Higher habitual intakes of flavonoids and flavonoid-rich foods are associated with a lower incidence of type 2 diabetes in the UK Biobank cohort.

AIM: To examine the associations of a diet high in flavonoid-rich foods, as reflected by a "Flavodiet Score" (FDS), the major individual food contributors to flavonoid intake, and flavonoid subclasses with type 2 diabetes (T2D) risk in the UK Biobank cohort. MATERIALS AND METHODS: Flavonoid intakes were estimated from ≥2 dietary assessments among 113,097 study participants [age at enrolment: 56 ± 8 years; 57% female] using the U.S Department of Agriculture (USDA) databases. Multivariable Cox proportional hazards models were used to investigate associations between dietary exposures and T2D. RESULTS: During 12 years of follow-up, 2628 incident cases of T2D were identified. A higher FDS (compared to lower [Q4 vs. Q1]), characterised by an average of 6 servings of flavonoid-rich foods per day, was associated with a 26% lower T2D risk [HR: 0.74 (95% CI: 0.66-0.84), ptrend = <0.001]. Mediation analyses showed that lower body fatness and basal inflammation, as well as better kidney and liver function partially explain this association. In food-based analyses, higher intakes of black or green tea, berries, and apples were significantly associated with 21%, 15%, and 12% lower T2D risk. Among individual flavonoid subclasses, 19-28% lower risks of T2D were observed among those with the highest, compared to lowest intakes. CONCLUSIONS: A higher consumption of flavonoid-rich foods was associated with lower T2D risk, potentially mediated by benefits to obesity/sugar metabolism, inflammation, kidney and liver function. Achievable increases in intakes of specific flavonoid-rich foods have the potential to reduce T2D risk.

Higher Habitual Dietary Intakes of Flavanols and Anthocyanins Differentially Associate with Lower Incidence of Ischemic Stroke Subtypes-A Follow-Up Analysis.

BACKGROUND: We previously reported that habitual consumption of dietary flavanol oligomers + polymers and anthocyanins is associated with a lower risk of ischemic stroke. However, no studies have investigated their relationship with ischemic stroke subtypes. OBJECTIVES: In this follow-up analysis, we aimed to examine the association of flavanol oligomers + polymers and anthocyanin intake with ischemic stroke subtypes, including the following: 1) large-artery atherosclerosis, 2) cardioembolism, 3) small-vessel occlusion, 4) other determined etiology, and 5) undetermined etiology. METHODS: Participants (n = 55,094) from the Danish Diet, Cancer, and Health Study were followed up for <16 y for first-time ischemic stroke events, which were classified according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. Intakes of flavanol oligomers + polymers and anthocyanins were calculated from food frequency questionnaires using the Phenol-Explorer database, and their relationships with ischemic stroke subtypes were investigated using restricted cubic splines within Cox proportional hazards models. After multivariable adjustment, higher habitual intakes (quintile 5 compared with quintile 1) of flavanol oligomers + polymers and anthocyanins were associated with a lower risk of specific ischemic stroke subtypes, including large-artery atherosclerosis [flavanol oligomers + polymers, hazard ratio {HR} (95% confidence interval {CI}): 0.64 (0.47, 0.87)], cardioembolism [anthocyanins, HR (95% CI): 0.45 (0.25, 0.82)], and small-vessel occlusion [flavanol oligomers + polymers, HR (95% CI): 0.65 (0.54, 0.80); anthocyanins, HR (95% CI): 0.79 (0.64, 0.97)], but not stroke of other determined or undetermined etiology. CONCLUSIONS: Higher habitual intakes of flavanols and anthocyanins are differentially associated with a lower risk of ischemic stroke from atherosclerosis and/or cardioembolism but not with other subtypes.

Performance of Urinary Phenyl-γ-Valerolactones as Biomarkers of Dietary Flavan-3-ol Exposure.

