Estimation of Flavonoid Intake in Older Australians: Secondary Data Analysis of the Blue Mountains Eye Study

Development of a food frequency questionnaire for the estimation of dietary (poly)phenol intake

Background: (Poly)phenol intake has been associated with reduced risk of non-communicable diseases in epidemiological studies. However, there are currently no dietary assessment tools specifically developed to estimate (poly)phenol intake in the UK population. Objectives: This study aimed to develop a novel food frequency questionnaire (FFQ) to capture the dietary (poly)phenol intake in the UK and assess its relative validity with 7 day diet diaries (7DDs) and plasma and urine (poly)phenol metabolites. Methods: The KCL (poly)phenol FFQ (KP-FFQ) was developed based on the existing EPIC (European Prospective Investigation into Diet and Cancer)-Norfolk FFQ, which has been validated for energy and nutrient intake estimation in the UK population. Participants aged 18-29 years (n = 255) completed both the KP-FFQ and the EPIC-Norfolk FFQ. In a subgroup (n = 60), 7DD, spot urine, and fasting plasma samples were collected. An in-house (poly)phenol database was used to estimate (poly)phenol intake from FFQs and 7DDs. Plasma and urinary (poly)phenol metabolite levels were analysed using a validated ultra-high-performance liquid chromatography-triple quadrupole mass spectrometry method. The agreements between (poly)phenol intake estimated using the KP-FFQ, EPIC-Norfolk FFQ and 7DDs, as well as plasma and urinary biomarkers, were evaluated by intraclass correlation coefficients (ICC), weighted kappa, quartile cross-classification, and Spearman's correlations, and the associations were investigated using linear regression models adjusting for energy intake and multiple testing (false discovery rate (FDR) < 0.05). Results: The mean (standard deviation, SD) of total (poly)phenol intake estimated from KP-FFQs was 1366.5 (1151.7) mg d-1. Fair agreements were observed between ten (poly)phenol groups estimated from KP-FFQs and 7DDs (kappa: 0.41-0.73), including total (poly)phenol intake (kappa = 0.45), while the agreements for the rest of the 17 classes and subclasses were poor (kappa: 0.07-0.39). Strong positive associations with KP-FFQ were found in ten (poly)phenols estimated from 7DDs, including dihydroflavonols, theaflavins, thearubigins, flavones, isoflavonoids, ellagitannins, hydroxyphenylacetic acids, total stilbenes, resveratrol, and tyrosols with stdBeta ranged from 0.61 (95% confidence interval CI: 0.42 to 0.81) to 0.95 (95% CI: 0.86 to 1.03) (all FDR adjusted p < 0.05). KP-FFQs estimated (poly)phenol intake exhibited positive associations with 76 urinary metabolites (stdBeta: 0.28 (95% CI: 0.07-0.49) to 0.81 (0.62-1.00)) and 19 plasma metabolites (stdBeta: 0.40 (0.17-0.62)-0.83 (0.64-1.02)) (all FDR p < 0.05). The agreement between KP-FFQs and the EPIC-Norfolk FFQs was moderate (ICC 0.51-0.69) for all (poly)phenol subclasses after adjusting for energy intake. Compared with the EPIC-Norfolk FFQs estimated (poly)phenol intake, stronger and more agreements and associations were found in KP-FFQs estimated (poly)phenol with 7DDs and biomarkers. Conclusion: (Poly)phenol intake estimated from KP-FFQ exhibited fair agreements and moderate to strong associations with 7DDs and biomarkers, indicating the novel questionnaire may be a promising tool to assess dietary (poly)phenol intake.

"I Always Buy the Purple Ones … If I See Them": Socioecological Factors Influencing Anthocyanin-Rich Food Consumption for Cognitive Health in Older Adults

