A series of large studies, including the Nurses' Health Study of 76,464 women and the Health Professionals Follow-Up Study of 42,498 men, has found the more nuts people eat, the less likely they are to die, especially of cancer or heart disease, at any given age.
And a clinical trial conducted in Spain shows that death rates are lower among those consuming a Mediterranean diet supplemented with extra nuts.
However, these studies were conducted almost entirely among relatively well-to-do, well-educated, white individuals, and despite the researchers' care in controlling for other factors that could have influenced the results, there remains the possibility that characteristics of the participants other than nut consumption could account for their reduced death rates.
But now, strong links between nuts and peanuts and better health have also been found in a major study of people from lower socioeconomic backgrounds and varied ethnic groups - many of whom had serious risk factors for premature death, such as smoking, obesity, high blood pressure and diabetes.
More nuts, lower death rate
The results were published last month in JAMA Internal Medicine by researchers at Vanderbilt University School of Medicine. Their study, conducted among more than 200,000 men and women in the southern US and Shanghai, found that the more nuts people consumed, the lower their death rates from all causes and especially from heart disease and stroke.
While it is true that more people today are allergic to nuts, and to peanuts in particular, than ever before, two recent studies have pointed to ways that may prevent children from developing a nut allergy.
The first study, published last year in JAMA Pediatrics, found that women who consumed the most nuts or peanuts during their pregnancies were least likely to have children with this allergy. The reduction in risk was highest among children whose mothers ate nuts five or more times a month.
Early introduction reduces allergy risk
The second study, published in February in The New England Journal of Medicine, found that introducing peanuts into the diets of infants four to 11 months old who were considered at high risk of developing a peanut allergy actually greatly reduced their risk of being allergic at age five years. The researchers, from King's College London, suggested that the common practice of withholding peanuts from babies may in fact account for the recent rise in peanut allergies.
When consumed in reasonable quantities, nuts are not fattening and can even help people lose weight and maintain the loss.
Relatively speaking, nuts are high in fat, and fat contains more calories per gram (9g) than protein or sugar (4g), even more than alcohol (7g). But a review of studies of large populations by Richard Mattes of Purdue University and co-authors most often found that adults who eat nuts weigh less than nut avoiders. And children who eat peanuts usually had a lower body mass index than those who do not.
Weight control
Clinical trials found that adding lots of nuts to diets had a limited effect on body weight. But more important, participants in studies that included nuts in a weight-loss regimen lost more weight and ended up with a smaller waist and less body fat than participants who did not eat nuts.
One explanation for the weight control benefit of nuts is the satiation provided by their high fat and protein content, which can reduce snacking on sweets and other carbohydrates. Another is that all the calories in nuts may not be absorbed because they resist breakdown by body enzymes.
In a 2013 study in The British Journal of Nutrition, Mattes and colleagues reported that consuming peanut butter or peanuts for breakfast helped to control hunger.
Nuts are rich sources of monounsaturated and polyunsaturated fats, which prompted a health claim by the Food and Drug Administration: "Scientific evidence suggests, but does not prove, that eating 1.5oz (about 42g) per day of most nuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease."
Two exceptions are macadamia nuts and cashews, which have too much saturated fat to qualify for this claim.
Source: AFP via I-Net Bridge