Rickets has reemerged recently as a problem in infants who are breastfed more than 6 months without vitamin D supplementation. This is true of all infants in more northern latitudes and dark skinned infants in all parts of the United States.
Breast milk is said to be a poor source of vitamin D; and geographic latitude and skin pigmentation are important factors in the production of Vitamin D.
Alfred F. Hess (1875-1933) did the original research in the early 20th century that studied rickets in the Columbus Hill district of New York City, and found rickets to be “universal” in Afro-American infants. Cod liver oil was found to prevent rickets in 92% of the infants treated and rickets nearly disappeared by 1960.
CONCLUSION: Rickets has returned in infants who are breastfed for more than 6 months as a result of inadequate vitamin D levels. Cod liver oil for the infants was found to prevent rickets in 92% of infants in a study by Alfred F. Hess in the early 20th century.
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