Nuts for Heart Health: What’s the Best Advice on How They Can Help?

Inside: What are the best nuts for heart health? Can you really include healthy nuts for weight loss? These are a few of the questions people ask as they try to make sense of conflicting fears and headlines on nuts in healthy eating habits.

Headline-making studies suggest that including nuts in an overall healthy diet could protect against not only heart disease, but perhaps cancer and diabetes, too. That makes it confusing when you see websites and diet books that claim to hold the key to disease-prevention and call for limiting or avoiding nuts.

So what does the big picture of current research say about nuts and health?

Nuts and Health: Does A Handful a Day Keep the Doctor Away?

Many studies identify nuts as valuable contributors to a plant-focused diet pattern.

People who ate more nuts had mortality rates nearly 20% lower during follow-up periods ranging from 5 to 30 years in an analysis of prospective studies that included more than 800,000 adults. There’s no need to go nutty about nut consumption, however.

• The greatest difference in mortality rates was between those who consumed any nuts weekly compared to those who ate none.
• No further reduction in mortality rates is seen above 15 to 20 grams of nuts per day. That’s the equivalent of having an ounce of nuts (about one handful) four or five days a week.
• Both tree nuts (including almonds, hazelnuts, pecans, pine nuts, pistachios, and walnuts) and peanuts show similar links to lower all-cause mortality rates. Peanut butter consumption is associated with smaller, if any, reduction in overall mortality rates. However, people in these large population studies who eat nuts primarily as peanut butter tend to differ from other nut consumers in several lifestyle factors that affect health, which could explain the different associations.

Nuts for Heart Health: Are They Terrific or Taboo?

Meta-analyses combining results of multiple large prospective cohort studies that followed people for years show that total nut consumption of an ounce per day is associated with 29% lower risk of heart disease (CHD) and 21% lower risk of cardiovascular disease (CVD).

• Evidence is rated even stronger from observational studies that show nearly 30% lower CVD mortality tied to an ounce of nuts consumed per day.
• These lower mortality rates are consistent regardless of whether follow-up time was shorter or longer than 9 to 15 years.
• CVD and CHD mortality decrease with each increase in nut consumption from no intake to amounts equivalent to eating an ounce four or five days per week. Amounts beyond that don’t show additional reduction in mortality rates. (However, it’s noteworthy that the studies weren’t set up to capture associations with much higher intake because it occurs so seldom in the populations studied.)

What’s behind the association of nuts and heart health?

(1) Reduced atherosclerosis-promoting lipids 
Nuts’ link with reduced levels of LDL (“bad”) cholesterol is an important element in the heart health benefits. An analysis of 38 randomized controlled trials shows LDL levels reduced 4.2 mg/dl for each ounce of nuts consumed daily. And in this case, more may be better. Two or more servings per day can reduce LDL even further. In these controlled trials, nuts also reduced levels of apoB, especially among people with type 2 diabetes. (This apoB protein is another indicator of cardiovascular risk. Higher numbers indicate greater number of atherogenic particles — LDL, VLDL and IDL.)

LDL-lowering is no surprise, since nuts are such important sources of unsaturated fat. But the degree of LDL-lowering is often greater than expected based on nuts’ fat content alone. Some evidence suggests that the additional cholesterol-lowering may come from phytosterols in nuts. Yet LDL-lowering recommendations suggest a target of two grams of phytosterols daily (usually requiring specially fortified products). A one-and-a-half-ounce serving of nuts supplies less than 6% of that target.

(2) Vascular health support
Blood vessel function is a key element of cardiovascular health. When cells lining the inside of blood vessels lose control of when and how much blood vessels relax or constrict, this can lead to elevated blood pressure, inflammation and clot formation. Several human intervention trials show that after several weeks of consuming about 1 ½ to 2 ounces of nuts daily, tests of blood vessel flow and ability to dilate properly improved.

• Nuts provide L-arginine, an amino acid. Cells lining blood vessels use L-arginine to produce nitric oxide, a compound that triggers blood vessels to relax and let blood flow more easily.
• Polyphenol compounds seem to reduce artery stiffness and enhance endothelial cell production of nitric oxide, which may also explain how nuts are among foods beneficial for vascular health.

