Nuts

According to the World Health Organization, a healthy diet consists of vegetables, fruit, legumes such as beans, lentils, and chickpeas, nuts, and whole grains; at the same time, you should eat less added sugar, salt, and trans fats, which are found primarily in industrial junk, meat, and dairy products. Meta-analyses of prospective studies have found a lower risk of all-cause mortality for all of these healthy foods. Each additional serving of vegetables per day was associated with a 4 percent lower risk of premature death, each additional serving of fruit reduced the risk by 6 percent, each serving of whole grains by 8 percent, each serving of legumes by 10 percent, and each half-serving of nuts per day by as much as 15 percent. The standout importance of nuts for mortality risk is further underscored by the fact that a half-serving of nuts means only about 15 grams, whereas in the other four groups the servings were larger, up to 100 grams per serving. Of all roughly a dozen food groups, nothing lowers the risk of dying prematurely better than nuts.

Healthy nuts

Few foods have such fundamentally proven effects as nuts, said a respected nutrition journal. Nut consumption is associated with a reduced risk of dying from stroke, heart disease, respiratory disease, infections, diabetes, and even cancer—more than half of the ten most common causes of death. (One study found that patients with stage III colon cancer who ate nuts at least twice a week had more than twice the chance of living an average of another six and a half years as those who didn’t.) So it is not surprising that nut consumption in general is associated with a lower risk of dying early. In one study in which participants were between 84 and 107 years old, daily nut consumption was associated with a longer life to the same extent that regular donut consumption shortened life. An editorial in the Journal of the American College of Cardiology put it succinctly: “Eat nuts, live longer.” Nuts are among the few foods that can extend life by years.

Based on studies that tracked the eating habits and deaths of about half a million people over time, inadequate nut intake worldwide could be responsible for the premature death of millions of people each year. What does that mean for the individual? Eating nuts twice a week means half the mortality risk compared to almost never eating nuts. Two handfuls of nuts a week could do as much for a long life as four hours of jogging. Or, put the other way around: Eating no nuts doubles the danger of dying prematurely. But there is a difference between relative and absolute risk.

The risk for a healthy middle-aged person of dying over the next ten years is about 2 percent. That corresponds to a probability of 1 in 50—if you don’t eat nuts. If you eat nuts, the risk drops to 1 percent. The risk is thus indeed cut in half, from two to one percent, but the absolute risk of dying has decreased by only one percentage point. That may not sound very impressive, but I would find it tragic to die now, when I still have so much life ahead of me, so I think it’s worth changing your lifestyle to keep the risk as low as possible—especially when one of the strategies is such a simple and delicious trick.

Of course, this applies only if the link between nut consumption and mortality really is one of cause and effect. There are many possible confounders. For example, people who eat nuts usually exercise more, smoke less, and eat less meat and more fruits and vegetables. But even after adjusting for these factors, the positive effect on mortality remains. Randomized controlled trials proved that nuts can positively influence some of the biggest risk factors for some of the leading causes of death, such as cholesterol, or, in the case of walnuts, arterial function. No other food group lowers LDL cholesterol so effectively. But there can still be displacement effects. When scientists asked study participants to add hundreds of calories a day in the form of nuts to their daily diet, the subjects naturally ate less animal protein, saturated fat, and salt, which would probably help even without nuts. But it isn’t only because you’re eating nuts instead of meat. Among vegetarians, heart attack risk goes down just as much, or even more, when they frequently reach for nuts.

How many nuts should you eat to get the maximum benefit? Remarkably, the optimal survival advantage is reached with about three servings of nuts per week, an average of 12 grams a day, because no further reduction in mortality risk was found even at more than 15 to 20 grams a day. So it’s at most a handful—for example, 9 hazelnuts, 10 walnut halves, 13 cashews, 17 almonds, or 25 peanuts.

How many nuts are too many?

Amazingly, none of the numerous studies in which subjects, on average, ate hundreds of extra calories a day in the form of nuts for 15 weeks led to significant weight gain. But you can still overdo it. For the same reason you also shouldn’t regularly consume more than a cup of nuts a day as you shouldn’t eat multiple cups of spinach, beet greens, Swiss chard, more than a few starfruits, multiple cups of rhubarb, or more than a few spoonfuls of chaga mushroom powder a day: oxalates.

For information on who is particularly at risk, see see.nf/oxalaterisk, and on other dangerous amounts, see see.nf/oxalatefood—incidentally, dangerously high includes 16 glasses of iced tea a day, regularly more than a cup of cashews or almonds, or a combination of five handfuls of almonds and six tablespoons of chia seeds a day. Note the warning about selenium overdose from Brazil nuts.