A daily vitamin pill could help reverse memory loss in old age and protect against Alzheimer's disease. The tablet, containing high doses of B vitamins and folic acid, slowed memory decline by 70 percent in some older people. It also halved the rate of brain shrinkage in some patients linked with forgetfulness that can cause full-blown Alzheimer's disease. The results were based on a trial of 270 people aged 70 years and above who suffered from memory lapses known as mild cognitive impairment ( MCI). More than 800,000 people in Britain alone suffer from dementia and the number is likely to double, the Telegraph reported. Celeste de Jager of Oxford University who led the vitamin trial said it had "definitively" shown that the vitamins were a good way of preventing mental decline. "A lot of the time brain changes start in your 40s and 50s before you get clinical symptoms," de Jager told the British Science Festival. "I would think that in middle age people should start thinking about their vitamin levels." Asked if she would take the vitamins as a precaution, de Jager said: "I would ask the doctor to check my B12 and my folic acid levels for starters."