People who ate nuts every day were 20 percent less likely to have died during a 30-year Harvard follow-up than those who never ate nuts, according to research published in the New England Journal of Medicine in 2013. The analysis drew on nearly 120,000 participants in the Nurses' Health Study and the Health Professionals Follow-up Study.
The daily nut eaters also had lower death rates from heart disease, cancer and respiratory disease. And the pattern was gradual. The more often people ate nuts each week, the lower their risk of dying early during the study period.
What the heart data actually show
A large BMC Medicine meta-analysis published in December 2016 pooled 20 prospective cohort studies and looked at what happens per extra 28 grams of nuts a day, roughly one small handful.
Each daily 28-gram serving was linked to a 21 percent lower risk of cardiovascular disease and a 29 percent lower risk of coronary heart disease specifically. The same analysis tied the daily handful to a 15 percent lower risk of total cancer and a 22 percent lower risk of dying from any cause. Most of the benefit appeared at intakes of only about 15 to 20 grams a day, so the curve flattens well before you reach a large portion.
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These are observational studies, so they show association rather than proof of cause. But the effect has now been replicated across many populations and long follow-ups, which is why nuts keep turning up in expert dietary advice.
Calorie-dense, yet linked to less weight gain
Nuts are energy-dense, and the intuitive worry is that a daily handful will show up on the scale. Long-term cohort data point the other way.
A study in BMJ Nutrition, Prevention & Health published in September 2019 followed roughly 290,000 US health professionals for more than two decades, with weight measured every four years. Adding half a serving of nuts a day was linked to less weight gain over each four-year interval.
Consistent daily intake of at least that amount was tied to a 23 percent lower risk of gaining 5 kilograms or more, and swapping half a serving of nuts for processed meats, refined grains or desserts prevented between 0.41 and 0.70 kilograms of gain per four-year period.
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One explanation, according to Harvard researcher Dr. Frank Hu, is that "nuts are high in protein and fiber, which delays absorption and decreases hunger."
Cholesterol, blood pressure and blood sugar
The heart-benefit signal is not just statistical. Nuts change measurable risk factors.
"Eating nuts lowers LDL ('bad' cholesterol), raises HDL ('good' cholesterol) and also lowers blood pressure," Dr. Penny Kris-Etherton of the University of Pennsylvania told Harvard Health. The unsaturated fats in most tree nuts are the main driver of the LDL effect, and several nuts also contribute magnesium and vitamin E.
For people with type 2 diabetes, the evidence on blood sugar is more modest. Small trials suggest that swapping refined carbohydrates for nuts may improve blood sugar control, but the effect size is smaller than for cholesterol, and anyone managing diabetes should discuss diet changes with their own doctor.
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How much, and which nuts
Most of the research points to roughly one small handful a day, about 28 grams. That is a modest portion, close to a quarter cup of almonds or 14 to 18 walnut halves.
Walnuts, almonds and pistachios have some of the strongest individual evidence, but the Harvard analysis found benefits across walnuts, almonds, peanuts and pistachios. Unsalted, unroasted or dry-roasted versions keep the sodium down. And there is no need to force a large portion. The dose-response curve in the meta-analysis flattens early, so a small daily handful appears to capture most of the gain.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.