Sex differences in the association between infant feeding and blood cholesterol in later life: the Newcastle thousand families cohort study at age 49-51 years.

Previous studies have suggested an association between being breastfed and later cholesterol levels. We investigated whether duration of total and exclusive breastfeeding were related to circulating total, HDL and LDL cholesterol and triglyceride measures at age 50, and whether such associations differ between men and women. Members of the Newcastle thousand families study were followed from birth in 1947. Men (n = 179) and 226 women (n = 226) with blood cholesterol and triglyceride measures at age 50 and with prospectively recorded duration of both total and exclusive breastfeeding were included. Neither total duration nor duration of exclusive breastfeeding were associated with the outcome measures when analysing both sexes together. However, in sex specific analyses significant associations between duration of exclusive breastfeeding and both total and LDL cholesterol (adjusted regression coefficient (r) per 30 days = 0.12 mmol/l (95% CI 0.04-0.20) P = 0.004 for total cholesterol and adjusted r per 30 days = 0.10 mmol/l (95% CI 0.02-0.18) P = 0.016 for LDL cholesterol) were seen for women with no significant associations observed in men. Significant interactions between duration of exclusive breastfeeding and sex were seen for total and LDL cholesterol (P = 0.02 and P = 0.03, respectively) with a near-significant interaction for HDL cholesterol (P = 0.06). In all cases, greater increases in cholesterol with increasing duration of exclusive breastfeeding were seen for women than for men. In conclusion, the association between breastfeeding and adult cholesterol levels differs between men and women and in women remains a significant association even after adjustment for potential confounders. However, our findings may not reflect the situation in younger generations.