Researchers reported in a study published in September 2013 that soy isoflavone supplementation improved some menopausal symptoms and increased bone density in menopausal women. The investigators assigned 80 women to receive 90 mg per day of soy isoflavones or placebo for six months. The researchers measured bone mineral density of the radius and tibia using quantitative ultrasound. The researchers measured indices of bone metabolism including calcium, phosphorus and alkaline phosphatase (ALP) and serum cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha). The subjects completed questionnaires regarding menopausal symptoms.
The results showed that tibial bone density increased significantly with isoflavone supplementation compared to the placebo group.
The investigators stated, “For menopausal women, soy isoflavone in the dose of 90 mg per day could improve some menopausal syndromes and was effective on increasing limb bone density."
I realize that soy is a very controversial, and online especially, soy-bashing is rampant. But, I eat some soy, and I will continue to eat some soy. I take it in the form of tofu and tempeh. I do not take soy supplements.
I'll admit that there is a negative case that can be made against soy. Soy is high in phytic acid. But, most and perhaps all plant foods contain some phytic acid. So, you can't avoid it. Phytic acid is thought to interfere with mineral absorption, but it should be kept in mind that in the normal course of eating and living, only a small percentage of the minerals in food get absorbed. At most, 20% of the calcium in food gets absorbed. It's presumed that only 10% of the iron in food gets absorbed- and it may be much less. About 15% of the zinc in food gets absorbed. The phytic acid in plants may be a reason why, but it would be toxic if we absorbed all the minerals in food. The evidence shows that, despite the phytic acid, plant-based diets are best for bone health, teeth health and mineralizatoin in general. The concern about phytic acid has been exaggerated.
Soy phyto-estrogens have also been a boogey-man to some. But again, many plant foods contain phytoestrogens, and some contain much more than soy, such as sesame seeds. Phyto-estrogens are weak estrogens, and they have been found to be protecxtive against breast cancer in women. Does soy cause feminizing effects in men from the phyto-estrogtens? Well, it hasn't happened to me. And my testosterone level is high for a 63 year old man.
Some of the complaints against soy relate to raw soy beans, such as the digestive antagonists and hemagluttins. These issues apply to all raw legumes, but they are neutralized by cooking. Cooked legumes have been included in the traditional diets of people from all over the world, and scientists agree that legumes are beneficial to health, being cardio-protective, diabetes-preventive, and very high in antioxidants. The USDA lists legumes as 3 of the top 5 foods in antioxidants, the other 2 being berries. The very highest antioxidant food, according to the USDA, is the red kidney bean.
So, beans, in general, are very good foods. I am them almost every day. And I'm not talking about soy. I'm talking about pinto beans, blacks beans, kidney beans, garbonzos, etc. They are truly a staple in my diet. What soy I eat is on top of that, but in smaller quantity.
I don't say that people should be eating large quantities of soy. But to include some is fine, and I do so myself and without worry. It has a positive effect on bones. It has a proven anti-cancer effect, including on prostate cancer in men. And it is definitely cardio-protective. In my book, a little soy is definitely A-OK.