Negative Soy Reports Don't Add Up

Feb. 20, 2008
After examining a surge of negative soy reports, experts are finding they don’t add up.

In 2007, controversies surrounding the health benefits of soyfoods made headlines. Soy is the “original”   and one of the most studied   functional food ingredients. But some of the negative press on soy disputed its benefits to heart health and cancer protection, while some of the unfounded stories promoted incorrect soy connections to reduced sperm count, thyroid disease and cancer.

It’s important processors understand such contrary ingredient alerts tend to focus on isolated indicators or “one-off” reports verified only by single sources. New discoveries and new research findings must be measured against the total body of existing evidence and research.

For example, one online news item about a study by Jorge Chavarro, M.D., of the Harvard School of Public Health, Boston, of 100 couples visiting fertility clinics reported soyfoods could lower sperm count. Despite a subsequent surge of negative stories on soy and fertility, reporters failed to clarify that sperm mobility and quality (major determinants of fertility) were not affected. Worse, reporters ignored major flaws in the study’s design: The subjects included men seeking treatment for possible fertility problems, and dietary data came from recollected intake (often suspect) of 15 soyfoods. No consideration was made of other foods, medications, supplements, existing medical conditions, sexual activities or environmental factors that could account for the results.

A reported association between soy and thyroid disease was based on a single study that looked at animals (already) deficient in iodine   essential for thyroid health   who were fed isoflavones from clover, not soy. A literature review by Mark Messina, Ph.D., and Geoffrey Redmond, M.D., in the journal Thyroid, found most of the evidence from clinical trials involving healthy adult men and women indicates neither soy protein nor isoflavones adversely affect thyroid function.

Scientific interest in soy has generated an enormous body of evidence. Existing research on diets containing soy shows no adverse side effects. In fact, an overwhelming amount of human-based research shows soy helps reduce blood cholesterol. Although research is ongoing, the body of evidence consistently shows soy and soyfoods decrease the risk of heart disease, as authorized by the FDA in the approved health claim for soy protein: “25g of soy protein a day as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.”

Soy continues to be a nutritious option. It is low in saturated fat and is a complete, cholesterol-free protein source. Of all beans, soy is the only one whose high-quality protein is equal to animal protein. While research continues to seek out benefits from soy, its versatility and marketability as a functional food ingredient is not in dispute.

Nancy Chapman, R.D., M.P.H., is executive director for the Soyfoods Assn. of North America. For more science-based information on soy and soyfoods and for information on the 14th Soy Symposium Soy: New Horizons, visit