Mothers who breastfeed their children may have a lower risk of developing Alzheimer's disease, a new study has claimed.
The study by University of Cambridge used data gathered from a small group of 81 British women. They observed a highly significant and consistent correlation between breastfeeding and Alzheimer's risk.
However, the connection was much less pronounced in women who already had a history of dementia in their family.
Dr Molly Fox, from the Department of Biological Anthropology at the University of Cambridge, who led the study and her colleagues - Professor Carlo Berzuini and Professor Leslie Knapp studied 81 women aged between 70 and 100.
The study revealed a number of clear links between breastfeeding and Alzheimer's.
These were not affected when the researchers took into account other potential variables such as age, education history, the age when the woman first gave birth, her age at menopause, or her smoking and drinking history.
They found that women who breastfed exhibited a reduced Alzheimer's disease risk compared with women who did not.
Longer breastfeeding history was significantly associated with a lower Alzheimer's risk, they said.
Women who had a higher ratio of total months pregnant during their life to total months breastfeeding had a higher Alzheimer's risk.
The trends were, however, far less pronounced for women who had a parent or sibling with dementia. In these cases, the impact of breastfeeding on Alzheimer's risk appeared to be significantly lower, compared with women whose families had no history of dementia.
The study argued that there may be a number of biological reasons for the connection between Alzheimer's and breastfeeding, all of which require further investigation.
One theory is that breastfeeding deprives the body of the hormone progesterone, compensating for high levels of progesterone which are produced during pregnancy.
Progesterone is known to desensitise the brain's oestrogen receptors, and oestrogen may play a role in protecting the brain against Alzheimer's.
Another possibility is that breastfeeding increases a woman's glucose tolerance by restoring her insulin sensitivity after pregnancy. Pregnancy itself induces a natural state of insulin resistance.
This is significant because Alzheimer's is characterised by a resistance to insulin in the brain (and therefore glucose intolerance) to the extent that it is even sometimes referred to as 'Type 3 diabetes'.
"Women who spent more time pregnant without a compensatory phase of breastfeeding therefore may have more impaired glucose tolerance, which is consistent with our observation that those women have an increased risk of Alzheimer's disease," Fox added.
