Snacking on a handful of walnuts just five times a week could add an extra 1.3 years to your life, research suggests.
Walnuts are high in healthy fats, as well as being a rich source of magnesium, fibre and protein.
To better understand the snack's benefits, a team of Harvard scientists analysed more than 93,000 adults – average age 63 – for around 20 years.
Every four years, the participants provided information on their diet, including their nut consumption.
Results, published in the journal Nutrients, suggest eating five or more portions of walnuts a week reduced the participants' risk of dying from any cause by 14% over the two decades.
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Incorporating walnuts into your diet is "a practical tip" that is "feasible" for most people, one scientist has said.
This comes after scientists from the University of Michigan found eating a handful of nuts adds 26 minutes to your "healthy" life years.
"What we've learned from this study is even a few handfuls of walnuts per week may help promote longevity, especially among those whose diet quality isn't great to begin with," said lead author Yanping Li.
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"It's a practical tip that can be feasible for a number of people who are looking to improve their health, which is top of mind for many people."
The scientists, supported by the California Walnut Commission, analysed the data of more than 67,000 women from the Nurses' Health Study and 26,000 men from the Health Professionals Follow-up Study.
All of the participants were free of cancer and heart disease at the start of the study. They then reported on their diet and lifestyle habits, such as how often they exercised and their smoking status, every four years.
Five or more walnut servings – with each portion being 1oz (28g) – a week was linked to an extra 1.3 years of life, compared to never eating the snack.
As well as reducing the risk of death by any cause, regular walnut consumption was found to cut the odds of cardiovascular mortality specifically by 25%.
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Snacking on walnuts two to four times a week was also found to have benefits – cutting the overall risk of death by 13% and cardiovascular mortality by 14%, while adding around one year of life.
Among the participants with "a suboptimal diet", just half a handful of walnuts a day was found to reduce the risk of death from any cause or heart disease specifically by 12% and 26%, respectively.
The Harvard scientists have stressed the study was observational, and therefore does not prove cause and effect. Nevertheless, the results shed light on how walnuts can be part of an overall healthy lifestyle, they added.
The study's walnut consumers were found to be more active, take supplements and have a lower alcohol consumption, all of which can influence our lifespan. The results remained the same after the scientists accounted for these lifestyle factors.
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