Dietary intake and cognitive function: evidence from the Bogalusa Heart Study

A Comprehensive Review of the Effects of Glycemic Carbohydrates on the Neurocognitive Functions Based on Gut Microenvironment Regulation and Glycemic Fluctuation Control

Improper glycemic carbohydrates (GCs) consumption can be a potential risk factor for metabolic diseases such as obesity and diabetes, which may lead to cognitive impairment. Although several potential mechanisms have been studied, the biological relationship between carbohydrate consumption and neurocognitive impairment is still uncertain. In this review, the main effects and mechanisms of GCs' digestive characteristics on cognitive functions are comprehensively elucidated. Additionally, healthier carbohydrate selection, a reliable research model, and future directions are discussed. Individuals in their early and late lives and patients with metabolic diseases are highly susceptible to dietary-induced cognitive impairment. It is well known that gut function is closely related to dietary patterns. Unhealthy carbohydrate diet-induced gut microenvironment disorders negatively impact cognitive functions through the gut-brain axis. Moreover, severe glycemic fluctuations, due to rapidly digestible carbohydrate consumption or metabolic diseases, can impair neurocognitive functions by disrupting glucose metabolism, dysregulating calcium homeostasis, oxidative stress, inflammatory responses, and accumulating advanced glycation end products. Unstable glycemic status can lead to more severe neurological impairment than persistent hyperglycemia. Slow-digested or resistant carbohydrates might contribute to better neurocognitive functions due to stable glycemic response and healthier gut functions than fully gelatinized starch and nutritive sugars.

Association of Whole Grain Consumption and Cognitive Decline: An Investigation From a Community-Based Biracial Cohort of Older Adults

BACKGROUND AND OBJECTIVES

To examine the association of whole grain consumption and longitudinal change in global cognition, perceptual speed, and episodic memory by different race/ethnicity.

METHODS

We included 3,326 participants from the Chicago Health and Aging Project who responded to a Food Frequency Questionnaire (FFQ), with 2 or more cognitive assessments. Global cognition was assessed using a composite score of episodic memory, perceptual speed, and the Mini Mental State Examination (MMSE). Diet was assessed by a 144-item FFQ. Linear mixed-effects models were used to estimate the association of intakes of whole grains and cognitive decline.

RESULTS

This study involved 3,326 participants (60.1% African American [AA], 63.7% female) with a mean age of 75 years at baseline and a mean follow-up of 6.1 years. Higher consumption of whole grains was associated with a slower rate of global cognitive decline. Among AA participants, those in the highest quintile of whole grain consumption had a slower rate of decline in global cognition (β = 0.024, 95% CI [0.008-0.039], p = 0.004), perceptual speed (β = 0.023, 95% CI [0.007-0.040], p = 0.005), and episodic memory (β = 0.028, 95% CI [0.005-0.050], p = 0.01) compared with those on the lowest quintile. Regarding the amount consumed, in AA participants, those who consumed >3 servings/d vs those who consumed <1 serving/d had a slower rate of decline in global cognition (β = 0.021, 95% CI [0.005-0.036], p = 0.0093). In White participants, with >3 servings/d, we found a suggestive association of whole grains with global cognitive decline when compared with those who consumed <1 serving/d (β = 0.025, 95% CI [-0.003 to 0.053], p = 0.08).

DISCUSSION

Among AA participants, individuals with higher consumption of whole grains and more frequent consumption of whole grain had slower decline in global cognition, perceptual speed, and episodic memory. We did not see a similar trend in White adults.

