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Nuts With Benefits

Posted May 21, 2018

“A boy puts his hand into a jar of filberts,” so the Aesop’s fable goes, “and grasps as many as his fist could possibly hold.  But when he tried to pull it out again, he found he couldn’t do so, for the neck of the jar was too small to allow the passage of so large a handful.”  A bystander chides the boy for being too greedy and suggests that he will be able to remove his hand if he can be satisfied with only half the amount.  The story is a familiar one, with a moral, “Do not attempt too much at once.”

For some, though, grabbing as many nuts as possible may not reflect greed: it may indicate a superior knowledge of the health benefits of nuts. What do we know about how nuts fit into our diet?

Nuts, particularly pistachios and almonds, say Allison and his colleagues, have been consumed since biblical times, and references appear in Genesis (Lewis et al, American Journal of Clinical Nutrition, 2014) and throughout the Bible. (https://bible.knowing-jesus.com/topics/Almonds) Though eaten for centuries, they were much maligned and considered "undesirable" due to their high-fat content from the mid-1950s until the mid-1990s. (Lewis et al, 2014) In recent years, though, we have begun to appreciate that not all fat is equal, and nuts may have plausible health benefits. Tree nuts include walnuts, hazelnuts (filberts), pecans, almonds, pistachios, cashews, Brazil nuts, and macadamia nuts. Peanuts are technically not nuts, but legumes. (For more on peanuts and their allergic potential specifically, see one of my previous blogs, The Brittle World of Peanut Allergy.)

Nuts are all "nutrient dense," and depending on the particular nut, contain different levels of healthy monounsaturated (mostly oleic) and polyunsaturated fatty acids (mostly linoleic), and low levels of saturated fats, as well as protein, soluble and insoluble fiber, vitamins E and K, folate, thiamine, minerals such as magnesium, copper, potassium, and selenium, and antioxidants. (De Souza et al, Nutrients, 2017) For example, walnuts have the highest level of polyunsaturated fatty acids. (Kim et al, Nutrients, 2017); almonds have the highest fiber of the tree nuts, and peanuts have the most protein and fiber. (De Souza et al, 2017) Even cashews, which initially had been exempt from health claims made by the FDA in the early 2000s because they "exceeded the disqualifying amount of saturated fatty acids," have been exonerated because a third of their saturated fat comes from stearic acid, now considered "relatively neutral" on blood lipids. And the majority of fat (60%) in cashews is monounsaturated (primarily oleic acid.) (Mah et al, American Journal of Clinical Nutrition, 2017) (For a comprehensive review of the nutrient contents of different raw nuts, see Kim et al, 2017)

Further, because of their high fiber content, nuts take more work to chew and digest (i.e., may enhance calorie expenditure) and may even act as an appetite suppressant (i.e., decrease food intake from other sources due to their satiating quality.) A review of 21 studies demonstrated no weight gain from consumption of various nuts, and "under most circumstances," nuts can be added (or at least substituted for other foods) in a diet without significant weight change. (Kim et al, 2017) The way, though, that nuts are processed can change the amount of calories absorbed.  For example, there are fewer calories in natural, roasted, or chopped almonds than in almond butter, and whole, natural almonds (without additional oil or salt) are the healthiest. (Gebauer et al, Food & Function, 2016) Further, not only can processing "differentially impact" the number of calories available, but studies now show that the degree of almond processing can change the ratios of bacteria in our gastrointestinal microbiome. (Holscher et al, Nutrients, 2018) Even without processing, in one small study, 42 grams (about one and one-half ounces) of walnut halves changed these ratios. (Holscher et al, Journal of Nutrition, 2018)

The notion that nuts can be part of a healthy diet grew out of a belief that a Mediterranean-style diet, which incorporates fresh fish, vegetables and fruits, grains, olive oil, wine, legumes, and nuts, may be cardio-protective. Researchers are especially interested to find connections between diet and cardiovascular disease (CVD) since CVD is the "primary global cause" of death, with 17 million deaths attributed to CVD each year. (Mattioli et al, Journal of Cardiovascular Medicine, 2017.) This type of diet had been systematically studied by Ancel Keys in the late 1950s, in his now classic Seven Countries Study. Keys' methodology had been criticized in the media in recent years, but researchers do believe Keys' work remains a "seminal study" and was a "first step" in exploring the important relationship of diet to cardiovascular health. (Menotti and Puddu, Current Opinion in Lipidology, 2018; see also Pett et al at: https://www.truehealthinitiative.org/wordpress/wp-content/uploads/2017/0... for a thorough discussion refuting criticisms of Keys' and his Seven Countries Study.)