Soy - Natural Alternative?
| Soy - Natural Alternative?|
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Ask A Doctor
November 12, 2000
Here's my short answer, after weeks of digging through the medical research, not to mention wading through the 80 pages of the FDA decision on soy--substituting whole soy protein, especially miso, tempeh, and tofu, for meat is a good thing; using isolate soy protein powder will probably give the benefits but might also increase the bad chemicals in soy; taking pills of soy isoflavones does not seem to be a good idea at this time.
The great interest in soy came from an observation about the health of Asian women in Japan compared to the health of Asian women in the United States. The trouble with epidemiological studies is that you can't always tell what's the cause and what's the effect, just that there seems to be something going on. The problem is that the traditional Japanese diet is better in many ways: the high level of fish and vegetables, the low level of saturated fat, the greater level of exercise, and drinking green tea--all of which has been shown to decrease the risk of breast cancer and help with menopause. There's also a controversy about the amount of soy eaten by the Japanese. It may not be large amounts that lead to a benefit.
The question here in the Hormone Jungle though is whether it can substitute as estrogen. The answer seems to be no, not for all the things that estrogen does. But it does have some benefits, especially whole soy protein.
Estrogens are hormones. Hormones are messengers that act like keys. They flow through the body looking for the locks in cells that match. They enter the lock, turn it on, and something happens. The locks appear in over 300 different tissues throughout the body. Phytoestrogens are chemicals in plants that are "skeleton keys". Some don't fit the locks at all. Some sort of fit the locks and either jam them or turn them on.
It's not an accident that plants make phytoestrogens. They are trying to poison the animals that graze on them, weakening them and creating havoc with their hormone systems so that they won't grow very large and they can't reproduce very well or at all. This is an advantage if you're a plant trying not to be eaten!
There are many different chemicals that count as phytoestrogens. The ones in soy beans are isoflavones--in particular, genistein and daidzein. Each phytoestrogen has different effects and different strengths. Phytoestrogens are a lot weaker than 17 beta estradiol (one of the three estrogens that we make ourselves). They can be 4,000 to 4,000,000 times weaker. But they may stay in the body for a long time, reaching levels that might get as high or higher than estradiol.
As research takes isoflavones apart, it seems as though some (maybe most) of their effects in animals and humans come, not from their "estrogen-like" quality, but from other effects on enzymes, protein synthesis, and calcium transport. A lot of the studies use levels of isoflavones that are impossible to reach in our bodies, so it's not clear how they connect to us. And they may not work like keys at all. They might have an effect because they stimulate sex hormone binding globulin, which then grabs our hormones and keeps them from entering the locks in the cells.
If I had breast cancer, I'd only use a soy protein powder product or concentrated isoflavones after talking with my doctor. The studies that show a positive effect use the whole soy protein, not isolated isoflavones. The problem in part is that there are many kinds of isoflavones and a number of different kinds of cells that form different kinds of breast cancer. Genistein, for instance, one of the main isoflavones in soy, slowed down the growth of MDA-MB-468 breast cancer cells when at really high levels, higher than a person could take, and slows down the growth of HME cells. But at low levels of genistein, MDA-MB-468 breast cancer cells increase. The same thing happens with MCF7 and MDA-MB-231 breast cancer cells.
The benefits that phytoestrogens bring might come from their interaction with your own estrogen and the estrogens that come from the environment in plastics and hormones injected into chickens and cattle. When genistein is present at the same time as other estrogens, it seems to prevent cancer from growing. If it is in the test tube alone with the cancer cells, it makes them grow. Several animal studies suggest that isoflavones slow down cancer development if they are taken before exposure to the carcinogen.
Even the whole soy protein picture is hazy. One study, using rats that are bred to have breast cancer, tested whether soy protein might prevent breast cancer. They used whey (a minor milk protein) with the control group. In the soy group, 77% of the rats developed one or more tumors, while in the whey group, only 54% of the rats developed breast cancer. The researchers had no idea what was causing the difference. A number of studies have shown that eating whole protein, such as tofu, lower the risk of breast cancer in premenopausal women, but eating tofu was no advantage for postmenopausal women.
