Americans have not always been in love with nuts.
Think about it: They're loaded with calories and fat. Plus, they can be expensive.
But Americans' views — and eating habits — when it comes to nuts are changing. Fast.
There's a growing body of scientific evidence that's putting a health halo over supermarkets' expanding nut aisles.
Earlier this year, a large diet study concluded that people who eat a Mediterranean-style diet supplemented with daily portions of nuts and olive oil have significantly lower risks of heart attacks and strokes.
And just last month, more evidence emerged that snacking on nuts helps control our appetites, which may stave off weight gain.
Now, a new study published in the New England Journal of Medicine finds that people in the habit of eating a daily handful (a 1-ounce serving) of nuts are more likely to live longer compared with people who rarely consume nuts.
"The preponderance of evidence suggests a health benefit [from eating nuts]," says researcher Charles Fuchs of the Dana-Farber Cancer Institute and Harvard Medical School.
To isolate the association between nut consumption and lifespan, Fuchs and his colleagues combined data from two long-term studies that include about 76,000 women and 42,000 men.
The participants in the study completed food frequency surveys every two to four years over several decades. They answered all kinds of questions about dozens of different kinds of foods, including how many servings of nuts they consumed.
"What we find is that regular nut consumers have about a 20 percent reduction in all-cause mortality" over the course of the study, Fuchs says. This includes lower death rates from heart disease and cancer.
Now, since death is inevitable for all of us, here's another way to think about the findings: Men and women who were regularly munching on peanuts or tree nuts like almonds, pecans and walnuts in their 30s and 40s when the study began were significantly more likely to reach their 70s, compared with folks who didn't eat nuts.
So how could a daily handful of nuts possibly be so beneficial? Fuchs says it's not entirely clear.
"What we think nuts do is that they affect metabolism," he explains. Prior research has shown that nuts help us feel fuller, faster. And nuts also help control blood sugar.
Fuchs says if nuts lead to a sense of satiety and help people eat less, many of the other benefits may follow. This could "reduce the risk of diabetes and also reduce the risk of cardiovascular disease," he says.
Of course, this study does not prove a cause and effect between eating nuts and living longer. The design of this type of long-term, observational study only enables researchers to establish an association — a link.
Going forward, researchers want to try to better understand what might explain this link. They want to know more about how the combination of beneficial plant compounds and minerals — such as magnesium, fiber and protein — found in nuts may be influencing the body.
With all the good news about nuts in the news, experts who track food trends say more Americans are eating them.
"Nuts are in the perfect spot right now," says John Frank of Mintel. The market research firm estimates that sales of nuts and dried fruit in the U.S. will grow from about $7 billion in annual sales in 2012 to over $9 billion by 2017.
Nuts check a lot of boxes that young adults are looking for: They're high in protein, they're easy to grab and eat on the go, and they're a natural, plant-based food.
"I'm a vegetarian, so nuts are an important part of my diet, for added protein," shopper Emily Williams told me as she added nuts to her shopping cart at a Trader Joe's in Washington, D.C.
Many grocery stores' expanding nut aisles now include lots of variety — everything from dark-chocolate-covered almonds to spicy, Asian-flavor-infused nuts.
And Frank says millennials love the variety. Young adults aren't just snacking on nuts — increasingly, they're tossing them in salads and sprinkling them in yogurt and cereal.
One note about the NEJM study on nuts: The major part of the study was funded by the National Institutes of Health. The researchers also accepted a grant from the International Tree Nut Council Nutrition Research and Education Foundation to cover the cost of analyzing the data.
"The [nut] council approved the grant without any knowledge of the results," says Fuchs. And there was an agreement that the researchers would have reported the findings no matter what the results showed.
ROBERT SIEGEL, HOST:
People who eat a handful of nuts each day are more likely to live longer than those who rarely eat nuts. That is according to a big, new study published in the New England Journal of Medicine, its part of a growing body of evidence linking nuts to all sorts of health benefits.
