The National Health and Medical Research Council's updated Infant Feeding Guidelines recommend infants be exclusively breastfed until they are six months old, when solid foods should be introduced.

The guidelines recommend breastfeeding continues until the child is one year old, and longer if desired, but healthcare workers should respect and support mothers who chose not to breastfeed.

The guidelines say studies show breastfeeding can reduce the risk and severity of gastrointestinal infections, respiratory illness, asthma and some childhood cancers.

Professor Linda Tapsell, a member of the Dietary Guidelines Working Committee, said new research had backed up previous advice on the value and benefits of breastfeeding.

''What has changed is we're feeling very confident about what we've been saying over the years … the evidence supporting the value of breastfeeding has been strengthened,'' she said.

Australian Breastfeeding Association spokeswoman Meredith Laverty welcomed the updated guidelines.

''It takes away the confusion for parents surrounding the introduction of solids, and it's evidence-based guidelines,'' she said.

Ms Laverty said most Australian mothers intended to breastfeed their children, but a lack of support meant nearly a third had switched to using a bottle by the time their infants were one month old.

She said employers had a role to play in creating workplaces where mothers returning to work were able to breastfeed their children.