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Journal of the American College of Nutrition, Vol. 22, No. 3, 208-216 (2003)
Published by the American College of Nutrition

Original Research

Effect of Five-Year Supplementation of Vitamin C on Serum Vitamin C Concentration and Consumption of Vegetables and Fruits in Middle-Aged Japanese: A Randomized Controlled Trial

Mi Kyung Kim, PhD, Shizuka Sasazuki, MD, Satoshi Sasaki, MD, Shunji Okubo, MD, Masato Hayashi, MD and Shoichiro Tsugane, MD

Epidemiology & Biostatistics Division, National Cancer Center Research Institute East, Chiba (M.K.K., S.S., S.S., S.T.), JAPAN
Hiraka General Hospital, Yokote (S.O., M.H.), JAPAN

Address reprint requests to: Shoichiro Tsugane, M.D., Epidemiology and Biostatistics Division, National Cancer Center Research Institute, 6-5-1 Kashiwanoha, Kashiwa City, Chiba 277-8577, JAPAN. E-mail: stsugane{at}east.ncc.go.jp

Objective: This study was aimed at evaluating the effect of long-term vitamin C supplementation on serum and dietary vitamin C and identifying the factors associated with change in serum concentration.

Methods: A total of 439 subjects with atrophic gastritis initially participated in a randomized clinical trial using vitamin C and ß-carotene to prevent gastric cancer. We originally randomized the participants into four treatment groups using a 2x2 factorial design, whereby 0 or 15 mg/day ß-carotene and 50 or 500 mg/day vitamin C were administered in a double-blind manner. The ß-carotene component was terminated early after a mean treatment duration of four months. Before and upon early termination of ß-carotene supplementation, 134 subjects dropped out this trial, while 120 and 124 subjects took the vitamin C supplement at either 50 mg or 500 mg daily for five years.

Results: Changes in serum vitamin C were significantly higher in the high-dose group (38.5% increase, 95% CI = 27.0–49.9) than in the low-dose group (13.0% increase, 5.1–20.9) or in the dropout group (3.3% increase, -2.1–8.6) after five-year supplementation. The serum vitamin C at baseline was negatively associated with changes in serum vitamin C (p < 0.0001), while high-dose (p < 0.0001) and low-dose (p < 0.05) supplementation and female gender (p < 0.001) were positively associated. Dietary intake of vitamin C in the supplementation group was almost identical before and after five-year supplementation of vitamin C (2.31 mg/day decrease, 95% CI = -15.3–10.7), while a 17.7 mg/day decrease (95% CI = -44.2–8.86) was observed in the drop-out group.

Conclusion: Five-year vitamin C supplementation induces a remarkable increase in serum vitamin C concentration, and our intervention program appears to have no effect on dietary vitamin C intake.

Key words: vitamin C supplementation, serum vitamin C, fruit and vegetable intake, randomized controlled trial, Japanese






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