Diet fat saturation and feeding state modulate rates of cholesterol synthesis in normolipidemic men.
Level 2 - randomized trial
Randomized crossover trial in humans
PubMed 9039836 · doi:10.1093/jn/127.2.332
What was done
Nine normolipidemic men were randomly assigned in a crossover design to receive three 2-week diets differing in fat saturation: monounsaturated (MONO), polyunsaturated (POLY), or saturated (SAT). Unesterified cholesterol fractional synthesis rates (FSR) were measured during consecutive fed and unfed periods using deuterium oxide. Absolute synthesis was calculated from FSR and cholesterol pool size determined via a [4-14C]cholesterol tracer decay curve.
What was found
Serum total cholesterol varied significantly across diets (P = 0.001), with the SAT diet producing the highest and POLY the lowest concentrations. Triglycerides were highest on SAT and lowest on POLY (P = 0.03), while MONO did not differ significantly. HDL cholesterol was highest on MONO and lowest on SAT (P = 0.05). Cholesterol FSR was higher during fed versus unfed periods (P = 0.001), and 12-hour FSR was higher on the POLY diet than the SAT diet (P = 0.045). Absolute synthesis was significantly higher in the fed state (P = 0.04) but did not differ by dietary fat type (P = 0.789).
Why it matters
The findings demonstrate that diurnal feeding state drives cholesterol synthesis, and that the lipid-lowering effect of polyunsaturated fats compared to saturated fats is not mediated by a reduction in absolute endogenous cholesterol synthesis.
Limits
The sample size was very small (n = 9) and restricted to normolipidemic men, limiting generalizability to women or individuals with dyslipidemia. The intervention periods were short (2 weeks), and exact numerical concentrations and synthesis rates were not reported in the abstract.
Cited by
- contradicts Saturated fat intake increases endogenous cholesterol production.