Despite the positive relationship between anthocyanin-rich foods and cognitive health, a dietary deficit exists in older adults. Effective interventions require an understanding of people's dietary behaviors situated in social and cultural contexts. Therefore, the aim of this study was to explore older adults' perceptions about increasing their consumption of anthocyanin-rich foods for cognitive health. Following an educational session and the provision of a recipe and information book, an online survey and focus groups with Australian adults aged 65 years or older (n = 20) explored the barriers and enablers towards eating more anthocyanin-rich foods and potential strategies to achieve dietary change. An iterative, qualitative analysis identified the themes and classified the barriers, enablers and strategies onto the Social-Ecological model levels of influence (individual, interpersonal, community, society). Enabling factors included a desire to eat healthily, taste preference and familiarity of anthocyanin-rich foods (individual), social support (community), and the availability of some anthocyanin-rich foods (society). The barriers included budget, dietary preferences and motivation (individual), household influences (interpersonal), limited availability and access to some anthocyanin-rich foods (community) and the cost and the seasonal variability (society). The strategies included increasing individual-level knowledge, skills, and confidence in utilizing anthocyanin-rich foods, educational initiatives about the potential cognitive benefits, and advocating to increase access to anthocyanin-rich foods in the food supply. This study provides for the first time, insight into the various levels of influence impacting older adults' ability to consume an anthocyanin-rich diet for cognitive health. Future interventions should be tailored to reflect the barriers and enablers and to provide targeted education about anthocyanin-rich foods.

Association between non-tea flavonoid intake and risk of type 2 diabetes: the Australian diabetes, obesity and lifestyle study

Studies examining the association between flavonoid intake and measures of insulin resistance and β-cell dysfunction, as markers of type 2 diabetes (T2DM) across the adult lifespan, may provide insights into how flavonoids influence T2DM risk. This study examined the cross-sectional associations between flavonoid intakes, from dietary sources other than tea, and biomarkers of glucose tolerance and insulin sensitivity in adults aged 25 years and older participating in the Australian diabetes, obesity and lifestyle (AusDiab) study. Additionally, longitudinal associations between non-tea flavonoid intakes and incident T2DM over 12 years were explored. Eligible participants (n = 7675) had no previous history of T2DM and had completed a food-frequency questionnaire at baseline (1999-2000) from which flavonoid intakes were calculated using United States Department of Agriculture Databases. Restricted cubic splines in regression models were used to examine cross-sectional associations between intakes of total non-tea flavonoids and selected flavonoid subclasses and measures of glucose tolerance and insulin sensitivity including glycated haemoglobin (HbA1c), homeostasis model assessment of β-cell function (HOMA2-% β) and insulin sensitivity (HOMA2-% S), 2-hour post load plasma glucose (PLG), fasting plasma glucose (FPG) and fasting insulin levels. Associations between flavonoid intakes and T2DM risk were estimated using Cox proportional hazards models. Cross-sectionally, significant beneficial associations were observed for intakes of total flavonoids and the flavan-3-ol-monomer, proanthocyanidin, flavonol and anthocyanidin subclasses with measures of glucose tolerance and insulin sensitivity (P < 0.05 for all), except fasting plasma glucose. During follow-up, 344 incident T2DM cases were recorded. Participants with the highest total flavonoid intake had a 21% lower risk of T2DM over 12 years, although this was not statistically significant in multivariable adjusted models [HR (95% CI): 0.79 (0.57, 1.09)]. This study provides some evidence that consuming flavonoid-rich foods may be protective against T2DM through mechanisms related to glucose tolerance and insulin sensitivity.

Flavonoid-statin interactions causing myopathy and the possible significance of OATP transport, CYP450 metabolism and mevalonate synthesis

3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors, statins, are a primary treatment for hyperlipidemic cardiovascular diseases which are a leading global cause of death. Statin therapy is life saving and discontinuation due to adverse events such as myotoxicity may lead to unfavourable outcomes. There is no known mechanism for statin-induced myotoxicity although it is theorized that it is due to inhibition of downstream products of the HMG-CoA pathway. It is known that drug-drug interactions with conventional medicines exacerbate the risk of statin-induced myotoxicity, though little attention has been paid to herb-drug interactions with complementary medicines. Flavonoids are a class of phytochemicals which can be purchased as high dose supplements. There is evidence that flavonoids can raise statin plasma levels, increasing the risk of statin-induced myopathy. This could be due to pharmacokinetic interactions involving hepatic cytochrome 450 (CYP450) metabolism and organic anion transporter (OATP) absorption. There is also the potential for flavonoids to directly and indirectly inhibit HMG-CoA reductase which could contraindicate statin-therapy. This review aims to discuss what is currently known about the potential for high dose flavonoids to interact with the hepatic CYP450 metabolism, OATP uptake of statins or their ability to interact with HMG-CoA reductase. Flavonoids of particular interest will be covered and the difficulties of examining herbal products will be discussed throughout.

