A diet rich in walnuts, or even walnut oil, might slow prostate cancer growth, according to new research out of the University of California-Davis. Though many suggest that walnuts’ high omega-3 content were offering the protection from progression of prostate cancer, these researchers say it’s not the omega-3 content. They say it’s something else in the walnuts that slows prostate cancer growth.
The research was published in the Journal of Medicinal Food. It adds an interesting twist to a warning letter sent to Diamond Foods, a walnut producer, from the FDA in 2010. In that letter, the FDA said that the walnut producer was making false claims about omega-3s found in walnuts. The FDA said that such unauthorized claims used in marketing made walnuts considered an unapproved drug in the eyes of the federal government. Interestingly, this new research indicates that, at least in the case of prostate cancer, it was components of the walnuts themselves, not simply the omega-3s, that earned the nuts the limelight in the Journal of Medicinal Food.
According to Medical News Today, earlier studies showed that increasing the intake of tree nuts might reduce cardiovascular disease risks and cancer. That article also pointed out that in 2013, a study showed that eating walnut oil can help “‘good’ cholesterol transport and remove extra cholesterol from the body more effectively.”
The scientists involved in this research have been studying the health benefits of walnuts for some time, according to lead scientist Paul Davis. Davis said they already knew there was a prostate cancer protective component in walnuts because a previous study they had done showed that walnuts reduced the size of prostate tumors. That study didn’t ask which part of the walnut was responsible.
The mice in the study were fed either whole walnuts, walnut oil, or omega-3s for 18 weeks. At the end of the study, the team found that both the groups that were given whole walnuts and walnut oil showed lower cholesterol and slowed prostate cancer growth. The control group taking in extra omerga-3s did not.
The current study still hasn’t isolated exactly what it is that makes walnuts protective against prostate cancer, but using omega-3 fatty acids for a control diet, they discovered that it wasn’t the omega-3s.
“For years, the US government has been on a crusade against fat, and I think it’s been to our detriment,” Davis explained. “Walnuts are a perfect example. While they are high in fat, their fat does not drive prostate cancer growth. In fact, walnuts do just the opposite when fed to mice.”
The researchers were able to narrow down other components that they do not believe were responsible for slowing the cancer growth. They ruled out fiber, zinc, magnesium, and selenium.
“We showed that it’s not the omega-3s by themselves, though, it could be a combination of the omega-3s with whatever else is in the walnut oil,” Davis said. “It’s becoming increasingly clear in nutrition that it’s never going to be just one thing; it’s always a combination.”
According to the researchers, the amounts of walnuts needed, if humans respond at a proportional amount, would not be difficult to consume.
“In our study, the mice were eating the equivalent of 2.6 oz of walnuts. You need to realize that 2.6 oz of walnuts is about 482 calories. That’s not insignificant, but it’s better than eating a serving of supersized fries, which has 610 calories. In addition to the [prostate] cancer benefit, we think you also get cardiovascular benefits that other walnut research has demonstrated.”
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