Vitamin D comes from the sun and from some foods such as beans, lentils and fish fat.
The researchers found that low levels of vitamin D may be linked to dementia and Alzheimer's disease, one of the most common forms of dementia. Alzheimer's can be very tiring for those who care for people with the disease and frightening those who are suffering.
"I've had a very bad thing when I want to get in the car, I not only forgot to go anywhere, but I also do not know where," said the dementia sufferer, Chris Roberts.
World Health Organization estimates that more than 47 million people suffer from dementia, and about 60 percent of whom come from the low and middle income countries, which are least able to cope with this disease.
US scientists studying the elderly and measure the level of vitamin D and their cognitive abilities: namely, the ability to remember and think.
