The FDA confirmed that is proposing a rule to revoke a previously authorized health claim that soy protein protects against heart disease. “For the first time, we have considered it necessary to propose a rule to revoke a health claim because numerous studies published since the claim was authorized in 1999 have presented inconsistent findings on the relationship between soy protein and heart disease,” the agency noted in a statement.
While some evidence does continue to suggest a relationship between soy protein and a reduced risk of heart disease, the FDA says that the “totality of currently available scientific evidence calls into question the certainty of this relationship.” Studies published after the FDA authorized the health claim, for example, are inconsistent in demonstrating that soy protein can lower levels of low-density lipoprotein cholesterol (LDL-C). The agency’s review of all of this combined evidence has led it to conclude that the relationship between soy protein and heart disease isn’t demonstrated clearly enough to merit authorization.
Even if the rule is finalized and the authorization is revoked, qualified health claims will still be permissible, as long as there is enough evidence to support a link between consuming soy protein and reduced risk of heart disease. Qualified health claims don't require the same level of scientific standard of evidence as authorized health claim, FDA notes, and this would allow the industry to use qualifying language that confirms the limited evidence linking dietary soy protein with heart disease risk reduction.
The rulemaking process involves a 75-day period for open comment. Manufacturers can keep the existing authorized claim on their products, until the agency makes a final decision on whether to revoke the authorization. Since 1990, the FDA has been responsible for evaluating health claims on packaged foods. To date,12 health claims have been authorized, including the effects of calcium and vitamin D in helping to lower the risk of osteoporosis and the cancer-lowering risks of certain fruits and vegetables.
Meanwhile, researchers in the U.S. report that a compound found in soy protein may help to suppress the risk of breast cancer. The studies, led by Donato F. Romagnolo, Ph.D., and Ornella I. Selmin, Ph.D., at University of Arizona (UA) Cancer Center, suggest that genistein, the primary isoflavone found in soy, may prevent methylation-mediated silencing of the tumor suppressor BRCA1 gene by the aromatic hydrocarbon receptor (AhR). They reported their findings in Current Developments in Nutrition.The paper is entitled, “Genistein prevents BRCA1 CpG methylation and proliferation in human breast cancer cells with activated aromatic hydrocarbon receptor.”
Only a small proportion of breast cancers have a mutated BRCA1 gene, the researchers explain. Many other breast patients have a normal BRCA1 gene, but methylation effectively silences the gene and prevents it from acting as a tumor suppressor. The UA Cancer Center team has a particular interest in AhR, which can be activated by environmental carcinogens, including tobacco smoke and UV light exposure. When activated, AhR silences BRCA1, which inhibits its tumor suppressor activity and allows cancer cells to proliferate. And when AhR silences BRCA1, estrogen receptor alpha (ER-alpha) is also lost, and this generates resistance to ER-alpha-targeting drugs such as tamoxifen.
The researchers’ initial studies in patient-derived breast cancer cells have now demonstrated that AhR can be targeted by the soy protein genistein. And having generated results in vitro, the team is now progressing their research into mouse models. “Lifetime intake of soy in Asian women has been linked to reduced risk of breast cancer,” comments Dr. Romagnolo, who is professor of nutritional and cancer biology at UA Cancer Center. “Genistein is the predominant isoflavone found in soy and it may actually block DNA methylation.”
There are still many questions to answer, including which types of soy foods, when, and for how long during a lifetime they should be consumed to have anticancer benefits. The UA Cancer Center team is also interested in whether exposure to soy genistein during pregnancy might provide the fetus with lifetime protection against breast cancer.