Getting a period is a social and developmental milestone that many American girls are reaching earlier than their mothers and grandmothers. About six months earlier on average, according to one 2024 study. Researchers, parents, and doctors, reasonably, want to understand why this is happening, and one commonly reached conclusion is higher obesity levels have corresponded to early puberty. But a more recent study published in Human Reproduction suggests it’s not obesity levels that affect the onset of menstruation, but diet.
Researchers led by Holly Harris at the Fred Hutchinson Cancer Center in Seattle studied more than 7,500 children, aged between 9 and 14 enrolled in the Growing Up Today Study (GUTS) in the U.S. The study had two waves in 1996 and 2004 and children were studied through 2001 and 2004 respectively.
Looking at the data, researchers found that eating a healthy diet as a child is linked to a later onset of menstruation, regardless of the girls’ body mass index (BMI) or height, both of which have been correlated to earlier periods in other studies.
“I think our findings highlight the need for all children and adolescents to have access to healthy meal options, and the importance of school-based breakfasts and lunches being based on evidence-based guidelines,” Harris said in a statement.
Now, certainly, diet can have an effect on BMI and/or height, hence why many studies have drawn the connection between those factors and menstruation. This study marks the first time researchers investigated the link between diet and menarche. After all, many children can eat an unhealthy diet and have a low BMI or eat a healthy diet and still be considered obese based on BMI which has been called into question regarding its usefulness in measuring health.
Before their periods started, the children were asked about their diet several times throughout the study. Researchers assessed the girls’ diets using the Alternative Healthy Eating Index (AHEI)— which awards more points for foods like vegetables, legumes and whole grains and fewer points for things like red and processed meats, trans fats and salt —and the Empirical Dietary Inflammatory Pattern (EDIP), which scores diets for their potential to cause inflammation in the body (red meat and refined grains, for example, can contribute to a higher score).
A total of 6,992 girls (93% of the whole group) had their first period during the study. Analysis of the 6,992 girls who started their period over the course of the study found that 20% of girls with the highest (healthiest) AHEI score were 8% less likely to have their first period within the next month compared to the 20% of girls who had the lowest AHEI score. Approximately 20% of girls with higher EDIP scores (aka who ate a more inflammatory diet) were 15% more likely to have their first period in the next month compared to the 20% who had the lowest EDIP score.
As earlier age at menarche is associated with multiple later life outcomes, including higher risk of diabetes, obesity, cardiovascular disease and breast cancer, this may be an important period for trying to reduce the risk of these chronic diseases,” Harris notes.
Look, we all pretty much know the more fresh veggies and fruits, whole grains, and lean proteins you can eat the better. A healthy diet is associated with all kinds of positive health outcomes. This is just one more, but it also has the benefit of showing us that health (and positive health outcomes) are possible regardless of size.