Effect of Freezing and Thawing on Human Milk Macronutrients and Energy Composition: A Systematic Review and Meta-Analysis

To conduct a systematic review of the effect of freezing and thawing on the macronutrients and energy composition of human milk (HM). Systematic review conducted in May 2019, including all studies reporting macronutrients and energy composition of HM, according to a search of MEDLINE, EMBASE, and Google Scholar using the keywords: HM, breast milk, macronutrients, fat, lipid, protein, carbohydrates, energy, calories, freezing, thawing, and of the references in studies identified as potentially relevant. Meta-analyses were conducted in all the studies that reported one or more of the following: total energy, true protein, fat, and carbohydrates. They were reported according to following groups of freezing duration: 1-7 days, 8-30 days, 31 days-3 months, and >3 months. They were calculated and expressed as weighted averages with pooled standard deviations. Eight studies remained in the final analysis. Regression analyses did not find any significant increase or decrease over time of protein content, lactose content, fat content, or energy content of milk. No dramatic changes in macronutrients and energy contents of milk are expected to occur within the first few months of freezing.