Researchers suggest just a handful of nuts daily can offer a wealth of health benefits.
So far, research has shown nut consumption to reduce the risk of coronary heart disease, stroke, and cancer, but new research suggests their health benefits may extend well beyond these major diseases.
Researchers from Imperial College London in the United Kingdom and the Norwegian University of Science and Technology in Norway analyzed a range of existing studies and tracked down associations between nuts intake and risk of various illnesses.
The findings have been published in the journal BMC Medicine.
The research consisted of a meta-analysis of 29 existing studies from around the world, including Europe, Asia, and Australia.
Researchers used the medical research databases PubMed and Embase to search for prospective studies of nut consumption and risk of cardiovascular disease (CVD), total cancer cases, all-cause mortality rates, and cause-specific mortality rates published up to 19 July, 2016.
The analysis included 819,448 participants and included over 12,300 cases of coronary heart disease, more than 9,200 cases of stroke, more than 18,600 cases of CVD, and around 18,400 cases of cancer.
The study examined the link between nut consumption and mortality from a variety of causes, such as respiratory disease, diabetes, neurodegenerative disease, infectious disease, and kidney disease.
The research included all kinds of tree nuts - including hazelnuts, walnuts, cashews, macadamia nuts, and pine nuts, as well as peanuts, which are actually legumes.
A handful of nuts a day enough to cut risk of various diseases
Consuming a handful of nuts daily was associated with an overall 22 percent decrease in the risk of all-cause mortality.
The analysis revealed that as little as 20 grams a day - the equivalent of a handful - can reduce the risk of coronary heart disease by almost 30 percent, the risk of CVD by 21 percent, and the risk of all cancers by 15 percent.
The risk of respiratory disease was shown to decrease by more than half, at 52 percent.
Eating a handful of nuts every day also decreased the risk of diabetes by almost 40 percent and the risk of infectious diseases by 75 percent.
Both peanuts and tree nuts seemed to reduce the risk of coronary heart disease, CVD, and mortality, but only peanuts reduced the risk of stroke. Additionally, only tree nuts were linked to a decreased risk of cancer.
Most of the reduction in risk was associated with an intake of approximately 15-20 grams per day, and no further reduction was noticed if the intake was increased.
Therefore, researchers suggest a minimum of 20 grams is needed to fully benefit from the nutritional properties of nuts and avoid preventable mortality:
"Under the assumption that the observed associations are causal we estimated that approximately 4.4 million premature deaths in the regions covered, including North and South America, Europe, Southeast Asia, and Western Pacific, may be attributable to a nut intake below 20 grams per day."
The authors caution, however, that such an estimate depends on the assumption that there is a causal relationship between nut consumption and health outcomes. This analysis cannot provide such causality.
Why nuts are good for you
Study lead author Dagfinn Aune, from the School of Public Health at Imperial College London, explains the significance of the results.
"We found a consistent reduction in risk across many different diseases," he says, "which is a strong indication that there is a real underlying relationship between nut consumption and different health outcomes. It's quite a substantial effect for such a small amount of food."
He also explains how the nutritional value of nuts may be responsible for the positive health outcomes.
"Nuts and peanuts are high in fiber, magnesium, and polyunsaturated fats - nutrients that are beneficial for cutting cardiovascular disease risk and which can reduce cholesterol levels," Aune says.
Previous studies have also shown nuts to be rich in antioxidants, with a single serving of walnuts providing more antioxidants than fruits and vegetables combined.
"Some nuts, particularly walnuts and pecan nuts are also high in antioxidants, which can fight oxidative stress and possibly reduce cancer risk," Aune says. "Even though nuts are quite high in fat, they are also high in fiber and protein, and there is some evidence that suggests nuts might actually reduce your risk of obesity over time."