The Relationship between Whole-Grain Intake and Measures of Cognitive Decline, Mood, and Anxiety-A Systematic Review

Greater intake of whole grains, compared to refined grains, is consistently associated with a reduced risk of cardiovascular disease and type 2 diabetes, both of which are associated with cognitive decline. To better understand the relationship between whole-grain intake, cognition, mood, and anxiety, a systematic review was conducted to synthesize available evidence linking whole grains to these outcomes. Four electronic databases were searched from inception to August 2021 for potentially relevant observational and interventional studies. Risk of bias (RoB) assessments were performed using the newly developed Nutrition Quality Evaluation Strengthening Tools, and the Grades of Recommendation, Assessment, Development, and Evaluation approach was used to determine the strength of evidence for each outcome. In total, 23 studies [4 randomized controlled trials (RCTs) and 19 observational studies] met the predefined eligibility criteria. Of these,12 studies included analysis of whole-grain intake and cognitive decline, 9 included mood outcomes, and 2 included both cognition and mood outcomes. The overall evidence for an association between whole-grain intake and cognition is inconclusive. With respect to mood outcomes, evidence from RCTs prospective cohort and case-control studies suggest that higher intake is linked to improved outcomes for mood and depression although the evidence is mixed for cross-sectional studies. Reporting of whole-grain intake fell short of suggested standards, and the strength of available evidence was low or very low for all outcomes. A high RoB toward studies reporting results was also noted, complicating both the interpretation of some studies and the combined evidence. Of note, few well-designed RCTs assessing the effect of whole-grain intake on measures of cognition, mood, and anxiety were identified, highlighting the need for more studies in this area. The available, although limited, evidence suggests that greater whole-grain intake is associated with better mood and anxiety-related scores and is inconclusive regarding cognitive outcomes. PROSPERO registration: CRD42021266355.

Associations of vitamin B6 turnover rate with the risk of cardiovascular and all-cause mortality in hypertensive adults

BACKGROUND AND AIM

This study was to assess the association between vitamin B6 turnover rate and mortality in hypertensive adults.

METHODS AND RESULTS

Vitamin B6 status including serum pyridoxal-5'-phosphate (PLP) levels, serum 4-pyridoxal acid (4-PA) levels, and vitamin B6 turnover rate (4-PA/PLP) were obtained from the 2005-2010 National Health and Nutrition Examination Survey (NHANES) dataset of hypertensive adults with follow-up through December 30, 2019. Using Cox proportional risk regression models, Hazard ratios (HRs) and 95% confidence intervals (CIs) were analyzed for PLP, 4-PA and 4-PA/PLP quartiles in relation to cardiovascular and all-cause mortality. A total of 5434 participants were included in this study (mean age, 58.48 years; 50.4% men), and the median 4-PA/PLP was 0.75. The median follow-up time was 11.0 years, with 375 and 1387 cardiovascular and all-cause deaths, respectively. In multivariate COX regression models, PLP was negatively associated with cardiovascular mortality (HR [95% CI] quartile 4 vs. 1: 0.66 [0.47-0.94], P_trend = 0.03) and 4-PA/PLP was positively associated with cardiovascular mortality (HR [95% CI] quartile 4 vs.1: 1.80 [1.21-2.67], P_trend = 0.01). Similarly, the higher the quartile of PLP, the lower the risk of all-cause mortality (HR [95% CI] quartile 4 vs. 1: 0.67 [0.56-0.80], P_trend < 0.01). The higher the quartile of 4-PA and 4-PA/PLP, the higher the risk of all-cause mortality (HR [95% CI] quartile 4 vs. 1: 1.22 [1.01-1.48], P_trend < 0.01; and 2.09 [1.71-2.55], P_trend < 0.01).

CONCLUSION

The findings suggested that higher vitamin B6 turnover rate was associated with an increased risk of cardiovascular and all-cause mortality in hypertensive adults.

MIND diet and cognitive function and its decline: A prospective study and meta-analysis of prospective cohort studies

BACKGROUND

Evidence on the association of the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet with cognitive aging is limited and inconsistent.

OBJECTIVE

We examined how the MIND diet is related to cognitive function and its decline among middle-aged and older adults.

METHODS

We included 4066 participants with baseline dietary assessment and at least one cognitive test from the China Health and Nutrition Survey (CHNS) in 1997, 2000, 2004, and 2006, with a median follow-up of 3 years. The modified MIND diet score (range: 0-12) was calculated based on nine healthy and three unhealthy food groups. Linear mixed-effect models were used to examine the association of adherence to the MIND diet with z-scores of cognitive function and cognitive decline. We also conducted a meta-analysis including our findings and seven other cohort studies.