BACKGROUND: Phenyl-γ-valerolactones (PVLs) have been identified as biomarkers of dietary flavan-3-ol exposure, although their utility requires further characterization. OBJECTIVES: We investigated the performance of a range of PVLs as biomarkers indicative of flavan-3-ol intake. METHODS: We report the results of 2 companion studies: a 5-way randomized crossover trial (RCT) and an observational cross-sectional study. In the RCT (World Health Organization, Universal Trial Number: U1111-1236-7988), 16 healthy participants consumed flavan-3-ol-rich interventions (of apple, cocoa, black tea, green tea, or water [control]) for 1 d each. First morning void samples and 24-h urine samples were collected with diet standardized throughout. For each participant, 1 intervention period was extended (to 2 d) to monitor PVL kinetics after repeat exposure. In the cross-sectional study, 86 healthy participants collected 24-h urine samples, and concurrent weighed food diaries from which flavan-3-ol consumption was estimated using Phenol-Explorer. A panel of 10 urinary PVLs was quantified using liquid chromatography tandem mass spectrometry. RESULTS: In both studies, 2 urinary PVLs [5-(3'-hydroxyphenyl)-γ-valerolactone-4'-sulfate and putatively identified 5-(4'-hydroxyphenyl)-γ-valerolactone-3'-glucuronide] were the principal compounds excreted (>75%). In the RCT, the sum of these PVLs was significantly higher than the water (control) after each intervention; individually, there was a shift from sulfation toward glucuronidation as the total excretion of PVLs increased across the different interventions. In the extended RCT intervention period, no accumulation of these PVLs was observed after consecutive days of treatment, and after withdrawal of treatment on the third day, there was a return toward negligible PVL excretion. All results were consistent, whether compounds were measured in 24-h urine or first morning void samples. In the observational study, the sum of the principal PVLs correlated dose dependently (Rs = 0.37; P = 0.0004) with dietary flavan-3-ol intake, with similar associations for each individually. CONCLUSIONS: Urinary 5-(3'-hydroxyphenyl)-γ-valerolactone-4'-sulfate and putatively identified 5-(4'-hydroxyphenyl)-γ-valerolactone-3'-glucuronide are recommended biomarkers for dietary flavan-3-ol exposure.

Intake of dietary flavonoids and incidence of ischemic heart disease in the Danish Diet, Cancer, and Health cohort.

BACKGROUND/OBJECTIVES: Few studies have investigated the association between dietary flavonoid intake, including all major subclasses, and the long-term risk of ischemic heart disease (IHD). We examined whether dietary flavonoid intake associated with IHD incidence, assessing the possible modifying role of sex and smoking, in participants from the Danish Diet, Cancer, and Health study. SUBJECTS/METHODS: In a cohort study design, 54,496 adults (46.8% male), aged 50-64 years, without a history of IHD, were followed for up to 23 years. Habitual dietary flavonoid intake was estimated from food frequency questionnaires using Phenol-Explorer. Incident cases of IHD were identified within Danish nationwide health registries. Restricted cubic splines in Cox proportional hazards models were used to examine associations between flavonoid intake and IHD risk. RESULTS: During follow-up, 5560 IHD events were recorded. No overall association was seen between total flavonoid intake, nor any subclass, and IHD, following adjustment for demographics, lifestyle, and dietary confounders. Stratified by sex and smoking status, higher intakes of specific subclasses associated with lower IHD risk among ever-smokers [Q5 vs. Q1 flavonols HR (95% CI): 0.90 (0.82, 0.99); flavanol oligo+polymers: 0.88 (0.80, 0.97)], but not among never-smokers, nor either sex specifically. CONCLUSIONS: While we did not find clear evidence that higher habitual dietary flavonoid intake was associated with lower IHD risk, these results do not exclude the possibility that certain subclasses may have a protective role in prevention of IHD among population sub-groups; this was evident among smokers, who are at a higher risk of atherosclerosis.

Higher Habitual Dietary Flavonoid Intake Associates With Less Extensive Abdominal Aortic Calcification in a Cohort of Older Women.

