Is Soy A Superfood Or Supervillain?
It seems every few months there is a new supposed superfood that will single-highhandedly provide you with health and vitality. Americans are addicted to the superfood or super-vitamin concept and through the years we have had love affairs with antioxidants, red wine, quinoa, fish oil, acai berries, and many others but the one that started it all is soy.
Now that soy has had a chance to be studied more thoroughly, its role in health is better understood.
What are soy’s benefits?
People can get soy from soybeans, edamame (immature soybeans), soy milk, tofu, tempeh, and miso. Since it has been around for a while, it has been more thoroughly studied and we have some answers.
In a report by the Federal Agency for Healthcare Research and Quality Evidence-based Practice Center in 2005, they reviewed data for all sorts of things people claimed soy would benefit like cardiovascular disease, bone health, and cancer. There were only two things that you can say with confidence that soy products do. They can slightly reduce bad cholesterol levels and triglycerides in the blood and mildly reduce some menopausal symptoms.
Other evidence since that time affirmed the impact of soy products on lowering bad cholesterol and reducing menopausal symptoms. In a preliminary trial, the impact on bad cholesterol is better with soy forms that also contain soy fiber. While this requires confirmation, we previously found that fiber, especially soluble fiber reduces bad cholesterol by itself.
Since the time of the Evidence-based Practice Center report, there are newer studies consistently suggesting that soy products may have a modest impact on helping women with fertility issues become pregnant but this needs to be validated in much higher quality studies. Finally, soy is a good source of vitamins, especially folate and vitamin K, and minerals, especially manganese and iron. It is also a good protein source for vegetarians and vegans.
Can soy harm you?
People have been worried that the phytoestrogens in soy products could cause breast cancer and could make men less manly. Estrogen, of course, has these effects but to-date, evidence suggests that soy products do not increase breast cancer incidence in women, do not reduce testosterone in men, and don’t do anything bad to men’s prostate gland (and may have a beneficial effect on reducing prostate cancer but this requires more study).
Nonhuman studies show there are constituents in soy products that could prevent the thyroid from taking up iodine and making thyroid hormone. However, human studies using reasonable daily intakes of soy products have not found an impact on thyroid hormone concentrations.
The final potential harm is soy causing aluminum toxicity in infants. The aluminum content of soy protein-based formula is 600 to 1300 ng/mL as compared to 4 to 65 ng/mL in human milk. The American Academy of Pediatrics has reviewed the data and feels that in children without kidney problems (which readily eliminates the aluminum concentrated in soy products), there is not a risk to be concerned. Those with kidney issues should be cautious about using it because too much aluminum (as seen in people with renal failure who were given aluminum antacids to treat high phosphate concentrations) can cause dementia and hurt bones. However, it does speak to not overdoing it with soy or any product for that matter.
What is the bottom line?
There is no one superfood that will be the fountain of youth or yield amazing health. Soy products are neither superfoods nor supervillains but can be a tasty addition to a balanced diet. Massive amounts of any food or nutrient can change the benefit to risk profile both from the overuse of that food or nutrient and the underuse of other foods or nutrients needed for a well-balanced diet.
What is a reasonable amount of soy? You can consume up to a cup of edamame, 2 cups of soy milk, or 6 ounces of tofu a day.
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