Confused About Soy? Know Its Pros And Cons

I don’t think a week goes by without one of my patients asking me about whether or not to eat soy products. The question of eating soy has become a fairly controversial subject as, indeed, there are some good health benefits gained by consuming certain types of soy, but there can also be some bad health effects of consuming soy as well. Allow me to share with you what I tell my patients about soy, its advantages and disadvantages, so you can make an informed decision on whether to include it in your diet.

What’s Bad About Good Ol’ Soy?

A little over 10 years ago, soy exploded onto the health food scene with proponents of it singing its praises promoting heart health, bone health, reducing cholesterol, preventing certain types of cancer, banishing the symptoms of menopause, as well as providing a complete vegetable protein source to vegans who don’t want to eat animal protein.

However, as good as all those health benefits sound, some negative news also began to surface about eating soy and SPI (soy protein isolate) such as the following:

Thought to depress thyroid function and contribute to goiter.
Feminization effects in men (lowers testosterone levels).
Lowered age of puberty onset in girls (phytoestrogens raise estrogen levels).
Raises the risk of breast and thyroid cancer (raises estrogen and thyroid hormones).
May contribute to mineral deficiencies (magnesium, calcium, iron, zinc).
May contribute to developmental disorders in infants.
May contribute to digestive problems (blocks trypsin, a digestive enzyme).
May contribute to blood clot formation (its hemagglutinin clumps red blood cells).
Now, when my patients hear that list of bad news, it’s enough to stop anyone in their tracks from eating soy. In addition, SPI, or soy protein isolate, is a chemical by product of soy oil and bears little resemblance to fermented soy. SPI is contained in most protein bars and some other processed foods (read labels).

SPI processing puts the soy through an acid wash processing which can leach aluminum into the product. As well, the high temperature handling can modify the natural proteins and nitrites (known carcinogens) that form during the spray drying process. Further, another toxin called lysinoalanine forms during the process of alkalinizing the mix. Sound like anything you want to eat? Not likely.

Let’s look at this issue fairly though. The majority of the health risks seem to come from eating ‘non’ fermented soy, or inadequately fermented soy, which basically means “raw” soy in which the phytic acid in it has not been denatured through fermentation. Forms of traditionally fermented soy such as tempeh, natto, miso, fermented soy bean paste, and soy sauce are soy items that are considered safe, without the above-mentioned negative health effects. In fact, the Japanese people claim that consuming miso after the bombing of Hiroshima is what kept a group of survivors in a hospital free from the effects of the radioactive fallout.

To further confuse the issue, manufacturers of soy-containing products (mostly soy protein isolate and nonfermented soy milk-containing items) flatly deny any adverse health effects of soy stating that the dangers are all “myths”. I would rather err on the side of caution in my patients’ health.

My Recommendations For Soy Consumption

As I tell my patients, consuming the traditionally fermented types of soy (tempeh, miso, tofu, soy sauce) in moderation can confer some of the good health benefits for specific people with very low-no risk of the bad effects. As far as SPI, or soy protein Isolate, I would recommend to just say no to this chemically altered soy product. Read labels carefully. Look instead for whey protein or milk/egg protein instead of SPI.

Edamame: You’ve likely seen bags of these little green soybeans in supermarket produce sections. Fast food places also use them in salads and people buy them as vegetable snacks. They are blanched, unfermented, immature, soybeans and contribute high amounts of phytic acid, isoflavones/ phytoestrogens. Eat in moderation (see below). I wouldn’t give to children.

Men: Men over 40, minimal consumption, 1-2 servings 2-3 times per week, naturally fermented soy. If you are being treated for hypogonadism, increased breast tissue/breast cancer, low testosterone levels, thyroid disease, do not consume soy products at all as their isoflavones, or phytoestrogens, can worsen these conditions.

Women: If you are post-menopausal, 1-2 servings a day, 3-4 times a week of naturally fermented soy types can be included. If you are on hormone replacement therapy, however, decrease your servings and/or ask your doctor about the estrogen effect from soy and your HRT. Also, if you have a history of breast cancer, fibroadenomas, endometrial, ovarian tumors, thyroid disease, possibly even uterine polyps, I recommend not to consume any soy as it can aggravate these conditions. If you are pregnant, do not consume soy products for your infant’s safety.

I encourage you to do your own research and draw your own conclusions about what is fact and what is myth in soy consumption. Also, talk to your doctor about their opinion. In the meantime, if you stick to the guidelines I’ve offered above, I feel you can enjoy the fermented forms of soy safely without fear of adverse health effects.

Stay Well,

Mark Rosenberg, M.D.