Breastmilk Nutrition Linked To Lower Blood Pressure In Later Life

Information linking poor nutrition in early life to health risks in later life was recently expanded to include confirmation of the relationship between infant feeding and hypertension¹. Previous epidemiological evidence² had strongly related the effects of breastfeeding as having a beneficial effect on childhood health and subsequent adult disease. To confirm the links between infant nutrition and risk reduction in later life a study design with prospective follow-up using a randomized, controlled for confounding factors trial was needed.

Atul Singhal and colleagues from Great Ormond Street Hospital, London, UK, measured blood pressure at age 13-16 years in 216 (23%) of a group of 926 children who were born prematurely and had previously (in 1982) taken part at birth in two parallel randomised trials in five neonatal units to determine the effect of early diet on later cognitive development³. Two parallel dietary trials, randomly assigned were used to compare the effects of early nutrition: donated banked breastmilk was compared with preterm formula (enriched with micronutrients, protein and fat); and in the second trial standard-term formula was compared with preterm formula. The sodium concentration in the preterm milk was: 19.9 mmol/L, in the pooled expressed breastmilk 11.0 mmol/L and 8.3 mmol/L in the term formula.

For the follow up at ages 13 and 16 years systolic, diastolic and mean arterial blood pressure were recorded, as well as height and weight and socio-economic data was taken. Weight gain, as expected was better for the infants assigned to expressed breastmilk and preterm formula. Of importance at the age of 13 and 16 was the significantly lower mean arterial pressure in children assigned banked breastmilk and preterm formula. The diastolic pressure was also significantly lower in infants assigned banked breastmilk compared to those receiving preterm formula. The differences for systolic pressure were not significant. Blood pressure measurements remained lower in infants fed banked breastmilk than in those fed preterm formulas after adjustment for sex, mean daily enteral sodium intake in infancy, and current body-mass index.

No differences were found in the group comparing term formula with preterm formula. Diastolic, systolic and mean arterial blood pressures did not differ significantly between children fed term formula versus preterm formula and remained non-significant after adjustment for sex, mean daily sodium intake in infancy and current body-mass index.

The investigators conclude that breastmilk consumption in children born prematurely was associated with lower blood pressure in later life. And the authors concluded that the data are also applicable to populations born at term as blood pressure in the adolescent population was not related to birth weight for gestational age nor affected by pubertal growth spurt.

The importance of this study as noted in comment⁴ by Susan Roberts of the US Department of Agriculture and Human Nutrition Research Center, is that the differences are found in the breastmilk and not related to levels of sodium or fat, but that "unique trophic factors" in human milk may cause structural or metabolic changes that influence blood pressure. She notes that this study adds to the body of publications "reporting the widespread effects of early diet on later body composition, physiology and cognition." Given that raised blood pressure is one of the risk factors for heart disease and premature mortality, further research will be needed to determine how the negative effects of formula feeding will influence the rates of cardiovascular disease. Nevertheless, this current evidence "indicates adverse affects of formula feeding on CVD risk factors, which is consistent with the observations of increased mortality among older adults who were fed formula as infants"⁵.

Public health implications for promotion and support of breastfeeding continue to escalate. As well the implications for full compliance to the International Code are significant. Obviously, the health care sector has clear responsibilities to ensure that their practices are evidence-based. The use of physicians' offices, hospital maternities and clinics to provide infant formulas and other artificial feeding products, which can result in demonstrable harm lasting a lifetime, is reprehensible. It is not only the infant formula industry that is liable for harm caused by its products, but also those who fail to comply with the requirements of the International Code, both governments and the health care system. Implications for health policy from this data also point towards the need for an effective system of human milk banks across Canada. The continued resistance by the Canadian Pediatric Society to human milk banking cannot be justified in the light of mounting evidence of the benefits banked human milk can provide to infants who are unable to receive their mother's milk, including those who are born prematurely.

References:

1. Singhal A, Cole TJ, Lucas A. Early nutrition in preterm infants and later blood pressure: two cohorts after randomised trials. The Lancet 357: 413-419, 2001 [BACK]

2. Wilson AC, Forsyth JS, Greene SA, Irvine L, Hau C, Howie PW. Relation of infant diet to childhood health: seven year follow up of cohort of children in Dundee infant feeding study. BMJ 316:21-25, 1998 [BACK]

3. Lucas A, Morley R, Cole TJ. Randomized trial of early diet in preterm babies and later intelligence quotient. BMJ 317: 1481-1487, 1998 [BACK]

4. Roberts SB. Prevention of hypertension in adulthood by breastfeeding? The Lancet 357: 406-407, 2001 [BACK]

5. Wingard DL, Criqui MH, Edelstein SL, Tucker J, Tomlinson-Keasy C, Schwartz JE, Friedman HS. Is breastfeeding in infancy associated with adult longevity? Am J of Public Health 84: 1458-1462, 1994 [BACK]