Vitamin C status and fatigue in obese adults consuming a reduced‐calorie diet

Abstract

Epidemiologic data suggest an inverse relationship between vitamin C status and body weight. Since vitamin C status can impact fatigue, we examined whether vitamin C status was associated with fatigue in obese adults participating in a weight loss trial. Healthy adults (body mass index ≥ 30 kg/m2) consumed a reduced-calorie, vitamin C-restricted diet (~40 mg/d) for 4 weeks. At the start of the trial, subjects were randomized to receive either placebo (CON group, n=10) or 500 mg/d ascorbic acid (VC group, n=10) using a double-blind protocol. Fatigue at rest was quantified weekly using the Profile of Mood States (POMS) questionnaire. At trial weeks 0 and 4, the perceived rate of exertion (Borg's RPE 6–20 scale) was recorded during a 60-min walk at 50% maximal oxygen consumption. After 4 weeks of diet/supplementation adherence, plasma vitamin C concentrations fell significantly in the CON group (0.805±0.197 [mean ± SD] and 0.626±0.214 mg/dL at weeks 0 and 4, respectively, p<0.001) and increased significantly in the VC group (0.841±0.034 and 1.089±0.148 mg/dL, p<0.001). RPE at 40 minutes of sub-maximal exercise fell significantly in the VC group (13.57± 0.98 and 12.14±0.69 at weeks 0 and 4, respectively, p=0.003), while RPE increased (ns) in the CON group (12.80±1.79 and 13.10±1.34). At rest, fatigue scores fell significantly in the VC group (11.29±4.95 and 5.57±3.91 at weeks 0 and 4, respectively, p=0.019), while fatigue scores were unchanged in the CON group (8.33±9.27 and 7.22±6.01). These data suggest that vitamin C status affects perceptions of fatigue both at rest and during sub-maximal exercise in obese adults consuming calorie-restricted diets. Hence, vitamin C status may impact success of weight loss regimens. This research was supported by the General Mills, Bell Institute of Health and Nutrition.