Study: Walnuts May Have Lifesaving Benefits

By Jane Farrell

The heart-health benefits of nuts have been known for some time, but now researchers say that walnuts slow the growth of prostate and breast cancer as well.

Investigators from the University of California, Davis, and other institutions also found that both walnuts and walnut oil helped to reduce cholesterol and increased sensitivity to insulin. The walnut diet also reduced levels of IGF-1, a hormone previously linked to both prostate and breast cancer.

The study was published in the Journal of Medicinal Food.

“For years, the United States government has been on a crusade against fat, and I think it’s been to our detriment,” said lead scientist and research nutritionist Paul Davis. “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 latest study builds on earlier research by Davis and his colleagues. In that study, the investigators found that walnuts reduced the size of prostate tumors in mice, but they weren’t sure which part of the walnut – the meat, the oil or the omega-3 fatty acids – was the source of this benefit.

In the newest study, researchers used a mixture of fats with virtually the same fatty acid content as walnuts as their control diet. They fed the mice whole walnuts, walnut oil or the walnut-like fat for 18 weeks. The conclusion: the walnuts and walnut oil reduced cholesterol and slowed prostate cancer growth. But the walnut-like fat didn’t have the same effect, meaning that other nut components, not omega-3s, provided the benefit.

“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.”

“The energy effects from decreasing IGF-1 seem to muck up the works so the cancer can’t grow as fast as it normally would,” Davis said. “Also, reducing cholesterol means cancer cells may not get enough of it to allow these cells to grow quickly.”

While it’s still not certain that walnuts would have the same effect in humans, Davis said there’s no harm in eating them in moderate quantities. “It’s the holiday season, and walnuts are part of any number of holiday dishes. Feel free to consume them in moderation.”