Fish intake, n-3 fatty acid body status, and risk of cognitive decline: a systematic review and a dose–response meta-analysis of observational and experimental studies

Abstract

Context Randomized controlled trials (RCTs) testing supplementation with eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids have failed to provide evidence supporting a suggested inverse association between fish intake and dementia risk. Objective Dose–response analyses were conducted to evaluate associations between fish intake, all-cause dementia or Alzheimer’s Disease (AD), and the effect of EPA/DHA supplementation on cognitive performance. Data Sources PubMed, Scopus and Web of Science databases were searched for original research evaluating either associations between fish intake and dementia or AD, or the impact of EPA and/or DHA supplementation on the risk of cognitive decline. Data Extraction Data were collected on study characteristics and methods; number of cases/deaths (for observational studies); categories of exposure; model covariates; risk estimates from the most-adjusted model; type and dosage of supplementation (from RCTs); fatty acid levels in blood; and differences in cognition test results before and after supplementation. Risk of bias was assessed through the ROBINS-E and RoB2.0 tools for observational and experimental studies, respectively. Data Analysis Weighted mixed-effects models were applied, allowing for the inclusion of studies with 2 levels of exposure. Based on findings with low/moderate risk of bias, fish intake of up to 2 portions (250 g) per week was associated with a 10% reduction (95% confidence interval [CI]: 0.79, 1.02, Ν = 5) in all-cause dementia and a 30% reduction (95% CI: 0.54, 0.89, Ν = 3) in AD risk. Changes in EPA and DHA body status had a positive impact on participants’ executive functions, but not on their overall cognitive performance. Conclusion The protection offered by fish intake against cognitive decline levels off at intakes higher than 2 portions/week and likely relates to the impact of EPA and DHA on the individual’s executive functions, although there remain questions about the mechanisms linking the short- and long-term effects. Systematic Review Registration PROSPERO registration no. CRD42019139528.

Estimation and predictors of the Omega-3 Index in the UK Biobank

“…A large number of epidemiological, clinical and experimental studies have been conducted over the past few decades investigating the role of long chain omega-3 polyunsaturated fatty acids (n3 PUFAs) for health. In particular, eicosapentaenoic acid (20:5, EPA) and docosahexaenoic acid (22:6, DHA) are viewed to have beneficial effects for cardiovascular disease (CVD) (1)(2)(3) , cancer (3,4) , diabetes (5,6) , metabolic syndrome (7) , dementia or Alzheimer's disease (8) , and depression (9) . However, results from randomized trials exploring the potential protective nature of n3 PUFAs on disease outcomes across this spectrum vary from beneficial to null (10) .…”

Associations of dairy, meat, and fish intakes with risk of incident dementia and with cognitive performance: the Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD)

“…Compared to dairy and meat, association between fish intake and dementia outcomes or cognitive performance is more coherent. According to systematic reviews and metaanalyses, higher fish consumption associates with lower risk of dementia or AD [10][11][12][48][49][50]. The association between fish intake and cognitive performance is not as clear, as only one [13] of the two published systematic reviews [12,13] has found a beneficial association.…”

The Potential Role of Gut Microbiota in Alzheimer’s Disease: From Diagnosis to Treatment

“…Diet is a rapid and direct way of modifying the gut microbiota composition and function, reducing inflammation, and helping in eubiosis maintenance [ 123 , 164 , 165 ]. Given the evidence of association between neuropsychiatric conditions and gut microbiota dysregulation, it is worth speculating that dietary interventions could represent effective candidates for preventing and delaying the pathogenesis and progression of AD [ 166 , 167 , 168 , 169 , 170 , 171 , 172 , 173 , 174 , 175 , 176 , 177 , 178 , 179 , 180 , 181 , 182 , 183 , 184 , 185 , 186 ] ( Table 2 ). Here, we present some of the most promising dietary therapies proposed in the literature, with a particular focus on Mediterranean and ketogenic diets.…”

“…Differently, fish intake is inversely associated with AD—likely related to omega-3 (EPA/DHA) contents [ 195 ]. Interestingly, the regular consumption of fish up to two portions per week seems to be more protective than EPA/DHA supplementation [ 184 ]. Even though many studies are supporting the protective effect of unsaturated fatty acids EPA/DHA, their role in the brain is still under debate [ 200 , 201 , 202 , 203 , 204 ].…”