Epidemiologist Eduardo Villamor, an associate professor at the University of Michigan School of Public Health, says early menstruation is a risk factor for behavioral and psychosocial problems in teens. Girls who had earlier menarche -- first menstruation -- appear to have increased risk of developing cardiometabolic diseases and cancer, particularly breast cancer, as adults.
The study involved 242 girls ages 5-12 from Bogota, Colombia, and tracked them for 30 months, Villamor said. Girls with low levels of vitamin D were twice as likely as those with sufficient vitamin D to start menstruation during the study than, Villamor said.
Villamor and colleagues found 57 percent of the girls in the vitamin D-deficient group reached menarche during the study, compared to 23 percent in the vitamin D-sufficient group.
Girls who were low in vitamin D were about 11.8 years old when they started menstruating, compared to the other group at about age 12.6 years old, Villamor said.
The 10-month difference is substantial, Villamor said, because even though 10 months may not seem like a long time, at that age a lot is happening rapidly to a young girl's body.
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