Soy: The Good, the Bad and the Best

Soy products are growing in popularity in the United States. However, there are a few big controversies over soy. How safe is soy? And how much should you be eating?

It’s hard to visit a supermarket without finding soybeans, soy milk, soy cheese, and the entire spectrum of soy products. However, there are several controversies concerning soy and its safety. What are these controversies? Should you avoid soy – or enjoy it?

Concern #1: Soy will give me breast cancer.

Verdict: One may associate soy with breast cancer because science associates excess estrogen exposure to breast cancer. Soy contains a group of natural plant chemicals called isoflavones. They are found in small amounts in a number of legumes, grains and vegetables; however, soybeans are the most concentrated source of isoflavones in our diet. Since isoflavones bind to estrogen receptors, they can have similar effects to estrogen, but not nearly as strong as animal-based estrogen. Human estrogen is over 1000-times stronger.

However, isoflavones also have non-hormonal effects on the body that are very positive. They help regulate cell growth, which actually safeguards against some cancers. They also play roles in regulating cholesterol levels. Multiple studies on soy have associated eating plenty of soy with lower rates of breast cancer, especially in Asian populations. Furthermore, there are lower rates of breast cancer in many Asian countries, where diets are higher in soy.

Concern #2: Soy is dangerous for my heart.

Verdict: Soy is actually good for your heart. One study suggests that eating foods that contain isoflavones (like soy products) every day may help young adults lower their blood pressure, particularly African-Americans. It is thought that the isoflavones work by encouraging your body to produce nitric oxide, which helps to dilate blood vessels and reduce the pressure created by blood against the vessel walls.

Whole soy foods contain high levels of healthy protein and fiber. Fiber helps to reduce bad cholesterol. Plus, soy is a much better source of protein for your heart than saturated-fat-rich animal-derived foods.

Concern #3: Soy is bad for my thyroid.

Verdict: The available research suggests that soy may not affect thyroid function, especially in those who have a normal thyroid.

However, soy may be dangerous for those who already have an existing thyroid problem and take medications for their thyroid. This is because soy products may interfere with how the body absorbs the medication in the GI tract, making it less effective. A general tip for those taking thyroid medication would be to wait a few hours between taking your thyroid medication and consuming any soy products as soy tends to alter how your intestines absorb the medication. Talk to your physician about soy and any thyroid medications you may be taking.

Soy Foods: Bad, Better, Best


Like all foods, you want to consume soy in moderation. One to two servings of whole and fermented soy foods is recommended. One average serving is a half-cup of tofu or 1 cup of soy milk.

But not all soy products are created equal. Thanks to savvy marketing and nutritional buzzwords, most of us think we are automatically doing a good thing for ourselves when we choose soy foods. Unfortunately, this isn’t always true. Make the right selections to ensure you’re getting the best and purest forms of nutrition from soy foods and soy products.

Avoid: Soy Burgers, Soy Energy Bars and “Frankensoy” Products

Soy burgers and soy energy bars are not your best choice. Why? Because these foods are made of processed forms of soy. Look for the words “soy protein” on the label – this means the soy it contains is processed. When soy is processed, the nutrients are stripped away. When it comes to this, nutritionists consider it to be a “ghost” of a health food.

Other highly processed "frankensoy" products look and taste just like frankfurters, steak strips, cheese and other foods. Avoid these. Foods like these are also likely to be loaded with added sugars, fats and refined flours.

Choose Wisely: Soy Milk

This is a tricky one. You just have to choose the right kind to reap soy’s true benefits. Soy milk is the liquid residue of cooked soybeans. However, many types of soy milk on the market are processed and not made with real soy beans. Fresh soy milk is best, and available at certain health food stores. If this isn’t easily found, you want to choose whole-bean soy milk – to avoid soy milk made from soy protein or soy isolate.

Also, be wary of a far-off expiration date. While it may seem like a good deal, the further out the expiration date, the more likely the soy milk will contain additives to extend its shelf-life. You will also want to check the label for hidden or added sugars. Look for “brown rice syrup” or “evaporated cane juice” – especially if they are one of the first ingredients listed. One cup of this kind of soymilk can easily wind up being 100 calories more than a cup of skim milk. 

Your Best Bet: Edamame, Tofu and Fermented Soy Foods

Whole soy foods are your best bet. They are not processed, so they retain the most nutritional benefits.

You are probably already familiar with foods like tofu and edamame. Tofu, soft and firm blocks of coagulated soymilk, is an Asian staple that is easy to prepare and packed with calcium. It's also high in omega-3 fats, which ensure normal brain function and lower the risk of dementia. Give tofu a try with this simple Asian stir-fry.

Edamame, or young green soybeans, are a great source of protein. Getting an adequate amount of protein in your diet can actually give your metabolism a boost. Just one half-cup serving of edamame provides 8 grams of protein – triple the amount of protein you’d get from most other vegetables. They steam in minutes and are perfect to eat as a snack or add to a salad. Try this fried rice dish made with edamame.

Other whole soy options include varieties like tempeh, miso and natto, made of fermented cooked soybeans. The fermentation allows nutrients to be more easily absorbed into the body, as fermented foods are brimming with good-for-your-belly probiotics, which help keep our gut flora healthy. 

Tempeh is a high-protein source of nutrients like vitamins B2, B6, and B3, and minerals magnesium, copper, iron, manganese, and phosphorous. In addition, it is a good source of monounsaturated fats.

Miso is rich in vitamin B12, which is a power player when it comes to metabolizing fats and carbohydrates. You can purchase miso pastes and soup in supermarkets. Be sure to purchase the low-sodium variety.

Natto is a sticky paste made by adding healthy bacteria to lightly cooked soybeans and fermenting. Natto is a powerful food rich in the enzyme nattokinase, which has been shown to reduce the risk of blood clots and help break up the plaque associated with Alzheimer’s disease. In Japan, people routinely enjoy natto for breakfast, served on top of rice with an egg split over it. You can find it at health food stories, Asian markets, or online.

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Presented by USANA.