Jan 162011
 

Dear Readers,

I was recently on a conference call with women physicians discussing the latest in Women’s Health and was asked about vitamin D and its effect on cognition. Indeed vitamin D has received a lot of media attention lately; attention focused on its potential effect on cardiovascular and bone health, in addition to its anti-inflammatory and anti-oxidative effects. Thus, it was not a surprise to me when the discussion turned to “cognitive health” and whether or not (1) vitamin D levels were associated with cognitive function and (2) whether its supplementation would provide an “added cognitive benefit” to female patients.

At the time the question was posed, I immediately thought about an article I read in Neurology that examined whether weekly dietary intake of vitamin D was associated with cognitive function in older women. Participants in this study came from the EPIDOS, a French community dwelling cohort study that was designed to evaluate the risk factors for hip fracture among women aged 75 years and older. Over a course of two years (1992- 1994) over 7000 women – free of a previous history of hip fracture or hip replacement – were recruited from five French cities to participate in this study. At baseline evaluation all participants received a full medical examination, which consisted of structured questionnaires, information about everyday dietary habits, chronic diseases, disability, sun exposure and a clinical examination. Medications and vitamin supplements were reported by interviewer questions and also by direct inspection of medications brought to the visit. Women were excluded from the study if over the last 18 months they had taken vitamin D drug supplements. A total of 5,596 women met the inclusion criteria and analyses were based on this sample size.

Dietary habits were assessed at baseline examination using a 21 question food frequency questionnaire that included questions on intake of fish (two items), dairy intake (six items) and the consumption of eggs, fruits, vegetables, starchy foods, chocolate and drinking history. The dietary intake of vitamin D per week was calculated by multiplying the content of individual food items (across all areas) by the frequency of consumption and adding this together. The vitamin D content for all food items was based on a dietary content database – continually updated by the French food and safety agency. For the French adult population, the dietary intake of vitamin D was 400 IU /day (or 35 micrograms/week). The assessment of cognitive function used– the Pfeiffer Short Portable Mental State Questionnaire (SPMSQ). This is a 10 item measure that has been in use in large scale studies as a screening tool to assess moderate to severe cognitive deficits. A score of 8 or below indicates cognitive impairment.

Although the mean weekly dietary intake of vitamin D for the entire group was well above the suggestive value of > 35 micrograms/week (mean 62.3 micrograms/week), approximately 14% of the women had inadequate dietary intakes of vitamin D. Based on the cognitive testing results, a total of 11% of the women were deemed to have cognitive impairment. Further, women who had lower levels of weekly vitamin D intakes had lower mean SPMSQ scores. These women were also older and reported more disability on a disability scale. To further examine the association between weekly vitamin D intake and cognitive function, other factors such as body mass index, sun exposure, number of chronic diseases, history of hypertension, depression, disability or use of antidepressants or other medications, were controlled for in their analyses. The association between dietary vitamin D and cognitive function remained significant even after adjusting for all of these factors.

Although the mean weekly dietary intake of vitamin D for the entire group was well above the suggestive value of > 35 micrograms/week (mean 62.3 micrograms/week), approximately 14% of the women had inadequate dietary intakes of vitamin D. Based on the cognitive testing results, a total of 11% of the women were deemed to have cognitive impairment. Further, women who had lower levels of weekly vitamin D intakes had lower mean SPMSQ scores. These women were also older and reported more disability on a disability scale. To further examine the association between weekly vitamin D intake and cognitive function, other factors such as body mass index, sun exposure, number of chronic diseases, history of hypertension, depression, disability or use of antidepressants or other medications, were controlled for in their analyses. The association between dietary vitamin D and cognitive function remained significant even after adjusting for all of these factors.

This study nicely demonstrates that in women free of vitamin D drug supplementation, weekly dietary intake of vitamin D was significantly associated with the cognitive performance. Few studies have examined the association of dietary vitamin D to cognition in a large population sample. Such studies are needed to clarify whether the associations reported in this study exist in other populations (i.e. U.S. based and those that involve substantial numbers of minority participants) and will guide future research as to whether or not to persue large scale clinical trials that examine the benefits of vitamin D supplementation to treat or prevent cognitive impairment.

Here are 3 articles you can refer to, to learn about this particular study or the latest research on vitamin D and cognitive function:

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