This latest study confirms the benefits of eating peanuts and nuts. The Netherlands Cohort Study has studied 120, 000 Dutch men and women since 1986, and they found that eating approximately 1/2 handful of peanut or nuts per day is linked to a lower risk of mortality. However, this beneficial effect did not apply to peanut butter, and they theorize that it may be due to the added ingredients in it (salt and vegetable oils that are trans fats) that negate the beneficial effects of nuts. And perhaps eating an all natural peanut butter would have the same beneficial effects as plain nuts.
Note: Since 2013 even the United States FDA has said that partially hydrogenated oils (they are artificially made through an industrial process and contain trans fats) are no longer "generally recognized as safe" because they are linked to heart disease. So in general avoid all products with "partially hydrogenated" in the ingredients. From Science Daily:
A paper published in the International Journal of Epidemiology confirms a link between peanut and nut intake and lower mortality rates, but finds no protective effect for peanut butter. Men and women who eat at least 10 grams of nuts or peanuts per day have a lower risk of dying from several major causes of death than people who don't consume nuts or peanuts.
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.
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.