These days it’s hard to glance at a health magazine, flip past the cooking channel, or chat with your one vegan friend without hearing the word “superfood”. It seems like they just keep coming up with new ones. One week its kale, the next its acai, then before you know it you’re on amazon wondering if you should order some Maca powder from the Andes because apparently it’s a natural energy booster and you can sprinkle it in your smoothie. It’s hard to keep up without getting swept up. So, many people (rightfully so) regard superfoods with a healthy amount of skepticism. A superfood is “a nutrient-rich food considered to be especially beneficial for health and well-being.” That’s a pretty broad definition– it’s no wonder they keep announcing new ones! But please read on about walnuts.
This week I read two interesting articles about walnuts and their correlation to reduced cancer deaths. The British Journal of Cancer recently published an article written by a Harvard researcher reporting that his research had shown that tree nuts in general were found to reduce a man’s chances of dying from prostate cancer. Tree nuts include walnuts, almonds, cashews, macadamias and pine nuts. Now, prostate cancer is typically a slow-growing cancer that occurs later in men’s lives. Interestingly, most men who have it will not die from it, but will die from a completely unrelated cause as the disease is very often asymptomatic. However, after lung cancer, prostate is still the second leading cancer killer among men. It’s an extremely hit-or-miss cancer, to say the least, and so we have to ask: how can men reduce their chances of suffering prostate cancer’s fatal effects? The study looked back at 47,000+ men and found that those who ate tree nuts five times per week had a 34% lower chance of dying from prostate cancer than men who ate nuts less often. Let me be clear: both groups had the same rate of diagnosis of prostate cancer regardless of how many nuts they ate. The tree nuts don’t appear to keep men from developing prostate cancer, but they do seem to make them less likely to die from it.
If you think that sounds bizarre, researchers were pretty puzzled too. The research remains largely inconclusive as to exactly why tree nuts correlate to lower prostate cancer deaths, but several other studies have noticed and documented this relationship as well. The next study I read was published in Cancer Prevention Research and was actually performed on mice not humans, but it still offered some new insights on the topic. Some mice had walnuts added to their standard diet- either a diet of typical mouse kibbles or a Western diet. The mice who consumed walnuts were found to have fewer colon cancer tumors (2.3 fold fewer in the western diet group). The researchers then analyzed the stool of all the mice in the study and found that the mice that had eaten walnuts, especially the males, had more diverse gut biomes than the mice that had not been fed walnuts. More definitive research is needed to determine whether the change in the gut flora is behind the decrease in tumor development or whether it is just yet another benefit of the walnuts. Regardless, the walnuts seem to have had a surprisingly beneficial impact.
So what is it in the nuts that contribute to our health? Is it the B vitamins? The magnesium? Or a plant-specific type of chemical that offers protection against inflammation and cancer and encourages the growth of healthy gut bacteria? Nobody’s totally sure, but I’ll be sure to keep eating Waldorf salad, snacking on walnuts, and adding them to my baked goods any chance I get.
Nakanishi M, Chen Y, Qendro V, et al. Effects of walnut consumption on colon carcinogenesis and microbial community structure [published online May 23, 2016]. Cancer Prev Res (Phila). doi:10.1158/1940-6207.CAPR-16-0026
Wang W, Yang M, Kenfield SA, et al. Nut consumption and prostate cancer risk and mortality. Br J Cancer. 2016 Jun 9. doi:10.1038/bjc.2016.181. [Epub ahead of print]