Soy Benefits May Have Age Cutoff
Health Protection Escape Women When Supplements Started After Age 60
July 6, 2004 -- With thousands of studies having been done, soy protein has emerged as one of the most researched foods in science. Even with this much information, studies still show conflicting results on the effects of this much ballyhooed protein.
From tempering menopausal symptoms to reducing the risk of several health problems that plague women following it, some women still turn to soy as an alternative to traditional estrogen therapy.
And yet in the latest study, researchers from the Netherlands find that daily soy supplements did not help preserve a women's thinking ability or bone density. The study also showed no evidence that the supplement provided heart protection by improving women's cholesterol levels following menopause.
Why the sudden departure from previous findings that have supported a beneficial effect from soy, the plant-derived estrogen-like compound? Perhaps because the women studied were between ages 60 and 75 when they started taking soy proteins -- when they may have been too old to reap its reported benefits.
Don't Wait too Long
"Timing is certainly a reasonable explanation as to why we didn't find an effect from soy in the women studied," researcher Sanne Kreijkamp-Kaspers, MD, PhD, tells WebMD.
"We know that immediately after menopause, there's a huge decline in bone loss and that's when [bad] cholesterol levels tend to increase," she says. "It could be that if you give soy before a woman reaches menopause, it is effective at preventing this."
If supplementation begins a decade of so after menopause, it may be too late, she explains.
In her study, published in this week's Journal of the American Medical Association, 200 women received either 25 grams of soy protein each day via a powder that could be mixed with food or beverages or a phony powder package. Each daily dose of soy contained 99 milligrams of isoflavones, such as genisten and diadzein, the most common form of phytoestrogen.
None of the women had ever consumed soy supplements prior to the study, according to Kreijkamp-Kaspers, an epidemiologist at University Medical Center in Utrecht. "Soy is not as popular in the Netherlands as it is in the U.S.," she explains.
No Change After 1 Year
The women were tested at the beginning of the study, and again one year later, on various aspects of their thinking, memory, and reasoning abilities; bone mineral density and cholesterol levels were also tested. These are health issues that worsen following menopause.
During the study period, test scores on health-related issues were virtually identical in both groups of women. This indicated that in this group of women a soy-supplemented diet had no beneficial health effects.
These findings come as no surprise to Mark Messina, PhD, a nationally known soy expert and adjunct associate professor of nutrition at Loma Linda University who is currently revising a book on the health impact of soy protein, which has estrogen-like properties and mimics some of the benefits of hormone replacement therapy, but without some of its risks.