Lipid lowering with diet or dietary supplements

INTRODUCTION

Lipid alterations can also be effected by a number of dietary approaches or specific dietary supplements [1,2]. Such approaches have been exploited by nutritionists and physicians as evidence-based and less costly alternatives to several classes of drugs. These differ with respect to mechanism of action and to the degree and type of lipid lowering. Thus, the indications for a particular dietary supplement are influenced by the underlying lipid abnormality.

The characteristics and efficacy of the lipid-lowering dietary supplements or dietary components will be reviewed here.

FISH OIL

Populations with high intakes of omega-3 (n-3) polyunsaturated fatty acids (such as the Eskimos) have low rates of heart disease; this observation has increased interest in the possible benefit of fish oils [3,4]. Rich sources of omega-3 fatty acids fatty acids come from fatty fish, especially salmon, and plant sources such as flaxseed and flaxseed oil, canola oil, soybean oil, and nuts. (See "Fish oil and marine omega-3 fatty acids" and "Dietary fat".)

Fish oil concentrate administered at high doses (>6 g/day) can reduce levels of triglycerides through inhibition of the synthesis of VLDL-triglycerides and apolipoprotein B [5,6]. In hypertriglyceridemic subjects, fish oils (in a dose of 15 g/day) lower triglyceride levels by approximately 50 percent [7,8].

Since fish oil lowers plasma triglyceride concentration, which in turn is a determinant of small dense LDL, it is possible that fish oils will decrease the concentration of smaller LDL. Support for this hypothesis comes from the observed reduction of cholesteryl ester transfer activity following fish oil therapy [9]. In addition, several studies have observed an increase in overall LDL particle size with 4 g purified docosahexaenoic acid [10-12]. In contrast, 2.5 g of omega-3 fatty acids daily for two months did not significantly change this fraction in 16 non-insulin-dependent diabetics when compared to placebo [13].