How effective are dietary interventions in lowering lipids in adults with dyslipedemia?

Dietary changes are recommended as first-line treatment for mild to moderate dyslipidemia. We examined evidence on 5 common dietary interventions for adults with dyslipidemia. The average effects on lipid levels are reported in the TABLE. Low-fat: A meta-analysis of 37 mostly good-quality controlled trials evaluated the former National Cholesterol Education Program (NCEP) Step I and Step II diets in 11,586 participants.¹ The Step I diet restricted intake of total fat (≤30% of total calories), saturated fat (≤10% of total calories), and cholesterol (≤300 mg/d). Step II goals were lower for saturated fat (<7%) and cholesterol (<200 mg/d). Mean baseline lipid values (mg/dL) were total cholesterol, 233.57; LDL, 155.10; HDL, 47.95; and triglycerides, 147.91. Both of these low-fat diets significantly reduced total cholesterol, LDL, and triglycerides. The Step II diet also reduced HDL. Soy: A meta-analysis of 23 good-quality controlled trials with 1381 participants reported that soy protein with naturally occurring isoflavones significantly reduced total cholesterol, LDL, and triglycerides while significantly increasing HDL.² The amount of soy isoflavone consumed varied across studies. One subgroup analysis showed that consumption of >80 mg/d was associated with a better effect on lipids. In subjects with baseline hypercholesterolemia (total cholesterol >240 mg/dL), greater reductions in total cholesterol, and greater increases in HDL were reported, with comparable changes in LDL and triglycerides. Soluble fiber: A meta-analysis of 67 good-quality RCTs evaluated the effects of soluble dietary fiber in 2990 subjects (mean baseline lipid values [mg/dL]: total cholesterol, 240.9; LDL, 164.4).³ Diets high in soluble fiber (average dose of 9.5 g/d) were associated with a statistically significant decrease in total cholesterol and LDL and no significant change in HDL or triglycerides. Type of fiber (oat, psyllium, or pectin) was not influential after controlling for initial lipid level. "Portfolio" diet: A fair-quality randomized crossover study with 34 participants found that a "portfolio diet," which combines the fat intake of the NCEP Step II diet with cholesterol-lowering "functional foods" (including plant sterols, nuts, soluble fibers, and soy protein), markedly reduced total cholesterol and LDL.⁴ Mean baseline lipid values (mg/dL) were: total cholesterol, 261.41; LDL, 174.40; HDL, 47.56; triglycerides, 199.28. Mediterranean diet: A fair-quality RCT with 88 participants reported reduced LDL among subjects assigned to a Mediterranean-type diet.⁵ Mean baseline lipid values (mg/dL) were total cholesterol, 255.22; LDL, 170.15; HDL, 58.01; triglycerides, 141.71.