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.