Flavonoids are promising safe therapy against COVID-19

Flavonoids are a class of phenolic natural products, well-identified in traditional and modern medicines in the treatment of several diseases including viral infection. Flavonoids showed potential inhibitory activity against coronaviruses including the current pandemic outbreak caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and designated as COVID-19. Here, we have collected all data related to the potential inhibitory mechanisms of flavonoids against SARS-CoV-2 infection and their significant immunomodulatory activities. The data were mapped and compared to elect major flavonoids with a promising role in the current pandemic. Further, we have linked the global existence of flavonoids in medicinal plants and their role in protection against COVID-19. Computational analysis predicted that flavonoids can exhibit potential inhibitory activity against SARS-CoV-2 by binding to essential viral targets required in virus entry and/ or replication. Flavonoids also showed excellent immunomodulatory and anti-inflammatory activities including the inhibition of various inflammatory cytokines. Further, flavonoids showed significant ability to reduce the exacerbation of COVID-19 in the case of obesity via promoting lipids metabolism. Moreover, flavonoids exhibit a high safety profile, suitable bioavailability, and no significant adverse effects. For instance, plants rich in flavonoids are globally distributed and can offer great protection from COVID-19. The data described in this study strongly highlighted that flavonoids particularly quercetin and luteolin can exhibit promising multi-target activity against SARS-CoV-2, which promote their use in the current and expected future outbreaks. Therefore, a regimen of flavonoid-rich plants can be recommended to supplement a sufficient amount of flavonoids for the protection and treatment from SARS-CoV-2 infection.

Dietary Assessment Methods to Estimate (Poly)phenol Intake in Epidemiological Studies: A Systematic Review

Nutritional epidemiological studies have frequently reported associations between higher (poly)phenol intake and a decrease in the risk or incidence of noncommunicable diseases. However, the assessment methods that have been used to quantify the intakes of these compounds in large-population samples are highly variable. This systematic review aims to characterize the methods used to assess dietary (poly)phenol intake in observational studies, report the validation status of the methods, and give recommendations on method selection and data reporting. Three databases were searched for publications that have used dietary assessment methods to measure (poly)phenol intake and 549 eligible full texts were identified. Food-frequency questionnaires were found to be the most commonly used tool to assess dietary (poly)phenol intake (73%). Published data from peer-reviewed journals were the major source of (poly)phenol content data (25%). An increasing number of studies used open-access databases such as Phenol-Explorer and USDA databases on flavonoid content since their inception, which accounted for 11% and 23% of the data sources, respectively. Only 16% of the studies reported a method that had been validated for measuring the target (poly)phenols. For future research we recommend: 1) selecting a validated dietary assessment tool according to the target compounds and target period of measurement; 2) applying and combining comprehensive (poly)phenol content databases such as USDA and Phenol-Explorer; 3) detailing the methods used to assess (poly)phenol intake, including dietary assessment method, (poly)phenol content data source; 4) follow the Strengthening the Reporting of Observational Studies in Epidemiology-Nutritional Epidemiology (STROBE-nut) framework; and 5) complementing dietary intake assessment based on questionnaires with measurement of (poly)phenols in biofluids using appropriate and validated analytical methods.

Habitual dietary intake of flavonoids and all-cause and cause-specific mortality: Golestan cohort study

BACKGROUND AND OBJECTIVES

Flavonoids are the most important group of polyphenols with well-known beneficial effects on health. However; the association of intake of total flavonoid or their subclasses with all-cause or cause-specific mortality is not fully understood. The present study aims to evaluate the association between intake of total flavonoid, flavonoid subclasses, and total and cause-specific mortality in a developing country.

METHODS

A total number of 49,173 participants from the Golestan cohort study, who completed a validated food frequency questionnaire at recruitment, were followed from 2004 till 2018. Phenol-Explorer database was applied to estimate dietary intakes of total flavonoid and different flavonoid subclasses. Associations were examined using adjusted Cox proportional hazards models.

