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Storing breastmilk reduces its value

Freezing or refrigerating expressed breast milk for longer than 48 hours substantially lowers its antioxidant content, according to US researchers.

Part of the benefits of breast milk may be related to its antioxidant levels which are thought to prevent or slow damage caused by free radicals which are produced under stressful circumstances, such as infection.

Antioxidants help protect against infections and the researchers, led by Professor Thomas Hegyi, believe their findings are of particular importance for premature babies who already have an under-developed immune system.

The team from the Robert Wood Johnson Medical School team published their findings from the small study in Archives of Disease in Childhood (Fetal Edition). They assessed fresh breast milk samples from eight mothers who had delivered premature babies and from eight who had delivered their babies at term.

Five brands of formula milk were tested along with the breast milk. Antioxidant levels were assessed in all samples when they were fresh, after refrigeration and after freezing.

Fresh human milk, irrespective of whether it came from a mother who had given birth to a premature or a term baby, had the highest antioxidant capacity of any of the samples, and significantly more than formula milk.

However, after 48 hours of freezing or refrigerating antioxidant levels in the fresh human milk fell significantly. The longer it was stored and the colder the temperature at which it was stored, the more the antioxidant levels fell.

Professor Hegyi suggests, "To preserve antioxidant capacity, breast milk should only be stored for a short time at refrigerator temperature and not frozen."

However, Rosie Dodds of the National Childbirth Trust said, "It's useful to know that the antioxidant levels go down...babies may need extra antioxidants. But I'm not sure that you can say as a result of this study that mothers cannot freeze breast milk.

"There are many situations where you do need to store milk. For example, for very premature babies who need to be tube fed or women who are going back to work. It's still going to be far, far better for their babies than formula milk."

She added that breast milk contained many other beneficial ingredients other than antioxidants.

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