Abstract
Keywords
Introduction
Chronic low-grade inflammation contributes to a broad range of non-communicable diseases, including cardiovascular disorders, metabolic syndrome, neurodegenerative conditions, and cancer.1–3 Persistent immune activation coupled with oxidative stress accelerates ageing and disease progression, forming self-reinforcing cycles of cellular injury and impaired repair.4,5 This state, often termed inflammaging, is characterized by sustained, subclinical inflammation and dysregulated redox balance that gradually undermines tissue function.6–8 Identifying dietary exposures that may modulate this inflammation milieu is therefore an important objective in preventive and nutritional medicine.
Flavonoids are a structurally diverse family of plant-derived polyphenols found in fruits, vegetables, tea, wine, and many medicinal plants, and have been widely studied for antioxidant, anti-inflammatory, and anticancer activities.9,10 Experimental evidence suggests that flavonoids can attenuate proinflammatory cytokine production, inhibit NF-κB and mitogen-activated protein kinase (MAPK) dependent pathways, and strengthen endogenous antioxidant defenses.11–14 Epidemiological evidence also associates higher flavonoid consumption with improved cardiometabolic health and reduced inflammation.15,16 However, associations vary across flavonoid subclasses and individual compounds, likely reflecting differences in chemical structure, dietary sources, metabolism, and bioavailability.
A growing body of evidence suggests that flavonoid actions in humans may be driven less by the parent compounds than by their metabolites.17,18 After ingestion, many flavonoids undergo rapid phase II conjugation and microbiome-dependent biotransformation to smaller phenolic acids that often predominate in circulation and may mediate biological activity. 19 This is particularly relevant for anthocyanins, whose metabolites have been implicated in redox and inflammation regulatory pathways. 20 For cyanidin-containing anthocyanins, protocatechuic acid has been proposed as a major metabolite with anti-inflammatory effects involving oxidative stress responses and NF-κB related pathways.21,22 These observations motivate exposure assessments that distinguish flavonoids at both the subclass and monomer levels.
To quantify systemic inflammation at scale, blood count derived indices provide pragmatic markers that capture coordinated shifts across innate and adaptive immune compartments. The neutrophil-to-lymphocyte ratio (NLR), systemic immune–inflammation index (SII), and systemic inflammation response index (SIRI) integrate neutrophils and lymphocytes with platelets or monocytes.23–25 Because redox regulation is tightly coupled to immune cell activation, these indices offer a useful framework for evaluating metabolite-informed hypotheses in population data.
Here, we used the National Health and Nutrition Examination Survey (NHANES, 2007-2008, 2009-2010, and 2017-2018) to examine associations between dietary flavonoid intake and systemic inflammation, quantified by NLR, SII, SIRI. We aimed to (i) compare total flavonoids and six subclasses across each inflammatory index, (ii) identify monomeric flavonoids most consistently associated with these indices, and (iii) generate testable mechanistic hypotheses by integrating network pharmacology and molecular docking to prioritize candidate targets and pathways.
Materials and Methods
Study Design
This cross-sectional analysis was conducted and reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement. 26 The NHANES is a biennial, cross-sectional program by the National Center for Health Statistics (NCHS) that evaluates the health and nutrition of the non-institutionalized U.S. population. 27 The NCHS Ethics Review Board approved the survey protocols, and all participants gave written informed consent following the revised Declaration of Helsinki principles. The NHANES data can be accessed publicly at https://wwwn.cdc.gov/nchs/nhanes/.
Dietary flavonoid intake data are available only in NHANES 2007-2008, 2009-2010, and 2017-2018. Therefore, we pooled participants from these cycles (initial n = 29 940) and restricted the analysis to adults aged ≥18 years (excluded n = 11 329). We then excluded participants with missing dietary flavonoid intake data (n = 1886), followed by those missing any systemic inflammation index required for the analysis (NLR, SII, or SIRI; n = 781). Finally, individuals with missing covariate data were excluded (n = 3263). After these sequential exclusions (Figure 1), the final analytic sample included 12 681 participants. Data quality was maintained by performing completeness and consistency checks without imputation. Potential selection bias was evaluated by comparing baseline characteristics of included versus excluded participants using weighted standardized mean differences and a weighted logistic regression model predicting inclusion.

Flowchart of participant inclusion.
Assessment of Flavonoid Intake
Dietary flavonoid intake was estimated using data from the Flavonoid Database of the United States Department of Agriculture (USDA) Food and Nutrient Database for Dietary Studies (FNDDS).28,29 This database provides comprehensive information on the content of 29 individual flavonoids, encompassing six major subclasses, and corresponds to each relevant NHANES dietary cycle.
