Nov. 6, 2007 -- To breast-feed or not to breast-feed? That question has plagued new moms for decades. But the findings of a new study that were presented at the American Heart Association conference Monday might help make this decision a little easier.
Observational data collected from the Framingham heart study suggests breast-fed babies have fewer cardiovascular risks as they mature into adults. By analyzing the data collected from two generations of participants in the study, investigators found that the breast-fed babies were more likely to have a lower body mass index (BMI) and higher level of HDL cholesterol — often referred to as "the good cholesterol" — when they reached adulthood. A low level of excess body fat and a high level of HDL are both associated with reduced risk for cardiovascular disease.
"Breast milk contains certain things that might be protective later on in life and might actually program an infant's metabolism at a very early stage," said Dr. Nisha Parikh, lead investigator of the study and cardiovascular fellow at the Beth Israel Deaconess Medical Center in Boston. "That programming will lead to either a baby with higher or lower weight later on in life. And that's the idea that we've only just scratched the surface of — that you're early exposure to nutrition might affect your metabolism in the long term."
Economics Can Affect Breast Milk
Investigators analyzed the data from 393 mothers enrolled in the study and 962 of their offspring, 26 percent of whom were breast-fed. The average age of the offspring was 41. Researchers found that the breast-fed offspring were 55 percent more likely to have high HDL cholesterol in adulthood. The average BMI of the breast-fed babies was also lower: 26.1 kilograms per meters squared, compared to 26.9kg/m2 for the bottle-fed infants.
Dr. Robert Morrow, professor of pediatrics and chief of the cardiology section at Arkansas Children's Hospital, emphasized the importance of taking into account socioeconomic differences when studying the impact of breast-feeding. When the Framingham study began in 1947, breast-feeding was considered "low class" and was done primarily by women who couldn't afford baby formula, Morrow explained.
Because many of the breast-feeding mothers were from lower socioeconomic status, their diets were often less nutritious than those of wealthier women. Their babies often did not get proper nutrition because the breast milk of women with less nutritious diets was likely to have high levels of cholesterol and fat.
These socioeconomic differences were accounted for by researchers via questionnaire. The results were altered based on what the mothers said about their social status and eating habits.
Parikh stressed that because the study was observational, no definitive clinical recommendations could be drawn from these findings, nor any absolute proof that breast-feeding directly contributes to the decrease in cardiovascular risk factors. However, a great amount of research over the last 20 years has added to the knowledge on the health benefits of breast-feeding.
"Even though all we can do is theorize about how all of this makes sense, theories are pretty acceptable, that is to say that eating patterns established as an infant do carry over into adolescence, young adulthood and middle age," said Dr. Clyde Yancy, professor of medicine and cardiology at the University of Texas Southwestern and associate dean of clinical affairs at UT Southwestern University hospitals. "As well, obesity as an infant and as a child is the most difficult obesity to overcome, and there's a clear link between being bottle fed and eventually becoming obese."
From Birth to Adulthood
Many doctors at the heart meeting said they believed this study was especially significant because it traced the effects of breast-feeding all the way into adulthood. Although health experts have known for years the immediate health benefits of breast-feeding for the baby, this is the first study to explore the long-term impact.
"Everything we … look at now seems to show us that there are periods in your early life when external factors have a continued effect on how we mature and the way the brain … develops. But here we have compelling evidence that this period [of breast-feeding] continues to affect us into adulthood," explained Morrow.
The primary difference between human breast milk and baby formula is the nutritional content. Human milk produced by a healthy mother contains a vital balance of fatty acids, amino acids, lactose and vitamins — all of which play a vital role in a child's growth, brain development, digestion and even metabolic rate. Baby formula is manufactured from cow's milk, which contains more fat that is harder for humans to digest.
The American Academy of Pediatrics recommends that mothers breast-feed for six to 12 months.
"Beyond the metabolic benefits of breast-feeding, we know that the period of breast-feeding is a time of rapid brain growth. It's a time when people's preferences for tastes as well as people's ability to feel satisfied with food are determined," said Jim Stein, associate professor of medicine in the division of cardiovascular medicine at the University of Wisconsin.
Parikh said she hopes that this study will inspire further research in this area, as researchers were unable to prove exactly what mechanisms are responsible for the reduced cardiovascular risk they observed in breast-fed babies.
"I think it would be interesting to do similar study where you actually have breast milk samples and measure the levels of cholesterol and nutritional content," Parikh said. "I hope our work will serve as impetus to pass baton onto researchers who would explore this in the future."