NURSING mothers who take vigorous exercise may find their babies reject their milk afterwards. Research in the journal Pediatrics points out that infant taste buds can distinguish between sweet and sour - and post-exercise breast milk tastes distinctly sour.

The study, undertaken by researchers at the University of Indiana in the United States, found that strenuous jogging, swimming, aerobics or walking resulted in a 400 per cent increase in lactic acid in breast milk, which alters its taste. Levels remained high for at least 90 minutes afterwards.

Babies tried to avoid the post-exercise milk, made faces, and one spat it out. The researchers suggest that breastfeeding mothers express milk before rigorous exercise.