A big part of the advantage that soy brings may be that soy protein is eaten instead of meat, with its saturated fat. The traditional Japanese diet had only 8% of the calories in fat. In the U.S., we think a low fat diet is 30% of total calories! But in a study of women in China, there was no association between eating soy and the risk of getting breast cancer. In a study in Singapore, eating a lot of soy reduced the risk in premenopausal women but not in postmenopausal women. The same thing happened in Japan among tofu eaters, though women who had a daily serving of miso soup appear to have half the risk of dying from breast cancer (perhaps because miso is fermented, more of the bad chemicals are eliminated and there may be more benefit). But among Asian-American women, eating tofu lowered the risk of breast cancer for everyone, possibly because the tofu replaced the saturated fat of animal protein.
Too often, soy seems to be no better than a placebo for fighting hot flashes, especially in the studies that isolate the isoflavones. But the placebo effect is strong when it comes to menopause. Women who ate a phytoestrogen rich diet for 12 weeks in a study that had no placebo control group said that their hot flashes and vaginal dryness improved. But a double blind, placebo study of women with breast cancer who were having bad hot flashes showed that soy phytoestrogens weren't any better than the placebo. In fact slightly more of the women preferred the placebo (37%) than preferred the soy (33%) for dealing with their symptoms. It's interesting that, while the data on the menopausal symptoms of Japanese women show that they don't have many hot flashes, they do get a lot of the other symptoms of menopause, such as shoulder stiffness, headache, back pain, and insomnia.
So, products of soy isoflavones alone are probably not the best approach to menopausal symptoms. However, whole soy products might offer a real improvement in hot flashes. Soy contains high levels of l-arginine, an amino acid. Arginine helps produce the chemical that allows blood vessels to relax. Hot flashes make blood vessels spasm, so arginine (in whole soy protein) might provide real help against hot flashes. One study using whole soy protein isolate in a powder found that hot flashes definitely improved more than a placebo. The whole soy protein reduced hot flashes by 45%. However, none of the other classic symptoms of menopause on the Kupperman Index (paresthesia, insomnia, nervousness, melancholia, vertigo, weakness, arthralgia, headaches, palpitations, or formication) were affected by the soy at all. So far, it's only estrogen that addresses all of these symptoms and reduces hot flashes by at least 83%.
So, what about the long-term benefits from estrogen--can soy replace those?
Though there is a debate about exactly what estrogen does to help the heart, everyone agrees that it improves cholesterol. It lowers total cholesterol and bad cholesterol and raises the good cholesterol. Luckily, if you have high cholesterol already, a soy-based diet can have the same effect, though milder. The FDA and the American Heart Association have both endorsed whole soy protein, in conjunction with a low fat diet, as a way to reduce cholesterol. Some of this good effect comes from substituting whole soy protein for the saturated fat of animal protein, as was shown in an analysis of many studies published in the New England Journal of Medicine. Epidemiological studies show that people who eat soy in their diets have lower cholesterol, but as soon as they do controlled clinical trials with phytoestrogens, they can't get the same effects.
As for other heart problems, isoflavones might help with artery muscle health. Genistein and other isoflavones do not seem to affect blood pressure, at least directly, for good or bad. One of the main reasons to look for an alternative to estrogen is the danger from blood clots. It's possible that genistein might help, but probably not from acting like an estrogen. It seems to block some enzymes that might cause platelets to clump.
There are not many studies yet of the long-term use of soy on osteoporosis. One study of a group taking 40 grams per day of soy protein with high levels of isoflavones added, or soy protein with moderate levels of isoflavones, or nonfat dry milk showed that the soy protein with high levels of isoflavones increased the bone mineral density of the lumbar region of the spine but had no effect on any other bones.
Apparently, it's not the same mechanism at work as estrogen. The benefit in the spine is from bone building, not bone preservation. However, there are some obvious problems with isoflavones as a way to prevent osteoporosis. Isoflavones are known calcium antagonists, that means that they attack calcium, which can't be good. Whole soy protein, on the other hand, has a high level of calcium so the effect might be counteracted by the whole protein.
One of the benefits from estrogen replacement is that mental function is maintained, in particular, some higher brain function, especially noun recognition. Unfortunately, soy doesn't have this effect and might have the opposite effect. In an epidemiological study (that is, the kind where you can't eliminate other things), 8,000 Japanese-American men who ate two or more servings of tofu a week for decades were more likely to show impairment and brain atrophy in old age. There were similar results in a study of 502 of their wives. There might be a number of clear reasons why soy might not be good for mental function. Estrogen is important for brain function. In men, an enzyme in the brain of men converts testosterone to estradiol. Soy prevents that conversion from happening because soy blocks the enzymes. Also, calcium-binding proteins protect the brain from degenerative disease, and soy blocks calcium. The hippocampus is the region of the brain that works a lot with learning and memory and it uses tyrosine kinase to do it. Soy interferes with tyrosine kinase.
