The plausible health benefits of nuts: associations, causal conclusions, and informed decisions

See corresponding articles on pages 256, 270, and 278. There is an old proverb that the gods send nuts to those who have no teeth. If there are gods of nutrition, they must have wonderful fun teasing us mortals with so many tantalizing signs of plausible causal effects that are so difficult to unequivocally confirm or refute. They send us nuts but do not give us much in the way of inferential teeth. Still, it is appealing to think about nuts. Nuts have had a special place in nutrition and cuisine for ages. The Book of Genesis, according to the Darby Bible translation (1), states: “And their father Israel said to them, If it is then so, do this: take of the best fruits in the land in your vessels, and carry down the man a gift: a little balsam and a little honey, tragacanth and ladanum, pistacia-nuts and almonds.” Were these biblical events transpiring or being written in today’s political climate of antifructose sentiment, we suspect the honey would be turned to ashes in the men’s mouths by the avenging angel Aldolase. But whether in biblical or present times, the nuts are seen as a great gift, and this seems to have been so throughout most of history. Alabama’s George Washington Carver is well known to have advocated consumption of peanuts (although peanuts are not true nuts) and their health benefits. A 1908 USDA farmer’s bulletin (2) on “Nuts and Their Uses as Foods” advocated nuts as good sources of protein for persons with diabetes and almond meal as a replacement for flour in selected baked goods, because nuts contain little carbohydrate. During World War II, nuts were advocated as a good alternative to meat to obtain protein (3). Yet, there was a period of exception. From approximately 1950 to the mid-1990s, nuts were often seen as undesirable because of their high fat content. A 1951 article in Circulation (3) describing the health benefits of implementing a low-fat diet suggested the following food groups to avoid: “(a) fried foods, (b) fatty cuts of meat, (c) cream, whole milk and their products, (d) concentrated vegetable oils such as peanut butter, shortening, mayonnaise, and similar substances, (e) avocados, nuts, olives, and soy beans.” The article specifically stated “No chocolate or nuts.” Ironically, although debate remains, many nutrition experts today believe with equal conviction that these are some of the best foods for us to eat. Then, in the heyday of anti–dietary fat sentiment, the worm started to turn for nuts. In the same year that the Planters (Nabisco) company was coming out with a new low-fat line of nuts (5), Jenkins (6) published an article advocating a healthy diet in which nuts played a vital role. A few articles had been published showing apparent health benefits in previous years, but in the late 1990s the flood gates seemed to open and a wave of short-term studies showed benefits of nuts on biomarkers and another wave of observational epidemiologic studies showed associations between greater nut consumption and reduced risk of some diseases. Now, 3 new integrative summaries give us a chance to pause and take stock. What do we really know about the health effects of nuts and what do we still need to learn?