BACKGROUND: The extent of abdominal aortic calcification (AAC) is a major predictor of vascular disease events. We have previously found regular apple intake, a major source of dietary flavonoids, associates with lower AAC. Whether total dietary flavonoid intake impacts AAC remains unknown. Here, we extend our observations to habitual intakes of total flavonoids, flavonoid subclasses, and specific flavonoid-containing foods, with the odds of extensive AAC. METHODS: We conducted cross-sectional analyses on 881 females (median [interquartile range] age, 80 [78-82] years; body mass index, 27 [24-30] kg/m2) from the PLSAW (Perth Longitudinal Study of Ageing Women). Flavonoid intake was calculated from food-frequency questionnaires. Calcifications of the abdominal aorta were assessed on lateral lumbar spine images and categorized as less extensive or extensive. Logistic regression was used to investigate associations. RESULTS: After adjusting for demographic, lifestyle and dietary confounders, participants with higher (Q4), compared with lower (Q1) intakes, of total flavonoids, flavan-3-ols, and flavonols had 36% (odds ratio [95% CI], 0.64 [0.43-0.95]), 39% (0.61 [0.40-0.93]) and 38% (0.62 [0.42-0.92]) lower odds of extensive AAC, respectively. In food-based analyses, higher black tea intake, the main source of total flavonoids (75.9%), associated with significantly lower odds of extensive AAC (2-6 cups/d had 16%-42% lower odds compared with 0 daily intake). In a subset of nonconsumers of black tea, the association of total flavonoid intake with AAC remained (Q4 versus Q1 odds ratio [95% CI], 0.11 [0.02-0.54]). CONCLUSIONS: In older women, greater habitual dietary flavonoid intake associates with less extensive AAC.

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 ß-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 ß-cell function (HOMA2-% ß) 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 intakes inversely associate with COPD in smokers.

INTRODUCTION: Higher flavonoid intakes are beneficially associated with pulmonary function parameters; however, their association with chronic obstructive pulmonary disease (COPD) is unknown. This study aimed to examine associations between intakes of 1) total flavonoids, 2) flavonoid subclasses and 3) major flavonoid compounds with incident COPD in participants from the Danish Diet, Cancer and Health study. METHODS: This prospective cohort included 55 413 men and women without COPD, aged 50-65 years at recruitment. Habitual flavonoid intakes at baseline were estimated from a food frequency questionnaire using Phenol-Explorer. Danish nationwide registers were used to identify incident cases of COPD. Associations were modelled using restricted cubic splines within Cox proportional hazards models. RESULTS: During 23 years of follow-up, 5557 participants were diagnosed with COPD. Of these, 4013 were current smokers, 1062 were former smokers and 482 were never-smokers. After multivariable adjustments, participants with the highest total flavonoid intakes had a 20% lower risk of COPD than those with the lowest intakes (quintile 5 versus quintile 1: HR 0.80, 95% CI 0.74-0.87); a 6-22% lower risk was observed for each flavonoid subclass. The inverse association between total flavonoid intake and COPD was present in both men and women but only in current smokers (HR 0.77, 95% CI 0.70-0.84) and former smokers (HR 0.82, 95% CI 0.69-0.97), not never-smokers. Furthermore, higher flavonoid intakes appeared to lessen, but not negate, the higher risk of COPD associated with smoking intensity. CONCLUSION: Dietary flavonoids may be important for partially mitigating the risk of smoking-related COPD. However, smoking cessation should remain the highest priority.

Higher habitual dietary flavonoid intake associates with lower central blood pressure and arterial stiffness in healthy older adults.

Flavonoids have shown anti-hypertensive and anti-atherosclerotic properties: the impact of habitual flavonoid intake on vascular function, central haemodynamics and arterial stiffness may be important. We investigated the relationship between habitual flavonoid consumption and measures of central blood pressure and arterial stiffness. We performed cross-sectional analysis of 381 non-smoking healthy older adults (mean age 66·0 (sd 4·1) years; BMI, 26·4 (sd 4·41) kg/m2; 41 % male) recruited as part of the Australian Research Council Longevity Intervention study. Flavonoid intake (i.e. flavonols, flavones, flavanones, anthocyanins, isoflavones, flavan-3-ol monomers, proanthocyanidins, theaflavins/thearubigins and total consumption) was estimated from FFQ using the US Department of Agriculture food composition databases. Measures of central haemodynamics and arterial stiffness included systolic blood pressure (cSBP), diastolic blood pressure (cDBP), mean arterial pressure (cMAP) and augmentation index (cAIx). After adjusting for demographic and lifestyle confounders, each sd/d higher intake of anthocyanins ((sd 44·3) mg/d) was associated with significantly lower cDBP (-1·56 mmHg, 95 % CI -2·65, -0·48) and cMAP (-1·62 mmHg, 95 % CI -2·82, -0·41). Similarly, each sd/d higher intake of flavanones ((sd 19·5) mg/d) was associated with ~1 % lower cAIx (-0·93 %, 95 % CI -1·77, -0·09). These associations remained significant after additional adjustment for (1) a dietary quality score and (2) other major nutrients that may affect blood pressure or arterial stiffness (i.e. Na, K, Ca, Mg, n-3, total protein and fibre). This study suggests a possible benefit of dietary anthocyanin and flavanone intake on central haemodynamics and arterial stiffness; these findings require corroboration in further research.

