Could eating nuts be a strategy to fight off the Big Three health problems: heart disease, cancer and diabetes?
Headline-making studies in recent months suggest that including nuts in an overall healthy diet could protect against not only heart disease, but perhaps cancer and diabetes, too. Yet some top-selling diet books that claim to hold the key to disease-prevention call for limiting or avoiding nuts.
So what does the big picture of current research say about nuts and health? It may be that nuts’ influence on health varies with how you use them.
Potential for Protection
Several studies over the past year are raising nuts’ profile as a beneficial part of a plant-focused eating pattern. Pooled data from two very large cohort studies (the Nurses’ Health Study and the Health Professionals Follow-up Study) shows that, people who ate at least seven servings of nuts a week had mortality rates 20% lower during the 24 to 30 years of follow-up than people who did not eat nuts. This link held up even when the researchers made statistical adjustments for risk factors like weight, family history, and activity level and for potential reductions in nut consumption after people developed a chronic disease. Nut consumption several times a week linked to reductions in mortality, too, though more modestly. Lower mortality rates reflected fewer deaths due to cancer and heart disease. In the PREDIMED study, among people all consuming a relatively Mediterranean-style diet, those who ate nuts more than three times a week showed 39% lower mortality rates, which again included fewer deaths from cardiovascular disease and cancer.
Several years ago, a pooled analysis of four large U.S. population studies showed that those who ate the most nuts showed about 35 percent lower risk of developing heart disease. Many scientists say research that links nut consumption with reduced levels of LDL (“bad”) cholesterol explains much of the heart health benefits. The LDL-lowering is often greater than expected, even considering nuts’ healthy types of fat. Some experts suggest that the extra cholesterol-lowering may come from phytosterols in nuts. Yet recommendations suggest a target of two grams of phytosterols daily (usually requiring specially fortified products), and a one-and-a-half-ounce serving of nuts supplies less than 6% of that target.
- A boost to heart health that won’t show up in blood cholesterol levels may come from nuts’ vitamin E, an antioxidant. Research now suggests that it is oxidized LDL cholesterol that is 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 its alpha-tocopherol form. That’s the form on which dietary recommendations are based. Research does suggest that other tocopherol and tocotrienol forms of vitamin E may also be important, and pecans, pistachios and walnuts all supply significant gamma-tocopherol.
- Blood vessel function is now seen as a key element of heart health. Disruption in function of the cells lining the inside of blood vessels can cause blood vessels to constrict, leading 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 improve. This is similar to effects seen in trials with tea and fruits that are high in polyphenol compounds (natural plant phytochemicals).
- Other scientists pin nuts’ apparent heart health benefits on potential to inhibit chronic low-grade inflammation.
Risk of Diabetes and Cancer?
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 type 2 diabetes and cancer. Indeed, in a 10-year study following women with metabolic syndrome, which includes several metabolic abnormalities and is associated with about five-fold increase in risk of type 2 diabetes, those who ate more nuts were less likely to develop diabetes. When looking at total nut consumption, at least five servings a week linked with 13% decreased risk, although the link disappeared when association with healthier weight was considered. However, even after statistically adjusting for weight, looking at walnut consumption in particular, consumption at least twice a week linked to 24% less chance to developing diabetes.
Some studies link nut consumption with less insulin resistance, although this is not seen across all studies. If confirmed in further research, that would give nuts a role in reducing risk of type 2 diabetes, as well as the types of cancer that seem to be promoted by elevated levels of insulin. More research is needed to understand whether differences seen reflect differences among some individuals who benefit more than others, differences in types of nuts, or how they are used in the diet.
What about Weight?
Many people are wary of nuts because they consider them “fattening”. Indeed, nuts are a concentrated source of calories. If you sat down in front of the TV and mindlessly munched your way through a can of nuts often, the calorie load would challenge weight control. However, large population studies show that people who eat nuts regularly are less likely to be obese than people who never or rarely eat nuts. In many studies, such as a recent publication from the Adventist Health Study-2, even after statistically adjusting for factors like physical activity, smoking and other dietary choices, this association with healthier weight tends to hold up. This could reflect “reverse causality” – people who are leaner 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.
What about Negative Press?
Several popular books that promote plant-based diets to prevent or reverse heart disease, diabetes and/or cancer call for avoiding all added fats, including olive oil and other oils, and nuts. Generally, these authors base a no-nuts recommendation on concern that nuts will add body fat and promote obesity, and/or the fact that even nuts contain some saturated fat.
My take on this? It is true that even though the dominant types of fat in nuts – by far – are mono- and polyunsaturated fats, they do all contain a small amount of saturated fat. However, an ounce of nuts every day contains a small fraction of today’s evidence-based recommended limits on saturated fat. Moreover, it seems to me that research is moving away from putting emphasis on saturated fat content as the primary definition of what makes a food “heart healthy”. Since studies like those listed above link nut consumption with lower risk of heart disease and lower mortality rates, it seems likely that overall impact reflects a balance between the effects of a negative, like saturated fat, and the protective effects on insulin, inflammation, blood vessel function, oxidation and more that may stem from other components in nuts.
As for weight, I’ve worked with plenty of patients over the years whose nut consumption contributed to an unhealthfully high calorie intake. However, there are many foods that can be eaten in moderation, but in excess add too many calories. Since studies clearly show that eating more nuts does not lead to excess weight in everyone, nor does avoiding nuts remove risk of obesity, I believe their potential nutritional contribution makes it worthwhile learning how to include nuts in an eating pattern that promotes a healthy weight.
Is it How Nuts Are Used?
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 all these “big three” health problems, that would be a significant negative.
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 with lower levels of insulin and a marker of inflammation and higher HDL (“good”) cholesterol than in those who did not eat nuts.
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 high-fat cheese or croutons.
- Add nuts’ crunch and flavor to low-fat stir-fried or steamed vegetables.
- Sprinkle nuts on pasta or rice dishes. If you have tended toward excessive portions on these grain products, cut your portion a bit, and you’ll end up with a filling, satisfying dish that has more nutritional balance.
- Use nuts to provide more protein at breakfast. They’re delicious on cold or hot cereal, or stirred into yogurt. Calories won’t be excessive if you keep your cereal portion moderate and you avoid the 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).
Be Nut Savvy
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 loaded with nutrients 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.
- 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.
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. Research has not yet clarified how much of nuts’ health benefits come from their healthy types of fat, fiber, vitamins, minerals (including selenium and magnesium), phytochemicals, or other compounds. So including a variety of nut types is a strategy that is smart – as well as delicious!
Let’s talk! Do you eat nuts regularly? If so, are you more likely to use them as a snack or mixed into dishes at meals?
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For more on research about nuts and health, check the International Tree Nut Council and the Foods that Fight Cancer section of the American Institute for Cancer Research (AICR) website. Both these spots also offer tips for using nuts and links to recipes, as do the websites of boards or commissions devoted to individual types of nuts, such as almonds and walnuts.
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