Mounting evidence suggests that dietary nitrate can improve cardiovascular health through its conversion to nitric oxide (NO). NO plays a significant role in both cardiovascular and brain health.(Reference Stephan, Harrison and Keage1) There is also a strong association between mid-life vascular risk factors and late life brain health.(Reference Lane, Barnes and Nicholas2) Whether habitual dietary nitrate intake is associated with better cognitive function and a reduced risk of cognitive decline has yet to be investigated. The objective of the study was to investigate the association between habitual intake of dietary nitrate and 1) cognitive function and 2) cognitive decline, in the presence or absence of the APOE ε4 allele. The study included 1254 participants of the Australian Imaging and Biomarkers and Lifestyle study of ageing who were cognitively normal at baseline. Plant, vegetable, and total nitrate intakes were calculated from baseline food frequency questionnaires using comprehensive nitrate databases. Cognition was assessed at baseline and every 18 months over a follow-up period of 126 months using a comprehensive neuropsychological battery. Multivariable-adjusted linear mixed effect models were performed to examine the association between baseline nitrate intake and cognition over the period of 9 years stratified by APOE ε4 carrier status. In non APOE ε4 carriers, participants in the highest tertile of plant nitrate intake (median 116 mg/d) had a 0.13-unit higher language score (0.13 [0.01, 0.25]) compared with those in the lowest tertile (median 52 mg/d). In APOE ε4 carriers, participants in the highest tertile of plant nitrate intake (median 112 mg/d) had a higher episodic memory score (0.24 [0.01, 0.33]) compared with those in the lowest tertile (median 48 mg/d). Similar associations were seen for the intakes of vegetable-derived and total nitrate. We did not find any evidence of an association of dietary nitrate intake with rate of cognitive decline in this study. A higher habitual intake of dietary nitrate is associated with better language in non-APOE ε4 carriers and better episodic memory and recognition in APOE ε4 carriers.
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