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Adding to the many benefits of nuts including reducing heart disease, researchers from Harvard Medical School have determined that increasing our intake of nuts decreases our risk of diabetes and pancreatic cancer.
The researchers followed 75,680 women from the Nurses' Health Study – started in 1976 and expanded in 1989. The researchers measured nut consumption among the subjects and updated it every two to four years.
Those who ate at least one ounce of nuts twice a week had a 35% lower incidence of pancreatic cancer and a 32% lower incidence of diabetes.
This effect remained after cancelling out other known causes of pancreatic cancer. Those included higher BMI, less physical activity, greater consumption of red meat and less consumption of fruits and vegetables.
Other research has found that eating more nuts helps prevent disease. In fact, another study from Harvard – this from the School of Public Health – found that eating more nuts and peanut butter reduced the risk of diabetes. Though peanuts are not really nuts – they are legumes – they are still considered nuts among most nutritionists and researchers.
Those who ate an ounce of nuts at least five times a week had 27% lower incidence of diabetes compared to those who ate no nuts. And those who ate an ounce of peanuts or peanut butter at least five times a week had 21% lower incidence of diabetes.
Other studies have shown that nuts reduce cholesterol, and reduce heart disease. A large review of research by scientists at California's Loma Linda University found that consuming nuts at least four times a week reduces the risk of coronary heart disease by 37%. And each weekly serving of nuts reduces the risk of heart disease by over 8%.
The reasons for nuts' ability to reduce cancer, diabetes and heart disease relate to a combination of their healthy fats, amino acids, antioxidants, minerals and other phytonutrients.
The Many Nutritional Benefits of Nuts
Nuts contain a balance of healthy fats. These include monounsaturated fats like oleic acid, polyunsaturated fats like linoleic acid, and long-chain polyunsaturates such as alpha-linolenic acid – in some (like walnuts and pecans) but not all nuts. Meanwhile, saturated fat levels are balanced, but reasonably low in nuts.
Almonds, for example, have 4% saturated fat, 32% monounsaturated fat, 12% polyunsaturated fat.
Nuts are also high in phytonutrients such as tocopherols and B vitamins, as well as phenols. Nuts also contain phytosterols – shown to be heart healthy as discussed above.
Phytosterols reduce cholesterol absorption because they displace cholesterol from microscopic intestinal biomolecules called micelles. This prevents the displaced cholesterol from being absorbed through the gut.
As such, phytosterols have been shown to reduce LDL – those oxidation-friendly containers that transport cholesterol (often incorrectly called "bad cholesterol" - it is "bad" but not cholesterol).
A review of research from the Netherlands' Wageningen University found that 2.15 grams of phytosterols per day reduced LDL by an average of 8.8%.
Nuts' antioxidant effects aren't often considered. Nuts have significant antioxidant effects within the body. In a crossover study from Thailand's Mahidol University found that a diet with increased intake of walnuts resulted in higher blood antioxidant values than either a diet with increased fish intake or a control diet.
Less known is the fact that nuts contain healthy doses of magnesium, calcium and potassium, and many contain good quantities of selenium. Brazil nuts are one of the richest sources of selenium, at 540 micrograms per ounce, according to the USDA database.
Most nuts are also complete proteins, containing all the essential amino acids for the body to build its own proteins, without the acidic plasma side effects. An ounce of nuts will typically contain 4-5 grams of plant-based protein, as well as a few grams of fiber to boot.
Nut processing has mixed effects upon their nutritional content. Blanching of nuts like almonds and pistachios can destroy many of the nut's antioxidants, but roasting seems to preserve many nuts' antioxidant phenolic compounds – at least better than blanching.
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Jiang R, Manson JE, Stampfer MJ, Liu S, Willett WC, Hu FB. Nut and peanut butter consumption and risk of type 2 diabetes in women. JAMA. 2002 Nov 27;288(20):2554-60.
Demonty I, Ras RT, van der Knaap HC, Duchateau GS, Meijer L, Zock PL, Geleijnse JM, Trautwein EA. Continuous dose-response relationship of the LDL-cholesterol-lowering effect of phytosterol intake. J Nutr. 2009 Feb;139(2):271-84. doi: 10.3945/jn.108.095125.
Ostlund RE Jr. Phytosterols and cholesterol metabolism. Curr Opin Lipidol. 2004 Feb;15(1):37-41.
Hudthagosol C, Haddad E, Jongsuwat R. Antioxidant activity comparison of walnuts and fatty fish. J Med Assoc Thai. 2012 Jun;95 Suppl 6:S179-88.
Kelly JH Jr, Sabaté J. Nuts and coronary heart disease: an epidemiological perspective. Br J Nutr. 2006 Nov;96 Suppl 2:S61-7.
Ros E. Health benefits of nut consumption. Nutrients. 2010 Jul;2(7):652-82. doi: 10.3390/nu2070683.