Forget “unhealthy”, peanuts and nuts may be good for you

Add this to the heap of stuff I’m having to unlearn/relearn. “Prospective Evaluation of the Association of Nut/Peanut Consumption With Total and Cause-Specific Mortality“:

Importance  High intake of nuts has been linked to a reduced risk of mortality. Previous studies, however, were primarily conducted among people of European descent, particularly those of high socioeconomic status.

Objective  To examine the association of nut consumption with total and cause-specific mortality in Americans of African and European descent who were predominantly of low socioeconomic status (SES) and in Chinese individuals in Shanghai, China.

Design, Setting, and Participants  Three large cohorts were evaluated in the study. One included 71 764 US residents of African and European descent, primarily of low SES, who were participants in the Southern Community Cohort Study (SCCS) in the southeastern United States (March 2002 to September 2009), and the other 2 cohorts included 134 265 participants in the Shanghai Women’s Health Study (SWHS) (December 1996 to May 2000) and the Shanghai Men’s Health Study (SMHS) (January 2002 to September 2006) in Shanghai, China. Self-reported nut consumption in the SCCS (approximately 50% were peanuts) and peanut-only consumption in the SMHS/SWHS were assessed using validated food frequency questionnaires.

Main Outcomes and Measures  Deaths were ascertained through linkage with the National Death Index and Social Security Administration mortality files in the SCCS and annual linkage with the Shanghai Vital Statistics Registry and by biennial home visits in the SWHS/SMHS. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% CIs.

Three huge cohort studies all bundled into one paper. Two were in China, and one was in the US. The gist is that they looked at the associations between mortality and nut/peanut consumption. They controlled for all the usual things. They followed people for a median 5.4 years in the US study and 6.5 and 12.2 years in the Chinese studies. In that period, 14,400 deaths occurred.

In all three cohorts, the more nuts you ate, the lower your total mortality. Compared to those who ate no nuts, if you were in the highest quintile, your relative risk of mortality was 21% lower in the US and 17% lower in China. It seems that this difference was driven mostly by reduced mortality from cardiovascular causes, especially ischemic heart disease. The results held true for both men and women, for all ethnicities, and wasn’t altered by having a metabolic condition.

It’s an epidemiologic study, of course, but why isn’t there an RCT going on? Drugs often don’t get results like these, and I have to agree with the editor’s note (emphasis mine):

Multiple studies have demonstrated the beneficial effects of eating nuts. Nonetheless, the editors felt it was worth publishing another such study for 2 reasons. First, this study combined 3 cohorts to produce a large and diverse sample, including a predominately low socioeconomic cohort of Americans and 2 Chinese cohorts. The authors found that higher nut intake was associated with lower mortality in all 3 cohorts. The consistency of the results between the cohorts and with prior studies that have been performed in higher-income populations increases our confidence that the beneficial effects of nuts are not due to other characteristics of nut eaters. Second, in the 2 Asian cohorts, nuts were limited to peanuts because there was very little tree nut consumption in these groups. This is important because peanuts are cheap and ubiquitous (and can be ground into delicious peanut butter!). Of course, peanuts are not really nuts (they are legumes since they grow in bushes, unlike tree nuts), but who cares if they help us to live longer at an affordable price.

Why aren’t we hearing this advice to prevent death from cardiovascular causes?


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