RESULTS

At baseline, median MIND diet scores for the increasing tertile were 3.0, 4.0, and 5.5, respectively. Participants with higher MIND diet scores had significant better global cognitive function. The adjusted difference in global cognitive function z-score for every three-point increment of MIND diet scores was 0.11 (95% CI, 0.06, 0.16, p-trend<0.001), which was approximately equivalent to being one year younger in age. Consumption of nuts, fish, red meats, and tea showed independent positive associations with cognitive function, and fried food consumption exhibited negative associations. In the meta-analysis of 26,103 participants, one standardized deviation increment of the MIND score was associated with 0.042 (95 % CI 0.020, 0.065) units higher in global cognitive function z-score and 0.014 (95 % CI -0.010, 0.037) units slower in annual cognitive decline.

CONCLUSIONS

Our findings suggest that higher adherence to the MIND diet was associated with better cognitive function and potentially slower cognitive decline in later life. Further large-scale observational and interventional studies are warranted to elucidate the cognitive effects of the MIND diet.

PROSPERO REGISTRY NUMBER

This meta-analysis was registered at PROSPERO as CRD42022330417.

Multi-Domain Interventions for Dementia Prevention - A Systematic Review

OBJECTIVES

There is a growing incidence of cognitive decline and dementia associated with the ageing population. Lifestyle factors such as diet, physical activity, and cognitive activities may individually or collectively be undertaken to increase one's odds of preventing cognitive decline and future dementia. This study will examine whether clinical trials using multidomain lifestyle intervention can significantly decrease the risk of cognitive decline and therefore dementia.

DESIGN, SETTING AND PARTICIPANTS

This systematic literature review of multidomain lifestyle interventions for the prevention of cognitive decline and dementia followed the PRISMA guidelines. Clinical trials involving multidomain intervention (i.e., diet and physical activity, or without cognitive training) in older adults (≥ 49 years old) at higher risk of dementia were identified through 5 electronic databases (EMBASE, MEDLINE, CINAHL, Cochrane, and Scopus). A comprehensive search was performed to identify and retrieve publications until 15 November 2022. Trials were published in English.

RESULTS

The included studies (n=15) assessed change in cognition in response to a multidomain lifestyle intervention. However, the cognitive outcome measures used in these studies were heterogeneous. Despite this heterogeneity, two thirds of the studies showed improvement in cognition following a multidomain intervention (n=10 with a total of 9,439 participants). However, five studies reported no improvement in cognition following the multidomain intervention. The most common form of dietary intervention included higher amount of fruit and vegetable intake; whole-grain cereal products instead of refined; low fat options in milk and meat products; and limiting sucrose intake to less than 50 g/day. Most clinical trial studies were powered to examining the effects of multidomain interventions in cognition but were not designed to test the contribution of individual domains (i.e., dietary changes, increased physical activity, or increased cognitive stimulation alone).

CONCLUSION

This systematic review aimed to determine the effect of multimodal lifestyle interventions on cognitive outcomes in older adults at risk of dementia. We found that participants with conditions that may increase the risk of dementia, (e.g., hypertension, cardiovascular fragility) do benefit from multi-modal lifestyle changes including diet, physical activity, and cognitive training. Two thirds of studies using multidomain lifestyle interventions showed improvements in cognitive function. Trials with a focus on cognitive training, dietary improvement, and physical activity may prevent or delay cognitive decline in older adults including those at risk of developing dementia. Future studies should consider longer follow-up periods and adequate power to be able to examine the effects of each lifestyle component in the context of multimodal interventions.

