Phytosterols (plant sterols) have been shown to reduce blood cholesterol, to decrease the risk of certain types of cancer and to enhance immune function. Similar in structure to cholesterol, phytosterols commonly refer to the 28- and 29-carbon 4-desmethyl sterols. In higher plants and typical human diets, β-sitosterol, campesterol and stigmasterol predominate.

Most intake studies have involved relatively high doses of phytosterols (2 to several grams per day) using specially formulated products. However, recent research has shown the effectiveness of much lower levels of phytosterols, such as those occurring naturally in diets rich in plant foods, in reducing cholesterol absorption. Comprehensive and accurate data on the naturally occurring phytosterols in foods are therefore needed for epidemiological studies.

Nuts and seeds are rich sources of phytosterols and have been associated with reduced blood cholesterol levels and decreased incidence of cardiovascular disease. They also have a favourable fatty acid profile and contain many other micronutrients and bioactive components. However, there is limited data on their phytochemical composition. Because routine analysis tends to measure only β-sitosterol, campesterol and stigmasterol, other phytosterols may also be present in significant levels in nuts and seeds.

A study by Phillips et al.¹ investigated the phytosterol contents and composition of nuts and seeds commonly consumed in the US. Total free, esterified and glycosidic sterols were analysed in almond, Brazil nut, cashew, hazelnut, chocolate, macadamia nut, peanut, pecan, pine nut, wheat germ, pistachio and walnuts, in flax, poppy, pumpkin, sesame and sunflower seeds, and in several of their products. The results showed that phytosterol concentrations were generally higher that those previously reported in food composition databases. This is attributed to the inclusion of steryl glycosides, which comprise a significant portion of total sterols in nuts and seeds.
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¹ Phillips, KM; Ruggio, DM; Ashraf-Khorassani, M (2005). Phytosterol composition of nuts and seeds commonly consumed in the United States. Journal of Agricultural and Food Chemistry 53 (24) 9436-9445.

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