Men who consume soy foods may be at lower risk for prostate cancer, according to an updated systematic review and meta-analysis of 30 observational studies, published in the journal Nutrients earlier this year. It included diet and health data from 267,000 men in Asia, Europe, and North America.
Overall, total soy intake was associated with a reduced risk of prostate cancer. In further analyses, this association held up for unfermented soy foods (soybeans, tofu, and soy milk), while fermented soy (miso and natto) showed neither benefit nor risk (that's good news since there has been some concern that fermented foods may increase prostate cancer risk). No link was seen between soy and the risk of advanced prostate cancer (perhaps due to the few studies addressing this), though a few studies not included in this review have suggested a protective effect. The studies did not look at soy supplements, which are of questionable value.
The researchers noted, however, that variability in participants, methodology, and findings across studies "makes it difficult to draw conclusions about whether ethnic differences, preparation methods, or eating patterns exist in soy food or isoflavone consumption and prostate cancer risk." Furthermore, the results "should be interpreted with caution" because other dietary and lifestyle factors not controlled for in the studies could have contributed to the decreased cancer risk observed. More studies are needed to support consuming soy as a prostate cancer preventive—and there is still too little research to fully understand soy's effects (good or bad) in men who already have the cancer.
In the U.S., prostate cancer is the second leading cause of cancer deaths in men (after lung cancer). The lower rate of prostate cancer seen in Asia has been attributed in part to soy being a staple food in most Asian diets. It's thought that isoflavone compounds in soy—which have been shown to accumulate in prostate tissue and act as weak hormones—may suppress cancer through both hormonal and non-hormonal mechanisms. For example, the isoflavone genistein preferentially binds to estrogen receptors in prostate tissue, and this may reduce growth of tumor cells and induce cell death.
This is not the first study to show a possible protective effect of soy against prostate cancer. In fact, there have been four previous meta-analyses, including a 2009 analysis of 15 studies, published in the American Journal of Clinical Nutrition, which found that men who consumed soy regularly had a 26 percent reduced risk of prostate cancer, compared with those who ate little or none.
As in the current study, the benefit was seen only with unfermented soy foods, while fermented foods had no effect.
Written by
Magnus1964
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Such observational studies are useless after we have better evidence from randomized trials.
Unfortunately, a randomized trial found that " Daily consumption of a beverage powder supplement containing soy protein isolate for 2 years following radical prostatectomy did not reduce biochemical recurrence of prostate cancer in men at high risk of PSA failure."
we were told never to consume soy milk or UNFERMENTED soy products....only soy that has been fermented like NATTO, TEMPEH, AND MISO and in the rare chance you can find it, TOFU that has later been fermented. the crap you get at the grocery store is unfermented.
I am currently one year out of treatment for prostate cancer. I was advised to be aware of how certain food items effect estrogen . I use soy based milk and avoid as much soy as possible. If you read the ingredient label, a lot of items have soy oil, etc. that we are not aware. The best nutrition advice is to follow a nutritional program wherever your husband is receiving care.
15 studies . Wow, A research doc at roswell hosp. used genistein in his formula for pc. At least this stu. offers possibe science behind it. Pick your studies wisely till there is a cure. Cheers. All. Rocco
I am currently one year out of treatment for prostate cancer. I was advised to be aware of how certain food items effect estrogen . I use soy based milk and avoid as much soy as possible. If you read the ingredient label, a lot of items have soy oil, etc. that we are not aware. The best nutrition advice is to follow a nutritional program wherever your husband is receiving care.
I'm unfamiliar with the journal Nutrients. It's a journal where the authors pay to be published.
"Until September 2018, the editor-in-chief was Jonathan Buckley of the University of South Australia. In 2018, Buckley and the other nine senior members of the editorial board resigned, claiming that MDPI "pressured them to accept manuscripts of mediocre quality and importance"."
I was particularly interested in what the study had to say about risk in the U.S.:
"Studies conducted in both North America (p = 0.009) and Europe (p = 0.021) were significantly associated with a reduced PCa risk, whereas studies conducted in Asia (p = 0.064) were not."
"Studies were conducted in both North America (p = 0.014) and Asia (p = 0.005), and there was a significantly reduced risk of PCa in both continents. Studies of medium quality were significantly associated with a lower PCa risk"
"Both North America (p = 0.014) and Asia (p = 0.005) showed a reduced risk of PCa when only considering unfermented soy foods. "
"dietary genistein intake and PCa risk ":
"Studies conducted in Asia (p = 0.004) showed a significantly reduced risk of PCa, while studies conducted in North America (p = 0.145) and Europe (p = 0.419) did not."
"dietary daidzein intake and PCa risk "
"Studies conducted in Asia (p = 0.012) showed a significantly reduced risk of PCa, while studies conducted in North America (p = 0.094) and Europe (p = 0.799) did not."
...
My view regarding U.S. risk, is that since neither genistein nor daidzein were associated with reduced risk, any reduction in PCa risk might be due to decreased intake of animal protein.
Below is a response I made privately. I thought I would repeat it here.
I took a soy supplement for years. It did not seem to harm me any way. I did so because in spite of being a vegetarian I hate tofu and soy hamburgers. Perhaps I did not study soy as extensively as I should have. One of the early studies showed that Japanese men have a much less incidence of PCa attributed to their soy diet.
As I now understand Japanese men have fewer incidents of Pac but more die from deadlier strains of Pca.
That's why epidemiological studies are useless for drawing treatment conclusions. In addition to genetic differences, there are all kinds of other confounders - other foods, drinks, microbiome, prevalence of other diseases, etc.
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