The Dark Side of Soy

Is America's favorite health food making us sick?

Tofu

Tofu

Image by Mo Riza, licensed under Creative Commons.

Content Tools

As someone who is conscious of her health, I spent 13 years cultivating a vegetarian diet. I took time to plan and balance meals that included products such as soy milk, soy yogurt, tofu, and Chick'n patties. I pored over labels looking for words I couldn't pronounce--occasionally one or two would pop up. Soy protein isolate? Great! They've isolated the protein from the soybean to make it more concentrated. Hydrolyzed soy protein? I never successfully rationalized that one, but I wasn't too worried. After all, in 1999 the Food and Drug Administration (FDA) approved labeling I found on nearly every soy product I purchased: 'Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.' Soy ingredients weren't only safe--they were beneficial.

After years of consuming various forms of soy nearly every day, I felt reasonably fit, but somewhere along the line I'd stopped menstruating. I couldn't figure out why my stomach became so upset after I ate edamame or why I was often moody and bloated. It didn't occur to me at the time to question soy, heart protector and miracle food.

When I began studying holistic health and nutrition, I kept running across risks associated with eating soy. Endocrine disruption? Check. Digestive problems? Check. I researched soy's deleterious effects on thyroid, fertility, hormones, sex drive, digestion, and even its potential to contribute to certain cancers. For every study that proved a connection between soy and reduced disease risk another cropped up to challenge the claims. What was going on?

'Studies showing the dark side of soy date back 100 years,' says clinical nutritionist Kaayla Daniel, author of The Whole Soy Story (New Trends, 2005). 'The 1999 FDA-approved health claim pleased big business, despite massive evidence showing risks associated with soy, and against the protest of the FDA's own top scientists. Soy is a $4 billion [U.S.] industry that's taken these health claims to the bank.' Besides promoting heart health, the industry says, soy can alleviate symptoms associated with menopause, reduce the risk of certain cancers, and lower levels of LDL, the 'bad' cholesterol.

Epidemiological studies have shown that Asians, particularly in Japan and China, have a lower incidence of breast and prostate cancer than people in the United States, and many of these studies credit a traditional diet that includes soy. But Asian diets include small amounts--about nine grams a day--of primarily fermented soy products, such as miso, natto, and tempeh, and some tofu. Fermenting soy creates health-promoting probiotics, the good bacteria our bodies need to maintain digestive and overall wellness. By contrast, in the United States, processed soy food snacks or shakes can contain over 20 grams of nonfermented soy protein in one serving.

'There is important information on the cancer-protective values of soy,' says clinical nutritionist Ed Bauman, head of Bauman Clinic in Sebastopol, California, and director of Bauman College. Bauman cautions against painting the bean with a broad brush. 'As with any food, it can have benefits in one system and detriments in another. [An individual who is sensitive to it] may have an adverse response to soy. And not all soy is alike,' he adds, referring to processing methods and quality.

'Soy is not a food that is native to North America or Europe, and you have issues when you move food from one part of the world to another,' Bauman says. 'We fare better when we eat according to our ethnicity. Soy is a viable food, but we need to look at how it's used.'

Once considered a small-scale poverty food, soy exploded onto the American market. Studies--some funded by the industry--promoted soy's ability to lower disease risk while absolving guilt associated with eating meat. 'The soy industry has come a long way from when hippies were boiling up the beans,' says Daniel.

These days the industry has discovered ways to use every part of the bean for profit. Soy oil has become the base for most vegetable oils; soy lecithin, the waste product left over after the soybean is processed, is used as an emulsifier; soy flour appears in baked and packaged goods; different forms of processed soy protein are added to everything from animal feed to muscle-building protein powders. 'Soy protein isolate was invented for use in cardboard,' Daniel says. 'It hasn't actually been approved as a food ingredient.'

Soy is everywhere in our food supply, as the star in cereals and health-promoting foods and hidden in processed foods. Even if you read every label and avoid cardboard boxes, you are likely to find soy in your supplements and vitamins (look out for vitamin E derived from soy oil), in foods such as canned tuna, soups, sauces, breads, meats (injected under poultry skin), and chocolate, and in pet food and body-care products. It hides in tofu dogs under aliases such as textured vegetable protein, hydrolyzed vegetable protein, and lecithin--which is troubling, since the processing required to hydrolyze soy protein into vegetable protein produces excitotoxins such as glutamate (think MSG) and aspartate (a component of aspartame), which cause brain-cell death.

Soy also is one of the foods--in addition to wheat, corn, eggs, milk, nuts, and shellfish--most likely to cause allergic reactions. Most people equate food allergies with anaphylaxis, or a severe emergency immune response, but it is possible to have a subclinical sensitivity, which can lead to health problems over time (and is exacerbated by the lack of variety common in today's American diet).

'People can do an empirical food sensitivity test by eliminating the food for a period of time and reintroducing it to see if there's an immune response, but most don't do this,' says Bauman. 'Genetically modified (GM) soy is the most problematic, and that's probably what most people are eating if they're not paying attention. People can develop sensitivity to a food that has antigens or bacteria not originally in the food chain, as is the case with GM foods.'

Yet avoiding GM soy doesn't mean all is well, Daniel says: 'One question I get all the time is, ?What if I only eat organic soy?' The assumption is that GM soy is problematic and organic is fine. Certainly, organic is better, but the bottom line is that soybeans naturally contain plant estrogens, toxins, and antinutrients, and you can't remove those.'

