Nuts and peanuts -- but not peanut butter -- linked to lower mortality rates, study finds

The reduction in mortality was strongest for respiratory disease, neurodegenerative disease, and diabetes, followed by cancer and cardiovascular diseases. The effects are equal in men and women. Peanuts show at least as strong reductions in mortality as tree nuts, but peanut butter is not associated with lower mortality, researchers from Maastricht University found.

This study was carried out within the Netherlands Cohort Study, which has been running since 1986 among over 120,000 Dutch 55-69 year old men and women. Nut consumption was assessed by asking about portion size and frequency of intake of peanuts, other nuts (tree nuts), and peanut butter. The researchers from Maastricht University analyzed the relationship with overall and cause-specific mortality since 1986.

The associations between nuts and peanut intake and cardiovascular death confirm earlier results from American and Asian studies that were often focused on cardiovascular diseases. However, in this new study, it was found that mortality due to cancer, diabetes, respiratory, and neurodegenerative diseases was also lowered among users of peanuts and nuts. Project leader and epidemiologist Professor Piet van den Brandt commented: "It was remarkable that substantially lower mortality was already observed at consumption levels of 15 grams of nuts or peanuts on average per day (half a handful). A higher intake was not associated with further reduction in mortality risk. This was also supported by a meta-analysis of previously published studies together with the Netherlands Cohort Study, in which cancer and respiratory mortality showed this same dose-response pattern."

Peanuts and tree nuts both contain various compounds such as monounsaturated and polyunsaturated fatty acids, various vitamins, fiber, antioxidants, and other bioactive compounds, that possibly contribute to the lower death rates. In contrast to peanuts, no association was found between peanut butter intake and mortality risk. However, besides peanuts, peanut butter contains also added components like salt and vegetable oils. In the past, it has been shown that peanut butter contains trans fatty acids and therefore the composition of peanut butter is different from peanuts. The adverse health effects of salt and trans fatty acids could inhibit the protective effects of peanuts.