Protect nutrients in breast milk
Nutritional elements in breast milk are damaged if heated up to more than 45˚ C or warmed / kept warm for longer time. The longer the time period, the bigger the damage. Consequently, quick and correct heating in microwave, if you make sure not to overheat for example by correct use of milkymeter, is a safe way to preserve nutrients in the milk.
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Bottle heater, water bath or microwave?
You may have heard that it is always better to heat a baby bottle in a water bath or bottle heater. However, this is not correct.
Most often you want to heat quickly, and to do this you will need very hot water in the water bath or the bottle heater. Research show a larger amount of milk to be heated to higher temperature for a longer time period when heating in waterbath or bottle warmer, than with controlled microwave heating (that is when using milkymeter and stopping the microwave when the light flashes green).
High temperatures and being exposed to heat for a long time damages nutrients - regardless of heating method.
Using milkymeter to heat safely in the microwave oven
milkymeter measures temperature while the baby bottle is being heated in the microwave. It flashes a green light when milk reaches body temperature making it possible for you to stop the microwave in time thereby obtaining the right temperature.
Research document that microwaves do not harm breast milk (Lassen, Anne and Ovesen, Lars. "Nutritional effects of microwave cooking." Nutrition & Food Science 95.4 (1995): 8-10). The nutritional elements in breast milk are damaged if overheated, regardless of heating method.
Recommendation about infant feeding and bottle warming
We support WHO's recommendation that breast feeding only the first 6 months is best as breast milk contains everything an infant needs - including valuable fats for brain development and important nutrients that help digestion. However, breast feeding must be enjoyable for both mother and child to be best.
Regarding heating of breast milk or formula, the Danish health authorities state that heating in microwave does not damage nutritional elements in breast milk or formula or any change of content that can be harmful for the baby.
The bottle must be suitable for microwave and should after microwave warming be swirled around a few times for heat to be distributed evenly. Finally, temperature must be controlled.
Guidance in Danish available here: https://www.sst.dk/da/sundhed-og-livsstil/ernaering/
Nutrition and heating of breastmilk. Scientific studies
Sharron Bransburg-Zabary, 1 ,* Alexander Virozub, 2 and Francis B. Mimouni 3, Umberto Simeoni, Academic Editor: "Human Milk Warming Temperatures Using a Simulation of Currently Available Storage and Warming Methods." PLoS One. 2015; 10(6): e0128806.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4465021/
Wardell J, Wright A, Bardsley W, D’Souza S. “Bile Salt-Stimulated Lipase and Esterase Activity in Human Milk after Collection, Storage, and Heating: Nutritional Implications” Pediatr Res 18: 382–386.PMID: 6718097. 1984
Lassen, Anne and Ovesen, Lars. "Nutritional effects of microwave cooking." Nutrition & Food Science 95.4 (1995)
https://www.emeraldinsight.com/doi/full/10.1108/00346659510088654
Pediatrics : September 1992, VOLUME 90 / ISSUE 3: Madeleine Sigman-Grant, Gloria Bush, Ramaswamy Anantheswaran: "Microwave Heating of Infant Formula: A Dilemma Resolved"