From The September 2000 Issue of Nutrition Science News

Fish: An Excellent Source of Vitamin D

Japanese women consume less calcium than their American counterparts and have skin less efficient at producing vitamin D, but they have significantly lower rates of osteoporosis. The results of a new study suggest that higher dietary vitamin D levels may help explain this paradox.

Kazutoshi Nakamura of the Niigata University of Medicine in Niigata, Japan, observed 136 women over age 40 (average age 65) in rural Japan in February 1999. Despite staying inside all winter, the mean serum vitamin D level of these women, 60 nmol/L, was one of the highest ever reported. Furthermore, only 5 to 8 percent of the women were deficient in the vitamin.

Researchers assessed diets via food frequency recall, and discovered that high fish and egg consumption could be linked to high vitamin D levels. For example, women eating fish at least four times per week had vitamin D levels 15 nmol/L higher than those who did not eat fish, and 10 nmol/L higher than those having fish one-three times per week. Moreover, women consuming eggs four times per week had vitamin D levels 15 nmol/L higher than those who did not eat eggs. Although vitamin D levels are commonly believed to decline with age, this study showed no such correlation.

Fish, a Japanese staple, contains between 400 and 4,800 IU of vitamin D per 100 g (3.5 oz). Average annual fish consumption in Japan is 70 kg in contrast to the American average of 22 kg. It should also be noted that Americans often avoid eggs. The results of this study suggest that the higher vitamin D levels found in the Japanese women may protect them from osteoporosis despite their lower calcium intake.

- American Journal of Clinical Nutrition, 2000 May;71:1161-5.