Background: Increasing evidence suggests that vitamin D may be protective in the development of cognitive impairment and dementia in older subjects.
Objective: The overall objective was to examine the cross-sectional relationship between intake of vitamin D and cognitive performance.
Design: The subjects (n=1916), aged 70-74 years, were recruited from the general population in Western Norway and underwent cognitive testing. The cognitive test battery included the Kendrick Object Learning Test, Trail Making Test part A, and modified versions of the Digit Symbol Test, Block design, Mini mental State Examination and Controlled Oral Word Association Test. Data on dietary habits were collected via a food frequency questionnaire. Poor cognitive performance was defined as the lowest 10th percentile for all of the tests, except the TMT-A were the 90th percentile was used as a cut-off.
Results: Sixty-four percent of the population did not meet the Nordic recommendations of vitamin D intake (≥10 µg/d). Of those that took cod liver oil as a supplement, 76.1% reached the recommended intake of vitamin D. Fish was the most important food source of vitamin D contributing with 38.3% of the total intake of vitamin D. Multivariate linear regression analyses showed that the S-task (verbal fluency) and KOLT (episodic memory) were significantly associated with intake of vitamin D. Logistic regression analyses showed that the risk of scoring poorly on the KOLT was significantly increased when the intake of vitamin D was low (≤3.57µg/d) . Intake of cod liver oil was not associated with KOLT score. For non-users of cod liver oil the risk of scoring poorly on the KOLT increased when the intake of lean fish was low (0.1 g/d – 25.0 g/d, P = 0.027).
Conclusions: In the present population consisting of elderly from the western part of Norway, cod liver oil supplementation was effective in achieving recommended intake levels of vitamin D. Even though the population had a high intake of vitamin D-containing foods compared to other studies, a high proportion of the individuals were not able to meet the Nordic recommendations (≥10 µg/d). A diet low in vitamin D was associated with a lower score on a verbal fluency test as well as an episodic memory test. In non-users of cod liver oil, episodic memory was negatively affected by a low intake of lean fish. Fish as a food item or dietary pattern may be more protective when it comes to cognitive decline than vitamin D as a single nutrient.