Consumption of ultra-processed food (UPF) has been associated with several chronic diseases and poor diet quality. It is reasonable to speculate that the consumption of UPF negatively associates with flavonoid dietary intake; however, this assumption has not been previously examined. The present study aims to assess association between the dietary contribution of UPF and flavonoid intake in the US population aged 0 years and above. We performed a cross-sectional analysis of dietary data collected by 24-h recalls from 7640 participants participating in the National Health and Nutrition Examination Survey 2017–2018. Foods were classified according to the Nova classification system. The updated US Department of Agriculture (USDA) Database for the Flavonoid Content of Selected Foods (Release 3.3) database was used to estimate total and six classes of flavonoid intakes. Flavonoid intakes were compared across quintiles of dietary contribution of UPF (% of total energy intake) using linear regression models. The total and five out of six class flavonoid intakes decreased between 50 and 70 % across extreme quintiles of the dietary contribution of UPF (Pfor linear trend < 0·001); only isoflavones increased by over 260 %. Our findings suggest that consumption of UPF is associated with lower total and five of six class flavonoid intakes and with higher isoflavone intakes, supporting previous evidence of the negative impact of UPF consumption on the overall quality of the diet and health outcomes.

Epidemiological studies have suggested that flavonoids exhibit preventive effects on degenerative diseases. However, lack of sufficient data on flavonoid intake has limited evaluating the proposed effects in populations. Therefore, we aimed to estimate the total and individual flavonoid intakes among Korean adults and determine the major dietary sources of these flavonoids. We constructed a flavonoid database of common Korean foods, based on the food list reported in the 24-h recall of the Korea National Health and Nutrition Examination Survey (KNHANES) 2007–2012, using data from the Korea Functional Food Composition Table, US Department of Agriculture flavonoid database, Phenol-Explorer database and other analytical studies. This database, which covers 49 % of food items and 76 % of food intake, was linked with the 24-h recall data of 33 581 subjects aged ≥19 years in the KNHANES 2007–2012. The mean daily intake of total flavonoids in Korean adults was 318·0 mg/d, from proanthocyanidins (22·3 %), flavonols (20·3 %), isoflavones (18·1 %), flavan-3-ols (16·2 %), anthocyanidins (11·6 %), flavanones (11·3 %) and flavones (0·3 %). The major contributing food groups to the flavonoid intake were fruits (54·4 %), vegetables (20·5 %), legumes and legume products (16·2 %) and beverages and alcohols (3·1 %), and the major contributing food items were apples (21·9 %), mandarins (12·5 %), tofu (11·5 %), onions (9·6 %) and grapes (9·0 %). In the regression analysis, the consumption of legumes and legume products, vegetables and fruits predicted total flavonoid intake the most. The findings of this study could facilitate further investigation on the health benefits of flavonoids and provide the basic information for establishing recommended flavonoid intakes for Koreans.

This study examines the relationship between long-term intake of six flavonoid classes and incidence of CVD and CHD, using a comprehensive flavonoid database and repeated measures of intake, while accounting for possible confounding by components of a healthy dietary pattern. Flavonoid intakes were assessed using a FFQ among the Framingham Offspring Cohort at baseline and three times during follow-up. Cox proportional hazards regression was used to characterise prospective associations between the natural logarithms of flavonoid intakes and CVD incidence using a time-dependent approach, in which intake data were updated at each examination to represent average intakes from previous examinations. Mean baseline age was 54 years, and 45 % of the population was male. Over an average 14·9 years of follow-up among 2880 participants, there were 518 CVD events and 261 CHD events. After multivariable adjustment, only flavonol intake was significantly associated with lower risk of CVD incidence (hazard ratios (HR) per 2·5-fold flavonol increase=0·86, Ptrend=0·05). Additional adjustment for total fruit and vegetable intake and overall diet quality attenuated this observation (HR=0·89, Ptrend=0·20 and HR=0·92, Ptrend=0·33, respectively). There were no significant associations between flavonoids and CHD incidence after multivariable adjustment. Our findings suggest that the observed association between flavonol intake and CVD risk may be a consequence of better overall diet. However, the strength of this non-significant association was also consistent with relative risks observed in previous meta-analyses, and therefore a modest benefit of flavonol intake on CVD risk cannot be ruled out.

Observational studies have suggested that the intake of flavonoids is associated with a decreased risk of CVD. However, the results of these studies remain controversial. The aim of the present study was to evaluate the association between dietary flavonoid intake and CVD risk by conducting a systematic review of prospective cohort studies. Electronic reference databases were searched to identify studies that met the pre-stated inclusion criteria. The studies were assessed for eligibility and data were extracted by two authors independently. For each study, relative risks (RR) and 95 % CI were extracted and pooled using either a fixed-effects or a random-effects model. Generalised least-squares trend estimation analysis was used to evaluate dose–response relationships. The inclusion criteria were met by fourteen prospective cohort studies. The intakes of anthocyanidins (RR 0·89, 95 % CI 0·83, 0·96), proanthocyanidins (RR 0·90, 95 % CI 0·82, 0·98), flavones (RR 0·88, 95 % CI 0·82, 0·96), flavanones (RR 0·88, 95 % CI 0·82, 0·96) and flavan-3-ols (RR 0·87, 95 % CI 0·80, 0·95) were inversely associated with the risk of CVD when comparing the highest and lowest categories of intake. A similar association was observed for flavonol intake and CVD risk. Sensitivity and subgroup analyses further supported this association. The summary RR for CVD for every 10 mg/d increment in flavonol intake was 0·95 (95 % CI 0·91, 0·99). The present systematic review suggests that the dietary intakes of six classes of flavonoids, namely flavonols, anthocyanidins, proanthocyanidins, flavones, flavanones and flavan-3-ols, significantly decrease the risk of CVD.