The highest risk is for infants who are fed soy formula. 'It's the only thing they're eating, they're very small, and they're at a key stage developmentally,' says Daniel. 'The estrogens in soy will affect the hormonal development of these children, and it will certainly affect their growing brains, reproductive systems, and thyroids.' Soy formula also contains large amounts of manganese, which has been linked to attention deficit disorder and neurotoxicity in infants. The Israeli health ministry recently issued an advisory stating that infants should avoid soy formula altogether.

Antinutrients in soy block enzymes needed for digestion, and naturally occur-ring phytates block absorption of essential minerals. This is most worrisome for vegans and vegetarians who eat soy as their main source of protein, and for women in menopause who up their soy intake through supplements.

Soy contains phytochemicals--plant nutrients with disease-fighting activity--called isoflavones. Studies claim isoflavones can mimic the body's own estrogens, raising a woman's estrogen levels, which fall after menopause, causing hot flashes and other symptoms. On the other hand, isoflavones may also block the body's estrogens, which can help reduce high estrogen levels, therefore reducing risk for breast cancer or uterine cancer before menopause. (High estrogen levels have been linked to cancers of the reproductive system in women.)

Although soy's isoflavones may have an adaptogenic effect (contributing to an estrogen-boosting or -blocking effect where needed), they also have the potential to promote hormone-sensitive cancers in some people. Studies on the effects of isoflavones on human estrogen levels are conflicting, and it's possible that they affect people differently. In men, soy has been shown to lower testosterone levels and sex drive, according to Daniel.

Bauman believes processed soy foods are problematic but maintains that soy has beneficial hormone-mediating effects. 'People are largely convenience-driven,' he says. 'We're looking at this whole processed-food convenience market and we're making generalizations about a plant. Is soy the problem, or is it the handling and packaging and processing of the plant that's the problem?

'Primary sources of food are a good thing. Once there was a bean, but then it got cooked and squeezed and the pulp was separated out, and it was heated and processed for better shelf life and mouth feel. Soy milk is second or third level in terms of processing.'

Bauman's eating-for-health approach calls for a variety of natural and seasonal unprocessed whole foods, including soy in moderation, tailored to individual biochemistry and sensitivities. 'Using soy as part of a diet can bring relief for perimenopause, for example,' he says. 'Throw out the soy and you throw out the isoflavones.' (It is possible to obtain plant estrogens to a lesser extent from other foods, such as lima beans or flax.) 'The literature is extensive on the benefits of soy, and that should always be stated, just as the hazards should be. That's science. These studies are not ridiculous or contrived, but take a look at them. Who's funding them?' asks Bauman.

'There are a lot of problems with these studies,' Daniel says, adding that the 1999 heart health claim was an industry-funded initiative. 'Even if there is positive information, and even if these studies are well designed, we need to weigh that against the fact that we've also got really good studies showing the dangers. Better safe than sorry is the precautionary principle. Possible bene-fits are far outweighed by proven risks.'

Daniel and Bauman agree on the benefits of variety. 'My experience as a clinical nutritionist is that people who have a varied diet tend not to get into trouble,' says Daniel.

'We like to demonize certain foods in this society,' says Bauman. 'If you want to find a fault, you'll find it. The bottom line is: What is a healthy diet?'


Reprinted from Terrain (Spring 2007), published by Berkeley's Ecology Center. Dedicated to fine feature writing about environmental issues, Terrain is distributed free throughout Northern California. Subscriptions: $15/yr. (3 issues) from 2530 San Pablo Ave., Berkeley, CA 94702; www.ecologycenter.org/terrain.



Soy 'Nuggets'

Tofu
Soy milk, curdled and pressed into cubes of varying firmness. Often used as meat substitute. A nonfermented product, tofu contains antinutrients, which can block absorption of essential minerals.

Miso
Fermented soybean paste, used in soups and sauces. Rich in probiotics, good bacteria that aid vitamin absorption. Miso is high in sodium but is considered one of the healthiest soy products.

Soybean Oil
To extract oil, soybeans are superheated, ground, pressed, mixed with chemicals, and washed in a centrifuge. Soybean oil accounts for 80 percent of all liquid oils consumed annually in the United States.

Soy Milk
A processed beverage made of ground soybeans mixed with water and boiled, which removes some toxins. Sugar is added to improve flavor. An eight-ounce serving contains up to 35 milligrams of isoflavones, which may change estrogen levels and hormonal function.

Snack Food
Highly processed, a source of trans fat. Check your labels: Potato chips, tortilla crisps, and many other deep-fried things have been cooked in soy oil--straight up or partially hydrogenated.

Tempeh
Whole soybeans pressed into loaves, which are then fermented. Often used as a meat substitute. Tempeh is rich in B vitamins, minerals, and omega-3 fatty acids.

Fast Food
A source of hidden soy. Processed soy proteins extend some burgers and chicken (nuggets, patties, even 'grilled breasts'). Buns contain soy oil and to a lesser extent soy flour and lecithin. Soy oil also appears in dressings and dips, in American 'cheese,' and as the No. 2 ingredient in fries. There's even soy in Big Mac's secret sauce: Soybean oil nets top billing.

Edamame
Whole soybeans, commonly boiled in the pod and eaten as a snack. Most commercial edamame has been preheated to make digestion easier, but it still contains antinutrients.

Image by Mo Riza, licensed under Creative Commons



Want more? Read the rest of Utne Reader's July/August package on the secrets of soy:

  • How Much Is Too Much?
    Clinical nutritionist Kaayla Daniel on the Dos and Don'ts of soy consumption
    interview by Mary Vance, from Terrain
  • Whole New Diet
    A health-savvy cookbook shows how to get away from processed foods
    by Julie Hanus
  • Biofuel's Big Bean
    How large-scale soy is threatening the environment and a South American way of life
    by April Howard and Benjamin Dangl, from In These Times