A key protein can cause damage to the brain leading to Alzheimer's
A vitamin found in meat, fish and potatoes may help protect the brain from Alzheimer's disease - and even boost memory in healthy people.
US researchers found vitamin B3 lowered levels of a protein linked to Alzheimer's damage in mice.
The Journal of Neuroscience study also showed the animals performed better at memory tests.
UK Alzheimer's charities said people should not start taking the vitamin before results from human studies.
The vitamin, also called nicotinamide by scientists, is sold in UK pharmacies and health food shops.
It has already been shown to help people suffering from diabetes complications and has some anti-inflammatory qualities.
The researchers, from the University of California at Irvine, added the vitamin to drinking water given to mice bred to develop a version of Alzheimer's disease, then tested the levels of certain chemicals associated with the condition.
They found that levels of one, called phosphorylated tau, were significantly lower in the animals.
This protein is involved in abnormal 'deposits' in brain cells, called 'tangles', which contribute to the brain damage which progressively affects people with Alzheimer's.
Using 'water mazes', the team also found some evidence that memory was enhanced in both 'Alzheimer's' mice and unaffected mice.
Dr Kim Green, who led the study, said that human tests were progressing: "Nicotinamide has a very robust effect on neurons. It prevents loss of cognition in mice with Alzheimer's disease, and the beauty of it is we already are moving forward with a clinical trial."
His colleague Professor Frank LaFerla, said: "This suggests that not only is it good for Alzheimer's disease, but if normal people take it, some aspects of their memory might improve."
Susanne Sorensen, the head of research at the Alzheimer's Society, said the research was "interesting" and pointed to new ways to treat the condition.
"From the research, it appears that Nicotinamide has more than one beneficial effect on nerve cells including the facilitation of the recycling of the 'bad' phosphorylated tau.
"Nicotinamide occurs naturally in meat, fish, beans, cereals and potatoes and is cheap and easy to take.
"However, more research is now needed to explore the possible mechanisms involved so we can better understand if Nicotinamide could have the same effect in people and, if it does, what level of vitamin intake would be required."
Rebecca Wood, Chief Executive of the Alzheimer's Research Trust, said until the human research was completed, people should not start taking the supplement.
"These are exciting findings, but until the results from the human clinical trial are announced, people should be wary about changing their diet or taking supplements. In high doses vitamin B3 can be toxic."