Vitamin B-12 deficiency is prevalent in 35- to 64-year-old Chinese adults.

Low vitamin B-12 status alone, or in combination with low folate status, is related to neural tube defects (NTD) and hyperhomocysteinemia, a risk factor for atherosclerotic disease, but little is known about vitamin B-12 status in Chinese adults. In a cross-sectional study, we measured plasma vitamin B-12 in 2407 apparently healthy Chinese men and women, 35-64 y old, living in the south and the north of China. Plasma vitamin B-12 concentrations were lower among the northerners than the southerners (geometric means, 209 vs. 309 pmol/L, P < 0.001). Controlling for gender, age, season (spring and fall), and area (urban and rural) had little impact on the difference. We estimated that 11% of the southerners and 39% of the northerners had plasma vitamin B-12 concentrations <185 pmol/L, a level to define vitamin B-12 deficiency. Within each region, men had lower plasma vitamin B-12 concentrations and higher prevalence of vitamin B-12 deficiency than women (279 vs. 333 pmol/L and 15 vs. 8% in the south; 192 vs. 233 pmol/L and 47 vs. 34% in the north; P < 0.001 for all the differences). Low intakes of animal-based food, especially fish and dairy products, were significantly associated with vitamin B-12 deficiency. In the north, 59% of the participants were deficient in either folate (<6.8 nmol/L) or vitamin B-12, and 17% had deficiency in both. The corresponding rates were 16 and 1% in the southerners. To our knowledge, our findings provide the first evidence that vitamin B-12 deficiency is common in 35- to 64-y-old Chinese adults, especially in the north. Further studies are needed to evaluate the health effects and possible intervention strategies in areas where B-12 vitamin deficiency is common.