the soy.
Researchers found that genistein either negated or overwhelmed the inhibitory effect of tamoxifen. Based on these findings, they urged postmenopausal women to exercise caution when consuming dietary genistein while taking tamoxifen.
In other words, these researchers believe that women taking tamoxifen to help stop the growth or spread of breast cancer would completely undo the positive effects of the medicine by eating soy.
The Soy Link to Thyroid Disorders
When it comes to the thyroid, soy opponents like to refer to studies that show that consuming isoflavones may lead to the development of thyroid disease…in animals. To highlight this, let’s look at one study that has tested the effects of genistein on thyroid function in rats(11).
Researchers gave rats a genistein-fortified diet, followed by testing their thyroid function. They found that “genistein was measured in the thyroid at levels that produced dose-dependent and significant inactivation of rat thyroid peroxidase (TPO)… Furthermore, rat TPO activity was dose-dependently reduced by up to 80 percent.”
In layman’s terms, the soy isolate practically shut down the rat’s thyroid function. However, it was a study done on rats. It would be nice to see a study showing this effect in humans.
Researchers themselves were not blind to this. Yet they concluded that even the possibility that widely consumed soy products may cause harm in the human population is of concern.
The Concern with Soy-Infant Formulas
While the studies on soy and cancer and the thyroid are concerning, the issue that has most soy opponents up in arms has to do with soy and infants.
And on this front, one study in particular presents some shocking findings.
Researchers at the Children’s Hospital Medical Center in Cincinnati, Ohio, performed a random, double-blind study12 to see how much phytoestrogen (meaning plant-based estrogen) 21 four-month-old infants received from soy-based formula.
They divided the infants into three groups. One received soy-based formula, one received cow milk formula, and the third had human breast milk. For the soy formulas, researchers tested five different brands, all of which showed similar soy isoflavones content and proportion of soy isolate.
They found that the infants receiving the soy formula had 214 times more genistein (a key isoflavone found in soy) in their blood than that found in the infants receiving cow’s milk, and 244 times more than that found in infants receiving breast milk.
The infants receiving soy also had 140 times more daidzen (another key isoflavone in soy) than those found in the infants receiving the cow’s milk formula, and 210 times more than in the infants taking the breast milk.
Researchers concluded that the “daily exposure of infants to isoflavones in soy infant formulas is six to 11 fold greater on a bodyweight basis than the dose that has hormonal effects in adults consuming soy foods.”
Worse yet, they go on to say that “circulating concentrations of isoflavones in the seven infants fed soy-based formula were 13,000 to 22,000 times higher than plasma oestradiol concentrations in early life, and may be sufficient to exert biological effects.”
Wow! That’s a lot of unnatural estrogen floating around in those little bodies.
And we wonder why girls are developing so much earlier than they did 20 years ago, and why boys seem to be behind the curve. Could it be all that excess estrogen?
Finally, those who are opposed to soy also point to a number of soy allergies and digestive problems soy can cause, including gas, cramping, bloating, or intestinal discomfort, all of which are signals that our bodies send us to indicate that the use of soy may not be in our best interest.
What Does It All Mean?
The reality is that there are good studies on both sides of the fence.
Soy does seem to have cardio-protective benefits, and it clearly helps ease menopause symptoms. However, the very reason soy works so well for lowering cholesterol and relieving hot flashes is because it is an effective estrogen mimic.
That being said, it stands to reason it could be a concern for those with estrogen-dependent cancers or thyroid issues. And, most problematic, it seems, is the feeding of those estrogens to infants whose little bodies aren’t prepared for the estrogen onslaught.
Or, in the words of those FDA researchers: “While isoflavones may have beneficial effects at some ages or circumstances, this cannot be assumed to be true at all ages. Isoflavones are like other estrogens in that they are two-edged swords, conferring both benefits and risk.”
Taking a common sense, objective approach, it seems that the vast majority of people should avoid soy. This is especially true for those with a personal or family history of estrogen-dependent cancer or thyroid disease. Also, under no circumstances should you use soy-based infant formula.
Another way to think about soy is that whatever benefits there MAY be to consuming soy, those benefits can be replicated through other natural means, such as by consuming other plants that have cardio-protective and cancer-preventing phytochemicals.
Therefore, simple common sense says that if you can get those same benefits naturally somewhere else, there’s little point in consuming something with such well-documented dangers.
The only exception we see for soy is for women going through menopause who DO NOT have any of the following issues:
- personal or family history of estrogen-dependent cancer, such as breast, uterine, cervical or ovarian cancer
- thyroid or family history of thyroid disease
- soy allergies
- problems digesting soy or other legumes
For this small population, soy may confer some benefit.
If you fit into this group, avoid soy supplements and processed soy foods and limit your soy consumption to organic soybeans (edamame) and organic, fermented soy foods, such as:
For everyone else, however, just say no to soy.
If you would think twice about popping a few birth control pills at lunch or slugging back some hormone replacement pills with dinner, then you shouldn’t be using soy either.
Treat soy like the true estrogen it is.
1 Anderson, JW et al. “Meta-analysis of the effects of soy protein intake on serum lipids.” N Engl J Med. 1995. 333:276-82.
2 Lichtenstein, AH et al. “Lipoprotein response to diets high in soy or animal protein with and without isoflavones in moderately hypercholesterolemic subjects.” Arteriosclerosis, Thrombosis, and Vascular Biology. 2002. 22:1852-8.
3 Bazzano, LA et al. “Legume consumption and risk of coronary heart disease in US men and women.” Arch Intern Med. 2001. 161:2573-8.
4 Ferrari, A. “Soy extract phytoestrogens with high dose of isoflavones for menopausal symptoms.” J Obstet Gynaecol Res. 2009, Dec. 35(6):1083-90.
5 Carmignani, LO et al. “The effect of dietary soy supplementation compared to estrogen and placebo on menopausal symptoms: A randomized controlled study.” Maturitas. 2010 Sept 10 [Epub ahead of print].
6 Sheehan, DM and Doerge, DR. 1999 Feb 18. Letter to FDA in reference to Docket #98P-0683.
7 Natural Medicine News (L&H Vitamins, 32-33 47th Avenue, Long Island City, NY 11101), 2000 Jan/Feb p. 8.
8 Harras, A (ed). Cancer Rates and Risks. National Institutes of Health, National Cancer Institute, 1996. 4th edition.
9 Searle, CE (ed.). Chemical Carcinogens. ACS Monograph 173, American Chemical Society, Washington, DC, 1976.
10 Ju, YH et al. “Dietary genistein negates the inhibitory effect of tamoxifen on growth of estrogen-dependent human breast cancer (MCF-7) cells implanted in athymic mice.” Cancer Res. 2002 May 1;62(9):2474-7.
11 Doerge, DR. “Goitrogenic and estrogenic activity of soy isoflavones.” Environ Health Perspect. 2002 June; 110 Suppl 3:349-53.
12 Setchell, KD et al. “Exposure of infants to phyto-oestrogens from soy-based infant formula.” Lancet. 1997 Jul 5. 350(9070):23-7.
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