"Given the many possible mechanisms of action of phytosterols on cholesterol metabolism, it is important to have quantitative estimates of total phytosterol content," reported the team of researchers from Virginia Polytechnic Institute and State University.
Previous studies have shown that nuts and seeds are a rich source ofphytosterols, plant sterols with a chemical structure very similar tocholesterol. When present in sufficient amounts, these compounds are believed to reduce blood cholesterol, enhance the immune system and decrease the risk of certain cancers.
The study, published in the Journal of Agricultural and Food Chemistry (Vol 53, pp. 9436-9445), is the most comprehensive analysis of nut and seed varieties to date. Twenty-seven different products, including American peanut butter, were evaluated and it was found that sesame seeds and wheat germ contained the highest concentration of phytosterols with over 400 mg per 100 g.
The list of products most commonly associated as snack foods was led bypistachio nuts with 279 mg of phytosterols per 100 g, closely followed bysunflower seed kernels (270 mg per 100 g). The lowest phytosterol contentwas found in Brazil nuts and English walnuts (95 and 113 mg per 100 g).
Smooth peanut butter contained, on average, a higher concentration ofphytosterols than the chunky variety, 135 versus 132 mg per 100 g.Beta-sitosterol was the main phytosterol identified for all nut and seedsamples.
Conducted as part of the USDA's National Food and Nutrient Analysis Program, the authors say the study is important for anyone involved in the formulation of research diets, and development of dietary recommendations related to the health impact of phytosterols.
Epidemiologists and clinical nutritionists can also draw on the new research to achieve greater accuracy and reduce errors during the multivariate correction of food surveys.
While the research was long overdue, it is uncertain how this will affectthe current sterol market. Global demand for phytosterols is estimated toexceed 10,000 tons by 2008, giving a potential market value of $200 to $250 million. Most plant sterols are currently extracted from soybean, corn, and tall (pine tree) oil.