Watching for signs of dementia
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.
High vitamin D intake linked to less dementia
In addition, the researchers found differences linked to vitamin D intake:
- Women who developed Alzheimer’s disease got less vitamin D in their diets than women who developed other types of dementia and women who stayed dementia-free.
- Alzheimer’s disease risk was reduced by 77% in women with the highest dietary vitamin D intake (averaging about 4,000 IU per week), compared to women with the lowest intake.
- More frequent midday sunlight exposure was also associated with a reduced Alzheimer’s disease risk.
- Sunlight exposure and dietary vitamin D did not appear to protect against other forms of dementia.
Fish is the way to extra high 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 tinned 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:
- Don’t spare the yolk. One large egg yolk has about 40 IU of vitamin D.
- Choose fortified juice. A glass of vitamin D–fortified orange juice provides over 100 IU of the vitamin.
- Use yoghurt. Whether on fruit, whole grain cereal, or a baked sweet potato, unsweetened yoghurt made from vitamin D–fortified milk adds vitamin D, as well as beneficial intestinal bacteria, to your diet.
- Supp it up. The women in the study did not use supplements, but those with high vitamin D intake may have been using fortified foods. The forms of vitamin D used in supplements and fortified foods are the same.
(J Gerontol A Biol Sci Med Sci 2012;67:1205–11)