In 1860, the average age of menarche, or a girl's first menstruation, was 16.6 years old. Less than 100 years later, in 1950, this had decreased to 13.1 according to The Museum of Menstruation and Women's Health. This has further gone down since then, although more slowly. Today, the average age of menarche is 12.6 years old for white girls, 12.1 years for African American girls and 12.2 years for Latinos. It is not known why there is a difference or whether this difference has existed for many years, as most early information only took girls who were white or had European ancestry into account during studies. Scientists and medical professionals aren't sure why the age of menarche continues to decrease.
In a recent study, published in the journal Human Reproduction, girls who drank 1.5 servings or more of sugary sodas per day had their first period 2.7 months earlier than those who did not drink soda, or who drank less than 2 sodas per week. The researchers took into consideration other risk factors for early menses, such as body mass index, how much food the girls ate and whether or not they exercised.
While the reason for the association between sugary drinks and the start of menses isn't clear, it is possible that, because of the high glycemic index of sodas, there is a rapid increase in insulin concentrations on the body, which can in turn cause higher concentrations of sex hormones, which in turn, causes menses to begin earlier. The researchers explain that the study shows only an association, not a cause and effect, and the possible reasons are guesses only.
The decrease in age doesn't seem like much. Girls who drank sugary soda on a daily basis started their period at 12.8 years old, while those that did not or drank less, started their period at 13 years old. However, an early start to menses has been linked to other health conditions. It is considered a risk for developing breast cancer later in life. It has also been linked to mental health issues, such as depression, during adolescence. .
The American Beverage Association points out that while science has shown the age of menarche has decreased over the years, this study does not show that sugary drinks are the cause of this and have not discovered a cause at all.
"Early Puberty for Girls: The New 'Normal' and Why We Need to Be Concerned," 2009, Sept/Oct, Women's Health Activist Newsletter, National Women's Health Network
"Soda Habit May Prompt Early Puberty in Girls," 2015, Jan. 28, Staff Writer, HealthDay
"Sugary Drinks Linked to Girls' Earlier Periods," 2015, Jan. 28, Alexandria Sifferlin, Time Magazine