As soy has made its way into Western diets, consumers have become interested in the many claimed health benefits. Soy products are often marketed specifically to women in part because of scientific evidence gathered over fifteen years suggesting that soy may be helpful for conditions and diseases associated with menopause, including hot flashes, vaginal dryness, night sweats, and mood swings. In addition, numerous medical journal reports have documented the positive affects of soy’s estrogenic properties on the brain, heart, bones, breasts, and uterus, as well as the skin, hair, and nails.¹

More and more evidence shows soy’s many benefits when used as part of a healthy diet. Here’s an update on some of the recent, noteworthy news on soy:

Improved Memory and Brain Function

New studies show that isoflavones may improve cognitive function and protect against degenerative diseases of the brain, such as dementia and Alzheimer’s. For example, results from the SOPHIA (Soy and Postmenopausal Health In Aging) study conducted in 2003 showed that significant improvements in markers such as “category fluency,” “logical memory,” and “memory recall” occurred after 12 weeks when postmenopausal women took 110 mg of soy isoflavones per day.² An additional study showed improvements in “spatial cognition” a week after participants added soy to their diet in high doses.³

Further, scientists recently confirmed an increase in the frontal lobe executive functioning in women who added only 60 mg of soy isoflavones to their daily diet for six weeks! ⁴ After twelve weeks, the improvements were even more noticeable. In addition to helping with cognitive activity, soy isoflavones help protect nerve cells in the brain from free radical damage. ⁵

Only Two Glasses a Day!

In the fall of 2005, findings of a study of more than 24,000 Chinese women were reported in the Archives of Internal Medicine. Researchers noted that women consuming 13 gmor more of soy protein every day were half as likely to incur a bone fracture as those eating 5 gm or less per day.⁶ This is exciting, since you can get this amount of soy protein simply by drinking two glasses of soy milk a day.

Another study was conducted in which half of the participants (postmenopausal women) were given two glasses of soy milk with isoflavones; the other half drank the same quantity without the isoflavones. Bone loss was measured after two years and four years. The first group had virtually no bone loss at either interval! The second group saw a decrease in bone mass by a little more than four percent—lower than what many postmenopausal women experience. Researchers concluded that although the soy milk they drank didn’t have isoflavones, the daily intake of soy protein still provided some protective benefits for these women’s bones.⁷

My Recommendation

I recommend 100–160 mg of soy isoflavones per day. Typically, a serving of soy contains 35–50 mg of soy isoflavones and 8 gm of soy protein. Some examples are 1 cup of soy milk, 1/2 cup of tofu; or 3 handfuls of roasted nuts. It’s always best to use a soy product that is made from whole, organic soybeans.

If eating soy isn’t currently a part of your daily ritual, I encourage you to incorporate it into your diet. You’ll be providing terrific protection against oxidative stress, adding a superior form of protein, balancing your hormones, protecting your bones, strengthening brain function, lowering your cholesterol, and so much more!

1. Anderson, J.J., et. al., 1999. Health potential of soy isoflavones for menopausal women, Public Health Nutr, Dec;2(4):489-504.
Celec, P., 2005. Endocrine and cognitive effects of short-time soybean consumption in women, Gynecol Obstet Invest, 59(2):62-6, Epub 2004 Nov 3.
File, S. E., et. al., 2005. Cognitive improvement after 6 weeks of soy supplements in postmenopausal women is limited to frontal lobe function, Menopause, Mar;12(2)193-201.
Jenkins, D.J, et. al., 2002. Effects of high- and low-isoflavone soyfoods on blood lipids, oxidized LDL, homocysteine, and blood pressure in hyperlipidemic men and women. Am J Clin Nutr, Aug;76(2):365-72.
Kritz-Silverstein, D., et. al., 2003. Isoflavones and cognitive function in older women: the Soy and Postmenopausal Health in Aging Study, Menopause, May-Jun;10(3):196-202.
Lee, Y.B., Lee, H.J., Sohn, H.S., 2005. Soy isoflavones and cognitive function.J Nutr Biochem, Nov;16(11):641-9. Epub 2005 Aug 10.
Lydeking-Olsen, E., et. al., 2004. Soymilk or progesterone for prevention of bone loss—a 2-year randomized, placebo-controlled trial, Eur J Nutr, Aug;43(4):246-57. Epub 2004 Apr 14.
Omoni, A.O., Aluko, R.E., 2005. Soybean foods and their benefits: potential mechanisms of action. Nutr Rev, Aug;63(8):272-83.
Sonee, M., et. al., 2004. The soy isoflavone, genistein, protects human cortical neuronal cells from oxidative stress, Neurotoxicology, Sept;25(5):885-91.
Zhang, X., et. al. 2005, Prospective cohort study of soy food consumption and risk of bone fracture among postmenopausal women, Arch Intern Med., Sep 12;165(16):1890-5.

2 Kritz-Silverstein, D., et. al., 2003. Isoflavones and cognitive function in older women: the Soy and Postmenopausal Health in Aging Study, Menopause, May-Jun;10(3):196-202.

3 Celec, P., et. al., 2005. Endocrine and cognitive effects of short-time soybean consumption in women, Gynecol Obstet Invest, 59(2):62-6, Epub 2004 Nov 3.

4 File, S. E., et. al., 2005. Cognitive improvement after 6 weeks of soy supplements in postmenopausal women is limited to frontal lobe function, Menopause, Mar;12(2)193-201. 

5 Sonee, M., et. al., 2004. The soy isoflavone, genistein, protects human cortical neuronal cells from oxidative stress, Neurotoxicology, Sept;25(5):885-91.

6 Zhang, X., et. al. 2005, Prospective cohort study of soy food consumption and risk of bone fracture among postmenopausal women, Arch Intern Med, Sep 12;165(16):1890-5.

7 Lydeking-Olsen, E., et. al., 2004. Soymilk or progesterone for prevention of bone loss—a 2-year randomized, placebo-controlled trial, Eur J Nutr, Aug;43(4):246-57. Epub 2004 Apr 14.

 About the Author

Christiane Northrup, M.D., a board-certified ob-gyn physician, is today’s leading expert on women’s health issues. Her new Menopause and Beyond: New Wisdom for Women special airs in March 2007 on PBS. She just published The Wisdom of Menopause Journal. Check out the latest health news or sign up for her newsletter:www.drnorthrup.com

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