Even the epidemiologists doing the research found the pun irresistible: good health costs peanuts. For what they describe as a relatively affordable benefit, their study has found that a diet high in nuts is linked to lower mortality - associated with death rates cut by as much as a fifth.
The results, published among the latest online papers from JAMA Internal Medicine, comes from three large prospective cohort studies.
These involved 71,764 people living in the southern US with mostly low incomes - black and white people, men and women - and 134,265 Chinese people - one a cohort of men, the other of women - living in Shanghai, China.
Consistent across all three separate cohorts, the study showed that nut intake was linked to a lower risk of total mortality (death from any cause), and death from cardiovascular disease.
Numerous previous studies, say the authors - including Dr. Xiao-Ou Shu from the Vanderbilt University School of Medicine, Nashville, TN - have found benefit from eating peanuts, but with the limitation that the people studied represented higher income groups - and the nuts were more expensive, too.
This study therefore looked at the diets of people from low-income groups, and diets that included predominantly peanuts - the least expensive nuts.
"Nuts," that is, in the common sense - since peanuts are in fact legumes, as are peas and beans, but have similar nutrients to true tree nuts, and are counted as nuts in epidemiological studies as well as by most ordinary people.
The combined analysis of the cohort studies cannot conclude a cause-and-effect relationship between eating nuts and a lower death risk because, for example, other factors can be responsible for observations, and in this study, there was no "dose-response" effect - no trend towards additional benefit from eating more and more nuts, just a benefit of eating nuts versus not eating them.
There is nonetheless strength in the prospectively observed link, as Dr. Michael Katz points out in an editor's note to the study:
"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."
The authors conclude:
"The findings highlight a substantive public health impact of nut/peanut consumption in lowering CVD [cardiovascular disease] mortality given the affordability of peanuts to individuals from all socioeconomic status backgrounds."