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 gm
or 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
