Risk Reduction and Prevention of Alzheimer's Disease: Biological Mechanisms of Diet.

Alzheimer's Disease (AD) incidence is increasing and with no disease modifying agents available, preventative measures through lifestyle factors are being investigated. Combined with the prevention of AD risk factors such as heart disease, diabetes, and with more recent evidence, microbiome dysfunction, there is a substantial foundation for diet as a modifiable risk factor and preventative measure for AD. Recent evidence suggests AD associated pathologies, such as oxidative stress and inflammation, can be modulated by the lipids, vitamins, and polyphenols obtained through nutritional intake. Furthermore, epidemiological and preclinical evidence has uncovered certain compounds within foods that may have beneficial effects in the prevention of AD, including omega-3 fatty acids, vitamin E, and resveratrol among others. However, clinical data examining specific compounds are often inconsistent and fail to replicate the preclinical data. On the other hand, dietary patterns such as the Mediterranean or MIND diet have shown promise in terms of clinical outcomes for patients, indicating a reductionist approach to diet is not as effective as a holistic dietary pattern. In this review, we summarize some of the biological mechanisms of key compounds in their relation to AD and how they fit into a dietary pattern that supports the role of diet as a risk reducing factor for AD.

A Mediterranean diet supplemented with dairy foods improves mood and processing speed in an Australian sample: results from the MedDairy randomized controlled trial.

Background The Mediterranean diet has been linked to improved cognitive function and reduced risk of dementia. However, a traditional Mediterranean diet may not meet calcium requirements for older non-Mediterranean populations, which could limit long-term sustainability in Western countries. The current study therefore aimed to determine the cognitive and psychological effects of a Mediterranean diet with adequate calcium for an ageing Australian population. Method: A randomized controlled cross-over design trial compared a Mediterranean diet with 3-4 daily serves of dairy food (MedDairy) with a low-fat (LF) control diet. Forty-one participants aged ≥45 years with systolic blood pressure ≥120 mm Hg and at least two other risk factors for cardiovascular disease completed each dietary intervention for 8 weeks, with an 8-week washout period separating interventions. Attention, processing speed, memory and planning were assessed at the start and end of each intervention using the Cambridge Automated Neuropsychological Test Battery. Mood and health-related quality of life were evaluated using the Profile of Mood States (POMS) and Short-Form Health Survey (SF-36). Dementia risk was also measured using the Framingham Vascular Risk and CAIDE scores. Results Significant improvements were observed for processing speed (P = .04), Total Mood Disturbance (P = .01), Tension (P = .03), Depression (P = .03), Anger (P = .02), and Confusion (P = .004) following the MedDairy intervention. No significant effects were found for attention, memory and planning, or measures of dementia risk. Conclusion Our study provides evidence that a Mediterranean diet supplemented with dairy foods may benefit cognitive function and psychological well-being in an ageing population at risk of dementia.

A Retrospective Cross-Sectional Population-Based Study on Prenatal Levels of Adherence to the Mediterranean Diet: Maternal Profile and Effects on the Newborn.

The Mediterranean diet (MD) is a dietary pattern with important benefits. The objectives of this study were to assess the adherence to the MD among pregnant women in Valencia (Spain) and characterize the pregnant women according to their level of adherence. Finally, we aimed to examine the role of MD adherence during pregnancy in the anthropometric development of the newborn. The study included 492 pregnant women who were followed at La Fe Hospital in 2017. The self-administered "Kidmed" questionnaire for data collection on dietary information evaluation was used and a clinical history review of mothers and newborns was performed. Two groups of mothers were identified: those with low adherence (LA) and optimal adherence (OA). The study revealed that 40.2% of the women showed LA to the MD. The newborns born to these women presented a higher risk of being small for gestational age (SGA) {adjusted odds ratio (aOR) = 1.68; 95% confidence interval (CI) 1.02⁻5.46} when adjusting for parental body mass index (BMI) and multiple gestation, but not when adjusting for all significant possible confounders (aOR = 2.32; 95% CI 0.69⁻7.78). The association between MD and SGA was not significantly affected by the use of iron and folic acid supplements (aOR = 2.65; 95% CI 0.66⁻10.65). The profile of the pregnant woman with LA is that of a young smoker, with a low level of education and a low daily intake of dairy products. These results suggest that LA to the MD is not associated with a higher risk of giving birth to a SGA newborn.

Individually modifiable risk factors to ameliorate cognitive aging: a systematic review and meta-analysis.

A number of health and lifestyle factors are thought to contribute to cognitive decline associated with age but cannot be easily modified by the individual patient. We identified 12 individually modifiable interventions that can be implemented during midlife or later with the potential to ameliorate cognitive aging. For ten of these, we used PubMed databases for a systematic review of long-duration (at least 6 months), randomized, controlled trials in midlife and older adults without dementia or mild cognitive impairment with objective measures of neuropsychological performance. Using network meta-analysis, we performed a quantitative synthesis for global cognition (primary outcome) and episodic memory (secondary outcome). Of 1038 publications identified by our search strategy, 24 eligible trials were included in the network meta-analysis. Results suggested that the Mediterranean diet supplemented by olive oil and tai chi exercise may improve global cognition, and the Mediterranean diet plus olive oil and soy isoflavone supplements may improve memory. Effect sizes were no more than small (standardized mean differences 0.11-0.22). Cognitive training may have cognitive benefit as well. Most individually modifiable risk factors have not yet been adequately studied. We conclude that some interventions that can be self-initiated by healthy midlife and older adults may ameliorate cognitive aging.

Mediterranean diet improves cognition: the PREDIMED-NAVARRA randomised trial.

