Soy Benefits May Have Age Cutoff
Health Protection Escape Women When Supplements Started After Age 60
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.
"By the time you reach 60, so much of that estrogen-related bone loss has already occurred that I'm not convinced you can get it back -- with soy or anything else," Messina tells WebMD. "The effect soy might have on cognitive function [such as thinking and memory] is questionable anyway, so I wouldn't expect to see much there. And despite some early studies, more recent research shows that soy's benefit on cholesterol is modest, and it usually seen mostly in those with high cholesterol."
Like Kreijkamp-Kaspers, Messina, who writes a soy newsletter distributed to 70,000 dieticians, suggests that timing could play a role in how much benefit women get from soy-rich foods or supplementation.
"Giving the preliminary data that is encouraging but certainly not definitive, I have no problem telling women that when they hit menopause, they should definitely consider adding some soy or other sources of isoflavones in their diet -- especially if they're concerned about their bones," he says.
What We Know About Soy
Past studies show that regular consumption of soy can reduce hot flushes by as much as 50%. And following menopause, daily soy consumption in the 25-gram per day range has been shown to improve cholesterol levels by about 8%, enough to prompt both the FDA and American Heart Association to tout soy as being heart-healthy. In one study last year, regular soy consumption benefited people with high cholesterol as well as aided their prescription cholesterol-lowering statin drugs. But many critics have said that these studies included only a small number of people and their findings cannot be generalized to the population. Others have said that these studies are of poor quality.