By: 17 September 2013

A new report suggests that breastfeeding may reduce the risk of Alzheimer’s, and the link may be to do with certain biological effects of breastfeeding.

Although they used data gathered from a very small group of just 81 British women, the researchers observed a highly significant and consistent correlation between breastfeeding and Alzheimer’s risk. They argue that this was so strong that any potential sampling error was unlikely. They also found that the connection was much less pronounced in women who already had a history of dementia in their family.

The study may act as an incentive for women to breastfeed, rather than bottle-feed, something which is already known to have wider health benefits for both mother and child.

Dr Molly Fox, who led the study, said: “Alzheimer’s is the world’s most common cognitive disorder and it already affects 35.6 million people. In the future, we expect it to spread most in low and middle-income countries. So it is vital that we develop low-cost, large-scale strategies to protect people against this devastating disease.”

Fox et al interviewed 81 British women aged between 70 and 100. These included both women with and without Alzheimer’s. In addition, the team also spoke to relatives, spouses and carers, gathering a full history.

Three main trends were observed: women who breastfed exhibited a reduced Alzheimer’s risk compared with women who did not; longer breastfeeding history was significantly associated with a lower Alzheimer’s risk; and 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, published in the Journal of Alzheimer’s Disease, proposes that one theory for the observed effects is that breastfeeding deprives the body of progesterone, compensating for high levels of the hormone 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’.