And for mood, it's a bit scary as well. The brain uses tyrosine to make dopamine and norepinephrine, brain chemicals that create alertness and activity. One cause of depression is low levels of these two chemicals. Soy disrupts tyrosine so dopamine and norepinephrine levels drop. Miso and tempeh, and to some extent tofu are made in ways that lower these effects on tyrosine.
Soy is notoriously hard to digest. It blocks the enzymes that are needed to digest protein. This causes a lot of unpleasantness. Soy also has high levels of phytic acid, which can block calcium, magnesium, iron, and zinc, all of which are crucial minerals. Again, miso, tempeh, and tofu are made in ways that lower phytic acid. Intestinal bacteria play an important role in processing soy, so eating yogurt or acidophilus might help.
In addition, isolate soy protein powders seem particularly hard to digest. One study using these powders found that 25% of the women had to drop out of the study because of nausea, vomiting, bloating, constipation, and other complaints. This seemed to be a problem with the powder itself, rather than the soy, because women in the control group had problems too.
For women in the Hormone Jungle, with disrupted endocrine systems, the questions about isoflavones as antithyroid agents are very important. If a lot of soy is eaten, but even more if concentrated powders or isoflavones in a pill are taken, the effect on thyroid levels have to be watched carefully. If taken at high enough levels for long enough, the effect on the thyroid might be irreversible. A number studies have shown that soy and its isoflavones genistein and daidzein can induce goiter. A study in Japan that had people eating 30 grams of soybeans a day for three months showed that half developed thyroid problems. A month after stopping soybeans, all were back to normal. There're even links to thyroid cancer. The FDA, in deciding whether soy growers and manufacturers could market soy with a health claim, said the effects of soy on thyroid function weren't proven. The Japanese study was presented to them as an abstract and not as a full article, they rejected all the studies that show that babies raised on soy formulas have thyroid problems because these were not infant formulas, and pointed out the remaining studies are rat studies. But two of the FDA's own researchers, Daniel Doerge and Daniel Sheehan, at the FDA's National Center for Toxicological Research, submitted a formal comment against the ruling, urging caution in consuming soy, especially soy isoflavones, saying they had serious concerns about the effects on thyroid, among other concerns.
Genistein, one of the main isoflavones in soy, is so strong at suppressing the immune system that it's being recommended as a medicine to prevent graft rejection in surgery patients. There are some indications that high soy use may increase the risk for stomach, esophageal, and pancreatic cancers. There's some indication that genistein can break DNA strands, which can't be good.
Kinds of Soy
So, whole soy, especially as a substitute for meat, seems to be the best bet, even a good thing. The FDA decided that 25 grams of soy protein a day was a good goal. Given all the doubts and possible problems, products of concentrated isoflavones don't seem to be a good idea.
Whole soy protein powders and similar isolated soy protein products may, depending on the way they are processed, have phytic acid, enzyme inhibitors, tyrosine kinase, or an increase in an alkaline by-product. They also may strip out the isoflavones altogether. So, use processed soy with moderation, or investigate the brand to see how it is processed.
The bad things in soy are reduced by fermentation. So tempeh and miso are the best kinds of soy to use. The process of making tofu also decreases the bad stuff, though the levels among individual brands of tofu are wildly different. These three are the best choices. An unknown factor is the large percentage of soy that is now genetically modified, another argument for moderation (or organic varieties).
The levels of soy protein in some readily available products are
Tofu, 4 oz., 8-13 grams
Soy flour, 1 oz., = 10-13 grams
Soy milk, 8 oz., = 4-10 grams.
It seems clear, at this time, that soy should be used with moderation and as a whole food, especially miso and tempeh. If you're looking for isoflavones, using a red clover tea or tincture might be a better approach. Red clover avoids the phytic acid and enzyme inhibitors and has higher levels of Biochanin A, an isoflavone with benefits of its own. And red clover blocks both estrogen receptor cells and progesterone receptor cells, so it might increase whatever cancer-inhibiting force these chemicals might prove to have. This is a hot area of research, so the picture should get a lot clearer in a year or so.
This content was written by staff of HysterSisters.com by non-medical professionals based on discussions, resources and input from other patients for the purpose of patient-to-patient support.
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