Determinants of plasma retinol concentrations of middle-aged women in rural China

The purpose of this study was to assess the correlates and possible determinants of plasma vitamin A among middle-aged women in rural China. The vitamin A adequacy of the different diets at the five widely varying survey sites was also assessed. Patterns of correlations among dietary and biochemical measurements were strikingly different from previous studies in Western subjects. Plasma β-carotene was uncorrelated with β-carotene intake even after adjusting for potential confounders. In counties with low preformed vitamin A intake, plasma retinol correlated with plasma copper (P = 0.007), which in turn was correlated with dietary intake of copper (P = 0.007). In these counties plasma retinol was correlated with plasma β-carotene (P = 0.001) and was increased 10% in women in the first 2 y of menopause (P = 0.028). Plasma retinol and C-reactive protein levels are inversely correlated (r = −0.15, P < 0.001), indicating that vitamin A status and inflammatory response may be related but the causal direction is unknown. Despite low intake of vitamin A (county averages of 13–78% of recommended daily allowance [RDA]), and particularly of preformed vitamin A, only 3% of these women had plasma retinol levels below 0.7 μmol/L, considered to indicate possible marginal deficiency. Plasma levels of retinol and β-carotene were more influenced by intrinsic factors such as menopause, lipid status, retinol requirements, and possibly copper status and inflammation than by extrinsic factors such as diet and lifestyle.