Refrigerating or freezing breast milk for more than 48 hours reduces health benefits that are particularly important for premature babies, according to a study on Thursday.
New research by scientists in the United States shows refrigerated breast milk has a lower antioxidant content than fresh breast milk or infant formula.
“We found that fresh human milk has the highest antioxidant capacity, which decreases with storage over time,” said Professor Thomas Hegyi of the Robert Wood Johnson Medical School in New Brunswick, N.J.
Antioxidants are molecules that work to reduce damage done to cells and DNA by free radicals — charged particles found in the environment and produced by processes in the body.
Vitamins A, E, C and beta-carotene, a precursor to Vitamin A, and the trace mineral selenium are antioxidants. Fruits and vegetables are good sources of antioxidants.
Premature infants have a reduced antioxidant capacity but are thought to need antioxidants more than full-term babies because they often suffer from infections, have blood transfusions and intravenous nutrition.
Hegyi and his team tested the antioxidant capacity of five brands of formula milk, fresh breast milk and breast milk that had been stored for 48 hours and for seven days.
Fresh breast milk had the highest antioxidant capacity of all. Levels of antioxidants remained the same in formula milk whether it was refrigerated or frozen.
In breast milk the longer the milk was stored and the lower the temperature, the more the levels of antioxidants fell.
“To preserve the antioxidant activity of human milk, storage time should be limited to 48 hours. Refrigeration is better than freezing and thawing,” Hegyi added in a report in the journal Archives of Disease in Childhood.
