The role of vitamin D in preventing and treating Alzheimer's disease is reviewed. Epidemiologic studies on diet showed it had a powerful effect in causing Alzheimer's disease. Dr. Grant's research shows that high energy, high fat diets lead to an acidic balance that has an effect on certain transition metals that leads to the production of free radicals that may cause Alzheimer's disease. A low level of vitamin D is a risk factor for dementia. This can be linked to tooth loss and may be an important marker of risk for Alzheimer's disease.