The study took place in France and included 498 women over 75 years old who were already participating in a larger osteoporosis trial. Women were only included if they had no signs of dementia and had not been using vitamin D supplements in the previous 18 months. They answered diet and lifestyle questionnaires at the beginning of the study and underwent thinking (cognitive) tests at the beginning and end of the study.
More than 27% of the women developed dementia during the study, about half diagnosed with Alzheimer’s disease and the other half with other forms of dementia. As expected, women who were older and had more disability and poorer cognitive function at the beginning of the study were more likely to develop dementia.
In addition, the researchers found differences linked to vitamin D intake:
The researchers offered some real-life ways for women to achieve the vitamin D intake seen to be beneficial in the study. “Women who did not develop dementia in our study consumed about 10 mcg [400 IU] per week of vitamin D more than those who developed Alzheimer’s disease. In a practical sense, this corresponds to approximately 115 grams (4 oz) of cooked salmon or cooked mackerel per week, or 170 grams (6 oz) of tuna canned in oil. Also, the highest quintile of vitamin D dietary intakes, which was associated with a lower risk of developing Alzheimer’s disease within 7 years, corresponds to the consumption of about 50 ml (10 teaspoons) of cod liver oil per week.” As the study took place in France, the amount of vitamin D regularly consumed by women in other areas might be higher or lower.
By regularly eating fish and taking fish oil, we can easily get an amount of vitamin D, and perhaps other nutrients like omega-3 polyunsaturated fatty acids, that might help protect against Alzheimer’s disease. Here are some other ways to increase your vitamin D intake:
(J Gerontol A Biol Sci Med Sci 2012;67:1205–11)