There’s still a fairly common misconception that high-fat foods may lead to weight gain and/or other metabolic issues. Depending on which so-called expert is quoted, one can see avocados and nuts being clumped together with lard and corn oil.
Thankfully, when it comes to nuts, research has been disproving this notion for the past few years and pointing the arrow in the exact opposite direction. Regular nut consumption has been associated with a reduced risk of several conditions in which oxidative stress may play a role, including coronary heart disease, hypertension, prediabetes, type 2 diabetes, inflammation, and endothelial dysfunction.
While the health-promoting benefits of nuts have been largely associated with their fatty acid profile, other bioactive compounds present in nuts also deserve credit for their health-promoting benefits.
Tree nuts, such as almonds, Brazil nuts, cashews, hazelnuts, pecans, pistachios and macadamias are complex whole foods containing a variety of essential nutrients, such as B-vitamins, and phytochemicals, including tocopherols, carotenoids, and polyphenols that possess antioxidant functions as well as other benefits.
Let’s take a closer look at these healthful bioactive compounds found in nuts.
Tree nuts are one of the highest sources of tocopherols (vitamin E), with almonds, hazelnuts, and pecans being rich in alpha-tocopherol, and pistachios and walnuts in gamma-tocopherol. Alpha and gamma tocopherols both have antioxidant functions, but alpha is more efficient at combating ROS (reactive oxygen species) while gamma is more efficient in fighting RNOS (reactive nitrogen oxide species), also acting an anti-inflammatory compound.
Nuts are also good sources of carotenoids, including beta-carotene and lutein/zeaxanthin. Pistachios are the highest source of these carotenoids, with 16-fold and 8-fold higher concentrations than its runner-up, hazelnuts. Polyphenols, such as anthocyanins, flavonoids, lignans, naphthoquinones, phenolic acids, proanthocyanidins, stilbenes, and hydrolyzable tannins, have also been identified in nuts.
The highest concentration of flavonoids is found in pecans (9.5 mg per 28 g serving size), followed by almonds (4.2 mg). Proanthocyanidins are present in high amounts in nuts, ranging from 140 mg in hazelnuts and pecans to 3 mg in cashews.
Even fat-phobes may take a second look at nuts after becoming acquainted with their impressive nutritional profile. But there is still one more challenge to nut consumption that doesn’t apply only to those who are weary of its high fat content—its taste.
Some individuals are repelled by the bland and earthy taste of nuts, so they completely avoid them or instead opt to consume roasted and salted nuts to improve palatability. The question then becomes whether the processing (roasting, salting) alters the nutritional composition, thus its health-promoting benefits.
A study published in the Food Chemistry Journal hinted that the answer to this question may be more nuanced than straightforward, as it was found that the nutritional composition of roasted versus raw nuts changed according to the nut and roasting time and temperature.
Roasting decreased thiamine (B1) significantly in almonds and walnuts, moderately in hazelnuts and macadamias, and negligibly in pistachios. Riboflavin (B2) and pyridoxine (B6) in tree nuts were scarcely affected by roasting, and even increased in hazelnuts and walnuts after roasting at 160/170 C.
The levels of lutein/zeaxanthin in roasted almonds and walnuts were significantly lower but were not affected in pistachios and hazelnuts. Roasting at 160/170 C decreased significantly the amount of beta-carotene in most nut varieties, and it was associated with a significant lower level of alpha-tocopherol in almonds and hazelnuts; gamma-tocopherol in hazelnuts and walnuts; and had no effect in alpha and gamma tocopherol concentrations in pistachios.
Another study compared the effects of consuming processed hazelnuts (lightly salted and dry roasted) versus raw hazelnuts on cardiovascular risk factors and concluded that there were minimal differences in clinical outcomes between the two forms of hazelnuts. There were no differences in total cholesterol, LDL, apolipoproteins, glucose, alpha-tocopherol concentrations, systolic blood pressure and body composition in the two groups (processed versus raw).
A similar study with almonds concluded that both raw and dry-roasted almonds were equally effective at lowering cholesterol.
Taken together, these studies suggest that despite changes in levels of bioactive components present in nuts following processing, its health benefits remain virtually unaltered. These findings are welcomed by those who don’t love the taste of raw nuts and can only eat them if they are processed in some way.
By broadening recommendations for roasted and/or lightly salted nuts, we could also expect an increase in compliance with the suggested 3 – 5 servings of nuts per week, thereby extending the benefits to a greater number of people.