The Role of Diet in the Prevention of Hypertension and Management of Blood Pressure: An Umbrella Review of Meta-Analyses of Interventional and Observational Studies

High blood pressure (BP) is a major pathological risk factor for the development of several cardiovascular diseases. Diet is a key modifier of BP, but the underlying relationships are not clearly demonstrated. This is an umbrella review of published meta-analyses to critically evaluate the wide range of dietary evidence from bioactive compounds to dietary patterns on BP and risk of hypertension. PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials were searched from inception until October 31, 2021, for relevant meta-analyses of randomized controlled trials or meta-analyses of observational studies. A total of 175 publications reporting 341 meta-analyses of randomized controlled trials (145 publications) and 70 meta-analyses of observational studies (30 publications) were included in the review. The methodological quality of the included publications was assessed using Assessment of Multiple Systematic Reviews 2 and the evidence quality of each selected meta-analysis was assessed using NutriGrade. This umbrella review supports recommended public health guidelines for prevention and control of hypertension. Dietary patterns including the Dietary Approaches to Stop Hypertension and the Mediterranean-type diets that further restrict sodium, and moderate alcohol intake are advised. To produce high-quality evidence and substantiate strong recommendations, future research should address areas where the low quality of evidence was observed (for example, intake of dietary fiber, fish, egg, meat, dairy products, fruit juice, and nuts) and emphasize focus on dietary factors not yet conclusively investigated.


Introduction:
The Mediterranean diet is marked by the regular intake of olive oil, which may play a role in preventing and protecting against cognitive deterioration and dementia.The strength of these effects have been examined by several recent randomized controlled trials (RCTs), but their findings have not been consistent.In light of this inconsistency, the present study performed a systematic review to examine the relationship between the consumption of olive oil and cognition.Methods: The Web of Science, Scopus, PubMed, and Google Scholar were systematically searched up to August 11, 2023.The review included RCTs, cross-sectional studies, cohort studies and case-control studies that explored the impact of olive oil consumption on cognitive performance among those older than 55 years old.Studies were excluded if they employed a design other than those mentioned above, involved participants under 55 years old, or did not specifically examine the cognitive effects of olive oil consumption.The quality of the included studies were measured using the Cochrane risk-of-bias tool and the Newcastle Ottawa Scale checklists.Results: Eleven studies were identified, which were comprised of four cross-sectional studies, four prospective cohort studies and three RCTs.The cohort studies and RCTs consistently found that olive oil consumption had a favorable effect on cognitive performance across a number of cognitive domains over time.Similarly, all of the cross-sectional studies reported that the consumption of olive oil was positively associated with cognitive health.Conclusion: The consumption of olive oil was found to enhance cognitive functioning and to reduce cognitive decline.Further large-scale investigations are required to strengthen this conclusion.

Dietary Pattern, Food and Nutritional Supplement Effects on Cognitive Outcomes in Mild Cognitive Impairment: A Systematic Review of Previous Reviews
Victoria Andrews, Gabrielle Zammit, Fiona O'Leary.Nutr Rev. 2023 Oct 10;81(11):1462-1489. doi: 10.1093/nutrit/nuad013. Article link Significance: A systematic review found few nutritional intervention studies were conclusive in outcomes related to cognitive improvement in mildly cognitively-impaired subjects.High-quality intervention research is needed to further investigate nutrition's impacts in this area.
Context: Nutritional interventions may benefit cognition in people with mild cognitive impairment (MCI).However, evidence is yet to be synthesized in a way that can inform recommendations for clinical and public health settings.Objective: To systematically review evidence on the effect of dietary patterns, foods, and nutritional supplements on cognitive decline in individuals with MCI .Data Sources: Guided by the Preferred Reporting items for Systematic Review and Meta-Analysis Protocols 2015 statement, the Medline, EMBASE, and CINAHL databases, the JBI Database of Systematic Reviews and Implementation Reports, Cochrane Database of Systematic Reviews, and Database of Abstracts of Reviews of Effects were searched (publication years 2005 to 2020).Included studies were English-language systematic reviews and meta-analyses of randomized controlled trials and cohort studies reporting on the effectiveness of nutritional interventions on cognition of individuals with MCI.Data Extraction: Two reviewers independently selected studies and extracted data on cognitive outcomes and adverse events.Review quality was assessed using AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews-2).Primary study overlap was managed following Cochrane Handbook guidelines.Data Analysis: Of the 6677 records retrieved, 20 reviews were included, which, in turn, reported on 43 randomized controlled trials and 1 cohort study that, together, addressed 18 nutritional interventions.Most reviews were limited by quality and the small number of primary studies with small sample sizes.Reviews were mostly positive for B vitamins, omega-3 fatty acids, and probiotics (including 12, 11 and 4 primary studies, respectively).Souvenaid and the Mediterranean diet reduced cognitive decline or Alzheimer's disease progression in single trials with <500 participants.Findings from studies with a small number of participants suggest vitamin D, a low-carbohydrate diet, medium-chain triglycerides, blueberries, grape juice, cocoa flavanols, and Brazil nuts may improve individual cognitive subdomains, but more studies are needed.Conclusions: Few nutritional interventions were found to convincingly improve cognition of individuals with MCI.More high-quality research in MCI populations is required to determine if nutritional treatments improve cognition and/or reduce progression to dementia.