Association between egg consumption and cognitive function among Chinese adults: long-term effect and interaction effect of iron intake

The association between egg consumption and cognitive function is inclusive. We aimed to assess the association between egg consumption and cognitive function in Chinese adults and tested the interaction between egg consumption and Fe intake. The data used were from a nationwide sample (n 4852, age ≥ 55 years) from the China Health and Nutrition Survey between 1991 and 2006. Assessment of cognitive function was conducted in 1997, 2000, 2004 and 2006. Dietary egg intake was obtained by 24-h dietary recalls of 3 consecutive days during home visits between 1991 and 2006. Multivariable mixed linear regression and logistic regression were used. Egg intake was positively associated with global cognitive function. In fully adjusted models, across the quartiles of egg intake the regression coefficients were 0, 0·11 (95 % CI -0·28, 0·51), 0·79 (95 % CI 0·36, 1·22) and 0·92 (95 % CI 0·43, 1·41), respectively. There was a significant interaction between egg intake and Fe intake. The association between high egg intake and cognitive function was stronger among those with low Fe intake than those with high Fe intake. In addition, there was a significant interaction between egg consumption and sex, with the association mainly observed in women but not men. Furthermore, compared with non-consumers, those with higher egg consumption (Q4) had the OR of 0·93 (95 % CI 0·74, 1·19), 0·84 (95 % CI 0·69, 1·02) for self-reported poor memory and self-reported memory decline, respectively. Higher egg intake is associated with better cognition in Chinese adults among those with low Fe intake.

Tea Consumption Is Associated with Reduced Cognitive Decline and Interacts with Iron Intake: A Population-Based Longitudinal Study on 4,820 Old Adults

Background: Previous studies suggest a positive effect of tea intake on cognition. Additional micronutrients that may moderate this association was not previously examined. Objective: To examine the association between tea consumption and cognition and explore the interaction between tea consumption and iron intake. Methods: Data from the China Health and Nutrition Survey between 1997 and 2011 was used. 4,820 individuals (≥55 years) were included in the analyses. Measurement of cognitive function was conducted in 1997, 2000, 2004, and 2006. Tea consumption was self-reported. Food intake was assessed by 24-hour dietary recalls of three consecutive days during home visits between 1997 and 2011. Multivariable mixed linear regression and logistic regression was used to assess the association. Results: Tea consumption was associated with reduced global cognitive function decline. In fully adjusted models, regression coefficients (95% CIs) for those who consumed 0 cups/day,<2 cups/day, 2–3.9 cups/day, and≥4 cups/day of tea were 0, –0.09 (–0.55–0.37), 0.05 (–0.34–0.45), and 0.87 (0.46–1.29), respectively. This effect was stronger in adults > 60 years. Tea consumption of≥4 cups/day was inversely associated with self-reported poor memory (OR 0.70 (95% CI 0.56–0.86)) and memory decline (OR, 0.73 (95% CI 0.62–0.87)). There was a significant interaction between tea consumption and iron intake in relation to cognition. High iron intake was inversely associated with cognition in non-consumers of tea but not in tea consumers. Conclusion: Higher tea intake is associated with reduced cognitive decline in adults and inhibits the adverse effect of high iron intake.

Effect of Dietary Intake Through Whole Foods on Cognitive Function: Review of Randomized Controlled Trials

PURPOSE OF REVIEW

This review evaluated recent randomized controlled trials (RCTs) examining the chronic intake of whole foods associated with the Mediterranean, Dietary Approaches to Stop Hypertension (DASH), Mediterranean-DASH Intervention for Neurogenerative Delay (MIND), and ketogenic (KETO) diets on cognitive function.

RECENT FINDINGS

We identified RCTs related to olive oil (N = 3), nuts (N = 7), fatty fish (N = 1), lean meats (N = 4), fruits and vegetables (N = 9), legumes (N = 1), and low-fat dairy (N = 4), with 26/29 reporting positive results on at least one measure of cognition. We also identified 6 RCTs related to whole food-induced KETO diets, with half reporting positive effects on cognition. Variations in study design (i.e., generally the studies are < 6 months and include middle-aged and older, cognitively intact participants) and small sample sizes make it difficult to draw conclusions across studies; however, the current evidence from RCTs generally supports individual component intakes of these dietary patterns as an effective, nonpharmacological approach to improve cognitive health in adults.

