Drinking Cow's Milk Not Linked to Early Puberty
According to research conducted by a team of researchers at the University of Hong Kong, consumption of milk from cows does not seem to increase the risk of early puberty.
The findings are published in the journal Pediatrics.
On average, girls experienced puberty at 9.6 years and boys at 11.7 years.
About 10 years later, mothers were ask to think back to how often their child consumed milk at ages 6 months, 3 years and 5 years and the children were periodically assessed for signs of puberty between ages 6 and 13. Puberty was considered to have begun when the girls' breasts or boys' genitalia reached a certain stage of development.
Researchers found that 57 percent of children were never breastfed, 36 percent were fed some breast milk and some baby formula, and 6.4 percent were exclusively breastfed for at least three months.
At age 5, 33 percent drank cow's milk one time per week or less, 21.2 percent consumed it two to six times per week, and 45.2 percent consumed it daily.
Researchers said they found no link between the amount of cow's milk children in Hong Kong drank between ages 6 months and 5 years, and the age at which they began puberty.
Researchers did not factor weight, which is known to affect puberty.
According to the researchers, whether or not the children were breastfed did not affect the age puberty began.
Breast-feeding has been found to be beneficial.
The American Academy of Pediatrics recommends exclusive breastfeeding for the first six months of a baby's life. Breastfed babies are much less likely than formula-fed babies to get ear, respiratory and gastrointestinal infections, and are also less likely to develop asthma. Breastfeeding is also beneficial to mothers -- women who breastfeed have a reduced risk of ovarian and breast cancers.
Previous studies done in the United States hint that a frequent consumption of cow's milk could lead to early puberty. In the new study, Experts say because the study was conducted in China, it's not clear whether the results apply to the United States since many ethnic groups have different breast-feeding and milk consumption habits, and different rates of development.
Research done in the the 1990s suggested that children were starting puberty earlier because of growth hormones in cow's milk were to blame. But it has been found that the hormone given to cows is degraded during digestion, and so would not be expected to have a biological effect.
Researchers said parents should not be withholding milk or milk products for the unsubstantiated fear of it causing early puberty.