title: Vitamin C supplementation slightly improves physical activity levels and reduces cold incidence in men with marginal vitamin C status: a randomized controlled trial.
abstract: The early indications of vitamin C deficiency are unremarkable (fatigue, malaise, depression) and may manifest as a reduced desire to be physically active; moreover, hypovitaminosis C may be associated with increased cold duration and severity. This study examined the impact of vitamin C on physical activity and respiratory tract infections during the peak of the cold season. Healthy non-smoking adult men (18-35 years; BMI < 34 kg/m2; plasma vitamin C < 45 µmol/L) received either 1000 mg of vitamin C daily (n = 15) or placebo (n = 13) in a randomized, double-blind, eight-week trial. All participants completed the Wisconsin Upper Respiratory Symptom Survey-21 daily and the Godin Leisure-Time Exercise Questionnaire weekly. In the final two weeks of the trial, the physical activity score rose modestly for the vitamin C group vs. placebo after adjusting for baseline values: +39.6% (95% CI [-4.5,83.7]; p = 0.10). The number of participants reporting cold episodes was 7 and 11 for the vitamin C and placebo groups respectively during the eight-week trial (RR = 0.55; 95% CI [0.33,0.94]; p = 0.04) and cold duration was reduced 59% in the vitamin C versus placebo groups (-3.2 days; 95% CI [-7.0,0.6]; p = 0.06). These data suggest measurable health advantages associated with vitamin C supplementation in a population with adequate-to-low vitamin C status.
authors.affiliation: School of Nutrition and Health Promotion, Arizona State University, 500 N. 3rd St., Phoenix, AZ 85004, USA. carol.johnston@asu.edu.
authors.forename: Carol S
authors.initials: CS
authors.lastname: Johnston
authors.affiliation: Isagenix® International LLC, 2225 S. Price Rd., Chandler, AZ 85286, USA. gillean.barkyoumb@isagenixcorp.com.
authors.forename: Gillean M
authors.initials: GM
authors.lastname: Barkyoumb
authors.affiliation: Cancer Treatment Centers of America®, 14200 W. Celebrate Life Way, Goodyear, AZ 85338, USA. sara.schumacher@ctca-hope.com.
authors.forename: Sara S
authors.initials: SS
authors.lastname: Schumacher
mesh_terms: D000293:Adolescent; D000328:Adult; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000097:blood; D001206:Ascorbic Acid Deficiency / Q000097:blood / Q000188:drug therapy; D015992:Body Mass Index; D003139:Common Cold / Q000097:blood / Q000517:prevention & control*; D019587:Dietary Supplements; D004311:Double-Blind Method; D006306:Health Surveys; D064368:Healthy Volunteers; D006801:Humans; D015994:Incidence; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009752:Nutritional Status; D011795:Surveys and Questionnaires; D014922:Wisconsin; D055815:Young Adult
chemical_list: D001205:Ascorbic Acid