Phytochemical Composition of Nuts

Authors: CHEN, CHUNG-YEN - JM USDA HNRCA @ TUFTS; Blumberg, Jeffrey

Submitted to: Asian Pacific Journal of Clinical Nutrition
Publication Type: Review Article
Publication Acceptance Date: 12/3/2007
Publication Date: 1/1/2008
Citation: Chen, C., Blumberg, J. 2008. Phytochemical Composition of Nuts. Asian Pacific Journal of Clinical Nutrition. 17(S1):329-332.

Interpretive Summary: Nut consumption is negatively associated with incidences of some chronic diseases, e.g. cardiovascular diseases, certain types of cancers, and diabetes. With such health benefits, nuts have recently been included in dietary guidelines in USA, Canada, and Spain. Nuts, including almonds, brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios, and walnuts, and peanuts, are rich in phytochemicals, which recently have been found to possess bio-mechanisms against CVD and cancers. Phytochemicals, defined as bioactive non-nutrient components in plant foods, are classified as alkaloids, carotenoids, organosulfurs, phenolics, and phytosterols, while more compounds still remain to be identified and characterized. Phenolics including families of phenolic acid, flavonoid, stilbene, and other polyphenol, are quantitated in nuts with walnuts being the largest at 1625 mg gallic acid equivalents/100 g. Recently, flavonoids with numerous putative bio-mechanisms have been found to associate with reduction in risk of chronic diseases. Their profile in nuts have been complied and published by the USDA (2006), with its content listed descending order as pecans, almonds, pistachios, and hazelnuts. Proanthocyanidins are polymers of catechin and are found in almonds, cashews, hazelnuts, pecans, pistachios, peanuts, and walnuts. An array of putative mechanisms may be responsible for the health benefits of phytochemicals in nuts, e.g. antioxidant, anti-inflammatory, anti-viral, and anti-proliferative activity. Although pharmacokinetics and bioavailabilities of phytochemicals, determining their health benefits, have been demonstrated in studies, our understandings on these matters are still in nascent stage.

Technical Abstract: Observational studies suggest nut consumption is inversely associated with the incidence of cardiovascular disease and cancer. In addition to being a rich source of several vitamins and minerals, unsaturated fatty acids, and fiber, tree nuts and peanuts contain an array of phytochemicals that may contribute to promoting health and reducing the risk of chronic disease. While many of these bioactive constituents remain to be fully identified and characterized, broad classes include carotenoids, phenols, and phytosterols. Phytosterols in nuts range from 95-280 mg/100 g. Alpha- and beta-Carotene, beta-cryptoxanthin, lutein, and zeaxanthin are found in ug/100 g amounts in some nuts but at 1-3 mg/100 g in pistachios and none at all in Brazils, macadamias, and peanuts. Plant phenols, including phenolic acids, flavonoids, and stilbenes, are present in nuts. Walnuts are particularly rich in total phenols with 1625 mg gallic acid equivalents/100 g. The stilbene resveratrol is found in peanuts and pistachios at 84 and 115 µg/100 g, respectively. The flavonoid content of nuts as provided in USDA Database for the Flavonoid Content of Selected Foods, lists totals in pecans at 34, almonds at 15, and pistachios and hazelnuts at 12 mg/100 g. Proanthocyanidins are found in almonds, cashews, hazelnuts, pecans, pistachios, peanuts, and walnuts, with concentrations varying from 9-494 mg/100 g. Nut phytochemicals have been associated with an array of bioactivities known to affect the initiation and progression of several pathogenic processes. However, as complete phytochemical profiles are lacking for most nuts, information is limited regarding their bioavailability and metabolism, so further research on this topic is warranted.