Effects of vitamin B12 on plasma melatonin rhythm in humans: Increased light sensitivity phase-advances the circadian clock?
- 88 Downloads
Vitamin B12 (methylcobalamine) was administered orally (3 mg/day) to 9 healthy subjects for 4 weeks. Nocturnal melatonin levels after exposure to bright light (ca. 2500 lx) were determined, as well as the levels of plasma melatonin over 24 h. The timing of sleep was also recorded. Vitamin B12 was given blind to the subjects and crossed over with placebo. We found that the 24-h melatlonin rhythm was significantly phase-advanced (1.1. h) in the vitamin B12 trial as compared with that in the placebo trial. In addition, the 24-h mean of plasma melatonin level was much lower in the vitamin B12 traial than with the placebo. Furthermore, the nocturnal melatonin levels during bright light exposure were significantly lower in the vitamin B12 trial than with the placebo. On the other hand, vitamin B12 did not affect the timing of sleep. These findings raise the possibility that vitamin B12 phase-advances the human circadian rhythm by increasing the light sensitivity of the circadian clock.
Key wordsCircadian rhythm melatonin bright light vitamin B12 entrainment
Unable to display preview. Download preview PDF.
- 2.Okawa, M., Mishima, K., Nanami, T., Shimizu, T., Iijima, S., Hishikawa, Y., and Takahashi, K., Slepp13 (1990) 15.Google Scholar
- 3.Morita, N., Chiba, T., Wada, T., Sumi, M., Kohsaka, M., Fukuda, N., and Honma, K., Jap. J. Psychiat. Neurol.43 (1989) 806.Google Scholar
- 4.Weitzman, E. D., Czeisler, C. A., Coleman, R. M., Spielman, A. J., Zimmerman, J. C., and Dement, W., Archs gen. Psychiat.38 (1981) 737.Google Scholar
- 15.Brainard, G. C., Lewy, A. L., Menaker, M., Fredrickson, R. H., Miller, L. S., Weleber, R. C., Casone, V., and Hudson, D., Ann. N. Y. Acad. Sci.453 (1985) 376.Google Scholar
- 16.Wever, R. A., in: The Circadian System of Man. Springer-Verlag, New York 1979.Google Scholar
- 18.Czeisler, C. A., Allan, J. S., Strogatz, S. H., Ronda, J. M., Sanchex, R., Rios, C. D., Freitag, W. O., Richardson, G. S., and Kronauer, R. E., Science133 (1986) 667.Google Scholar
- 19.Zatz, M., and Browsnstein, M. J., Science208 (1979) 358.Google Scholar