Should You Eat Lots of Nuts?
Some years ago a medical paper was published that caused a run on Brazil nuts throughout the western world. For a time they disappeared entirely from supermarket shelves; for Brazil nuts contain a high level of selenium and the medical paper had suggested that the high rate of heart attacks in a certain province of China was caused by the exceptionally low level of selenium in the inhabitants’ diet.
But of course for every panacea there is an equal and opposite health scare. Brazil nuts concentrate radium and give off more radiation than any other food; they also often contain relatively high levels of aflatoxin, produced by a fungus of the Aspergillus genus. Aflatoxins are very carcinogenic, leading to cancer of the liver.
So where Brazil nuts are concerned, the question boils down to whether you would prefer to die of heart attack or cancer.
A paper in a recent edition of the New England Journal of Medicine suggests that, overall, nuts are very good for you. The authors compared the death rates among female nurses and male health nurses according to their self-reported consumption of nuts. They divided nut consumption into true nuts and peanuts, the latter being legumes rather than nuts.
I never cease to be amazed at the organizational feat of such studies: 76,464 women and 42,498 men were followed up between 1980 and 2010 and 1986 and 2010, respectively. After various statistical manipulations which 99 percent of the readership of the NEJM would not understand it was found that the more nuts people ate (including the false nuts known as peanuts), the lower their all-cause mortality. They didn’t just die less of such illnesses as heart attack, stroke and cancer, but of all illnesses whatsoever. At last, then, the panacea!
People who ate nuts more than seven times a week(!), hunter-gatherer style, had a 20 percent less chance of dying in the period of follow up than those who never ate nuts. This is a very big effect, for me almost too big to be believed.
As everyone knows, nuts are fattening, or at least of high caloric content. But strangely enough those who ate nuts more than seven times a week were not fat, and this suggested to me that something more than the mere consumption of nuts accounted for their low death rate. People who lie on couches at the first opportunity watching television are not the kind of people, on the whole, who nibble nuts rather than guzzle hamburgers, but the authors claim that the protective effect of nuts still exists even when they controlled for weight.
This is far from the first study that indicates the healthfulness of nuts. Indeed, so persuasive have these studies been that the Food and Drug Administration says a daily consumption of one and a half ounces of nuts might reduce the risk of heart disease. Nuts are said to reduce inflammation, fat deposition round the viscera, the level of sugar in the blood, blood pressure and damage to the lining of the blood vessels, among other desiderata. Increased nut consumption is "associated with" (weasel words) a reduction in the rate of colon cancer, gallstones, diverticulitis and type II diabetes.
The authors warn that "epidemiological observations establish associations, not causality, and not all findings from observational studies have been confirmed in controlled, randomized clinical trials." But I would not be at all surprised if nut consumption rocketed with the publicity given to this paper – and perhaps nut allergy too. At the moment, only about 100 people a year die in the United States of nut allergy, but who knows what the future may hold?
In the meantime, I suggest the following notice at the entrance to every hospital: May contain nuts.
images courtesy shutterstock / Krzysztof Slusarczyk