When I used to work at the juice bar in Hollywood, girls (for the most part) would come into the store asking about being vegetarian or vegan. I remember one story in particular confessed by a naive customer . She had recently "gone vegan" and she began replacing almost all her dairy and meat items with soy products. She was gaining weight, was moody and lathergic. Why? Wasn't she supposed to go vegan, drop meat, and all the sudden drop the weight along with it?
There are a few common misconceptions about soy that I hope to clear up.
How much soy is too much? Is it dangerous for babies or kids to consume? Are there benefits to consuming soy?
Firstly, a "safe" amount of soy to consume is debatable. Each person is unique in the way we digest foods and what we are sensitive to.
Foods that contain whole soy can be a good source of protein for vegetarians and vegans because they provide all the amino acids — a type of nutrient — that people need to stay healthy. (People who eat meat get all their essential amino acids from animal products.) Soy is sometimes added to foods like breads, cereals, and meat products, and used as a meat substitute in vegetarian products such as soy burgers and soy hot dogs.
Here are some common soy products/foods:
Edamame: soy beans that have been boiled in water.
Soy Milk: a beverage made from soybeans, mixed with water. can be a good alternative to dairy. (not for children and definitely not as a formula or breast milk replacement)
Tofu: the white, soft processed soy milk coagulated with a chemical- (such as calcium sulfate) similar process to cheese. Should probably avoid this, almost all is genetically modified.
Tempeh: the natural fermented version of soy. Considered the healthiest of all soy varieties.
Soy Sauce: the soy contained in this salty mix is actually comparatively low.
Soy Lecithin: a great emulsifier (promotes solidity) for many different products. Research is showing many positive health benefits including lowering cholesterol, improving brain functioning and memory and aiding in the breaking down of fats to be used as energy. Check before using to make sure you are not allergic, allergies can cause many complications and side effects.
Soy protein: unless you know differently, most soy protein is produced in a large commercial factory and is typically in an aluminum container which isn't safe. MSG is often added as well.
The FDA has authorized use of health claims about the role of soy protein in reducing the risk of coronary heart disease (CHD) on labeling of foods containing soy protein. This final rule is based on the FDA's conclusion that foods containing soy protein included in a diet low in saturated fat and cholesterol may reduce the risk of CHD by lowering blood cholesterol levels. Recent clinical trials have shown that consumption of soy protein compared to other proteins such as those from milk or meat, can lower total and LDL-cholesterol levels.
The real health benefits of soy might lie in its nutritional content and the fact that people often use soy foods as a replacement for less-healthy foods. Soy foods are a great source of protein and contain other important nutrients, such as fiber, B vitamins, and omega-3 fatty acids. Foods containing soy protein are also a healthy alternative to meats and other animal products that contain cholesterol and saturated fat.
But soy's greatest advantage may lie in it being a rich source of isoflavones - plant hormones that have been linked to several health benefits. For example, researchers believe a soy-based diet could account for Asia's low rate of heart disease. The leading cause of death in the United States, one of the risk factors for coronary heart disease is high levels of LDL or "bad" cholesterol. In recent clinical trials, men and women with high LDL levels were able to reduce them by consuming soy over an extended period. In October, the FDA (Food and Drug Administration) announced that certain foods containing soy will be able to claim that they may help reduce the risk of coronary heart disease. (To qualify, the food must contain at least 6.25 grams of soy per serving, one-quarter of the daily recommended serving of 25 grams). And that's not all. It is possible that isoflavones may help prevent bone loss, therefore lowering the risk of osteoporosis.
Isoflavones have been credited with reducing the rates of certain types of cancer. For example, there is some evidence that eating soy may reduce your risk of developing breast cancer. And isoflavones were the primary ingredients in a "smart bomb" - a drug that University of Minnesota scientists believe holds the potential to cure childhood leukemia. Finally, a study by the Cancer Research Center of Hawaii indicates that consumption of soy products may help reduce the risk of uterine cancer.
Soy milk, soy burgers, and soy snacks are available in many supermarkets and specialty stores. When selecting soy foods, be sure to check food labels to be sure that the food is a good source of soy protein and is low in saturated fat, cholesterol, and added sugar.
If you're interested in eating more soy, introduce it into your diet gradually. And remember that the key to good health is to eat a wide variety of nutritious foods without focusing too much on any one food.
Possible Negative Side Effects?
More to the point, the real problem is not whether soy is inherently bad (after all, people have been consuming plants with hormones for centuries) but that no one is sure how much soy it is safe to consume. While Asians have been consuming soy for centuries, there have been conflicting claims about how much soy they consume. Nonetheless, since soy is turning up in everything from cereal to ice cream, we may be consuming far higher amounts than is normally found in the Asian diet, without any real idea of the consequences. A related issue is that modern preparation methods for soy products may increase the health risks. For example, some companies use chemical hydrolization instead of traditional fermentation methods to make soy sauce. It's something to think about.
Time to get science-y: Apart from the question as to whether soy even has demonstrable health benefits, there are long-standing concerns that soy may have negative effects on thyroid function and hormonal health. Soy falls into a category of foods known as goitrogens -- vegetables, grains and foods that promote formation of goiter -- an enlarged thyroid. Some goitrogens also have a definite antithyroid effect, and appear to be able to slow thyroid function, and in some cases, trigger thyroid disease. A huge danger is soy infant formula, this should never be given to your child in such a vulnerable age. Infants that consume soy have up to 20,000 times the amount of estrogen circulating in their blood stream.
Most importantly, soy is rated as the second most allergenic food to humans, with the first being peanuts. So before you go soy crazy, check it out with your doc to be sure you aren't allergic.
In January 2006 an American Heart Association review (in the journal "Circulation") of a decade-long study of soy protein benefits casts doubt on the FDA allowed "Heart Healthy" claim for soy protein. The panel also found that soy isoflavones do not reduce post menopause "hot flashes" in women, nor do isoflavones help prevent cancers of the breast, uterus, or prostate. Thus, soy isoflavones in the form of supplements is not recommended. Among the conclusions, the authors state, "In contrast, soy products such as tofu, soy butter, soy nuts, or some soy burgers should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fibre, vitamins, and minerals and low content of saturated fat. Using these and other soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health." -- Sacks et al. 113 (7): 1034
The common amounts of phytoestrogens in soy beans are not to be compared to concentrated estrogen. One study followed over 3000 Japanese men between 1965 and 1999, and that showed a positive correlation between brain atrophy and consumption of tofu.
A study on elderly Indonesian men and women found that tempeh consumption was independently related to better memory.
Lastly, soy contains trypsin inhibitors, which means the proteins in soy are not as absorbent by the body. They block the enzyme trypsin, which is secreted by the pancreas and breaks down protein in the small intestine. Basically what this means is that your body will not be able to properly break down proteins unless you take extra enzymes separately.