Habitual flavonoid intake and ischemic stroke incidence in the Danish Diet, Cancer, and Health Cohort.

BACKGROUND: Flavonoid-rich foods have antiinflammatory, antiatherogenic, and antithrombotic properties that may contribute to a lower risk of ischemic stroke. OBJECTIVES: We aimed to investigate the relationship between habitual flavonoid consumption and incidence of ischemic stroke in participants from the Danish Diet, Cancer and Health Study. DESIGN: In this prospective cohort study, 55,169 Danish residents without a prior ischemic stroke [median (IQR) age at enrolment of 56 y (52-60)], were followed for 21 y (20-22). We used Phenol-Explorer to estimate flavonoid intake from food frequency questionnaires obtained at study entry. Incident cases of ischemic stroke were identified from Danish nationwide registries and restricted cubic splines in Cox proportional hazards models were used to investigate relationships with flavonoid intake. RESULTS: During follow-up, 4237 individuals experienced an ischemic stroke. Compared with participants in Q1 and after multivariable adjustment for demographics and lifestyle factors, those in Q5-for intake of total flavonoids, flavonols, and flavanol oligo + polymers-had a 12% [HR (95% CI): 0.88 (0.81, 0.96)], 10% [0.90 (0.82, 0.98)], and 18% [0.82 (0.75, 0.89)] lower risk of ischemic stroke incidence, respectively. Multivariable (demographic and lifestyle) adjusted associations for anthocyanins and flavones with risk of ischemic stroke were not linear, with moderate but not higher intakes associated with lower risk [anthocyanins Q3 vs. Q1 HR (95% CI): 0.85 (0.79, 0.93); flavones: 0.90 (0.84, 0.97)]. Following additional adjustment for dietary confounders, similar point estimates were observed; however, significance was only retained for anthocyanins and flavanol oligo + polymers [anthocyanins Q3 vs. Q1 HR (95% CI): 0.86 (0.79, 0.94); flavanol oligo + polymers Q5 vs. Q1 0.86 (0.78, 0.94)]. CONCLUSIONS: These findings suggest that moderate habitual consumption of healthy flavonoid-rich foods is associated with a lower risk of ischemic stroke and further investigation is therefore warranted.

Performance of Predictive Equations and Biochemical Measures Quantifying Net Endogenous Acid Production and the Potential Renal Acid Load.

INTRODUCTION: A limited number of studies have assessed the accuracy and precision of methods for determining the net endogenous acid production (NEAP) and its components. We aimed to investigate the performance of methods quantifying the diet dependent acid-base load. METHODS: Data from metabolic balance studies enabled calculations of NEAP according to the biochemical measures (of net acid excretion [NAE], urinary net endogenous acid production [UNEAP], and urinary potential renal acid load [UPRAL]) as well as estimative diet equations (by Frassetto et al., Remer and Manz, Sebastian et al., and Lemann) that were compared among themselves in healthy participants fed both acid and base forming diets for 6 days each. RESULTS: Seventeen participants (mean ± SD age, 60 ± 8 years; body mass index, 23 ± 2 kg/m2) provided 102 twenty-four-hour urine samples for analysis (NAE, 39 ± 38 mEq/d [range, -9 to 95 mEq/d]). Bland-Altman analysis comparing UNEAP to NAE showed good accuracy (bias, -2 mEq/d [95% confidence interval {CI}, -8 to 3]) and modest precision (limits of agreement, -32 to 28 mEq/d). Accurate diet equations included potential renal acid load (PRAL) by Sebastian et al. (bias, -4 mEq/d [95% CI, -8 to 0]) as well as NEAP by Lemann et al. (bias, 4 mEq/d [95% CI, -1 to 9]) and Remer and Manz (bias, -1 mEq/d [95% CI, -6 to 3]). CONCLUSIONS: Researchers are encouraged to collect measures of UPRAL and UNEAP; however, investigators drawing conclusions between the diet-dependent acid-base load and human health should consider the limitations within all methods.

