Update on the Healthful Lipid Constituents of Commercially Important Tree Nuts

Abstract

Uncharacteristic of most whole foods, the major component of tree nuts is lipid; surprisingly, information on the lipid constituents in tree nuts has been sporadic and, for the most part, not well reported. Most published papers focus on only one nut type, or those that report a cultivar lack a quality control program, thus making data comparisons difficult. The present study was designed to quantify the healthful lipid constituents of 10 different types of commercially important tree nuts (i.e., almonds, black walnuts, Brazil nuts, cashews, English walnuts, hazelnuts, macadamias, pecans, pine nuts, and pistachios) according to standardized, validated methods. The total lipid content of each nut type ranged from 44.4 ± 1.9% for cashews to 77.1 ± 1.7% for macadamias. As expected, the major fatty acids present in the tree nuts were unsaturated: oleic (18:1 ω9) and linoleic (18:2 ω6) acids. A majority of the lipid extracts contained <10% saturated fatty acids with the exceptions of Brazil nuts (24.5%), cashews (20.9%), macadamias (17.1%), and pistachios (13.3%). The total tocopherol (T) content ranged from 1.60 ± 1.27 mg/100 g nutmeat in macadamias to 32.99 ± 0.78 in black walnuts. The predominant T isomers in the nut types were α- and γ-T. Tocotrienols were also detected, but only in 6 of the 10 nut types (i.e., Brazil nut, cashews, English walnuts, macadamias, pine nuts, and pistachios). In most cases, total phytosterol contents were greater in the present study than reported in peer-reviewed journal papers and the USDA National Nutrient Database for Standard Reference, which is attributed to total lipid extraction and the inclusion of steryl glucosides in the analysis; the levels were highest for pistachios (301.8 ± 15.4 mg/100 g nutmeat) and pine nuts (271.7 ± 9.1 mg/100 g nutmeat). Minor sterols were also quantified and identified using GC-FID and GC-MS techniques.

Influence of roasting conditions on health-related compounds in different nuts

“…Pistachios contained appreciable amounts of c-tocotrienol (c-T3; 1.9-2.4 mg 100 g À1 ), whereas a-tocotrienol (a-T3) was the only isoform identified in macadamia nuts (1.8-2.8 mg 100 g À1 ). The tocopherol and tocotrienol contents in our nut varieties were comparable to levels reported in other studies (Kornsteiner, Wagner, & Elmadfa, 2006;Lux et al, 2012;Robbins et al, 2011), though the absolute values differed, likely due to varying cultivation conditions. The present study reveals that the different roasting conditions affected the content of the distinct vitamin E isoforms differentially.…”

“…Despite slight variations, the lipid composition of raw and roasted nuts is in line with values reported by Robbins et al (2011) who analysed lipid constituents of ten different tree nuts, including hazelnuts, almonds, macadamia nuts, pistachios and walnuts. The authors also pointed out that variations could be due to differences regarding the cultivars and growth conditions.…”

“…The EPIC study, for example, showed that nut consumption is inversely correlated with colon cancer risk in women (Jenab et al, 2004). Nuts are also an important source of vitamin E isomers as antioxidant active compounds, although the contents of distinct vitamin E isomers vary between different types of nuts (Robbins, Shin, Shewfelt, Eitenmiller, & Pegg, 2011).…”

Investigation of the antioxidant capacity and phenolic constituents of U.S. pecans

“…From a placebo-controlled, three-way crossover design clinical trial with a one-week washout period between pecan treatments, Hudthagosol et al (2011) reported that γ-tocopherol and the proanthocyanidin (PAC) flavan-3-ol monomers of pecans were absorbable and contributed to postprandial antioxidant defenses in the human body. The increased interest in pecans is partially due to their healthful lipid components (i.e., fatty acids, tocopherol homologues, and phytosterols) (Robbins, Shin, Shewfelt, Eitenmiller, & Pegg, 2011), but it is also associated with their beneficial phenolics and PAC content (Amarowicz, Troszyń ska, & Shahidi, 2005). Reactive oxygen species (ROS) are free radicals found naturally in the human body.…”

“…Pecans are unique in that a significant portion of their Ts (89.4 %) are represented by the γ-T homologue (Robbins et al, 2011). From a health standpoint, γ-T is considered important because it has been shown to be a better free-radical scavenger than α-T (Christen et al, 1997).…”