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

BACKGROUND

Early exposure to cow's milk has been implicated in the occurrence of insulin-dependent diabetes mellitus but there is little information about infant-feeding practices and subsequent non-insulin-dependent diabetes mellitus (NIDDM). We examined the association between breastfeeding and NIDDM in a population with a high prevalence of this disorder, the Pima Indians.

METHODS

Glucose-tolerance status was obtained from a 75 g oral glucose-tolerance test. A standard questionnaire given to mothers was used to classify infant-feeding practices for the first 2 months of life into three groups; exclusively breastfed, some breastfeeding, or exclusively bottlefed. The association between the three infant-feeding groups and NIDDM was analysed by multiple logistic regression.

FINDINGS

Data were available for 720 Pima Indians aged between 10 and 39 years. 325 people who were exclusively bottlefed had significantly higher age-adjusted and sex-adjusted mean relative weights (146%) than 144 people who were exclusively breastfed (140%) or 251 people who had some breastfeeding (139%) (p = 0.019). People who were exclusively breastfed had significantly lower rates of NIDDM than those who were exclusively bottlefed in all age-groups (age 10-19, 0 of 56 vs 6 [3.6%] of 165; age 20-29, 5 [8.6%] of 58 vs 17 [14.7%] of 116]; age 30-39, 6 [20.0%] of 30 vs 13 [29.6%] of 44). The odds ratio for NIDDM in exclusively breastfed people, compared with those exclusively bottlefed, was 0.41 (95% CI 0.18-0.93) adjusted for age, sex, birthdate, parental diabetes, and birthweight.

INTERPRETATION

Exclusive breastfeeding for the first 2 months of life is associated with a significantly lower rate of NIDDM in Pima indians. The increase in prevalence of diabetes in some populations may be due to the concomitant decrease in breastfeeding.