Not so long ago, nutrition experts cautioned people to avoid nuts, as they were considered a "fatty" food. During the "fat-free" era of the 1980s, people across the country shunned fat--no matter its source. Now, health researchers have come full circle, understanding that the type of fat is far more important than how much fat you eat.
Research supports that healthy fats--monounsaturated fat (MUFA) and polyunsaturated fat (PUFA)--actually lower your risk of cardiovascular disease and type 2 diabetes. A body of evidence has accumulated on the health benefits of tree nuts--almonds, Brazil nuts, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts--which provide an excellent source of MUFAs, PUFAs and other health-protective nutrients.
Each nut kernel is a concentrated source of key nutrients, including protein, vitamin E, folate, fiber, minerals and phytochemicals, such as flavonoids, proanthocyanidins and phenolic acids. In addition to their healthy MUFAs and PUFAs, walnuts, contain omega-3 fatty acids.
Nuts' nutrient-rich package boosts their ability to reduce oxidative stress and inflammation that are the root of chronic disease. In addition, studies show that if you include nuts for a snack instead of other choices, your overall nutrient intake for the entire day will be improved.
While scores of studies have examined the impact of eating nuts on a variety of conditions, the most concrete link exists for heart health.
"It's well established that people who eat nuts on a regular basis have a lower risk of heart disease," says nutrition researcher Joan Sabate, M.D., Dr. P.H., Chair of the Department of Nutrition at Loma Linda University in California. "It is clear that there are many mechanisms by which eating nuts reduce heart disease. They reduce 'bad' LDL cholesterol, contain powerful antioxidants and influence inflammatory parameters. This is well established in clinical trials of different populations and different countries."
Indeed, in a pooled analysis of 25 intervention trials led by Sabate, which was published in a 2010 issue of the Archives of Internal Medicine, results showed that nut consumption improves blood lipid levels in a dose-related manner, with greater results among people who ate a typical Western diet (high saturated fat, low-fiber) and had high LDL cholesterol levels.
Fighting type 2 diabetes
Eating nuts can help manage and prevent type 2 diabetes.
"Research shows that females who regularly eat nuts in general, and in particular walnuts, have a lower risk of developing type 2 diabetes. And a small clinical trial found that nuts incorporated into the diet of diabetics helped control blood cholesterol levels," says Sabate.
A 2011 study in Diabetes Care found that two ounces of nuts daily as a replacement for carbohydrate foods improved both glycemic control and serum lipids in type 2 diabetes. "There is a double effect for diabetes--nuts can improve the metabolism of glucose, and lower cholesterol and inflammatory parameters for heart disease, the leading cause of death in those with type 2 diabetes," says Sabate.
The brain and beyond
New studies have also found a protective link between nut consumption and cognitive health. Animal research, published in the British Journal of Nutrition, linked a diet containing as much as six percent walnuts (equivalent to one ounce in humans) with reversing age-related motor and cognitive deficits in aging rats. While Sabate reports that there is not enough evidence to know for sure if walnuts can protect your brain from age-related decline, the preliminary results are promising.
Additional studies have found that nuts may offer benefits for fertility, bone health and cancer protection, but more research needs to occur before we can fully understand nuts' potential in these conditions.
No weight worries
While dieters once feared nuts as concentrated sources of calories that might lead to weight gain, new research indicates that those fears are unfounded.
"Twenty years ago, we noticed that people who ate nuts on a regular basis were thinner than those who refrained from eating nuts. Subsequent studies have found that including nuts in a diet with the same amount of calories, results in weight loss. If you add nuts on top of your regular diet, it doesn't help, but if you replace some of your calories with nuts, they help with weight maintenance and weight loss," says Sabate.
He explains that some of the calories in nuts are not fully absorbed during mastication and digestion. If you eat a nut oil, you will absorb 100 percent of its calories; 90 percent of the calories for a nut butter and 70 to 80 percent of the calories for a nut.
Results from the PREDIMED study, which included 847 older Mediterranean adults, found that body mass index and waist circumference decreased by 0.78 and 2.1 centimeters, respectively, for each 30-gram (1 ounce) serving of nuts (Nutrition, Metabolism and Cardiovascular Diseases).
Aim for one handful--about 1-½ ounces--per day of a variety of tree nuts to make the most of their benefits. Sprinkle nuts on salads, vegetables, side dishes, cereals, fruit and yogurt. Stir them into baked goods, such as pancakes and cookies. Let their earthy, delicious flavor--and potent nutrients--shine in your favorite foods every day.