Making Sense of Soy

(Originally published as a newsletter for The Dragontree Holistic Day Spa)

The soybean is an amazingly useful, versatile plant. It has been manufactured into everything from printing inks, plastics, and textiles, to a fire-extinguishing foam. Soybean oil and soy protein have found their way into an enormous portion of manufactured foods. Soy products have been cherished as foods for thousands of years in East Asia. Currently, however, the United States produces far more soy beans than Asia does, and we are also the biggest global consumers of soy.

Big claims have been made of soy’s health benefits, including protecting against heart disease, lessening symptoms of menopause, reducing bone loss in osteoporosis, reducing the risk and progression of breast and prostate cancers, and possibly reducing risk of colon cancer. In 1999, the FDA allowed food makers to begin labeling foods which contain 6.25 grams of soy protein per serving as “heart healthy.” Soybeans are a “complete” protein, as they contain all the essential amino acids our bodies cannot manufacture. There is a scale called the Protein Digestibility Corrected Amino Acid Score (PDCAAS) which ranks the quality of protein sources based on their amino acid composition and how usable they are by the human body. On this scale, isolated soy protein is at the top of the list (along with whey and egg whites), and whole soy beans are at 91 out of 100 – meaning both are considered excellent proteins. Soy beans also contain large amounts of calcium and potassium.

In stark contrast to these praises are the many negative claims about soy: that it reduces function of the thyroid gland, increases risk of breast cancer and rate of tumor growth, does not improve menopausal symptoms or osteoporosis, is harmful as a baby formula, causes brain shrinkage and memory loss, binds up minerals in the gut and makes them unusable, interferes with digestion, and is altogether unfit for human consumption. The details of this great debate would take pages to cover.

The focus of much of the attention is a group of chemicals called soy isoflavones, sometimes termed “phytoestrogens” (“phyto” means plant) because they can bind to estrogen receptors on cells. Since many breast cancers grow in response to estrogen, women with this disease are typically prescribed a drug that blocks estrogen receptors so that estrogen cannot plug into them and stimulate tumor growth. Soy proponents say soy isoflavones occupy these receptors, keeping estrogen out. Opponents say soy isoflavones act just like low doses of estrogen, potentially stimulating tumor growth the same way estrogen does.

How do we make sense of all this? Well, there aren’t a lot of solid answers. So far, the jury is out on most of the research. There is very little credible research relating soy to the medical conditions mentioned above – good or bad. Soy has not been consistently demonstrated to be of significant value for hot flashes or osteoporosis. For both conditions, there have been studies showing that soy isoflavones (genistein in particular) are beneficial, but there are also studies that showed no benefit. The link between soy consumption and memory loss has only been mentioned in one study, which some have criticized as being poorly executed.

The data linking soy to a modest decline in LDLs (“bad” cholesterol) and total cholesterol is pretty clear. One study of nearly 5000 Japanese men and women showed that those who ate the most soy had the lowest cholesterol levels. However, many people question the value of cholesterol levels as a useful predictor of cardiovascular disease. There is also research indicating that Asians who eat lots of soy (up to 55 grams a day – or two ounces) have lower rates of heart disease than those who eat more of a Western diet, with less than five grams of soy a day. The American Heart Association (AHA) now recommends that people add 25 grams of soy protein to their diet each day. Despite the research and the AHA recommendation, I think there are factors that may not have been adequately considered, such as, what is a person not eating when they opt for soy. What if the key is that soy consumers eat less meat? Or that they eat soy because they believe it is healthy – and they are more broadly committed to being healthy than the non-soy eaters are? 

As for the link between soy consumption and breast cancer, although people on opposing sides are making polar opposite claims – that soy either causes more breast cancer or that it reduces risk of breast cancer – we have a little bit more to go on here. Some studies indicate that soy may interfere with the effect of the estrogen-blocking drug tamoxifen, and certain test tube- (in vitro) and animal-based studies indicate the potential for soy to provoke breast cancer growth. However, soy isoflavones also appear to have the ability to inhibit tumor growth. And one of the most thorough studies to date showed that in post-menopausal women who’d had breast cancer, those with the highest rates of soy consumption actually had the lowest rates of recurrence. Women who consumed the least soy had the highest rates of recurrence.

Part of the confusion stems from the unfortunate term, “phytoestrogen.” It was coined before we really understood the implications (actually, we’re still not entirely clear on how these compounds affect the body) and the term just stuck. In fact, no plants produce human hormones. There is no estrogen in any plant, and nothing that reliably converts to estrogen in the body in any significant amount. And, while there are plant compounds that bind to estrogen receptors on cells, people tend to think about this action too simplistically. When a compound binds to a receptor, it’s like putting a key into the ignition of a car. Just inserting the key doesn’t start the car. In the case of soy and estrogen receptors, it may be that the isoflavones occupy these receptors (“inserting the key”) without activating cell growth (“turning the key”). It may even be that they deactivate cell growth when they plug in. In any case, it appears to be safe for women to consume soy, and it may even be beneficial.

It has been suggested that soy is also beneficial in other hormone sensitive cancers, such as that of the prostate and uterus. But the research here is even less clear. For instance, rates of prostate cancer are about the same in Asian and Western countries, but Asian men (who eat more soy) are less likely to die from it. In my opinion, this is a flimsy connection.