RESULTS

During a mean follow-up of 10.63 years, 5104 deaths were reported. After adjusting for several potential confounders, the hazard ratios (HRs) of all-cause mortality for the highest versus the lowest quintile of dietary flavanones, flavones, isoflavonoids, and dihydrochalcones were 0.81 (95% confidence interval = 0.73-0.89), 0.83(0.76-0.92), 0.88(0.80-0.96) and 0.83(0.77-0.90), respectively. However, there was no association between total flavonoid intake or other flavonoid subclasses with all-cause mortality. In cause-specific mortality analyses, flavanones and flavones intakes were inversely associated with CVD mortality [HRs: 0.86(0.73-1.00) and 0.85(0.72-1.00)] and isoflavonoids and dihydrochalcones were the only flavonoid subclasses that showed a protective association against cancer mortality [HR: 0.82(0.68-0.98)].

CONCLUSION

The results of our study suggest that certain subclasses of flavonoids can reduce all-cause mortality and mortality rate from CVD and cancer.

Low anthocyanin plum nectar does not impact cognition, blood pressure and gut microbiota in healthy older adults: A randomized crossover trial

Queen Garnet plum (QGP), known for its high levels of anthocyanins, is a hybrid of the Japanese plum developed in Queensland, Australia. Anthocyanins provide the red, blue, and purple pigments in plants with demonstrated beneficial health effects. This study hypothesized that low-dose anthocyanin QGP intake will have a significant positive effect on cognition, blood pressure, and gut microbiota in healthy older adults. A randomized crossover trial was conducted to determine the effect and within subject variance on cognition and 24 hr. ambulatory blood pressure in older adults without cognitive impairment following daily consumption of 200 mL low-dose anthocyanin (5 mg/100 g) QGP nectar (intervention) or raspberry cordial (control). Secondary outcomes included inflammatory markers (C-reactive protein), nerve growth factor (BDNF), and gut microbiota (16S rRNA gene sequencing). Twenty-eight participants (55+ years) were recruited. Each randomized treatment arm lasted for 8 weeks with a 4-week washout period. Cognition, blood pressure, and urine samples were measured at each visit (5 total) while blood and fecal samples were collected at baseline, 8 weeks, and 20 weeks. Repeated-measures ANOVA was used to analyze the data. Across the treatments, no significant difference was observed for the different domains of cognition, blood pressure, or anti-inflammatory biomarkers. No intervention effect was found for genera or class of gut microbes. Low anthocyanin nectar derived from the QGP did not have any significant effects on cognition, blood pressure, or gut microbiota in healthy older adults.

Estimated intake and major food sources of flavonoids among Australian adolescents

PURPOSE

The consumption of dietary flavonoids from plant-based foods has been related to the prevention of multiple chronic diseases. However, intake data from adolescents are lacking. We aimed to characterise the intake and major sources of dietary flavonoids among Australian adolescents and investigate changes during adolescence.

METHODS

The Raine Study Gen 2 participants completed a 212-item food frequency questionnaire at age 14 years and 17 years, with repeated measures for n = 883. Items were assigned a content for six flavonoid subclasses using the Phenol-Explorer database, which were summed for total flavonoid intake. Daily intakes and sources of flavonoids and flavonoid-subclasses were determined, and change assessed between 14 and 17 years, for males and females.

RESULTS

Major food sources of flavonoids and each subclass were similar at 14 and 17 years, with fruit juice the major contributor to total flavonoid intake at both time points (providing 44% and 38%, respectively). Citrus flavanones (predominantly hesperitin) were the major subclass at 14 years, while tea flavan-3-ols were a major subclass (predominantly procyanidin dimers) at 17 years. The mean intake of total flavonoids at 14 years was 210 ± 133 mg/day, reducing by 5% (10 mg/day) by 17 years. Females consumed a more flavonoid-dense diet compared to males (104.5 ± 71.5 mg/1000 kcal vs 80.4 ± 50.3 mg/1000 kcal per day; p < 0.001).

CONCLUSION

This study provides a comprehensive estimation of flavonoid intake and their major food sources in a sample of Australian adolescents, which may be useful in the development of practical dietary recommendations.

