Babies adapt to low-fat mother's milk.

While adults fight the yen for rich, fattyfoods, newborn babies require lots of fat to fuel their explosive growth. But what happens when mother's milk is low in fat?

A new study provides reassuring evidence that most babies will compensate for their mother's low-fat yield by nursing longer.

Some new mothers have difficulty breast-feeding, and pediatricians have speculated that such mothers can't keep up with a newborn's voracious demand, leading to a cranky baby and a frustrated mom. To find out more about nursing success, pediatrician Jon Tyson took a closer look at the fat content and volume of breast milk.

Tyson and his colleagues at the University of Texas Southwestern Medical Center at Dallas recruited new mothers who wanted to breast-feed their infants. The researchers obtained breast milk samples from the recruits and used a centrifuge to measure the fat layer. They calculated milk-fat yield by factoring in both the fat content and the amount of milk each woman produced.

The team identified 20 women with a low-fat milk yield. In most cases, these women produced milk with the usual amount of fat but in low volumes, Tyson says. Next, the researchers selected 20 women with a high-fat milk yield and sent both groups of mothers home to care for their 2-week-old infants.

Six weeks after birth, babies in the low-fat group weighed slightly less than those in the high-fat group, the researchers report in the February Pediatrics. But the small weight difference probably doesn't mean much, Tyson says. On two other measures of growth -- body length and head size -- the babies in the low-fat group progressed just as rapidly as their counterparts in the high-fat group, he notes.

Rather than crying over less milk, infants in the low-fat group seemed to make up for the loss by spending more time at their mother's breast. The Texas team found that these babies nursed longer and emptied the breast more completely than their peers in the high-fat group.

Nonetheless, women in the low-fat group may develop breast-feeding problems in the future, Tyson says. Although babies adapt to the low-fat environment by sucking more, this leaves the mother with scant milk reserves. If mom gets sick and her already-low milk production drops even lower, the baby might not get enough to eat. During such periods, Tyson recommends more frequent feedings, which spur a mother's milk production.