Plasma vitamin C is inversely related to body mass index and waist circumference but not to plasma adiponectin in nonsmoking adults

We examined the relationships between plasma vitamin C, adiposity, and the collagen-like adipokine, adiponectin. Of 118 sedentary, nonsmoking adults participating in the cross-sectional trial (35 men and 83 women aged 38.7 ± 1.0 y with BMI of 30.4 ± 0.6 kg/m², plasma vitamin C concentrations of 43.5 ± 1.3 μmol/L, and plasma adiponectin concentrations of 8.9 ± 0.3 mg/L), 54% were obese and 24% were overweight. Plasma vitamin C was inversely related to BMI, percentage of body fat, and waist circumference in both women and men (r = -0.383 to -0.497, P < 0.025). In women but not men, these associations remained significant after controlling for body mass. Plasma vitamin C was directly related to plasma adiponectin in the women after controlling for age and vitamin C supplement use (r = 0.222, P = 0.049) but not after controlling for body mass. Twenty obese men and women participated in an intervention trial and consumed an energy-restricted diet low in vitamin C (≈38 mg/d) for 8 wk. Subjects were stratified by age, gender, and BMI and randomly assigned to receive placebo or vitamin C (500 mg) capsules daily. At baseline, plasma adiponectin was directly related to plasma vitamin C (r = 0.609, P = 0.021) and inversely related to body mass (r = -0.785, P = 0.001). Body mass decreased significantly during the 8 wk study in both the vitamin C (n = 6, -5.9 ± 0.9 kg) and placebo groups (n = 8, -6.5 ± 0.7 kg). Plasma adiponectin increased 13% from baseline by wk 8 in both groups (P < 0.05). In summary, plasma vitamin C was inversely related to markers of adiposity, particularly in women, but vitamin C supplementation did not influence the circulating concentration of adiponectin.