NPR's Allison Aubrey looks at what might explain the longevity effect and how the good health news about nuts has helped fuel a boom in consumption.
ALLISON AUBREY, BYLINE: Americans have not always been in love with nuts. Think about it: They're loaded with calories, have lots of fat and they tend to be expensive. So many people trying to lose weight are told to avoid nuts altogether. But perhaps that's not such good advice.
A huge, new study from Harvard researchers that tracked the diet of over 100,000 men and women for over three decades finds there may be a big benefit to be gained from eating seven little handfuls of tree nuts or peanuts per week. Here's study author Charles Fuchs.
CHARLES FUCHS: What we find is that regular nut consumers have approximately a 20 percent reduction in all-cause mortality, that is dying from any cause.
AUBREY: Including death from heart attacks, strokes and cancer. Now, of course, death is ultimately inevitable so another way to think about these findings is that the men and women who were in the habit of munching on nuts in their 30s and 40s were much more likely to make it to their 60s and 70s without these life threatening diseases. So what's going on here?
How could a daily handful of nuts possibly be so beneficial? Fuchs says it's not entirely clear, but the theory goes something like this.
FUCHS: You know, what we think nuts do is that they affect metabolism.
AUBREY: Making us feel fuller quicker. Nuts also help control blood sugar, which, in turn...
FUCHS: Reduces the risk of diabetes and through that also reduces the risk of cardiovascular disease.
AUBREY: And certain cancers. Fuchs says there does not seem to be one magic compound contained in almonds or walnuts or peanuts. Instead, think of nuts of containing a combination of potentially beneficial things.
FUCHS: Nuts are a smorgasbord of potential bioactive compounds, minerals, vitamins, fiber, protein, amino acids.
AUBREY: Not to mention healthy fats, all of which may play a role. Now experts who study food trends say people do seem to be listening to the good news about nuts. Several studies over the last decade have all hinted at health benefits and Americans are now eating more of them.
JOHN FRANK: I think nuts are definitely in the perfect spot right now.
AUBREY: That's John Frank of the firm Mintel. He estimates that nuts, along with dried fruit, account for over $7 billion in annual sales. And nuts are now growing faster than any food category, perhaps with the exception of yogurt. I called Frank from my local supermarket where nuts seemed to be everywhere.
Here I am in the snack aisle. Wow. The snack aisle has grown quite a bit.
FRANK: You can find them in the produce section, too.
AUBREY: He says, look at the shelves. There are glazed and coated nuts, from chocolate-covered to spicy Asian infused. I'm seeing trail mixes. I'm seeing wasabi and soy sauce almonds. This is a lot of variety here. All of this appeals to shopper Emily Williams.
EMILY WILLIAMS: I'm a vegetarian and for me, nuts are an important part of my diet for getting added protein.
AUBREY: John Frank says many young adults aren't just snacking on nuts. They're tossing them in salads and sprinkling them in yogurt and adding them to cereal. And they love the novelties of all the new flavors. And what's your favorite of these newer things?
WILLIAMS: Oh, that's a good question.
AUBREY: Lime and chili.
WILLIAMS: Lime and chili looks really good. I don't know that I've tried those, but that's something that I might throw in my cart, absolutely.
AUBREY: So back to the results of the new study. I decided to tell some of these shoppers in the nut aisle about the findings, that eating nuts regularly might actually help them live longer. Zach Denani(ph) was buying nuts for his wife.
ZACH DENANI: I am a nut guy, yes.
AUBREY: What kind of nuts do you like?
AUBREY: A new study finds that people who eat nuts actually have less heart disease and live longer.
DENANI: That is a surprise.
AUBREY: Do you believe that?
DENANI: Uh, no, not really, no.
AUBREY: It's healthy skepticism. After all, lots of lifestyle choices play into good health, but study author Charles Fuchs says if you like nuts, adding a handful to your diet is a good idea. Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.