I believe we can say with some certainty that the negative allegations about soy’s digestibility are true. Gastric sensitivity to it is very common. Many people experience gastric upset and gas from eating it. These folks would do well to avoid it. If you fart a lot and you eat soy products on a regular basis, the soy – whether as tofu, soy milk, veggie burgers, soy hot dogs, other fake meats, protein bars, tempeh, edemame, miso, soy sauce, tamari, natto, soy ice cream, or another form – is probably the first thing you should consider cutting out. Soy formulas are also not great for babies as soy protein is quite different from human milk, and in an underdeveloped digestive system, the same sensitivity that plagues many adults may result in painful colic for a baby. If breast feeding is absolutely not an option, parents should first try a goat milk-based formula.

As for the claims that soy interferes with certain nutrients and enzymes, there is some truth to this. Soy is a known “goitrogen” (along with flax, raw broccoli, cabbage, and a handful of other healthy foods). It can interfere with the absorption of iodine, which the thyroid gland uses to make thyroid hormone. Thyroid hormone has many functions in the body, including contributing to the regulation of our metabolism, hair growth, sex drive, mood, body temperature, and more. Soy consumption seems to have the potential (though a low potential) to provoke hypothyroidism – low thyroid function – and to cause the development of a goiter (thyroid enlargement). Getting enough dietary iodine probably counteracts this risk. However, many parts of the country have very low iodine in the soil, so using iodized salt and eating sea vegetables is important.

Soy also contains a significant amount of a substance called phytic acid (or phytates), which is something of a mixed bag. On the good side, phytic acid is an anti-oxidant and it could possibly be of benefit in osteoporosis. On the down side, phytic acid can bind up certain essential minerals, including zinc, iron, magnesium, and calcium, rendering them unusable by the body. It can also bind up vitamin B3 (niacin). For this reason it is sometimes referred to as an “anti-nutrient.” People with low mineral intake should probably try to reduce their phytic acid consumption.

Thorough cooking is helpful at breaking down some of the phytic acid, and fermenting or sprouting soybeans is even more effective. (Another good reason to cook soybeans thoroughly is that in their raw state they are toxic and an inhibitor of the enzyme trypsin, which is essential for the digestion of protein.) You could also try taking a digestive enzyme complex containing the enzyme phytase when you consume soy. Phytase break down phytic acid. Ruminants – animals that chew their cud – such as cows, deer, goats, and sheep, have phytase in their stomachs. Humans, sadly, do not. By the way, soybeans aren’t the only thing we eat that contains phytic acid. It also occurs in the hulls of many other seeds, grains, and nuts – flax seed, sesame, and pinto beans all have more than soy.

Another reason for soy’s bad rap is that, as of 2010, about 93% of the soy grown in the U.S. is genetically modified (GM). The environmental and health consequences of GM soy are not yet known, although one recent study showed that pigs that were fed GM soy and corn developed much more inflammation in their stomachs as compared to pigs that were fed the same amounts of non-GM soy and corn. (Aside: lots of the pigs in both groups had stomach inflammation, and I think this highlights the fact that farm animals are not meant to survive on soy and corn – a diet that is dramatically different from what they would eat in the wild – and people should probably be moderate in their consumption of these potential irritants, too.) There are two things we can say for certain about GM soy, though. One, it’s produced predominantly by a corporation (Monsanto) that cares little about their impact on the planet and its inhabitants. Two, GM soy is basically guaranteed to be contaminated with the herbicide glyphosate (Round-Up). Monsanto developed GM soy to be resistant to glyphosate, so farmers can spray their soy fields with it and kill all the weeds without affecting their soy crop. However, the consumers of this soy may not be so lucky. Long term consumption of glyphosate is not good.

Unless it is specifically labeled as “non-GMO,” (the “O” in GMO stands for Organism) assume all soy is genetically modified, and avoid it whenever possible. If you get tofu or tempeh at a restaurant, unless it’s a restaurant that specifically advertises as having organic ingredients, there’s no reason to believe they aren’t using low quality, genetically modified soy. As a former restaurant owner, I can tell you, one of the most important ways for restaurants to stay profitable is to keep their food costs down. They almost always choose the best balance of low cost and decent quality, and low cost usually wins. If a low quality ingredient can’t be readily perceived as low quality in the final dish by the average customer, this ingredient will be considered acceptable by most restaurants. Why would a restaurant pay more for a higher quality ingredient if most people won’t be able to tell the difference? The point is, you’re rarely likely to get non-GM soy at a restaurant.

Another drawback of soy, even if it’s not genetically modified, is that many soy products are highly processed. While fermentation of soy beans tends to make them more digestible (as in miso, soy sauce/tamari, and tempeh), rendering textured, modified soy protein into meat-like substances is likely to produce food with very little life left in it. And while soy milk may help you avoid some of the drawbacks of cow milk, if it’s got sugar in it (AKA “evaporated cane juice”) its not healthy stuff. I’ve had a soy latte from Starbucks that tasted like it had several spoonfuls of sugar in it. Guess where it came from … the soy milk. And remember, if you consume soy milk, it is, after all, bean juice. Don’t be surprised if you need to leave the room after having some.

So, in conclusion, and I say this about every food, it’s important to determine your own ability to tolerate soy. If it makes you gassy, it’s probably not suitable for you. If you have a known sensitivity to it, it’s definitely not suitable for you. If you handle it well, it’s probably just fine to consume it in moderate amounts. Get it organic and eat it in minimally processed forms. Stay away from fake meats, like “veggie sausage.” They’re garbage. And keep in mind that “moderate” may be less than you think. In studies that categorized Asians by how much soy they ate, heavy consumers actually had only about two ounces of soy protein a day. The average Asian, it turns out, only eats an average of about 1/3 of an ounce per day. Since it’s added to a huge range of foods, look at labels. Remember: don’t listen to zealots on either side of an issue, read your food labels, question highly promoted trends in eating, and always savor your food.