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In my video on nuts and breast cancer prevention, I featured data from the Harvard Nurses’ Study, suggesting early nut consumption may be “a viable means for breast cancer prevention.” A follow-up study involving the daughters of the nurses corroborated the findings. Those eating more peanut butter, nuts, beans, lentils, soybeans, or corn were found to just have a fraction of the risk for fibrocystic breast disease, which places one at higher risk for cancer. And, the protective effects were found to be strongest for those most at risk—the ones with a family history of breast cancer.

A new study even found just two handfuls of nuts a week may protect against pancreatic cancer, one of our deadliest cancers. We’re not sure why they work. Nuts are described as “nutritionally precious,” packed with all sorts of goodies, which may explain some of the mechanisms by which nut components “induce cancer cell death,” and inhibit cancer growth and spread in vitro.

But, which nuts work the best? In my video “#1 Anticancer Vegetable,” we learned that two classes of vegetables—the broccoli family vegetables and the garlic family vegetables—most effectively suppressed cancer cell growth. Then in “Which Fruit Fights Cancer Better?”, cranberries and lemons took the title. What about nuts? Well, in terms of antioxidant content, walnuts and pecans steal the show. Twenty-five walnuts [have] the antioxidant equivalent of eight grams of vitamin C. That’s like the vitamin C found in a hundred oranges. Ah, but how do they do against cancer?

Here is a graph of human cancer cell proliferation versus increasing concentrations of the ten most common nuts eaten in the United States. If you drip water on these cancer cells as a control, nothing happens. They start out powering away at 100% growth, and they keep powering away at 100% growth. And hazelnuts, pistachios, and Brazil nuts don’t seem to do much better.

Pine nuts, cashews, and macadamia nuts start pulling away from the pack. Almonds appear twice as protective, halving cancer cell growth at only half the dose. But these final three are the winners, causing a dramatic drop in cancer proliferation at just tiny doses: walnuts and pecans, with the bronze going to peanuts.

This was nuts versus human liver cancer cells, like they did in the fruit study. They found similar results pitting nuts against human colon cancer cells—which is particularly useful, since ingested nuts would come in direct contact with colon cancer tumors in the real world, whereas for something like breast cancer, even if nuts suppressed breast cancer growth in a petri dish, that doesn’t necessarily mean nut consumption would suppress breast cancer growth in the breast, since the protective nut compounds might not even get absorbed into the bloodstream.

To test that, you’d have to design an experiment where you drip the blood of nut-eaters versus non-nut-eaters on breast cancer. And, that’s exactly what researchers at Penn State recently did. And, they wanted to know what it was about nuts that was so protective. So, they fed people whole walnuts, just the walnut oil, or just the walnut skins. And then dripped their blood on human breast cancer cells in a petri dish over the next six hours. And, the blood of those eating walnuts suppressed the growth of human breast cancer—but just the oil or just the skin didn’t seem to.

And, most importantly, these data suggest that some “components of walnuts are [indeed] absorbed, circulate in the [blood], and [can] affect…breast cancer cell proliferation.”

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