The New England Journal of Medicine recently published a study looking at the health benefits of nut consumption.
The study is impressive because of its scope and size. The conclusions are derived from subsets of two very large studies: the Nurses’ Health Study, which tracked 76,464 women for 20 years, and the Health Professionals Follow-up Study, which tracked 42,498 men for 14 years. In total, this study captured over 3 million years of data.
In a nutshell (pun intended), the main message is that eating nuts is good for you. The more you eat, the better.
Despite the good news, the absolute benefit is modest, so you might want to digest the full details (below) before concluding that the Planters Nut Co is a purveyor of health and longevity.
This study evaluated whether eating nuts influenced mortality (rate of death). As it turns out, those who ate nuts indeed had a lower mortality. Compared to nut abstainers, if you ate nuts once per week or so, your rate of death was 7-10% lower. Eating nuts several times per week lowered mortality by about 15%. Eating nuts every day cut the mortality rate by about 20%.
Amazing, right? Well, yes, but medical studies love to talk about relative benefit. It’s important to consider the benefit in absolute terms. The mortality rate was about 1% per year in the nut-abstainers. In comparison, ‘nut-eaters’ in aggregate had a mortality rate of about 0.85% per year. This is meaningful but modest. To put this in context, over a twenty year period, out of 100 people, 20 will have died of the nut-abstainer group versus about 17 deaths in the nut-eating group.
I think the overall message is that, if you like nuts, you’re golden. Chomp away. If you have a nut-allergy, don’t fret; it’s not a big deal.
As an aside, it’s interesting that eating a Mediterranean diet (rich in fish, olive oil, wine, and nuts [hmmm. . . maybe nuts are the magic ingredients]) confers a similar or perhaps slightly larger benefit (see here). Conversely (and also interesting), fish oil supplements do not have any benefit at all (see here, here, and here). But I digress.
Going back to the results, the driver of the benefit was heart disease (fewer heart attacks) for ‘nut eaters,’ though there seemed to be fewer infections, less kidney disease, and less respiratory disease as well.
It remains unclear why eating nuts is beneficial. Perhaps, as the NEJM mentions, the value of nuts lies in their being rich in unsaturated fatty acids and antioxidants. However, there’s also the possibility that nuts themselves do not cause good health but are merely correlated with that outcome (the question of causation versus correlation is always tricky). The authors of this study tried to correct for other variables such as smoking, alcohol consumption, etc. In doing so, they tried to isolate just the impact of nut consumption. However, real life has too many variables. Maybe ‘nut eaters’ have healthier snacking habits. Maybe the benefit came from avoiding Twinkies or pastries or any other number of snacks that nuts might have replaced. Perhaps ‘nut eaters’ had some other behavior pattern, and eating nuts was simply correlated/associated with that other behavior. Indeed, ‘nut eaters’ on average were thinner, smoked less, had physical check-ups more often, and ate more fruit/vegetables. While the study adjusted for all of these factors, it seems quite plausible that there could have been other activities that were not captured that could have conferred the observed health benefit.
Happy Thanksgiving. Consider enjoying a serving of nuts (and a glass of wine) with your meal.
sources: Association of Nut Consumption with Total and Cause-Specific Mortality (New England Journal of Medicine); Primary Prevention of Cardiovascular Disease with a Mediterranean Diet (New England Journal of Medicine);