Fructose in Breast Milk Is Positively Associated with Infant Body Composition at 6 Months of Age

Dietary sugars have been shown to promote excess adiposity among children and adults; however, no study has examined fructose in human milk and its effects on body composition during infancy. Twenty-five mother-infant dyads attended clinical visits to the Oklahoma Health Sciences Center at 1 and 6 months of infant age. Infants were exclusively breastfed for 6 months and sugars in breast milk (i.e., fructose, glucose, lactose) were measured by Liquid chromatography-mass spectrometry (LC-MS/MS) and glucose oxidase. Infant body composition was assessed using dual-energy X-ray absorptiometry at 1 and 6 months. Multiple linear regression was used to examine associations between breast milk sugars and infant body composition at 6 months of age. Fructose, glucose, and lactose were present in breast milk and stable across visits (means = 6.7 μg/mL, 255.2 μg/mL, and 7.6 g/dL, respectively). Despite its very low concentration, fructose was the only sugar significantly associated with infant body composition. A 1-μg/mL higher breast milk fructose was associated with a 257 g higher body weight (<i>p</i> = 0.02), 170 g higher lean mass (<i>p</i> = 0.01), 131 g higher fat mass (<i>p</i> = 0.05), and 5 g higher bone mineral content (<i>p</i> = 0.03). In conclusion, fructose is detectable in human breast milk and is positively associated with all components of body composition at 6 months of age.