I have many, many cookbooks in my house. Half promote soy products as healthy. The other half recommend avoiding soy because new research shows it can be harmful. Which are right?
What Is Soy?
As many farmers around the world can attest to, soy is a product of the soybean. Soybeans have been grown in China since almost 3,000 BC and valued as a crop. The soybean plant is a short bush that grows podded beans. Soybeans were brought to the US in the mid-1700s. They are eaten whole as a food, squashed for their oil or, most often, mashed to form a base for other food products. The US currently has 65 million acres of soybean planted to support the gigantic processed food industry. 60% of all food on store shelves contain soy.
As a side note, the asians did not by and large EAT their soy. They fermented it for up to 3 years and then used it as a light condiment. 65% of the asian diet consisted of fish (Japan) or pork (China) - i.e. natural meats. The soy intake was around 2 Tbsp a day - a far cry from the huge amounts of "modified soy" found in a modern developed country diet.
Soy Consumption in China and Japan
Why is Soy Valued?
Unlike just about any other plant, soybeans are high in protein and iron. This makes them especially valuable for vegetarians and vegans, but also of interest to anyone who cannot afford to eat meat or wants an alternative. In rural communities where animals were incredibly expensive, soybeans were a cheap alternative.
Soy's Health Claims
Soy has been shown to help lower cholesterol when taken as part of a healthy diet. The diet included 23g/day of soy protein powder. Another study in 2003 found that soy helped reduce the risk of cancer in mice, results which they attributed to the isoflavones in soy.
Current Issues with Soy
Often, soybeans are used as a protein substitute in vegetarian diets because they are high in iron. Women especially need adequate iron intake to remain healthy. However, a study done in 2001 shows that only 27% or so of the iron in soybeans is actually absorbed. Previous studies put the absorption amount as low as 2%. Both agree that women not eating meat should take vitamins to ensure adequate iron intake.
There are "phytates" in soy which block a body from properly absorbing zinc. So eating soy *while you eat* other plant materials means that you won't absorb the zinc in those plants. It doesn't affect the zinc IN your body already but it does harm your ability to absorb new zinc while you are eating soy. Meaning either you need some non-soy-eating times to get your zinc into you, or you need to take vitamins at a different time of day to compensate. Zinc is critical for proper brain functioning. Read about Soy, Alzheimers and Brain Aging. Phytates also interfere with absorption of calcium, magnesium and iron.
Two thirds of soybean oils in use are hydrogenated. Read more about Trans Fatty Acids to learn about the risks of hyrogenated oils. Even if you eat soy in other manners, you should try to avoid using soybean oil.
Soy has been shown to interfere with the thyroid and immune system. A doctor at the National Center for Toxicological Research noted in a letter to the FDA that "Infants consuming soy infant formula rich in isoflavones have about a two-fold risk of developing [goiter and autoimmune thyroiditis]". Isoflavones have been bred into soybeans in modern times and are an estrogen-like compound. In addition, the high isoflavone levels in soy products have been associated with earlier puberty rates in girls in developed countries. 1% of girls have some signs as early as age 3.
Soy formulas often have high levels of manganese in them, which can harm the brains of infants and even lead to ADHD problems. Some soy formula manufacturers are putting warning labels on their products as a result.
The US grows more soybeans than any other country, and over half of all US soybeans have been genetically modified to handle "roundup" - a weed killer. Unfortunately, while this was meant to reduce the pesticides needed, studies have shown that actually the soybeans now get up to 5 times as much pesticide laid on them as before because the crops are so valuable.
Many people are allergic to soy, just as people are intolerant of lactose and wheat products. This can cause bloating and other symptoms. It's always wise to try going without something for 2 weeks to see how you feel - and then to reintroduce it slowly to see how you react. Unfortunately this can be VERY tough with soy since just about every processed food could have soy in it. Because it is such a cheap bulker, it is used in everything from gum to cereal to cardboard.
Because the soy industry is a multi-million-dollar moneymaker, it is easy to find studies backed by this industry that support their claims of 100% worry free safety. But as in all things regarding your health, it is important to evaluate your options and to balance your food in moderation. The more you can eat fresh, natural foods, and avoid processed foods of any kind, the better off you will be.
Trans Fatty Acids
Soy Consumption in China and Japan
Soy, Alzheimers and Brain Aging
Soy and Fertility Problems
Lisa Shea's Library of Low Carb Books