Why You Can't Microwave Breastmilk

When I was pregnant with my daughter I made the choice to breastfeed. I didn't really know that much about breastfeeding, but it just seemed to me like the right thing to do. With this decision came several questions about breastfeeding and breastmilk.

Any answer that is often given for why breastmilke can not be microwaved also can apply to formula. The general answer given is that, according to babylab, "Often the reason given is that the milk will have hot spots that scald the baby, but being a liquid, a quick shake would eliminate that danger, and a mother would shake the thawed milk anyways because the fat separates from the thin milk. Hot spots do not appear to be the true reason for avoiding the microwave."

During my research I saw over and over again that breastmilk can not be heated in the microwave. I just didn't know why microwaving for formula worked and breastmilk did not. The number one reason not to microwave breastmilk is that, according to kidsgrowth.com, "Microwaving breastmilk can change the milk's composition."

Studies have shown that "there is a substantial loss of the anti-infective properties of breast milk when it is microwaved to a temperature between 72 [degree] -98 [degree] C, a temperature easily reached in most microwave ovens. Even at lower temperatures (20 [degree] -53 [degree] C) the anti-infective action is a significantly lessened."

It has been found that, "Microwaving breastmilk, or heating it on the stove, can cause a loss of Vitamin C content, along with loss of some of the milk's special anti-infective properties. The higher the temperature, the more pronounced the effect."₁

It is important to note that the above statement included heating milk on the stove as another no-no. We often think that microwaving is the only thing you can't do with breastmilk. However, heating breastmilk on the stove has the potential to spike the tempature to a point where vitamin and mineral loss is likely to happen.

I have also found that microwave warming, can result in uneven heating with "hot spots" can be hazardous. The center of the fluid may be much hotter and the milk may scald you or your infant. Microwaving breast milk you run the risk of overheating it and burning your baby's mouth.

¹(Quan R, Yang C, Rubenstein S, et al: Effects of microwave radiation on anti-infective factors in human milk,Pediatrics 89:667, 1992; Sigman M, et al: Effects of microwaving human milk: changes in IgA content and bacterial count, J Am Diet Assoc 89:690-92,1989)