Eating Soy – Good or Bad?


Sometimes, there’s never an easy answer. Take soy, for example. One moment you’ll be reading a wonderful report on its superfood properties and the next thing you know, there’s a news story about its toxic, hormone disrupting dangers.

Looking at the evidence on soy is extremely confusing and can send you on an endless loop of ‘good’ versus ‘bad.’ It would be impossible to give you a breakdown of all the complicated issues surrounding soy in a single blog post, but as it’s such a popular global food, I do want to begin to scratch the surface of the potential benefits and problems – Buckle up!

Good – Soy Lowers Cholesterol

Scientists initially became interested in the health benefits of consuming soy after observing that Asians have fewer heart attacks, instances of cardiovascular disease, cancers and milder menopause symptoms than Westerners. Obviously, Asians typically eat far more soy products than Westerners, so could there be a connection?

Although studies indicated a link between soy and lower cholesterol levels, it was a 1998 report in the American Journal of Clinical Nutrition that first cemented soy’s heart-friendly characteristics. In a controlled study, men who ate a low-fat diet for five weeks using soy as their main protein source saw their LDL cholesterol levels drop by up to 14 percent.

Bad – Soy Ages the Brain

So it’s all good news for soy lovers, right? Not quite. Despite the cholesterol-lowering effects of soy, further research now suggests eating too much could be harmful. Dr. Lon White, senior neuroepidemiologist at the University of Hawaii, worries that soy may speed up the aging of brain cells. His study found evidence that the brains of elderly people who ate tofu at least twice a week for 30 years were aging faster than normal.

Bad – Soy Dampens Thyroid Function

Another fear is that estrogen-like substances in soy called isoflavones may diminish the function of the thyroid – a gland which secretes hormones regulating growth and development. According to Dr. Larrian Gillespie, author of The Menopause Diet, consuming 40 milligrams of isoflavones a day can slow the production of thyroid hormone, and after a few weeks of regular consumption, women can feel fatigued and achy all over. Dr. Mark Messina, professor of nutrition at Loma Linda University in California says, “Healthy people should not consume more than 100 milligrams of isoflavones a day.” Four ounces (113 grams) of tofu contain about 25-30 milligrams of isoflavones. 

Good – Soy Prevents Breast and Prostate Cancers

But wait, here’s another twist! – According to some research, isoflavones could prevent the growth of estrogen-dependent breast cancer cells. That’s because isoflavones appear to encourage estrogen to be broken down quickly in the body. Before it lingers in the blood, stimulating cancer cells to grow, estrogen molecules pass out of the body through urine.

Furthermore, a 2009 analysis indicates that consumption of soy foods is associated with a reduction in prostate cancer risk in men, possibly by slowing the cancer cells from growing.

Should you eat Soy?

As you’ve probably gathered by now, the question of whether the health risks associated with soy consumption outweigh the benefits is a complicated one to answer. Another factor that must be considered is the distinction between traditionally fermented and unfermented soy products.

Let’s go right back to the start of this article and re-examine why Western science began to study soy consumption in the first place. For centuries, Asian people have been consuming soy products and enjoying their health benefits, but it’s fermented soy products they’re mainly consuming, such as soy sauce, natto and tempeh. After a long fermentation process, the ‘anti-nutrient’ phytate levels of the soybeans are reduced. Furthermore, they are not eating soy products by the ton, as sometimes we tend to do in the west, believing that if something is good for you, more is better. What Asians are doing in addition to eating fermented whole soy products (i.e. not or less processed), is consuming a wide variety of vegetables in their diet and use meat as a flavor enhancer, rather than the main attraction on their dish.

What are Fermented Soy Products?

  • Miso – A paste made from soybeans, rice or barley that has been fermented with salt, water and a fungus. Miso has a salty, buttery texture.
  • Tempeh – A fermented soybean cake with a nutty, mushroom flavor and a firm texture.
  • Soy Sauce – One of the oldest condiments in the world. Soy Sauce is made from fermented soy beans, water, enzymes and roasted grains. Be careful: a lot of commercially available varieties are made using a chemical process and it is high in sodium.
  • Natto – A traditional Japanese dish, usually eaten for breakfast, made from fermented soybeans. Natto has a strong, cheese-like flavor and a sticky texture. It is definitely an acquired taste…but, you can get used to it.

For more information about fermented foods – check out my previous article.

Genetically Modified (GM) Soy

In the US, more than 90 percent of all soy grown is ‘Roundup Ready,’ which means it is genetically modified to survive a heavy application of toxic herbicides. Unsurprisingly, GM crops have been the focus of studies into potentially dangerous effects on the environment and human beings. If you’re committed to a healthy, youth preservation lifestyle, unfermented and processed soy products like soymilk, soy burgers, soy ice cream and soy cheese are not your friends.

So, do I eat soy or not?

As I mentioned at the start of this post, the issue of soy’s healthy status is a complicated one and requires more studies. If you do plan to eat soy, I would suggest only eating organic soy that has been properly fermented and to make sure you’re not eating too much of it. You may want to avoid soy products entirely if you have breast cancer, in remission or a family history of breast cancer until the jury is truly out.

Another thing to consider if you are in normal health, is to weigh the pros and cons when given a choice of eating soy. When I am traveling and find myself in a cafe that serves only mystery meat or processed tofu, I feel the safer choice for me would be tofu. Or, perhaps, if I feel I am eating too much fish and need to be mindful of my mercury levels, I will opt for a tempeh dish instead. The key is to add a wide variety of foods in your diet sticking to mainly whole food plant based options.

Each of us processes foods and nutrients differently, so I get a yearly blood test and check up with my doctor to see how my lifestyle and food choices are working for me. What works for some, may or may not work for you too and the only way to find out is to do a little self experimentation and investigation.

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