(3) Potential defender

• A boost to heart health that won’t show up in blood cholesterol levels could come from antioxidants in nuts. Research suggests that oxidized LDL particles are the most damaging to blood vessels. Almonds, hazelnuts and pine nuts are the nuts you’ll see labeled as rich in vitamin E, because they contain high amounts of alpha-tocopherol. That’s the form on which dietary recommendations are based. But gamma-tocopherol, and other tocopherol and tocotrienol forms of vitamin E, also demonstrate antioxidant effects in cell and animal studies. Pecans, pistachios and walnuts all supply significant gamma-tocopherol.
• Laboratory studies with flavonoids and other phenolic phytochemicals found in nuts suggest potential to support the body’s own (endogenous) antioxidant defenses. More research is needed to understand if such effects occur with human consumption of these compounds.
• Other research suggests that nuts’ association with heart health could stem from potential to inhibit chronic low-grade inflammation. Results of human research — observational population studies that follow people for many years and controlled intervention trials — have been inconsistent, however. Characteristics of the people participating in a study and details of an intervention may affect the ability to detect anti-inflammatory effects, and some evidence suggests that effects may be more apparent in trials that last at least 12 weeks.

(4) Better blood pressure? Unclear.

• Nut consumption is consistently linked with lower risk of hypertension in observational studies that follow large population groups over time. This makes sense, since nuts are good sources of magnesium. Part of the benefits of magnesium for heart health seem to include blood pressure control. (You may hear nuts touted as a good source of potassium, another helper for blood pressure. But although nuts provide some potassium, none include enough to be considered a good source.)
• Controlled intervention trials don’t show effects of nuts on hypertension, however. An analysis of 17 randomized controlled trials found no effect on systolic or diastolic blood pressure. It’s possible that the connection of nuts and hypertension in observational studies is due to some other factor in the diet or lifestyle of people who eat more nuts. Or perhaps controlled trials need to dig deeper to find amount, time duration, or individual characteristics in which nuts can help manage blood pressure.
• In “real life”, your food choices influence health based on what you eat and what you don’t eat. When you choose nuts, what are they replacing? For example, even if nuts don’t directly reduce blood pressure, if you choose them instead of a high-sodium, ultra-processed snack food, then your choice of nuts is likely to help keep a healthy blood pressure.

Can Nuts Protect Against Risk of Diabetes and Diabetes’ Risks?

Earlier observational population studies suggested an association of nut consumption with lower risk of developing type 2 diabetes. But so far, overall results of this research does not show an association of nut consumption with risk.

However, cardiovascular disease is a major cause of death among people with diabetes. And these studies link nut consumption to decreased cardiovascular mortality and all-cause mortality among people with type 2 diabetes.

Some randomized controlled trials lasting 3 months to 1 year have shown decreased A1C (a marker of longer-term blood sugar control) or decreased fasting insulin among people with type 2 diabetes or prediabetes.

How Do Nuts Fit in a Diet to Reduce Cancer Risk?

Antioxidant, anti-inflammatory effects could do more than lower risk of heart disease.  If research confirms such benefits from nuts, that could give them a role in a diet to lower risk of cancer.

• Observational population studies link higher nut consumption with lower overall cancer risk compared to people who don’t eat nuts. When limited to prospective cohort studies (the observational studies that provide strongest evidence), analysis of 33 cohorts shows 10 percent lower overall cancer risk among those with highest consumption. In these studies, “high” consumption typically averages an ounce or less per day. And analysis shows modest reductions in risk with smaller amounts.
• Laboratory studies with phytochemicals found in nuts show several mechanisms that could inhibit cancer development. For example, in cell and animal studies, these compounds influence gene expression in ways that decrease growth and stimulate self-destruction of cancer cells.
• Greatest evidence for nuts and cancer risk so far is available from studies involving walnuts and the phytochemicals they contain. Some protection against inflammation and cancer may involve prebiotic effects on the gut microbiome. For example, bacteria in the colon convert ellagitannins and ellagic acid (found in walnuts) to compounds called urolithins that may have protective effects within the colon and after they are absorbed out of the digestive tract.

Overall analysis by the American Institute for Cancer Research classifies research on nuts and cancer risk too limited to draw any conclusions about nuts and cancer risk at this time. But it’s clear that nuts can fit comfortably — and add flavor — to the overall eating habits that reduce cancer risk.

Are Nuts Good for Weight Loss? New Research Challenges Old Fears

Many people are wary of nuts because they consider them “fattening”. Indeed, nuts are a concentrated source of calories. If you frequently sit down in front of the TV and mindlessly munch your way through a can of nuts, the calorie load will likely challenge weight control.

But fear of the very real health risks of weight gain and obesity are not a good reason to avoid nuts.

