Two glasses of milk a day could keep Alzheimer's disease at bay, new British research reveals.
Milk is one of the best sources of a key vitamin thought to reduce the neurological damage to the brain that can lead to forms of dementia, scientists at the University of Oxford say.
Elderly patients with low levels of the vitamin, known as B12, suffer twice as much shrinkage of the brain as those with higher levels of the substance in their bodies.
It is possible then that increasing the intake of vitamin B12 among the elderly could help slow down cognitive decline. They are conducting a clinical trial that aims to show that it may be possible to treat memory problems in the elderly with vitamin supplements.
They also believe it may be possible to protect people against devastating degenerative conditions such as Alzheimer's disease, which affects 150,000 new patients every year in the UK, by improving their dietary intake of the vitamin.
Professor David Smith, from the Oxford Project to Investigate Memory and Ageing, said drinking just two glasses of milk a day would be enough to increase levels of vitamin B12 to an adequate level.
He said: ''There are 550 people who come down with dementia, mainly Alzheimer's, every day in the UK - it is a major epidemic.
''These patients have had nerve cells that have died, so it is unlikely we are ever going to be able to find ways of repairing that damage or treating them with drugs.
''Instead we have to look at preventing it in the first place. Our study shows that consuming around half a litre of milk or more per day, and it can be skimmed milk, could take someone who has marginal levels of B12 into the safe range. But even drinking just two glasses a day can protect against having low levels.''
Vitamin B12 is one of the eight B vitamins and is found mainly in meat, fish and dairy products.
The research, published in the American Journal of Clinical Nutrition, revealed that while meat contained some of the highest levels of the vitamin, it was poorly absorbed by the body when eaten.
Instead Professor Smith, together with colleagues at Oslo University and Bergen University, in Norway, found the highest levels of vitamin B12 absorbed by the body came from milk, despite having lower B12 concentrations than meat.
Around 55 per cent of the vitamin in milk entered the blood stream. Fish provided the second highest source of the vitamin, followed by other dairy products.
Professor Smith said: ''In meat, B12 can be tightly bound to protein and this bond has to be broken down by acid in the stomach before the body can use it.
''Older people have lower levels of acid and so it is much harder for them to get B12 from certain foods. In milk, the binding is readily reversible.''
Brain scans of patients who have a vitamin B12 deficiency have revealed that they suffer more brain loss, or atrophy, than those with higher intake of the vitamin.
Professor Smith and his team found in a separate study that even elderly patients eating enough vitamin B12 to be considered to have normal concentrations of vitamin B12 were at risk of increased brain atrophy.
He found that those in the lower third of the normal range suffered twice as much brain loss, about one per cent a year, than those who had higher concentrations of the vitamin in their bodies.
It is thought that vitamin B12 is essential for maintaining the sheath that forms around and insulates nerve cells. Without adequate levels of the vitamin, this sheath cannot be kept in a good functional state, leading the cells to malfunction and die.
Previous studies by the group have indicated that chocolate and wine may have a similar effect.
Professor Smith said: ''There is a beautiful dose effect with foods that contain high levels of vitamin B12, but the causal relationship with cognitive function is far from clear and we need more work on this.
''We are currently preparing to unmask a two-year trial of 180 people over the age of 70 with memory problems, who were either given Vitamin B12 or a placebo.
''We have been taking volumetric MRI scans to look at whether the vitamin treatment has slowed down the atrophy in the brain.
''We need to do more clinical studies on vitamin B12 before we can start offering advice to help protect against dementia and cognitive decline, but until then prudence would suggest adopting a healthy lifestyle and a diet that is high in vitamin B12.''
Alzheimer's disease has recently been thrown into the spotlight after author Terry Pratchett, 60, announced in 2007 that he has been diagnosed with a rare form of the disease called posterior cortical atrophy, Richard Gray reported for Telegraph.
He has since donated more than $1 million (Ł690,000) to the Alzheimer's Research Trust and become a high profile campaigner for Alzheimer's research. Around 700,000 people in the UK live with dementia.
Rebecca Wood, chief executive of the Alzheimer's Research Trust, welcomed the latest research but said it was vital more research into Alzheimer's disease received funding.
She said: ''With vitamin B12 deficiency a common problem among elderly people in the UK, and further links between this deficiency and dementia, these findings will be of particular interest close to home and could encourage us to move dairy products higher up on the shopping list.''