An overview and update on the epidemiology of flavonoid intake and cardiovascular disease risk.

There is an accumulating body of literature reporting on dietary flavonoid intake and the risk of cardiovascular disease (CVD) in prospective cohort studies. This makes apparent the need for an overview and update on the current state of the science. To date, at least 27 prospective cohorts (in 44 publications) have evaluated the association between estimated habitual flavonoid intake and CVD risk. At this time, the totality of evidence suggests long-term consumption of flavonoid-rich foods may be associated with a lower risk of fatal and non-fatal ischemic heart disease (IHD), cerebrovascular disease, and total CVD; disease outcomes which are principally, though not exclusively, composed of cases of atherosclerotic CVD (ASCVD). To date, few studies have investigated outcome specific ASCVD, such as peripheral artery disease (PAD) or ischemic stroke. Of the flavonoid subclasses investigated, evidence more often implicates diets rich in anthocyanins, flavan-3-ols, and flavonols in lowering the risk of CVD. Although inferences are restricted by confounding and other inherent limitations of observational studies, causality appears possible based on biological plausibility, temporality, and the relative consistency of the reported associations. However, whether the associations observed represent a benefit of the isolated bioactives per se, or are a signal of the bioactives acting in concert with the co-occurring nutrient matrix within flavonoid-bearing foods, are issues of consideration. Thus, the simple interpretation, and the one most relevant for dietary advice, is that consumption of flavonoid-rich foods or diets higher in flavonoids, appear nutritionally beneficial in the prevention of CVD.

Spot-testing urine pH, a novel dietary biomarker? A randomised cross-over trial.

AIM: Spot-tests of urine pH are claimed to be an accessible biomarker of net acid excretion (NAE), and as such, they may be able to determine changes in an individual's intake of acid- or base-forming foods. To test this hypothesis, we aimed to determine if spot-tests of urine pH could index NAE and relay the consumption of a fruit and vegetable (F&V) concentrate whilst determining this concentrate's capacity to modulate NAE. METHODS: In a double blind, placebo-controlled, cross-over trial, healthy adults (n = 13) were allocated by simple randomisation to receive a F&V concentrate or placebo for three days each, with diet standardised throughout. Measurements of 24-hour NAE, 24-hour urine pH and spot-tests of urine pH were taken throughout the study. RESULTS: The 24-hour urine pH predicted 24-hour NAE (P = <0.0001). However, spot-tested urine pH displayed prediction intervals too wide to infer 24-hour NAE and inconsistent ability to reflect concentrate ingestion, despite 24-hour NAE and 24-hour urine pH decreasing (-25.8 mEq, 95% CI -44.3 to -7.4, P = 0.01, d = 0.94) and increasing (+0.51, 95% CI 0.25-0.79, P = 0.002, d = 1.3), respectively, following supplementation. CONCLUSIONS: Spot-tests of urine pH are not a valid dietary biomarker of daily NAE and were unable to reliably track changes, despite a F&V concentrate clearly modulating the daily rate of NAE.

Accuracy and precision of estimation equations to predict net endogenous acid excretion using the Australian food database.

AIM: The gold standard of measurement for net endogenous acid production (NEAP) is net acid excretion (NAE), a test that is not readily available, and consequently, estimative equations by Remer and Manz and Frassetto et al. are often used. These equations rely on nutrient databases and it is recommended that their validity be assessed using a country's database before their application in research in that country. We sought to delineate the accuracy and precision of these estimation equations using the Australian food database. METHODS: In a double blind, randomised, cross-over fashion, healthy participants (n = 13) residing in regional Australia were exposed to varying net acid loads while they collected weighted food diaries and 24-hour urine samples for measurement of NAE. RESULTS: In comparison to the Frassetto et al. equations (equation one bias = -57.1 mEq/day, equation two bias = -32.8 mEq/day), only the Remer and Manz equation was accurate (bias = -5.4 mEq/day); however, all equations were imprecise. CONCLUSIONS: Using the Australian database, the performance of these equations to predict NEAP appears equal to other databases; however, caveats apply in their application. For future research, the equation by Remer and Manz is preferential for group estimates. None of the equations are recommended for individual estimates.