Though a young girl might not expect it at the time, her prepubescent dietary habits can have major effects on when she hits puberty.
According to University of Michigan research released last week, girls who eat red meat more often start menstruation about five months earlier than girls of the same age who consume less red meat.
The study also showed that eating fatty fish more often, however, has the opposite effect and may delay a girl’s menarche, or first period, by a few months.
“Animal protein is important for child growth and development,” wrote senior study author Eduardo Villamor, professor of environmental health sciences and epidemiology, in an e-mail interview. “However, it is possible that some sources of animal protein may be healthier than others.”
The study, which focused on the diets of 456 pre-pubescent girls in Bogota, Colombia, was led by Public Health student Erica Jansen. The girls participated in a six-year longitudinal study as part of the Bogota School Children Cohort. Jansen wrote in an e-mail interview she and Villamor focused on this region of the world due to its unique dietary factors.
“Colombia is currently undergoing a nutrition transition, where consumption of red meat may be increasing,” Jansen wrote.
The researchers, after asking when the girls had their first period, found that those who reported consuming meat two or more times a day began their periods, on average, at the age of 12 years and three months. Those who ate red meat less than four times a week began their periods, on average, at the age of 12 years and eight months.
For fish, on the other hand, girls who consumed tuna or sardines at least once a week during their middle childhood years experienced menarche later than girls who consumed these fatty fish less than once a month.
Jansen noted that it cannot be said for sure whether environmental factors, such as higher availability of red meat in Bogota also contributed to the results. She noted that there also are no correlations between their findings and a generally earlier onset of puberty in Colombia compared to other countries.
However, this five month difference in age of first period ultimately has indications for both physical and behavioral health later in life, Jansen wrote.
“Earlier menarche has been related to higher risk of breast cancer in addition to other adverse health outcomes including obesity, type 2 diabetes, and all-cause mortality,” she wrote. “In the short term, an earlier age at menarche has been associated with earlier sexual debut, teen pregnancy, and abuse of alcohol and tobacco.”
Those physical health outcomes could be related to a number of factors, she added.
“We cannot say for sure what could explain the association, but it could be related to macro- or micronutrients present in red meat, substances fed to cattle, or components related to preservation or preparation of these meat sources,” Jansen wrote.
Sarah Ball, assistant dietetic internship director in the Department of Nutritional Sciences, echoed Jansen’s statement and said the way the cattle is raised can make a big difference in what humans end up consuming.
“At least in this country there’s a big difference between, or could potentially be a big difference between, your small ranching, grass-fed cattle and the meat we consume from that compared to your big, large industry-based grain-fed cattle production,” Ball said.
Ball said other factors besides red meat intake, such as body mass index, could also contribute to the time of puberty onset of young women. BMI can increase based on higher consumption rates of sugar-sweetened beverages and lower consumption rates of fruits and vegetables.
Ultimately, because this is only an observational study, earlier menarche cannot solely be attributed to higher red meat intake, Jansen wrote. Researchers suggested prepubescent girls should not necessarily limit their red meat intake to avoid menarche, but rather should consume red meat in moderation.
“We cannot conclude for sure that red meat intake causes early puberty from this study,” Villamor wrote. “Excessive red meat intake is probably not a good idea in general. It does not need to be completely abolished from the diet, but it can be eaten sparsely and replaced with other sources of animal protein, for example, fish.”
Though recommended diets change based on demographics and geographics, the general recommendation for the best diet for people living in the United States, including children in middle childhood years, is a varied diet as found in the Current Dietary Guidelines for Americans, according to Ball.
“It’s a (dietary) pattern that includes a variety of fruits and vegetables, whole fruits instead of juice, vegetables from a variety of different groups and different colors, whole grains, low-fat dairy and a variety of protein foods,” she said.”Really focusing on seafood and those lean meats — poultry, eggs, beans, nuts and seeds — and then healthy oils, with a limit on sugar-sweetened beverages and more processed products.”