Breastfeeding and incidence of non-insulin-dependent diabetes mellitus in Pima Indians

D J Pettitt, M R Forman, R L Hanson, W C Knowler, P H Bennett

The Lancet, 1997, Vol 350, 166-168

Non-insulin-dependent diabetes mellitus (NIDDM) has reached epidemic proportions in the Pima Indians living in the USA, i.e. an increase of 50% has been noted in this population group since 1965. In view of the fact that exposure to cow's milk has been linked to the development of insulin dependent diabetes mellitus (IDDM), the authors of the present study set out to determine if the use of formulas in place of breast milk, influences development of NIDDM in this diabetes-prone population.

The mothers of 933 Pima Indians born between 1950 and 1978 were interviewed to determine what method of feeding had been used after birth, the duration of breast- feeding and time of introduction of bottlefeeding. 741 persons aged 10 to 39 in the study population were examined, height and weight were measured, an oral glucose test was performed, and diabetes or impaired glucose tolerance, were diagnosed using WHO criteria.

The following results were obtained:

 Age-specific rate of diabetes by infant feeding group

(According to Pettitt et al, 1997, p 167)

The rate of NIDDM increases with age and within each age group, breastfeeding is associated with a lower incidence of diabetes. The odds ratio for diabetes between subjects who were exclusively breastfed, and those who were exclusively bottlefed, was 0.41 (0.18-0.93, p = 0.032).

The authors conclude that exclusive breastfeeding for periods of 2 months and longer after birth, is associated with a lower incidence of NIDDM in the Pima Indian population. Another disturbing fact that emerges from this study, is the finding that breastfeeding was more common earlier in this century and decreased as time went by, i.e. breastfeeding fell from 65% before 1962 to 40% in 1973-1977. In each age group that was studied there was a lower, but not statistically significant, incidence of NIDDM in persons who had been breastfed after birth for at least two months.

Pettitt et al, speculate that bottlefeeding can lead to overfeeding and excess weight gain in infants, which in turn predisposes these children to obesity in the teenage years and in adulthood, resulting in increased insulin resistance, which again predisposes to NIDDM. Hormonal responses to breastfeeding may also play a role. Because bottlefed infants have higher basal and postprandial concentrations of insulin, neurotensin (a hormone that modulates insulin and glucagon release) and motilin (a hormone that assists in the development of gastric and intestinal motility), these factors may contribute to the development of insulin resistance and NIDDM.

The authors state that, "given the possible protective effect of breastfeeding on NIDDM in the Pima Indian population, the disturbing worldwide trends towards less breastfeeding, and the increased rates of NIDDM - particularly in developing countries - further data about the risk of NIDDM and breastfeeding practices from other populations are clearly needed".

Editor's Note:

Although additional research is required to further unravel this association, there is no doubt that breastfeeding can protect infants against a multitude of ills and sequelae. Pettitt and co-workers have sounded a warning note that populations the world over, especially in developing countries, should not abandon breastfeeding for bottlefeeding at the cost of their children's health.

Health workers should make a concerted effort to promote and encourage breastfeeding, whenever, and wherever possible. It would also be valuable to have similar studies performed in this country, so research workers, here is an interesting topic that needs investigation, "Do infant feeding practices in Thailand correlate with NIDDM and IDDM ?".

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