Huge study from Harvard
The Harvard Medical School 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 also shows similar result
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%.
Other research has found that red meat diets increase pancreatic cancer risk.
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.
Studies on nuts and urolithins
New research is finding that when we eat whole natural nuts such as walnuts, hazelnuts, pistachios, and almonds, intestinal probiotics will consume a healthy element from the nuts called ellagitannin.
When our probiotics eat ellagitannins they produce a group of compounds called urolithins. As it turns out, these urolithins prevent artery damage and the resulting inflammation that leads to atherosclerosis – the hardening of the arteries.
In a study from Spain’s Rovira Virgili University, when patients with metabolic syndrome consumed a moderate amount of nuts daily for twelve weeks, their intestinal bacteria produced higher quantities of these heart-healthy urolithin metabolites. These were found circulating within their bloodstream, while the group that did not eat the nuts did not have these metabolite levels.
Other research confirms findings
In a follow-up study published in May, researchers from Spain’s Research Group on Quality, Safety and Bioactivity of Plant Foods from the government’s Department of Food Science and Technology (CEBAS-CSIC) conducted laboratory studies that confirmed the mechanisms of the urolithin metabolites produced when probiotics consumed nuts. The researchers utilized human cells from the walls of the aortic artery and duplicated inflammation associated with the buildup of artery plaque.
They introduced urolithin A and urolithin B produced from probiotic colonies fed with ellagitannins – which are abundant in nuts and some other plant-based foods.
The researchers found that the urolithins blocked the process of inflammation among the artery cells. This, they discovered, was produced by the urolithins blocking the process of adhesion by pro-inflammatory monocytes.
The researchers concluded that, “our results suggest that these metabolites might be involved, at least in part, in the beneficial effects against cardiovascular diseases attributed to the consumption of ellagitannin-containing foods.”
Brazil nuts also reduce inflammation according to other research.
In April, the Spanish researchers published another study that showed how urolithins produced by probiotic bacteria consumption of pomegranate ellagitannins (as pomegranates, like nuts, have significant quantities of ellagic acid) significantly reduced inflammatory factors within the colon. The study was published in the Journal of Agricultural Food Chemistry.
What all this means is that when we feed our (healthy) intestinal probiotic colonies ellagitannin-containing foods such as nuts and pomegranates, they produce compounds that keep our arteries healthy, keep our colon healthy, and likely reduce inflammation throughout the body.
Tree nuts even more heart-healthy
A study by researchers from the University of Georgia has found that tree nuts have even more heart-healthy nutrients than previously thought.
The researchers studied healthful constituents of ten tree nuts: almonds, black walnuts, Brazil nuts, cashews, English walnuts, hazelnuts, macadamias, pecans, pine nuts, and pistachios. (Peanuts are legumes – not tree nuts). They found that the percentage of heart-healthy fats to be primarily unsaturated oleic and linoleic fatty acids.
Most of the nuts maintained lower than 10% saturated fats, except for Brazil nuts (24%), cashews (21%), macadamias (17%), and pistachios (13%). These are also known as the more fatty nuts.
The tree nuts also contained heart-healthy tocopherols (natural form of vitamin E), which ranged from 1 to 33 milligrams for every 100 grams of the nut meat.
The researchers also found that six nuts also contained tocotrienols (another type of natural vitamin E): Brazil nuts, cashews, English walnuts, macadamias, pine nuts, and pistachios.
They also found that all the nuts contained significant phytosterol content, and mostly above the levels that have been reported in the USDA National Nutrient Database for Standard Reference.
Heart-healthy phytosterol content was highest in pistachios, containing over 300 milligrams for every 100 grams of the nut meat. Pine nuts came in second, with 272 mg/100 g nutmeat.
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.
While tree nuts are most known for great protein sources – most having all the essential amino acids – a number of studies have confirmed that diets with more nuts provide cardiovascular prevention. The reasons, as this study presents, are their lipid content, phytosterol content, and tocopherol and tocotrienol content.
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.
REFERENCES:
Bao Y, Hu FB, Giovannucci EL, Wolpin BM, Stampfer MJ, Willett WC, Fuchs CS. Nut consumption and risk of pancreatic cancer in women. Br J Cancer. 2013 Oct 22. doi: 10.1038/bjc.2013.665.
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.
Robbins KS, Shin EC, Shewfelt RL, Eitenmiller RR, Pegg RB. Update on the Healthful Lipid Constituents of Tree Nuts. J Agric Food Chem. 2011 Oct 27.
Giménez-Bastida JA, González-Sarrías A, Larrosa M, Tomás-Barberán F, Espín JC, García-Conesa MT. Ellagitannin metabolites, urolithin A glucuronide and its aglycone urolithin A, ameliorate TNF-α-induced inflammation and associated molecular markers in human aortic endothelial cells. Mol Nutr Food Res. 2012 May;56(5):784-96.
Tulipani S, Urpi-Sarda M, García-Villalba R, Rabassa M, López-Uriarte P, Bullo M, Jáuregui O, Tomás-Barberán F, Salas-Salvadó J, Espín JC, Andrés-Lacueva C. Urolithins are the Main Urinary Microbial-Derived Phenolic Metabolites Discriminating a Moderate Consumption of Nuts in Diagnosed Metabolic Syndrome. J Agric Food Chem. 2012 May 27.
Heber D. Pomegranate Ellagitannins. In: Benzie IFF, Wachtel-Galor S, editors. Herbal Medicine: Biomolecular and Clinical Aspects. 2nd edition. Boca Raton (FL): CRC Press; 2011. Chapter 10.
Giménez-Bastida JA, Larrosa M, González-Sarrías A, Tomás-Barberán F, Espín JC, García-Conesa MT. Intestinal Ellagitannin Metabolites Ameliorate Cytokine-Induced Inflammation and Associated Molecular Markers in Human Colon Fibroblasts. J Agric Food Chem. 2012 Apr 16.