Why Dietitians Won’t Shut Up About Nuts

Eating a handful of nuts on a regular basis is good for you, but where are the snack’s health benefits coming from?

Photo: Peter Feghali/Unsplash

IfIf you regularly snack on nuts, you can trace your healthy habit back to a nutrition lab in Southern California. The year was 1990, and Joan Sabaté, MD, DrPH, executive director of the Center for Nutrition at the School of Public Health at Loma Linda University, was studying the potential effects of walnuts on heart health. At the time, thinking that nuts could have any health benefits was a long shot. Almost relegated to the realm of “forbidden foods,” nuts were known for being high in fat and calories. They were far from a health food.

Yet Sabaté’s results, which he published in a landmark study in a 1993 issue of the New England Journal of Medicine, fundamentally changed how health experts thought about nuts. The study highlighted both their nutritional powers and cholesterol-lowering abilities, which worked to improve cardiovascular health.

Since then, hundreds of studies that have expanded and confirmed a wide variety of health benefits of nuts — perhaps part of the reason you’re snacking them today.

Why are nuts so healthy in the first place?

“Nuts are what I like to call nutrient-dense, meaning they pack in a whole lot of nutrition,” says Jenny Friedman, RD, a Philadelphia-based dietitian.

One aspect of this nutrition density comes down to the “healthy” fats all nuts contain. “Nuts really helped the whole conversation about different types of fat,” explains Wendy Bazilian, DrPH, RD, a dietitian and doctor of public health who studied at Loma Linda University. Thirty-some years ago, before Sabaté likely ever thought about studying walnuts, most people viewed fat as the enemy, as low-fat diet crazes took over the country. But as Bazilian says, “Not all fats are created equal.”

Nuts are full of both polyunsaturated and monounsaturated, “heart-healthy,” “good” fats, she says. Adding them into your diet to replace other kinds of fats — such as the saturated kinds found in fatty cuts of beef or store-bought treats — can have anti-inflammatory and other benefits that promote heart health, Bazilian says.

On top of unsaturated and omega-3 fats (walnuts are an excellent source), which promote heart health in part by reducing irregular heartbeats and lowering cholesterol, nuts also contain:

  • Fiber, which is associated with lower cholesterol, gut health, and weight maintenance.
  • L-arginine, an amino acid associated with improved blood flow and the relaxation of constricted blood vessels (think: reduced risk of blood clots).
  • Vitamin E, a powerful antioxidant that can improve blood flow and prevent clotting.
  • Plant-based protein, which helps promote satiety and fullness.
  • Other unique nutrients, vitamins, and minerals, including niacin, thiamin, copper, magnesium, manganese, molybdenum, phosphorus, selenium, and zinc.

Because of all these health-promoting nutrients, Bazilian says nuts have been researched in terms of metabolic health, blood sugar regulation, certain types of cancer, fertility, gut health, and more.

Notably, though, nuts are often hailed for the role they play in weight maintenance. Last month, a long-term study published in BMJ Nutrition, Prevention, and Health found that eating a half-ounce more of nuts per day was linked to less weight gain over time and a lower risk of developing obesity.

“There is some evidence that the body spends more energy digesting nuts than it does other types of fats,” Friedman says. While study results are mixed, this essentially means you could burn more calories by eating nuts, she explains.

Generally, to reap the most health benefits from any nut, eat the least-processed version: nuts in their raw form, instead of, say, honey roasted.

The human body also doesn’t appear to completely absorb all the calories in whole nuts. After testing people’s poop (what a job) to measure amounts of energy, researchers from the U.S. Department of Agriculture found that walnuts, almonds, pistachios, and cashews had 6% to 25% fewer calories than their nutrition labels suggested. (For example, a one-ounce serving of walnuts had 146 calories — 39 calories fewer than what the label said.)

Nuts have a tough cell wall made of fiber, Friedman explains: “There is some evidence that our bodies are unable to completely digest this wall, and what we can’t digest is eliminated in our stool.” In short: We poop out some of the calories.

Research also suggests that chewing nuts takes some effort, leaving less energy for eating other foods. Nuts might also increase appetite-regulating hormones such as cholecystokinin and peptide YY, which might play a role in weight loss, Friedman says.

It’s this combination — high fiber, unsaturated fats, a variety of nutrients, as well as protein (nuts don’t stand up against chicken or salmon, but they do have some protein) — that contributes to nuts’ health and weight benefits.

They satisfy the body, Friedman explains, and they don’t leave you craving more food.

How can you work nuts into your diet?

The FDA-approved health claim suggests that a handful (1.5 ounces) of nuts per day can reduce the risk of heart disease.

You could also reap benefits from eating less or a bit more than this amount. If you’re exercising a lot, going over 1.5 ounces a day could likely have benefits without leading to weight gain, Bazilian says.

If you don’t want to eat them on their own, try mixing nuts into salads, where they’re a welcome contrast in texture and flavor to vegetables, or as a natural addition to baked goods and oatmeal, Friedman suggests. Savory dishes, such as almond-crusted fish or cashew chicken, are also healthful, she notes.

Which nuts are healthiest?

A food’s “healthfulness” boils down to more than calories and which nutrients it contains, requiring you to consider other factors, such as how often and how you’ll eat the food. Generally, to reap the most health benefits from any nut, eat the least-processed version: nuts in their raw form, instead of, say, honey roasted. Whole nuts also require your body to work harder than eating a nut butter or a pesto made with nuts would, which means you’ll get more of that calorie-burning effect. Grinding nuts is a form of processing or “predigesting,” says Dominic Matteo, a coach at Precision Nutrition.

Many nuts have been studied for their heart-health benefits, and big scientific reviews suggest that incorporating them into your diet could lower cholesterol, improve blood pressure, and slash risk factors associated with cardiovascular disease. But on top of nuts generally being a good choice in a heart-healthy diet, specific nuts have unique ingredients that could offer additional health benefits.

Consider the six nuts below for their research-backed health profiles.

(Not included: cashews, which were excluded from the FDA-approved health claim for tree nuts based on their content of saturated fats, and hazelnuts, which are less commonly consumed and less researched.)

Pistachios

Pistachios have more lutein, a phytonutrient that can help protect eye health, than any other nut, Bazilian says. They’re also high in nutrients, such as beta-carotene and zeaxanthin, that play a role in eye health.

Walnuts

“Walnuts are the only nut that are an excellent source of plant omega-3s,” Bazilian says. Omega-3s are known to be important for heart and cognitive health.

Pecans

Pecans have the greatest amount of filling fiber among nuts, which can help with weight control, Bazilian says. They’re also full of vitamin E, known to clear potentially damaging free radicals from the body.

Peanuts

Peanuts are an excellent source of niacin, which can increase your metabolism by helping convert food into energy, Bazilian says. This legume also has the most amount of protein among the nuts.

Almonds

A serving (23 pieces) of almonds provides 35% of your daily vitamin E, which is linked to maintaining brain health as we age. It also has more calcium than other nuts, Bazilian says, which is important for bone health. Since an almond’s outer membrane may help decrease the absorption of fat and calories, it also plays a role in weight loss.

Brazil nuts

“A single Brazil nut has a full day’s recommendation of selenium,” Bazilian says. “Research has shown higher selenium levels to be associated with more robust immune function.” Studies have also suggested that selenium promotes thyroid health.

Cassie Shortsleeve is a Boston-based writer. Her work has been published in Men’s Health, Women’s Health, Shape, + other publications. Follow her @cshortsleeve.

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