The association between dairy product consumption and cognitive function in the National Health and Nutrition Examination Survey

The present cross-sectional study sought to determine the potential relationships between the intake of dairy foods (total dairy products, milk and cheese) and cognitive function through information garnered in the National Health and Nutrition Examination Surveys (1988-94 and 1999-2002). Cognitive measures of vasomotor speed, coding speed and immediate memory recall were assessed from a simple reaction time task (SRTT), symbol-digit substitution test (SDST) and serial digit learning task, respectively, in adults 20-59 years of age. A summation of the percentile rank scores on each of the three tests provided a measure of overall cognitive function. In adults 60 years of age and above, a story recall test and a digit-symbol substitution test (DSST) were utilised to determine cognitive function in an elderly population. The results indicated that cognitive scores for the SRTT were not different between consumers and non-consumers of dairy foods. However, there were associations observed between 20- and 59-year-old consumers of total dairy foods and a higher SDST percentile score (53.2 (SE 1.3) to 49.4 (SE 2.0)) and a calculated global cognitive percentile score (53.3 (SE 1.1) to 50.2 (SE 1.4)) compared with non-consumers. A similar significant association was observed with cheese consumers. In adults over 60 years of age, an association between total dairy product consumption and higher DSST percentile scores (51.5 (SE 1.9) to 46.2 (SE 3.0)) was also observed. These findings highlight the need for additional research on how dairy products may affect cognition and by what mechanisms, through its nutrients or other components.