• Large population studies show that people who eat nuts regularly are less likely to have overweight or obesity than people who never or rarely eat nuts. Even after studies statistically adjust for factors like physical activity, smoking and other dietary choices, this association with healthier weight tends to hold up.
  • In some cases, this could reflect “reverse causality” – people who are leaner may be less afraid of nuts’ calorie load than people who are already carrying extra body fat. However, other types of studies show that consuming nuts does not hurt, and may even help, weight loss and weight maintenance efforts.
  • Increased consumption of nuts over time was associated with lower risk of having obesity and less weight gain (regardless of baseline weight). This was seen in observational studies over four-year periods and over 20 to 24 years of follow-up.
• In controlled clinical trials, even without instructions to substitute nuts as replacement for some other food, including nuts does not lead to weight gain or increased waist size.
  • Limited research shows that nuts don’t provide as many calories to the body as would be predicted based on standard calculations.
  • Nuts may promote satiety, particularly compared to refined grains, sweets, chips and other common snack foods. Emerging evidence suggests this may be due to fiber and fat content, and may involve effects on the gut microbiome.

Is It Which Nuts Are Best? Or How to Best Use Nuts?

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Although nuts share many similar nutrients and phytochemicals, nuts differ from each other, too.

Many studies on nuts – especially controlled intervention trials – focus on a single nut. Results of research conducted on one nut can’t be assumed to apply to other nuts. But it does not indicate that the specific nut tested is unique in providing beneficial effects seen.

• Almonds and hazelnuts are highest in the alpha-tocopherol form of antioxidant vitamin E. And pecans, pistachios and walnuts are highest in the gamma-tocopherol form, which may act in somewhat separate roles.
• All nuts contribute to bolster magnesium intake. Almonds, cashews, and peanuts are top sources.
• Walnuts are relatively unique content in their level of ellagitannin phytochemicals that may support a healthy gut microbiome.
• Some research suggests that at least half of the phytochemicals (natural plant compounds) in nuts are lost when the soft skin called the pellicle is removed. Walnuts are almost always eaten with this pellicle attached, but almonds and peanuts, for example, may or may not be.
• Evidence on support for a healthy weight and avoiding weight gain is consistent among all nuts studied, including peanuts. And analysis of studies of tree nuts effects on LDL cholesterol shows no differences between nuts.

In the U.S., nuts are mostly consumed as snacks, and when consumed as ingredients in recipes, it’s primarily in candy, bakery and cookies. Although the nutrients and types of fat in nuts are healthful, when we consume them in foods that are loaded with sugar, unhealthy fats and excess calories, the potential benefits of nuts may be undermined. When we simply add nuts’ concentrated calories to a diet that already includes more calories than we burn, that could make weight control more difficult.  Since overweight increases risk of heart disease, cancer and type 2 diabetes, that would be a significant negative effect.

When “out of hand” nut consumption (which would not include nuts consumed in candy and bakery) was specified, higher consumption in U.S. adults was linked adults was linked with higher diet quality (including lower sodium intake and higher fiber and unsaturated fat). Even modest consumption of nuts in this form was associated with lower levels of insulin and CRP (a marker of inflammation) compared to people who did not eat nuts Although only cross-sectional research, this suggests how nuts are used may be an important nuance in the interpretation of inconsistencies in population studies on nuts and health.

Here are five examples of ways to add nuts by easy swaps, ideally for less nutritious foods: 

• Try toasted nuts in salads as replacements for bacon or croutons.
• Add nuts’ crunch and flavor to stir-fried or steamed vegetables.
• Sprinkle nuts on pasta or rice dishes. If you tend to choose excessive portions of these grain products, cut your portion a bit. With the added nuts, you’ll end up with a nutrient-rich dish that’s filling and satisfying dish.
• Use nuts to provide more protein at breakfast. They’re delicious on cold or hot cereal and stirred into yogurt. Calories won’t be excessive if you keep your cereal portion moderate and you avoid pre-sweetened, high-sugar yogurt. If your breakfast is a grab-and-go, a handful of nuts adds nutritional balance to your fruit and other choices.
• Nuts make a tasty snack that many find seems to provide longer-lasting energy than sweets, chips or crackers. Scoop out one handful into a small dish (not a cereal bowl).

How Eating Habits Can Include Nuts for Heart Health: Doable Tips

With all these potential positive effects on health that can come from including nuts among your other healthy choices daily, or at least several days a week, don’t let a “health halo” lead you astray.

• Unsalted nuts are extremely low in sodium, but 1.5 ounces of salted nuts are as high in sodium as a small bag of potato chips.
• Nuts are nutrient-rich and a great addition as part of a healthy diet. That doesn’t refer to chocolate nut spreads that are loaded with added sugars and unhealthy added fat, making them more dessert than dietary staple.
• If you are looking for ways to boost calories to help you gain weight or meet your needs as you ramp up your exercise, then nuts are an excellent choice. They provide concentrated calories in a food that is far more nutritious than people get when they boost calories with huge bowls of ice cream or large amounts of sugar-laden drinks. However, if you aren’t trying to gain weight, make sure that you keep nut portions modest and that you substitute them for other foods.