Continuous and Marked Increase of Japanese HDL Associates Paradoxically with their Nutritional Shift

Aims: Plasma HDL has evidently increased for decades among Japanese, exclusively in HDL particles containing apoA-I but not A-II. Its metabolic background is yet to be elucidated. Methods: Trends in plasma lipoproteins were analyzed by examining data on total cholesterol, triglyceride and HDL-cholesterol, which are available in the public database of the National Health and Nutrition Examination Survey of Japan (NHNESJ) and in the clinical data of SRL Co., from 1989 to 2019, estimating cholesterol (C) in non-HDL, VLDL, LDL, and sub-fractions of LDL using the equations by Sampsonet al. Food intake and supply data in NHNSJ and in the UN Food and Agriculture Organization were also analyzed in relation to the lipoprotein analysis. Results: HDL-C levels showed a steady increase in men and women throughout the period as per the data retrieved in NHNSJ and SRL data. It is noted to be higher in women than men (from 46.8 to 52.7, and from 58.4 to 68.3 in mg/dl, respectively). Triglyceride and VLDL-C were higher in men but sex difference was not apparent in non-HDL-C and LDL-C levels, while these parameters slightly decreased in both sexes. The increase in HDL was most prominent in women in the age of 50 - 59 (from 57.0 to 73.4). The age-dependent HDL trend was reversed among women during the study period, as increasing instead of decreasing. This increase in HDL was found to coincide with lowered fish/meat ratio in food intake among Japanese. Conclusion: Marked increase in plasma HDL among Japanese is age- and sex-dependent and exhibited an apparent paradoxical association with lowered fish/meat ratio in their diet. Further investigation is required to elucidate the background for these findings.