Effects of Trace Components of Dietary Fat on Cholesterol Metabolism: Phytosterols, Oxysterols, and Squalene

Abstract

The effect of dietary fats on serum cholesterol is widely assumed to be due solely to the fatty acids and cholesterol they contain. Phytosterols, sterol oxidation products, and sterol precursors such as squalene, however, are often present in dietary fats. Little is known of the physiology of these substances in natural foods and most published diet studies do not consider them at all. Supplementation of the diet with high-dose phytosterols is now recommended for prevention of heart disease, but both recent and old data strongly suggest that the lower levels of phytosterols naturally present in vegetable fats may also reduce cholesterol absorption and serum cholesterol substantially. Moreover, unmeasured phytosterols may confound otherwise well-controlled diet studies because there is an inverse correlation between phytosterol and saturated fatty acid content of vegetable fats. Sterol oxidation products, many of which are found in foods, are potent regulators of lipoprotein and cholesterol transport pathways in vitro. Squalene is a phytosterol precursor abundant in olive oil that is at least partly absorbed and then quantitatively converted to cholesterol. The effects of dietary triglyceride-derived fatty acids have not been experimentally separated from the effects of trace fat components in most clinical studies. A better understanding of the activity of sterol-related dietary components is needed to reduce variability in diet studies, accurately assess the effects of dietary fatty acids and to maximize the effectiveness of dietary treatment for hypercholesterolemia.

Cholesterol oxidation: Health hazard and the role of antioxidants in prevention

“…Atherosclerotic lesions not only contain cholesterol, but also a series of oxysterols (Ostlund et al, 2002). In the widely accepted model for the pathogenesis of atherosclerosis, the impact of oxidatively modified low-density lipoprotein (LDL) particles is very important (Brown & Jessup, 1999).…”

Influence of production system, age an sex on carcass parameters and some biochemical meat quality characteristics of reindeer (Rangifer tarandus tarandus L.)

“…It is known that minor components of the diet, such as plant sterols or phenolic compounds, can affect consumer health (Parr & Bolwell, 2000;Piironen et al, 2000;Ostlund et al, 2002), and thus we also aimed to identify an unknown substance found in the neutral lipid (NL) fraction of reindeer meat during fatty acid analyses (Sampels, 2005).…”

Different apoptotic mechanisms are involved in the antiproliferative effects of 7β-hydroxysitosterol and 7β-hydroxycholesterol in human colon cancer cells

“…Numerous laboratory studies focused on their potential to reduce cholesterol absorption by the small intestine, [1][2][3][4] and cholesterol uptake by LDL. [5][6][7] In addition, it was reported that phytosterols prevent coronary heart disease, 8 and cardiovascular risks. [9][10][11] However, their potential to reduce the risk of cancer remains controversial.…”