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Dietary flavanols improve cerebral cortical oxygenation and cognition in healthy adults.
Gratton, G, Weaver, SR, Burley, CV, Low, KA, Maclin, EL, Johns, PW, Pham, QS, Lucas, SJE, Fabiani, M, Rendeiro, C
Scientific reports. 2020;10(1):19409
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Fruits and vegetables contain flavonoids that can protect against vascular diseases and cognitive ageing. Studies have shown that cocoa flavonoids can enhance the function of endothelial cells and blood vessels in peripheral arteries. This randomised, double-blinded, placebo-controlled crossover study assessed the effects of cocoa flavanols on cerebral and peripheral vascular and cognitive function. The healthy young subjects showed greater tissue oxygenation and cerebrovascular reactivity in the frontal parts of the brain during the carbon dioxide challenge after high cocoa flavonoid intervention. Furthermore, the cocoa flavonoid intervention improved cognitive and peripheral endothelial functions in healthy young subjects. Even though the mechanistic link behind the beneficial effects of flavonoids is not understood completely, the positive effects could be due to the ability of flavanols to enhance the bioavailability of circulation Nitric Oxide (NO). The study also found that flavonoids improved cognitive function in healthy individuals only when there was a high cognitive demand. Further robust studies are required to evaluate the mechanisms behind the benefits associated with acute flavonoid intake. Healthcare professionals can utilise the findings from this study to gain insight into the advantages of consuming a flavonoid-rich diet. Additionally, they can learn about the differing responses to flavanol intake between individuals.
Abstract
Cocoa flavanols protect humans against vascular disease, as evidenced by improvements in peripheral endothelial function, likely through nitric oxide signalling. Emerging evidence also suggests that flavanol-rich diets protect against cognitive aging, but mechanisms remain elusive. In a randomized double-blind within-subject acute study in healthy young adults, we link these two lines of research by showing, for the first time, that flavanol intake leads to faster and greater brain oxygenation responses to hypercapnia, as well as higher performance only when cognitive demand is high. Individual difference analyses further show that participants who benefit from flavanols intake during hypercapnia are also those who do so in the cognitive challenge. These data support the hypothesis that similar vascular mechanisms underlie both the peripheral and cerebral effects of flavanols. They further show the importance of studies combining physiological and graded cognitive challenges in young adults to investigate the actions of dietary flavanols on brain function.
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Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis.
Seidelmann, SB, Claggett, B, Cheng, S, Henglin, M, Shah, A, Steffen, LM, Folsom, AR, Rimm, EB, Willett, WC, Solomon, SD
The Lancet. Public health. 2018;3(9):e419-e428
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Previous trials have shown that low carbohydrate diets are beneficial for short-term weight loss. However, the long-term impact of carbohydrate restriction on mortality is less clear, with research producing conflicting results. Additionally, previous studies have not addressed the source or quality of proteins and fats consumed in low-carbohydrate diets. This study aimed to find out whether there is an association between carbohydrate consumption and mortality. It also looked at whether animal-based or plant-based foods had any impact on the association. The researchers began by studying over 15,000 adults in the US, enrolled between 1987 and 1989. At the start of the study and again six years later, participants completed food frequency questionnaires. These were used to estimate the percentage of calories they derived from carbohydrate, fat and protein. The results showed a U-shape association between overall carbohydrate intake and life expectancy, with low (less than 40% of calories from carbohydrates) and high (more than 70%) intake of carbohydrates associated with a higher risk of mortality compared with moderate intake (50-55% of calories). The researchers estimated that the average life expectancy was 4 years shorter for those with low carbohydrate consumption, and 1 year shorter for those with high carbohydrate consumption, compared to those with a moderate carbohydrate intake. However, the authors point out that since diets were only recorded at the start of the trial and six years later, participants’ diets could have changed during the 25-year follow-up period. Next, the authors performed a meta-analysis of data from eight previous studies. This revealed similar trends, with participants whose overall diets were high and low in carbohydrates having a shorter life expectancy than those with moderate consumption. In further analyses examining the source of proteins and fats, animal-derived protein and fat sources, such as lamb, beef, pork and chicken, were associated with higher mortality, whereas plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter and whole-grains, were associated with lower mortality. The authors suggest that, when restricting carbohydrate intake, replacement of carbohydrates with predominantly plant-based fats and proteins could be considered as a long-term approach to promote healthy ageing.