Usual dietary anthocyanin intake, sources and their association with blood pressure in a representative sample of Australian adults

BACKGROUND

Anthocyanins represent an important subgroup of non-nutritive components of food as evidence continues to build related to their beneficial bioactive effects. Using a recently developed Australian anthocyanin database, the present study aimed to estimate the intake of both total anthocyanins and their subclasses, identify food sources of anthocyanins, and determine associations between anthocyanin intake and measured blood pressure (BP).

METHODS

The present study comprised a secondary analysis of the 2011-12 National Nutrition and Physical Activity component of the Australian Health Survey. Anthocyanin intake was estimated using an Australian anthocyanin database. Usual anthocyanin intake, as estimated from 24-h diet recall data, was computed using multiple source methods, whereas food sources were determined by calculating contribution of food groups to total anthocyanin intake. Regression analysis, adjusted for covariates (age, gender, body mass index, high BP diagnosis, smoking status and physical activity) assessed the relationship between anthocyanin intake and BP in adults aged ≥50 years.

RESULTS

Mean anthocyanin intake was 24.17 ± 0.32 mg day^-1 . Across age groups, berries were the top sources: blackberry (5-65%), cherry (2-24%), blueberry (2-13%) and raspberry (3-12%). There was a significant inverse association between anthocyanin intake and systolic BP (β = -0.04, F = 16.8, d.f. = 6, r²  = 0.05, P < 0.01) and diastolic BP (β = 0.01, F = 5.35, d.f. = 6, R²  = 0.013, P < 0.01), in models that adjusted for covariates.

CONCLUSIONS

In comparison with the world composite database, anthocyanin intake in the Australian population was above average [mean (SD): 24.17 (0.32) mg day^-1 versus 18.05 (21.14) mg day^-1 ]. Berries were the primary source of anthocyanins. Anthocyanin intake in older adults aged ≥50 years was inversely associated with BP.

Quercetin and iron metabolism: What we know and what we need to know

Iron is a life-supporting micronutrient that is required in the human diet, and is essential for maintaining physiological homeostasis. Properly harnessing a redox-active metal such as iron is a great challenge for cells and organisms because an excess of highly reactive iron catalyzes the formation of reactive oxygen species and can lead to cell and tissue damage. Quercetin is a typical flavonoid that is commonly found in fruits and vegetables and has versatile biological effects. From a classical viewpoint, owing to its unique chemical characteristics, quercetin has long been associated with iron metabolism only in the context of its iron-chelating and ROS-scavenging activities. However, within the field of human iron biology, expanding concepts of the roles of quercetin are flourishing, and great strides are being made in understanding the interactions between quercetin and iron. This progress highlights the varied roles of quercetin in iron metabolism, which involve much more than iron chelation alone. A review of these studies provides an ideal context to summarize recent progress and discuss compelling evidence for therapeutic opportunities that could arise from a better understanding of the underlying mechanisms.

Dietary flavonoid intake in older adults: how many days of dietary assessment are required and what is the impact of seasonality?

BACKGROUND

Within- and between-person variation in nutrient intake is well established, but little is known about variability in dietary flavonoid intake, including the effect of seasonality.

METHODS

Within- and between-individual variability of flavonoid intake, and intake of flavonoid subclasses was examined in older adults (n = 79; mean age 70.1 y (range: 60y-80y)), using three separate 4-day weighed food records (WFR) collected approximately 4 months apart. The effects of seasonality were also examined. Mixed-effects linear regression models were used to estimate within- and between-individual variance components for flavonoids and subclasses. The number of days of dietary assessment required for a high level of hypothetical accuracy was calculated from variance ratios.

RESULTS

Within- and between-individual variability was high for flavonoid intake, and intake of flavonoid subclasses, with variance ratios > 1. It was calculated that six days of WFR data are required for total flavonoid intake, and between 6 and 10 days was required for flavonoid subclasses. There was no effect of seasonality for total flavonoid intake or intake of flavonoid subclasses, with the exception that flavan-3-ol and flavanone intakes which were relatively low in summer, and in summer and winter, respectively.

CONCLUSION

While the effects of seasonality on total flavonoid intake may be small, within- and between-individual variation associated with flavonoid intake assessment appears to be substantial across 12 days of WFR data in older adults. It is recommended that a minimum of 6 days of weighed food records are collected to minimise the impact of within- and between-individual variability on total flavonoid intake assessments in this population.

