Maternal Diet Quality and BMI as Predictors of Human Milk C-Reactive Protein Concentrations.

Background: Little is known regarding joint associations of maternal diet quality and adiposity in relation to milk concentrations of inflammatory markers.

Objectives: We evaluated whether maternal diet quality and prepregnancy body mass index (BMI) predict C-reactive protein (CRP) concentration in human milk.

Methods: We used Cincinnati data from Global Exploration of Human Milk study, a prospective cohort of healthy mother-infant dyads (n = 100). We computed a dietary inflammatory index (DII) from diet recalls obtained 4-13 wk postpartum, where higher score indicating a more proinflammatory diet. CRP concentrations in week 4 milk samples were measured after validating a high-sensitivity enzyme-linked immunosorbent assay (ELISA) kit. Participants were categorized into low and high DII groups at the median and BMI groups defined as normal (<25) or elevated (≥25). The associations of categorical DII score and BMI with milk CRP concentrations were tested using linear regression. Then, we compared milk CRP concentrations across 4 combinations of DII × BMI.

Results: Median (Q1, Q3) values were as follows-DII: 0.13 (-1.54, 1.27); BMI: 25.4 (22.8, 30.4); and milk CRP: 101.7 (54.8, 172.3) ng/mL. Across the 4 DII × BMI groups, milk CRP was significantly different (P = 0.009) but there was no significant difference in maternal age, education, or ethnicity. Having BMI ≥ 25 was associated with higher milk CRP concentrations than having BMI <25 (β ± SE: 96.19 ± 27.23 ng/mL; P = 0.0006), although the main effect of DII was not statistically significant. The DII × BMI interaction was significant: BMI predicted milk CRP concentrations only when DII was low. Women with low DII and normal BMI had lower CRP concentrations [n = 30; 64.3 (38.2, 121.4) ng/mL] than those in the other 3 groups combined [n = 70; 124.1 (71.2, 181) ng/mL; P = 0.019].

Conclusions: Diet modifies the relation between maternal BMI and milk CRP. The study of milk cytokines and other bioactive compounds should include measures of diet quality, when feasible, in addition to maternal adiposity.