By Anne Harding
Infants born to women who consumed the most vitamin A were half as likely to have a cleft palate as children whose mothers consumed the least, Anne Marte W. Johansen of the University of Oslo and her colleagues found.
"This supports other evidence that a healthy and varied diet during pregnancy is important," Johansen told Reuters Health.
Both excessive and deficient vitamin A intake have been tied to "a wide range of malformations" in humans and animals, Johansen noted. In humans, she added, the level at which vitamin A may have adverse effects on foetuses is not known, but "it is generally agreed that an intake up to three milligrams per day is safe."
Norwegians have a fairly high intake of vitamin A, Johansen and her team note in the American Journal of Epidemiology, while the incidence of cleft lips and/or cleft palates among Norwegian babies is relatively high, they add.
To investigate the relationship between vitamin A and orofacial clefts, the researchers compared 535 women who gave birth to a child with a cleft palate only or cleft lip with or without cleft palate between 1996 and 2001 and 693 women who delivered children without the defect during that time period.
Women in the top 25 percent for vitamin A consumption were 53 percent less likely to have a child with cleft palate alone than those in the bottom 25 percent, the researchers found. Intake of vitamin A was not related to the risk of cleft lip with or without cleft palate, supporting the theory that the two cleft types have different causes.
"Even though vitamin A may reduce the risk of cleft palate, it is important to avoid particularly high doses," Johansen added. "As for other vitamins, too little and too much vitamin A can be harmful for the foetus."
However, among the women in the top five percent of vitamin A consumption, who consumed an average of about 3,8 milligrams daily, there was no increased risk of clefts.
Maternal smoking, which is fairly common in Norway, could be a factor in the high rate of oral clefts among children born in the country, Johansen commented.