Lipids Association of Dietary Fatty Acids with the Risk of Atherosclerotic Cardiovascular Disease in a Prospective Cohort of United States Veterans
Kerry L Ivey, Xuan-Mai T Nguyen, Ruifeng Li, Jeremy Furtado, Kelly Cho, John Michael Gaziano, Frank B Hu, et. al. Am J Clin Nutr. 2023 Oct;118(4):763-772.doi: 10.1016/j.ajcnut.2023.07.014.Article link Significance: Unlike trans-and conjugated fatty acids, not all classes of fat are associated with increased risk of cardiovascular disease.This suggests that general conclusions on individual fatty acids' effect on health cannot always be drawn.
Background: Atherosclerotic cardiovascular diseases (ASCVDs) are the leading cause of worldwide adult mortality.Although broad classes of dietary fats have been shown to alter ASCVD risk, the roles that individual dietary fatty acids play in influencing ASCVD risk are unclear.Objectives: The aim of this cohort study was to examine the relationships of the total fat classes and individual fatty acids with the risk of ASCVD.Methods: The Million Veteran Program is a prospective cohort whereby dietary intake of fatty acids was assessed in 158,198 participants that had enrolled between January 2011 and November 2018 and were free of ASCVD at baseline.Incident ASCVD was ascertained from the Veterans Affairs electronic health records and the National Death Index.Multivariable-adjusted hazard ratios (HRs) for the relationship between fat intake and ASCVD risk were computed using Cox regression models.Results: The mean age was 61 years, 88% were males.A total of 11,771 ASCVD events were identified during the follow-up.When compared with the lowest quintile, participants in the highest quintile of dietary trans-monounsaturated fats and conjugated linoleic acids had an increased risk (HR [95% CI]) of ASCVD events: 1.10 (1.04, 1.17) and 1.11 (1.05, 1.18), respectively.When compared with low consumers, participants in the highest quintile of total cis-polyunsaturated fatty acid intake had a lower risk of experiencing an ASCVD event 0.93 (0.87, 0.99).Conclusion: Although higher intakes of specific trans-fatty acids and conjugated linoleic were associated with an increased risk of ASCVD, the same cannot be said for all other fat classes.This work suggests that care must be taken when drawing general conclusions regarding the health effects of dietary individual fatty acids.
Background: Sodium chloride intake far exceeds the guidelines from health and regulatory agencies.Acknowledging the positive relationship between sodium intake and blood pressure, interest in substances that assist in sodium reduction, while contributing to a savory taste such as umami, are highly investigated.Objective: The objective of this scoping review was to identify and characterize studies investigating umami tastants on sodium reduction in food, with the goal of informing future research.Methods: A literature search was conducted in Ovid MEDLINE, Ovid Embase, Ovid Cochrane Database of Systematic Reviews, EBSCO PsycInfo, PROSPERO, National Institutes of Health RePORTER, ClinicalTrials.gov,and the World Health Organization International Clinical Trials Registry Platform and completed in March 2022 to identify peer-reviewed publications among adults (18 years and older) with interventions focusing on umami tastants to reduce sodium content.Results: The literature search identified 52 studies, among which monosodium glutamate was the most studied umami tastant or food.Furthermore, most of the research on umami was represented through cross-sectional sensory studies to determine acceptability of foods with part of the original sodium chloride replaced with umami tastants.Only 1 study investigated the use of an umami tastant on overall daily sodium intake.Conclusions: To assist individuals in adhering to sodium reduction intake goals set forth by regulatory agencies and their guiding policies, these findings indicated that additional research on umami tastants, including systematic reviews and prospective trials, is warranted.In these prospective studies, both intermediate outcomes (ie, dietary pattern changes, daily dietary intake of sodium, and blood pressure) and hard outcomes (ie, incidence of hypertension or stroke, as well as cardiovascular composite outcomes) should be considered.Background: Short-chain fatty acids (SCFAs) are considered beneficial to human health.The associations between bacterial capacity to produce SCFAs, diet, and health are not fully understood.Objective: We aimed to evaluate the capacity of human fecal microbiota to produce SCFAs and to metabolize soluble and insoluble fiber and to study its associations with human diet, anthropometric parameters, and carbohydrate and lipid metabolism.Methods: A cross-sectional study was carried out with 200 adult participants.Diet was evaluated using food records.Capacity to produce acetate, butyrate, and propionate and to degrade soluble fiber were assessed in an ex vivo experiment where fecal samples were inoculated in a pectin-containing broth.Fecal βglucosidase activity was measured to assess potential to degrade insoluble fiber.Results: The main dietary determinants of high capacity to metabolize fiber were high intake of vegetables, fruits, nuts, and seeds.After adjusting analyses for confounders, glucose and lipid parameters were not significantly associated with any of the studied microbial capacities, but the capacity to produce propionic acid was significantly associated with hip circumference (β = -0.018,P = 0.044), which was seen especially in people eating healthy.Conclusions: We confirmed that high intake of fiber-rich products is positively associated with the capacity of fecal microbiota to degrade soluble and insoluble dietary fiber and that people eating healthy food might benefit from enhanced microbial capacity to produce propionic acid.