| Summary: | Substantial evidence supports a role of diet in glucose metabolism, but only a few reports have investigated the impact of diet during pregnancy on risk of gestational diabetes (GDM). Although metabolic hormones have been detected in milk, no studies have investigated the impact of maternal metabolic status assessed during pregnancy on insulin and adiponectin concentrations in human milk. The purpose of this thesis was to investigate the association of maternal macronutrient intakes with metabolic status during pregnancy and its subsequent impact on human milk hormones.
Participating women (n=216) underwent a 3-hour oral glucose tolerance test at 30 (95% confidence interval [CI] 25, 33) weeks gestation, recalled their second trimester dietary intake, and donated early (the first week) and mature (3 months postpartum) milk.
Higher vegetable and fruit fiber intake was associated with reduced insulin resistance (beta±SE -0.100±0.029, p=0.0008) and increased insulin sensitivity (0.029±0.012, p=0.01) among those with a family history of type 2 diabetes. Lower % carbohydrate and higher % total fat were associated with increased GDM risk (odds ratio 0.60 [95% CI 0.40, 0.90] and 1.61 [1.06, 2.44], respectively). Prenatal metabolic abnormalities including higher pregravid body mass index (beta±SE 0.053±0.014, p=0.0003), in addition to gravid hyperglycemia (0.218±0.087, p=0.01), insulin resistance (0.255±0.047, p<0.0001), lower insulin sensitivity (-0.521±0.108, p<0.0001), and higher serum adiponectin (0.116±0.029, p<0.0001) were associated with higher insulin in mature milk. Obstetrical measures including nulliparity (0.171±0.058, p=0.004), longer duration of gestation (0.546±0.146, p=0.0002), and unscheduled caesarean section (0.387±0.162, p=0.02) were associated with higher adiponectin in early milk. Holder pasteurization, a process recommended by the Human Milk Bank Association of North America before distributing human donor milk, reduced milk adiponectin and insulin concentrations by 32.8% and 46.1%, respectively (both p<0.0001).
In conclusion, the distribution of macronutrient intakes during pregnancy was associated with risk for abnormal glucose metabolism later in pregnancy. In addition, maternal prenatal metabolic abnormalities were associated with high insulin concentrations in mature milk, while only obstetrical parameters were associated adiponectin concentrations in early milk. Our findings support the need for continued work to determine optimal prenatal nutritional strategies to prevent GDM and subsequently to improve infant nutrition.
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