In order to establish how cold storage of human milk affects levels of bioavailable vitamin C, 11 samples were stored for 24 h in the refrigerator or up to 2 mo in the freezer. Total vitamin C levels decreased on average by one-third in the refrigerator or after I mo of freezing, with wide variations between individuals (6 to 76% and 3 to 100%, respectively). After 2 mo of freezing, the average decrease was two-thirds (7-100%).
Conclusion: We recommend a change in human milk storage practices, to under 24 h in a refrigerator or under 1 mo in a freezer. Alternatively, vitamin C supplementation may be considered.