Circadian variation of human circulating cholesterol components on vegetarian and omnivorous diets in healthy Indians

Abstract

Circadian periodicity of human circulating total (T), high-density lipoprotein (HDL) and low-density lipoprotein (LDL + VLDL; briefly LDL) cholesterol (C) was studied in 30 clinically healthy, diurnally active, norturnally resting young volunteers divided into two groups of 15 each (10 men; 5 women) taking vegetarian and non-vegetarian diets. A marked circadian variation in T-C, HDL-C and LDL-C was recorded in all volunteers irrespective of the diety habits. However, total mean values and the acrophase differed between the two groups. Lower MESOR of studied variables for the vegetarians and higher MESOR for the omnivores in both the sexes exhibited endogeneous rhythmic changes as well as lower values of cholesterol components in vegetarians as compared to omnivores. Fasting unmasks a presumably endogeneous change around a lower MESOR with a smaller circadian amplitude both of HDL and LDL cholecterol metabolism. The recognition that the human circulating cholesterol components oscillate physiologically, in the peripheral blood with a shift of acrophase according to a circadian rhtyhm in two dietry schedules may prove to be of significance in the clinical interpretation of the laboratory result under tropical conditions.