Snacking on walnuts instead of biscuits or sweets may add years to your life, according to new research.
A handful a day reduces the risk of heart attacks, strokes and other life threatening conditions linked to obesity.
The 'superfood' is packed with chemicals that protect DNA by destroying reactive molecules, or oxidants.
A study found regular consumers were slimmer and fitter as they got older. They had fewer harmful fats, called tryglycerides, and lower blood pressure.
Lead author Professor Lyn Steffen, of the University of Minnesota, said: "Walnut eaters seem to have a unique body phenotype that carries with it other positive impacts on health like better diet quality.
"This is especially so when they start eating walnuts from young into middle adulthood - as risk of chronic diseases like heart disease, obesity, and diabetes elevates."
The findings are based on more than 3,000 individuals across the US who were tracked for three decades - into their fifties.
This is when men and women are most prone to developing a 'pot belly' or 'muffin top' - which can lead to cardiovascular disease, diabetes or some cancers.
Participants were identified as 'walnut', 'other nut' or 'no nut' consumers. Diets were self-reported at the outset and after seven and 20 years.
The former had higher quality of life and physical activity scores than the other two groups. Overall heart health was also better.
Average weight gain was less, there were fewer cases of obesity and fasting blood glucose was lower. They also had lower 'bad' cholesterol than eaters of 'other nuts'.
Prof Steffen and colleagues analysed data from CARDIA (Coronary Artery Risk Development in Young Adults Study), one of the longest and most extensive of its kind.
He said: "There is a good degree of diversity in terms of the research field locations geographically speaking and the population studied.
"Following these black and white women and men for 30 years provides an unparalleled window of study into how lifestyle decisions made in free-living environments in young adulthood can affect health in middle-age.
"Nut consumers showed an advantage in relation to diet quality, but walnut consumers appear to have a better heart disease risk factor profile than other groups, even after accounting for overall diet quality.
"The surprising, healthy shifts in the overall dietary pattern of walnut consumers suggests walnuts may act as a bridge or 'carrier' food for helping people form healthy nutrition and lifestyle habits throughout lifestyle."
Walnuts are rich in healthy plants chemicals including polyunsaturated fat and omega fatty acids which combat bad cholesterol.
They dampen inflammation that can lead to a clotted vessel - and trigger a heart attack or stroke.
Previous studies have found five helpings of nuts a week halve the risk of cardiovascular disease.
The study in Nutrition, Metabolism, & Cardiovascular Diseases says walnuts might be an easy and accessible food choice to boost the heart when eaten up to middle age.
It could be due to the "unique combination of nutrients" and their effect on health, said Prof Steffen.
About an ounce a day - equivalent to seven whole walnuts - has four grams of protein and two grams of fibre.
It is also a good source of magnesium which is important for the muscles and nerves, and increases energy.
The study - backed by the National Heart, Lung, and Blood Institute in the US - was also part funded by the California Walnut Commission.
It took into account other heart disease risk factors including overall diet, smoking and body composition.
Including walnuts in young adulthood improved total diet quality when compared to peers.
