Vitamin A and clefting: putative biological mechanisms.

Nutritional factors such as vitamin intake contribute to the etiology of cleft palate. Vitamin A is a regulator of embryonic development. Excess vitamin A can cause congenital malformations such as spina bifida and cleft palate. Therefore, preventive nutritional strategies are required. This review identifies putative biological mechanisms underlying the association between maternal vitamin A intake and cleft palate. Excessive vitamin A may disturb all three stages of palatogenesis: 1) during shelf outgrowth, it may decrease cell proliferation and thus prevent tissue development; 2) it may prevent shelf elevation by affecting extracellular matrix composition and hydration; and 3) during shelf fusion, it may affect epithelial differentiation and apoptosis, which precludes the formation of a continuous palate. In general, high doses of vitamin A affect palatogenesis through interference with cell proliferation and growth factors such as transforming growth factor β and platelet-derived growth factor. The effects of lower doses of vitamin A need to be investigated in greater depth in order to improve public health recommendations.