Tea and a Daughter’s Puberty

A series of studies in recent years has chronicled a disturbing trend—a decline in the age at which many children, principally girls, begin their sexual maturation. Though no one has conclusively tied precocious puberty to a particular dietary, environmental, or medical factor, suspicions abound that it stems from exposure to hormonelike agents in the environment.

The latest study in this area supports the idea that certain environmental factors can modify the timing of puberty—if the exposures to them occur in the womb. For women concerned about diminishing the likelihood that they’ll trigger such a phenomenon in their own daughters, a cup of tea might be called for—on a regular basis.

Gayle C. Windham and her colleagues at the California Department of Health Services and at a La Jolla, Calif., consulting firm report that the age of menarche—when a girl first starts her monthly menstrual periods—is later among daughters of tea drinkers than among daughters of moms who typically choose coffee or another beverage. If confirmed, the findings may reflect “hormonal effects,” the researchers say.

There is considerable variability in when a child reaches developmental milestones, be they growth spurts or teenage mood swings and impulsivity. In girls, this is especially true for the timing of changes related to puberty. For instance, although breast development typically occurs between the ages of 9 and 11, it can happen as early as 6—and in a few truly perplexing waves of early development, it has reached back to girls as young as 2 (SN: 9/9/00, p. 165: Girls may face risks from phthalates). Similarly, menstrual periods typically begin around age 12, but they can start as early as 10 or as late as15.

Suspecting that hormone-mimicking agents in the diet or environment might program some girls to undergo early puberty, Windham’s group investigated prenatal exposures for some 1,000 teens—girls whose mothers had been recruited for a long-running Child Health and Development Study when they were pregnant with these children. All the moms began the study in the San Francisco area.

Both mothers and their daughters were periodically examined by doctors participating in the study. In each case, both family members were questioned about the timing of the girls’ reproductive development and exposures to chemical or other factors that might have affected it.

The findings, reported in the May 1 American Journal of Epidemiology, “were all a surprise, in a way,” says Windham, because “little work had been done looking at how prenatal exposures might relate to these later outcomes.” Certainly, she acknowledges, she never expected to unearth a potentially beneficial effect of tea.

Tea delays, smoking advances

Although most of the moms recruited for the study drank coffee, a third drank tea. By sifting through the data, the researchers found that in general, the more caffeine a woman consumed, the older her daughter would be at menarche. Further probing showed that this link traced almost entirely to the tea.

There was a nearly 5-month delay in the mean age of menarche for daughters of women who drank 3 or more cups of caffeinated tea per day, on average, during pregnancy. Indeed, among white girls, the rate of late menarche—that is, onset of menstrual periods at age 13 or later—was increased 72 percent in those whose mothers were heavy tea drinkers.

Exposure to cigarette smoke produced the opposite effect. “The mean age was somewhat earlier at menarche among girls whose mothers smoked heavily during pregnancy,” Windham says. Overall, they were about 2.5 months younger at menarche than girls whose mothers hadn’t smoked.

Moreover, she notes, there seemed to be a racial disparity in the potency of this effect. Among whites, for instance, the daughters of women who smoked at least a pack of cigarettes a day during pregnancy started menarche about 2 months earlier than nonsmokers’ daughters, but among blacks, the heavy smokers’ daughters reached menarche some 6 months earlier than nonsmokers’ girls did.

Racial differences have been reported previously by others. For instance, a representative survey of the U.S. population turned up a similar dichotomy of when different ethnic groups enter various stages of puberty. Germaine M. Buck of the National Institute of Child Health and Human Development and her coworkers noted that among black girls, the mean age for onset of pubic hair, breast development, and menarche were 9.5, 9.5, and 12.1 years. Among Mexican Americans, those milestones came slightly later, and among white girls, they occurred some 6 to 12 months later than among the black girls.

In Windham’s new study, somewhat less than one-quarter of the heavy smokers’ daughters were on the late side in reaching menarche—that is, at least age 13—compared with fully 36 percent of daughters born to heavy tea drinkers.

What’s the big deal?

“Our concern,” Windham says, is that the smoking-related results from the new study signal “that something is going on that’s affecting hormones early on . . . and that for some girls, [the advance in menarche is] more than a few months.”

Aside from advancing the age at which parents must worry about how a daughter will handle sexual advances from men, what difference does a girl’s early sexual-maturity make? Plenty.

Early menarche is one of the more significant risk factors for breast cancer. It tends to signal when a woman begins ovulating and thus producing high monthly elevations in estrogen, a hormone that can feed the growth of most tumors starting in the breast and other reproductive tissues.

In follow-up research, Windham will be looking for evidence of smoking’s impact on menarche in data from a previous study of mother-daughter pairs living on the East Coast. The volunteers in this study contain a larger share of blacks than the newly reported West Coast study does. Windham will also take part in a large federal study of institutions around the country that are investigating environmental factors that might be altering the timing of girls’ reproductive development.