Over the years, much research has confirmed that breastfeeding helps keep babies healthy. Breastfeeding has been shown to reduce the risk of respiratory and gastrointestinal infections, a type of blood infection called bacteremia, and meningitis. While the practice may improve infant survival rates -- particularly in developing countries -- does having been breastfed make any difference to an adult’s lifespan?
This type of question is a challenging one for epidemiologists who track how diseases develop. They must usually rely on observational studies conducted over a long period of time, ruling out confounding or additional factors that are at play. Long-term or longitudinal research may discover which lifestyle factors (smoking, exercise level, or in this case, breastfeeding) are associated with better health or longevity, but that’s not the same thing as establishing whether one aspect of behavior caused a certain outcome.
One of the few investigations into breastfeeding and longevity per se was conducted on a group of more than a thousand Californians, tracked from childhood in the 1920s by psychologist Lewis Terman and others. Data on breastfeeding was available for 1,170 of the subjects, showing that being breast-fed was not significantly associated with greater longevity.
In 2011, a team of population health experts led by Christopher Owen from the University of London examined a number of observational studies to examine whether breastfeeding has any effect on the development of cardiovascular disease and other life-threatening conditions later in life. Published in the Proceedings of the Nutrition Society, the paper cites a number of factors hindering firm conclusions about the long-term benefits of breastfeeding:
- Breastfeeding is rarely exclusive, without any additional water, formula or food
- Precise duration of breastfeeding is difficult to determine
- Feeding practices may not be accurately recalled in surveys
- A mother’s weight may affect her general state of health, though it is rarely accounted for in the available observational studies
- Her socio-economic status will likely affect her nutritional health, though it is rarely available for analysis
Despite these limitations, the researchers drew some interesting conclusions from the papers they reviewed:
Cholesterol: Drawing from 37 different studies involving more than 10,000 people, the British scientists cite data showing marginally lower (though consistently so) total cholesterol in adults who had been breastfed in infancy. This finding held, for subjects ranging in age from 17 to 64 years, and birth years 1920 to 1975.
Blood pressure: Breastfeeding has been shown to be associated with markedly lower blood pressure in childhood, according to the review’s authors, though only a modest effect in adulthood was found.
Diabetes: The authors cite a number of studies that examined the link between breastfeeding and the development of diabetes and consistently found a lower risk for breastfed babies versus those fed formula. While the findings held in a number of different populations, and in three separate studies (after adjustment for birth weight, parental weight and diabetes), Owen’s team cautions that confounding factors not considered in other, similar trials should be considered before promoting breastfeeding as a means of reducing the incidence of diabetes. They conclude that addressing the problem of adult obesity would likely have a more profound influence on whether diabetes develops later in life.
Obesity: Owen’s paper cites a review of nine studies involving more than 69,000 people, which concluded that adults who were breastfed as infants had a 22% lower risk of obesity, compared to their formula-fed counterparts. That study accounted for factors like birth weight, smoking, parental obesity and socio-economic factors. A larger review, involving 28 studies and 298,900 participants, also showed breastfeeding was linked to a lower risk of obesity, though the benefit diminished significantly once confounding factors like parental obesity and smoking were accounted for.
In conclusion, the authors write that determining the exact impact of breastfeeding on long-term health is very difficult, mostly because it’s tough to nail down exactly how long breastfeeding occurred, whether babies were fed breast milk exclusively, and the potential for error in a parent’s recall of the precise conditions of infant feeding. They recommend further research to establish the optimum duration of breastfeeding -- with adequate follow-up study -- strictly accounting for and recording possible influencing factors like maternal health, weight, nutrition and income.
Christopher G. Owen, Peter H. Whincup and Derek G. Cook. “Breast-feeding and cardiovascular risk factors and outcomes in later life: evidence from epidemiological studies.” Proceedings of the Nutrition Society, November 2011. 70 : pp 478-484.
D L Wingard, M H Criqui, S L Edelstein, J Tucker, C Tomlinson-Keasey, J E Schwartz, and H S Friedman. “Is breast-feeding in infancy associated with adult longevity?” American Journal of Public Health September 1994: Vol. 84, No. 9, pp. 1458-1462.