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)

Purpose

To investigate if dairy, meat, and fish intakes associate with dementia and cognitive performance.

Methods

We included 2497 dementia-free men from Eastern Finland, aged 42–60 years in 1984–1989 at the baseline examinations. Data on cognitive tests [Mini Mental State Exam (MMSE), trail making test (TMT), verbal fluency test (VFL), selective reminding test (SRT), and Russell’s adaptation of the visual reproduction test (VRT)] at the 4-year re-examinations were available for 482 men and on the ApoE phenotype for 1259 men. Data on dementia events were obtained by linkage to national health registers. Diet was assessed with baseline 4-day food records. Cox regression and analysis of covariance were used for analyses.

Results

During a mean 22-year follow-up, 337 men had a dementia diagnosis. Among the foods, only cheese intake associated with dementia risk (hazard ratio in the highest vs. the lowest quartile = 0.72, 95% confidence interval = 0.52–0.99, P-trend = 0.05). In the cognitive tests, higher non-fermented dairy and milk intakes associated with worse verbal fluency (VFT). Higher processed red meat intake associated with worse verbal (SRT) and visual memory (VRT), whereas higher unprocessed red meat intake associated with better general cognitive functioning (MMSE) and processing speed and executive functioning (TMT). Higher fish intake associated with better verbal memory (SRT). Among APOE-ε4 carriers, especially non-fermented dairy intake associated with higher risk of dementia outcomes, and higher fish intake indicated better cognitive performance.

Conclusion

Although higher intake of some food groups associated with cognitive performance, we found little evidence for associations with dementia risk.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-022-02834-x.

MIND diet and cognitive performance in older adults: a systematic review

Cognitive decline is a rapidly increasing public health concern. A healthy diet has potential in preserving brain and maintaining cognitive health. This systematic review was designed to evaluate the relationship between Mediterranean-DASH diet intervention for neurodegenerative delay (MIND) diet and cognitive functioning in older adults. PubMed, SCOPUS, Embase, Cochrane Library, and Google Scholar databases were searched to extract original studies on humans published until July 2020, without date restrictions. Articles that evaluated the association between MIND diet and cognitive performance in older adults were included. Duplicated and irrelevant studies were screened out and data were obtained through critical analysis. Quality of the articles and risk of bias was assessed by Newcastle-Ottawa and Cochrane Collaboration's quality assessment tools. Of the 135 studies retrieved, 13 articles (9 cohort, 3 cross-sectional, and 1 RCT studies) were included in the final review. All of the included studies indicated that adherence to the MIND diet was positively associated with specific domains, but not all, of cognition and global cognitive function (78% of the studies) in older adults. MIND diet was superior to other plant-rich diets including Mediterranean, Dietary Approaches to Stop Hypertension, Pro-Vegetarian and Baltic Sea diets, for improving cognition. Adherence to the MIND diet may possibly be associated with an improved cognitive function in older adults. MIND diet may be superior to other plant-rich diets for improving cognition.

In Pursuit of Healthy Aging: Effects of Nutrition on Brain Function

Consuming a balanced, nutritious diet is important for maintaining health, especially as individuals age. Several studies suggest that consuming a diet rich in antioxidants and anti-inflammatory components such as those found in fruits, nuts, vegetables, and fish may reduce age-related cognitive decline and the risk of developing various neurodegenerative diseases. Numerous studies have been published over the last decade focusing on nutrition and how this impacts health. The main objective of the current article is to review the data linking the role of diet and nutrition with aging and age-related cognitive decline. Specifically, we discuss the roles of micronutrients and macronutrients and provide an overview of how the gut microbiota-gut-brain axis and nutrition impact brain function in general and cognitive processes in particular during aging. We propose that dietary interventions designed to optimize the levels of macro and micronutrients and maximize the functioning of the microbiota-gut-brain axis can be of therapeutic value for improving cognitive functioning, particularly during aging.