Eat Nuts!

A recent study reported in the New England Journal of Medicine found that consuming nuts on a daily basis significantly decreased mortality in an adult population over a 30-year period. More specifically, people who ate nuts at least 7 times per week were 20% less likely to die than people who did not eat nuts. These results were nicely summarized in a Washington Post article:

"This study analyzed data on 118,962 men and women who had never had cancer, heart disease or a stroke. Over a span of nearly 30 years, 27,429 of them died. Those who ate a one-ounce serving of nuts — roughly, a small handful — seven or more times a week were 20 percent less likely to have died for any reason than those who never ate nuts. Even those who ate nuts less than once a week had a 7 percent reduction in risk. Consuming nuts at least five times a week corresponded to a 29 percent drop in mortality risk for heart disease, a 24 percent decline for respiratory disease and an 11 percent drop for cancer."

Importantly there was a dose-dependent effect, i.e. the more frequently you ate nuts the better the health outcome. Those who ate nuts once a week had a reduction in mortality of 11% (health hazard ratio of 0.89 compared to non-nut eaters), those who ate nuts 5 or 6 times per week had a mortality rate reduction of 15% (hazard ratio = 0.85), and those who ate nuts 7 or more times per week were 20% less likely to die (hazard ratio = 0.80). Note the study quantified how frequently participants ate one serving (~1 oz, a handful) of nuts over a given period of time (i.e. week).

Eating nuts impacted a range of diseases with mortality declines observed for heart disease, respiratory disease, and cancer. The study distinguished between peanuts and tree nuts (e.g. walnut, almond, hazelnut, cashew, pistachio, and Brazil nuts), but there was not a significant difference between these two types of nuts.

What is the explanation? One possibility is that the nuts possess healthful ingredients such as unsaturated fatty acids, high-quality protein, fiber, vitamins, and minerals. Indeed nuts are an important part of the Mediterranean diet which has been shown to be associated with a reduced risk of lethal cardiovascular events like heart attacks and stroke. Another related hypothesis is that nuts might substitute for (and reduce consumption of) junk food like french fries and potato chips, which are unhealthy because of their large number of calories and high levels of trans and saturated fats.

It is important to note some caveats. First, the study was sponsored by the NIH and the International Tree Nut Council Nutrition Research and Education Foundation, and so there may be some conflict of interest with the latter. Second, nut consumption was calculated based on the self-reporting of the participants, which can be inaccurate at times. Third, and most importantly, there are numerous confounding variables that correlate with nut eating that can also contribute to health. For example, "as compared with participants who consumed nuts less frequently, those who consumed nuts more frequently were leaner, less likely to smoke, more likely to exercise, and more likely to use multivitamin supplements; they also consumed more fruits and vegetables and drank more alcohol." Thus, nut-eaters lead a more healthy lifestyle overall than non-nut-eaters. In their results, the investigators were able to adjust for the above confounding variables, but it is possible that there are additional confounding factors that were not controlled for in the study.

Despite these caveats, the results are quite striking, which is why the study was published in the New England Journal of Medicine, the premiere journal for medical research. Further studies are warranted, but in the meantime Quantified Health advises you to eat some nuts on a regular basis (see Figure 1) especially as a substitute for junk food!

Figure 1. Be a health nut, or else at least eat healthy nuts.