Meta Analysis Associates Increased Soy Intake With Lower Lung Cancer Risk

Meta-analysis associates increased soy intake with lower lung cancer risk

Meta-analysis associates increased soy intake with lower lung cancer risk

Tuesday, November 22, 2011. The results of a meta-analysis published online on November 9, 2011 in the American Journal of Clinical Nutrition add evidence to preliminary findings concerning a protective effect for soy against the development of lung cancer.

In their introductory remarks, Yong-Bing Xiang of Shanghai Jiaotong University School of Medicine and colleagues observe that approximately one-fourth of the cases of lung cancer that occur worldwide are not caused by the use of tobacco. Although cell culture and animal studies have uncovered inhibitory effects for genistein (a major isoflavone found in soy) against lung cancer, no summary of epidemiologic results concerning soy's association with the disease had yet been conducted.

The researchers selected eight case-control and three prospective cohort studies for their review, which included 8,436 cases of lung cancer. All of the studies utilized food frequency questionnaires to estimate soy intake. The analysis uncovered a 23 percent reduction in lung cancer risk in association with high versus low soy consumption. When the analysis was limited to five studies of high quality, a 30 percent reduction was revealed. In analyses of specific groups, significant protective effects were observed for women, never smokers and Asian populations. For studies that documented intake of soy isoflavones, an approximate 27 percent reduction in lung cancer risk was associated with high intake. While unfermented soy foods were associated with a protective effect, fermented foods such as miso were not.

"To our knowledge, this is the first meta-analysis to report an association between soy intake and lung cancer risk," the authors announce. Possible estrogen-dependent and independent anticancer mechanisms involve the estrogen receptor (ER) signaling pathway and the epidermal growth factor receptor (EGFR) mediated pathway.

"Our analysis indicates that soy intake is associated with lower lung cancer risk," the authors conclude. "Because of the limited number of studies, the findings from our study need to be confirmed in future research in well-designed cohort or intervention studies."

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Soy peptide aids in blocking metastasis

Soy peptide aids in blocking metastasis

An article published online on September 10, 2011 in the journal Cancer Letters describes the discovery of Elvira Gonzalez de Mejia and Vermont P. Dia of the University of Illinois in Urbana of a benefit for lunasin, a peptide that occurs in soy, in preventing the spread of colon cancer to the liver, the predominant site of metastasis for this type of cancer. "When lunasin was used in combination with the chemotherapy drug oxaliplatin, we saw a sixfold reduction in the number of new tumor sites," revealed Dr de Mejia, who is an associate professor of food chemistry and food toxicology at UI.

The current study utilized mice bred to develop colon cancer that metastasizes to the liver. The researchers divided the animals to receive daily injections of lunasin, lunasin plus the chemotherapy drug oxaliplatin, oxaliplatin alone or neither compound. "The group that received lunasin alone had 50 percent fewer metastatic sites," reported Dr de Mejia. "But an even more exciting result was seen in the group that received both lunasin and the chemotherapy drug—only 5 new cancer sites when compared with 28 in the control group."

"This huge reduction in metastasis was achieved with the amount of lunasin in only 25 daily grams of soy protein, the amount recommended in the FDA health claim," noted Dr Dia, who is a University of Illinois postdoctoral fellow. "In this study, we have learned that lunasin can penetrate the cancer cell, cause cell death, and interact with at least one type of receptor in a cell that is ready to metastasize."

"Two glasses of soy milk a day generally provide half the amount of lunasin used in our study," Dr de Mejia remarked. "It certainly seems feasible to create a lunasin-enriched product that people could consume in a preventive way."

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