State of Soy
RESEARCH UPDATES: BONE HEALTH, HOT FLUSHES, BREAST CANCER
By Mark Messina, Ph.D. (Reprinted from The Soy Connection, Volume 9, Number 2, Spring 2001)
Over the past few years, several short-term studies have examined the effects of soy consumption on markers of bone formation and resorption, and bone mineral density (BMD). These studies are generally only a few months in duration and so do not provide insight into the possible effects of life-long soy consumption on bone health. Recently, though, researchers from Japan conducted a cross-sectional study of diet and the lumbar spine BMD of 85 postmenopausal women. They found that soy was one of four nutritional factors associated with higher BMD. Soy had a more favorable impact than energy, protein, or even calcium. Despite the limitations of all epidemiologic studies like this, the findings of this study are particularly intriguing because average soy protein intake was only 12.6 grams per day. Thus, it is possible that fairly modest amounts of soy may benefit bones when consumed chronically. (Osteoporosis Int 11: 721, 2000)
Hot Flushes
There is quite a bit of interest in the potential for soy to relieve hot flushes, but thus far the results are mixed. Unfortunately, the most recent study to examine this issue showed no benefits. In this study, for six months daily, perimenopausal women were fed soy protein (40 g) low in isoflavones (4 mg), soy protein (40 g) high in isoflavones (80 mg) or, whey protein (40 g). Hot flush frequency decreased in all groups, but there was no difference according to treatment.
Thus, this study shows that there was a marked placebo effect and/or that hot flushes decrease over time. This is the longest hot flush study involving soy to date. But given the positive results of several other studies, only more research can fully determine whether soy is effective against hot flushes. (Menopause 8:17, 2001)
Breast Cancer
Much of the current interest in soy can be traced to early enthusiasm over the potential role of soy in reducing breast cancer risk. During the past 10 years there have been more than 10 epidemiologic studies to examine this issue and, not surprisingly, most have been conducted in Asia. However, researchers in Australia recently examined this issue. They found that women with breast cancer (59.3 years of age) excreted significantly less urinary daidzein (a soy isoflavone) compared with controls (57.3 years of age), and there was a trend toward lower excretion of genistein (another soy isoflavone). These results suggest soy intake is protective since previous research has shown that urinary excretion of the isoflavones is a good indicator of soy intake. However, not surprisingly, soy intake was minimal in this study. Thus, there is the possibility that the findings were not due to soy per se, but some other factor(s) associated with soy consumption by Western women.
(Menopause 7: 289, 2000)
Checkout the State of Soy, which is based on an interview with Mark Messina