Metabolic Characterization of the Anthocyanidin Reductase Pathway Involved in the Biosynthesis of Flavan-3-ols in Elite Shuchazao Tea (Camellia sinensis) Cultivar in the Field

Anthocyanidin reductase (ANR) is a key enzyme in the ANR biosynthetic pathway of flavan-3-ols and proanthocyanidins (PAs) in plants. Herein, we report characterization of the ANR pathway of flavan-3-ols in Shuchazao tea (Camellia sinesis), which is an elite and widely grown cultivar in China and is rich in flavan-3-ols providing with high nutritional value to human health. In our study, metabolic profiling was preformed to identify two conjugates and four aglycones of flavan-3-ols: (-)-epigallocatechin-gallate [(-)-EGCG], (-)-epicatechin-gallate [(-)-ECG], (-)-epigallocatechin [(-)-EGC], (-)-epicatechin [(-)-EC], (+)-catechin [(+)-Ca], and (+)-gallocatechin [(+)-GC], of which (-)-EGCG, (-)-ECG, (-)-EGC, and (-)-EC accounted for 70-85% of total flavan-3-ols in different tissues. Crude ANR enzyme was extracted from young leaves. Enzymatic assays showed that crude ANR extracts catalyzed cyanidin and delphinidin to (-)-EC and (-)-Ca and (-)-EGC and (-)-GC, respectively, in which (-)-EC and (-)-EGC were major products. Moreover, two ANR cDNAs were cloned from leaves, namely CssANRa and CssANRb. His-Tag fused recombinant CssANRa and CssANRb converted cyanidin and delphinidin to (-)-EC and (-)-Ca and (-)-EGC and (-)-GC, respectively. In addition, (+)-EC was observed from the catalysis of recombinant CssANRa and CssANRb. Further overexpression of the two genes in tobacco led to the formation of PAs in flowers and the reduction of anthocyanins. Taken together, these data indicate that the majority of leaf flavan-3-ols in Shuchazao's leaves were produced from the ANR pathway.

Relative Validity and Reproducibility of an Interviewer Administered 14-Item FFQ to Estimate Flavonoid Intake Among Older Adults with Mild-Moderate Dementia

There is a large burden on researchers and participants when attempting to accurately measure dietary flavonoid intake using dietary assessment. Minimizing participant and researcher burden when collecting dietary data may improve the validity of the results, especially in older adults with cognitive impairment. A short 14-item food frequency questionnaire (FFQ) to measure flavonoid intake, and flavonoid subclasses (anthocyanins, flavan-3-ols, flavones, flavonols, and flavanones) was developed and assessed for validity and reproducibility against a 24-hour recall. Older adults with mild-moderate dementia (n = 49) attended two interviews 12 weeks apart. With the assistance of a family carer, a 24-h recall was collected at the first interview, and the flavonoid FFQ was interviewer-administered at both time-points. Validity and reproducibility was assessed using the Wilcoxon signed-rank sum test, Spearman's correlation coefficient, Bland-Altman Plots, and Cohen's kappa. Mean flavonoid intake was determined (FFQ1 = 795 ± 492.7 mg/day, 24-h recall = 515.6 ± 384.3 mg/day). Tests of validity indicated the FFQ was better at estimating total flavonoid intake than individual flavonoid subclasses compared with the 24-h recall. There was a significant difference in total flavonoid intake estimates between the FFQ and the 24-h recall (Wilcoxon signed-rank sum p < 0.001; Bland-Altman plots indicated large bias and wide limits of agreement), but they were well correlated (Spearman's correlation coefficient r = 0.74, p < 0.001; Cohen's kappa κ = 0.292, p < 0.001). The FFQ showed good reproducibility, with a small mean percentage difference (12.6%). The Wilcoxon signed-rank sum test showed no significant difference, Spearman's correlation coefficient indicated excellent reliability (r = 0.75, p < 0.001), Bland-Altman plots visually showed small, nonsignificant bias and wide limits of agreement, and Cohen's kappa indicated fair agreement (κ = 0.429, p < 0.001). A 14-item FFQ developed to easily measure flavonoid intake in older adults with dementia demonstrates fair validity against a 24-h recall and good reproducibility.