Swedish researchers have found in a study on rheumatoid arthritis that breastfeeding protects women from the disease.
A team at Malmo University Hospital found that women who breastfeed for more than a year reduce their chance of rheumatoid arthritis by half.
The researchers compared 136 women with rheumatoid arthritis to 544 without it and found women who had breastfed for 13 months or more were half as likely to develop rheumatoid arthritis as those who had never breastfed and those who breastfed for between one and 12 months had a 25% decreased risk.
It was also found that having children and not breastfeeding did not seem to protect the women against developing rheumatoid arthritis.
Rheumatoid arthritis is an autoimmune disease that causes chronic inflammation of the joints and can also cause inflammation of the tissue around the joints, as well as in other organs in the body.
The chronic inflammation can lead to the destruction of the cartilage, bone and ligaments, causing deformity of the joints - it is three times more common in women than in men.
It affects people of all races equally and can begin at any age, but it most often starts after age 40 and before 60.
Millions around the world are affected by what can be a debilitating disease which affects mobility and lifestyle.
It is already known that breastfeeding is linked to raised levels of the hormone oxytocin, which can reduce stress hormone levels, lower blood pressure and induce well-being.
However, breastfeeding also raises levels of another hormone - prolactin - which is known to stimulate the immune system, and may actually raise the risk of rheumatoid arthritis.