Abstract
BACKGROUND Low carbohydrate diets, which restrict carbohydrate in favour of increased protein or fat intake, or both, are a popular weight-loss strategy. However, the long-term effect of carbohydrate restriction on mortality is controversial and could depend on whether dietary carbohydrate is replaced by plant-based or animal-based fat and protein. We aimed to investigate the association between carbohydrate intake and mortality. METHODS We studied 15 428 adults aged 45-64 years, in four US communities, who completed a dietary questionnaire at enrolment in the Atherosclerosis Risk in Communities (ARIC) study (between 1987 and 1989), and who did not report extreme caloric intake (<600 kcal or >4200 kcal per day for men and <500 kcal or >3600 kcal per day for women). The primary outcome was all-cause mortality. We investigated the association between the percentage of energy from carbohydrate intake and all-cause mortality, accounting for possible non-linear relationships in this cohort. We further examined this association, combining ARIC data with data for carbohydrate intake reported from seven multinational prospective studies in a meta-analysis. Finally, we assessed whether the substitution of animal or plant sources of fat and protein for carbohydrate affected mortality. FINDINGS During a median follow-up of 25 years there were 6283 deaths in the ARIC cohort, and there were 40 181 deaths across all cohort studies. In the ARIC cohort, after multivariable adjustment, there was a U-shaped association between the percentage of energy consumed from carbohydrate (mean 48·9%, SD 9·4) and mortality: a percentage of 50-55% energy from carbohydrate was associated with the lowest risk of mortality. In the meta-analysis of all cohorts (432 179 participants), both low carbohydrate consumption (<40%) and high carbohydrate consumption (>70%) conferred greater mortality risk than did moderate intake, which was consistent with a U-shaped association (pooled hazard ratio 1·20, 95% CI 1·09-1·32 for low carbohydrate consumption; 1·23, 1·11-1·36 for high carbohydrate consumption). However, results varied by the source of macronutrients: mortality increased when carbohydrates were exchanged for animal-derived fat or protein (1·18, 1·08-1·29) and mortality decreased when the substitutions were plant-based (0·82, 0·78-0·87). INTERPRETATION Both high and low percentages of carbohydrate diets were associated with increased mortality, with minimal risk observed at 50-55% carbohydrate intake. Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality. FUNDING National Institutes of Health.
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Vegetarian dietary patterns and mortality in Adventist Health Study 2.
Orlich, MJ, Singh, PN, Sabaté, J, Jaceldo-Siegl, K, Fan, J, Knutsen, S, Beeson, WL, Fraser, GE
JAMA internal medicine. 2013;173(13):1230-8
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Vegetarian diets have been associated with reduced risk of several chronic cardiometabolic diseases. The aim of this cohort study was to evaluate the effect of vegetarian diets on mortality. The study followed 73,308 male and female Seventh-day Adventists for a mean of 5.79 years. At baseline, just under half were non-vegetarians. Vegetarians had a lower mortality than non-vegetarians: death rates (deaths per 1000 person-years) were 5.4 for vegans, 5.61 for ovo-lacto vegetarians and 5.33 for pesco-vegetarians, which were significantly lower than that of non-vegetarians (6.61). After adjustment for a variety of factors, the lowered hazard ratio seen with vegetarian diets only remained statistically significant in pesco-vegetarians (compared to non-vegetarians). The non-vegetarians had on average higher rates of other risk factors, such as smoking, they consumed more alcohol, exercised less and had lower educational level. The authors concluded that vegetarian dietary patterns were associated with lower mortality.
Abstract
IMPORTANCE Some evidence suggests vegetarian dietary patterns may be associated with reduced mortality, but the relationship is not well established. OBJECTIVE To evaluate the association between vegetarian dietary patterns and mortality. DESIGN Prospective cohort study; mortality analysis by Cox proportional hazards regression, controlling for important demographic and lifestyle confounders. SETTING Adventist Health Study 2 (AHS-2), a large North American cohort. PARTICIPANTS A total of 96,469 Seventh-day Adventist men and women recruited between 2002 and 2007, from which an analytic sample of 73,308 participants remained after exclusions. EXPOSURES Diet was assessed at baseline by a quantitative food frequency questionnaire and categorized into 5 dietary patterns: nonvegetarian, semi-vegetarian, pesco-vegetarian, lacto-ovo-vegetarian, and vegan. MAIN OUTCOME AND MEASURE The relationship between vegetarian dietary patterns and all-cause and cause-specific mortality; deaths through 2009 were identified from the National Death Index. RESULTS There were 2570 deaths among 73,308 participants during a mean follow-up time of 5.79 years. The mortality rate was 6.05 (95% CI, 5.82-6.29) deaths per 1000 person-years. The adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined vs nonvegetarians was 0.88 (95% CI, 0.80-0.97). The adjusted HR for all-cause mortality in vegans was 0.85 (95% CI, 0.73-1.01); in lacto-ovo-vegetarians, 0.91 (95% CI, 0.82-1.00); in pesco-vegetarians, 0.81 (95% CI, 0.69-0.94); and in semi-vegetarians, 0.92 (95% CI, 0.75-1.13) compared with nonvegetarians. Significant associations with vegetarian diets were detected for cardiovascular mortality, noncardiovascular noncancer mortality, renal mortality, and endocrine mortality. Associations in men were larger and more often significant than were those in women. CONCLUSIONS AND RELEVANCE Vegetarian diets are associated with lower all-cause mortality and with some reductions in cause-specific mortality. Results appeared to be more robust in males. These favorable associations should be considered carefully by those offering dietary guidance.