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July 2013

Soy Supplementation Studied For Prostate Cancer Recurrence

Daily consumption of a soy protein supplement after prostate gland removal may lack effect on prostate cancer recurrence, a study reports.

Soy is a subtropical plant, native to southeastern Asia. This member of the pea family (Fabaceae) grows from one to five-feet tall and forms clusters of three to five pods, each containing two to four beans per pod. Soy has been a dietary staple in Asian countries for at least 5,000 years, and during the Chou dynasty in China (1134-246 B.C.), fermentation techniques were discovered that allowed soy to be prepared in more easily digestible forms such as tempeh, miso, and tamari soy sauce. Tofu was invented in 2nd-Century China.

Soy contains protein, isoflavones, and fiber, all thought to provide health benefits. Soy is an excellent source of dietary protein, including all essential amino acids. Soy is also a source of lecithin or phospholipid. Soy isoflavones and lecithin have been studied scientifically for numerous health conditions. Isoflavones such as genistein are believed to have estrogen-like effects in the body, and as a result are sometimes called "phytoestrogens."

Soy consumption has been studied for possible effects on the risk or recurrence of prostate cancer. In the current study, researchers evaluated the potential benefit of a soy protein supplement. The team recruited 177 men who had undergone prostate gland removal for prostate cancer and were considered to be at high risk of recurrence. They conducted the study from July 1997 to May 2010. Beginning four months after surgery, participants randomly received either a beverage powder containing 20 grams of soy protein or a placebo. The researchers measured prostate-specific antigen (PSA) (a protein that may indicate prostate cancer when found in high levels) every 2-3 months during the course of the two-year study. Recurrence rate was defined as the development of a PSA level of 0.07 nanograms per milliliter or greater.

The trial was discontinued early due to a lack of treatment effects. The results suggested that 28.3 percent of participants developed recurrence within two years of beginning the trial. Among these, more than 27.2 percent were in the soy protein group, while 29.5 percent were in the placebo group.

The authors reported that daily consumption of a soy protein beverage for two years following prostate gland removal may lack effect on prostate cancer recurrence. More research is needed to better understand and confirm these findings.

Many integrative therapies have been studied for use in prostate cancer and related conditions. There is strong scientific evidence to support the effectiveness of light therapy, strontium, and vitamin A for this purpose.

For more information about soy, please visit Natural Standard's Foods, Herbs & Supplements Database.

References

  1. Bosland MC, Kato I, Zeleniuch-Jacquotte A, et al. Effect of soy protein isolate supplementation on biochemical recurrence of prostate cancer after radical prostatectomy: a randomized trial. JAMA. 2013 Jul 10;310(2):170-8. doi: 10.1001/jama.2013.7842. 
  2. Natural Standard: The Authority on Integrative Medicine.

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