The analysis of all current studies on nut consumption and disease risk has revealed that 20g a day - equivalent to a handful - can cut people's risk of coronary heart disease by nearly 30 percent, their risk of cancer by 15 percent, and their risk of premature death by 22 percent.
‘Even though nuts are quite high in fat, their high fiber and protein content lowers risk of obesity over time.’
An average of at least 20g of nut consumption was also associated with a reduced risk of dying from respiratory disease by about a half, and diabetes by nearly 40 percent, although the researchers note that there is less data about these diseases in relation to nut consumption.
The research team analysed 29 published studies from around the world that involved up to 819,000 participants, including more than 12,000 cases of coronary heart disease, 9,000 cases of stroke, 18,000 cases of cardiovascular disease and cancer, and more than 85,000 deaths.
The study included all kinds of tree nuts, such as hazel nuts and walnuts, and also peanuts - which are actually legumes. The results were in general similar whether total nut intake, tree nuts or peanuts were analysed.
Study co-author Dagfinn Aune from the School of Public Health at Imperial said, "We found a consistent reduction in risk across many different diseases, 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."
What makes nuts so potentially beneficial, said Aune, is their nutritional value: "Nuts and peanuts are high in fibre, magnesium, and polyunsaturated fats - nutrients that are beneficial for cutting cardiovascular disease risk and which can reduce cholesterol levels. Some nuts, particularly walnuts and pecan nuts are also high in antioxidants, which can fight oxidative stress and possibly reduce cancer risk. Even though nuts are quite high in fat, they are also high in fibre and protein, and there is some evidence that suggests nuts might actually reduce your risk of obesity over time."
The study also found that if people consumed on average more than 20g of nuts per day, there was little evidence of further improvement in health outcomes.
The team are now analysing large published datasets for the effects of other recommended food groups, including fruits and vegetables, on a wider range of diseases.
- Dagfinn Aune et al. Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis of prospective studies
, BMC Medicine (2016)