By Anne Harding
New York - A study shows that milk from mothers who have been breastfeeding their infants for more than a year is richer in fat and energy than milk from moms who have been breastfeeding for just a few months.
The study is the first to look at the nutritional value of breast milk after prolonged breast-feeding, Dr Dror Mandel of Tel Aviv University in Israel said.
"It might be that because the infant is breastfed less times a day, the milk is more concentrated," he noted in an email interview.
Mandel and colleagues compared milk from 27 women who had been nursing for two to six months and 34 mothers who had been nursing for 12 to 39 months.
They report, in the journal Pediatrics, that the average fat content of milk from the shorter-duration breast-feeding group was just over seven percent, compared to about 11 percent from the longer-duration group.
A litre of milk from the women breastfeeding for a shorter period of time contained about 740 calories, compared to 880 for the women who had been breastfeeding for a year or longer.
The American Academy of Pediatrics recommends that mothers exclusively breastfeed their infants up to six months of age, and that nursing for a year or more will give a baby the "full benefits of breastfeeding," which include cutting rates of illnesses such as ear infections and diarrhoea and reducing the risk of childhood obesity.
However, Mandel and his colleagues note in their report that "the optimal duration of breastfeeding is unknown".
While one study suggested a link between extended breastfeeding and increased heart disease risk, "many objections have been raised against this accusation," the authors point out. It would be necessary to evaluate the types of fats contained in breast milk after a year of lactation before such a possibility can be raised, they add.
They also point out that, "at the present time, the official policy of the American Academy of Pediatrics is not to put any limit on the duration of lactation".
"The results showed that the caloric contribution of breast milk to the infant diet is not negligible," Mandel added.
"Hence, we can tell mothers that continue to breastfeed their infants that, from a caloric standpoint, their milk is of nutritional value."
Source: Pediatrics, September 2005.