OBJECTIVE: Previous observational studies reported beneficial effects of the Mediterranean diet (MedDiet) on cognitive function, but results were inconsistent. We assessed the effect on cognition of a nutritional intervention using MedDiets in comparison with a low-fat control diet. METHODS: We assessed 522 participants at high vascular risk (44.6% men, age 74.6 ± 5.7 years at cognitive evaluation) enrolled in a multicentre, randomised, primary prevention trial (PREDIMED), after a nutritional intervention comparing two MedDiets (supplemented with either extra-virgin olive oil (EVOO) or mixed nuts) versus a low-fat control diet. Global cognitive performance was examined by Mini-Mental State Examination (MMSE) and Clock Drawing Test (CDT) after 6.5 years of nutritional intervention. Researchers who assessed the outcome were blinded to group assignment. We used general linear models to control for potential confounding. RESULTS: After adjustment for sex, age, education, Apolipoprotein E genotype, family history of cognitive impairment/dementia, smoking, physical activity, body mass index, hypertension, dyslipidaemia, diabetes, alcohol and total energy intake, participants allocated to the MedDiet+EVOO showed higher mean MMSE and CDT scores with significant differences versus control (adjusted differences: +0.62 95% CI +0.18 to +1.05, p=0.005 for MMSE, and +0.51 95% CI +0.20 to +0.82, p=0.001 for CDT). The adjusted means of MMSE and CDT scores were also higher for participants allocated to the MedDiet+Nuts versus control (adjusted differences: +0.57 (95% CI +0.11 to +1.03), p=0.015 for MMSE and +0.33 (95% CI +0.003 to +0.67), p=0.048 for CDT). These results did not differ after controlling for incident depression. CONCLUSIONS: An intervention with MedDiets enhanced with either EVOO or nuts appears to improve cognition compared with a low-fat diet. ISRCTN:35739639.

Worldwide variation of adherence to the Mediterranean diet, in 1961-1965 and 2000-2003.

OBJECTIVE: The present study aimed to analyse the worldwide trends of adherence to the Mediterranean diet (MD), in 1961-1965 and 2000-2003. DESIGN: Data were obtained from the FAO food balance sheets in two periods: 1961-1965 and 2000-2003. In order to have a sample from across the world, forty-one countries were selected. The average of available energy for different food groups was calculated for all selected countries. These values were used to evaluate the adherence to the MD through a variation of Mediterranean Adequacy Index (MAI). RESULTS: The majority of the forty-one countries in this study have tended to drift away from a Mediterranean-like dietary pattern. Mediterranean Europe and the Other Mediterranean country groups suffered a significant decrease in their MAI values. The Mediterranean European group, especially Greece, experienced the greatest decrease in MAI value. In both periods, the Other Mediterranean countries showed the highest MAI values. In an analysis by countries, Iran had the highest increase in MAI across the time periods, and Egypt occupied the first place in the ranking in 2000-2003. The Northern European group was the only one that registered an increase in MAI, although this was not statistically significant. CONCLUSIONS: Many countries in the Mediterranean basin are drifting away from the Mediterranean dietary pattern (MDP). However, countries in Northern Europe and some other countries around the world are taking on a Mediterranean-like dietary pattern. The Other Mediterranean countries have the closest adherence to the MDP, currently and in the 1960s. Nutrition policy actions to tackle dietary westernisation and preserve the healthy prudent MDP are required.

Mediterranean diet and depression.

OBJECTIVE: The adherence to a Mediterranean Dietary Pattern ensures an adequate intake of B vitamins and w-3 fatty acids. A protective role on depression has been suggested for both nutrients. DESIGN: Cross-sectional analysis from the SUN (Seguimiento Universidad de Navarra) prospective cohort study. Data from 9670 participants (4211 men and 5459 women) were analised. Logistic regression analyses were fitted to assess the association between B-vitamins and w-3 fatty acids intake (quintiles) and the prevalence of depression. RESULTS: Folate intake was inversely associated with depression prevalence among men, especially smokers. Among women, B12 vitamin intake was inversely associated with depression, especially among smokers and physically active women. No significant associations were observed for w-3 fatty acids intake. CONCLUSIONS: The adherence to a Mediterranean Dietary Pattern ensures an adequate intake of fruits, nuts, vegetables, cereals, legumes or fish, important sources of nutrients linked to depression prevention.

Evaluating associations between Mediterranean diet adherence indexes and biomarkers of diet and disease.

OBJECTIVE: We examined associations between two Mediterranean diet (MD) adherence indexes (the MD index, MDI, and the MD score, MDS) and several blood biomarkers of diet and disease. SUBJECTS: We studied 328 individuals from Catalonia (Northeastern Spain), ages 18-75, who provided fasting blood samples, a subset of the 2346 individuals as part of a larger representative and random sample from the 1992-1993 Catalan Nutritional Survey. DESIGN AND METHOD: Diet was measured using 24-h recalls. Biomarkers studied were plasma levels of beta-carotene, alpha-tocopherol, retinol, vitamins B12, C and folates as well as serum total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides. Multivariate linear regression was used to analyse associations of the nutrient biomarkers with the dietary pattern indexes, adjusting for potential confounders. RESULTS AND CONCLUSIONS: Subjects with higher MD adherence, as measured by the two dietary indexes, had significantly higher plasma concentrations of beta-carotene, folates, vitamin C, alpha-tocopherol and HDL cholesterol. The most highly significant relationship was that between folates and the adherence to the MD Pattern, as determined by both indexes. These research findings suggest the potential usefulness of biomarkers as complementary tools for assessing adherence to a dietary pattern. This type of data not only informs the development of robust dietary adherence indexes, but it also provides specific clues about the potential physiological mechanisms that explain the beneficial effects of the MD pattern on chronic disease risk.