Participants’ daily intake of total and specific flavonoid subclasses was estimated using two 24-h dietary recalls. 30 They were assisted by trained interviewers to detail all foods and beverages consumed in the previous 24 h, including meals, snacks, and drinks, with specific descriptions and quantities. The first recall was completed through an in-person interview, followed by a telephone interview approximately one week later. The average daily intake for each participant was determined by calculating the mean of the two recalls, or using the single available recall if only one was provided. To facilitate comparisons, total dietary flavonoid intake was categorized into weighted quartiles Q1–Q4.
Measurement of Systemic Inflammation
Systemic inflammation was assessed through three composite indices: the NLR, the SIRI, and the SII. These parameters offer a comprehensive assessment of inflammatory and immune status, indicating the dynamic equilibrium between innate and adaptive immune responses.31–34 They have been increasingly recognized as reliable indicators of systemic inflammation and immune surveillance in epidemiological research.
Certified medical personnel collected venous blood samples following standardized protocols at the Mobile Examination Centers (MECs). 35 All procedures adhered to rigorous quality assurance standards to minimize preanalytical variability. Complete blood counts (CBCs) were obtained using automated hematology analyzers that quantified leukocyte subtypes and platelets based on optical scatter, laser detection, or electrical impedance. Neutrophils, lymphocytes, monocytes, and platelets were quantified as cells per microliter of blood. Quality control was maintained through routine calibration with standardized reference materials and ongoing performance monitoring of analytical instruments. Each assay underwent internal validation to ensure precision and reproducibility. The NHANES Laboratory and Medical Technologists Procedures Manual provides comprehensive laboratory procedures (accessible at https://wwwn.cdc.gov/nchs/nhanes/).
The indices were calculated using the formula: NLR = Neutrophil Count / Lymphocyte Count. SIRI is calculated by multiplying the neutrophil count by the monocyte count and dividing the result by the lymphocyte count. SII is calculated by multiplying the platelet count by the neutrophil count and dividing by the lymphocyte count.
Covariates
Based on prior literature and biological considerations, we prespecified a comprehensive set of covariates with established links to inflammation. Sociodemographic variables included age (years, continuous), sex (male or female), race/ethnicity (non-Hispanic White, non-Hispanic Black, other Hispanic, or other race), education (below high school, high school graduate, or above high school), poverty–income ratio (PIR, continuous), and marital status (married/living with partner, widowed/divorced/separated, or never married). Health behaviors included smoking status, categorized as never (<100 cigarets in lifetime), former (≥100 cigarets in lifetime and not currently smoking), and current (≥100 cigarets in lifetime and currently smoking). Alcohol use was defined as ever consuming ≥12 alcoholic drinks in one year. Physical activity was classified using guideline-based thresholds 36 : active (≥150 min/week moderate activity or ≥75 min/week vigorous activity, or an equivalent combination), insufficiently active (some activity but below these thresholds), and inactive (no reported moderate or vigorous activity). Clinical and nutritional covariates included body mass index (BMI), 37 categorized as underweight (<18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), and obese (≥30.0 kg/m2); total energy intake (kcal/day, continuous); and glycated hemoglobin (HbA1c; %, continuous). We additionally accounted for self-reported physician diagnoses of chronic conditions that may influence inflammation milieu: asthma, congestive heart failure, coronary heart disease, myocardial infarction, stroke, cancer or malignancy, and chronic obstructive pulmonary disease (COPD).
Statistical Analysis
All analyses accounted for NHANES's complex, multistage sampling design using the survey package in R (version 4.5.1), incorporating sampling strata, primary sampling units, and Mobile Examination Center (MEC) examination weights to obtain nationally representative estimates.
38
To facilitate comparisons across flavonoid variables with different distributions, exposures were standardized to an interquartile-range (IQR) increment. Associations between each flavonoid and inflammatory index were evaluated using weighted linear regression:
We constructed three models: Model 1 (M1): unadjusted; Model 2 (M2): adjusted for age and sex; Model 3 (M3): adjusted for the full covariate set. Estimates are presented as regression coefficients (β) per IQR increase in intake with 95% confidence intervals (CIs), and were visualized in forest plots. To address multiple comparisons, false discovery rate (FDR) correction was applied within each outcome for subclass and monomer level analyses, with FDR-adjusted q values reported alongside nominal
Potential dose–response patterns were assessed using restricted cubic spline (RCS) models within the fully adjusted framework. Spline curves are presented as adjusted differences relative to the survey-weighted median intake (reference), with two-sided tests for both the overall association and nonlinearity. For descriptive comparisons across quartiles of total flavonoid intake, categorical variables were compared using survey-weighted χ2 tests, and continuous variables using survey-weighted linear regression. All tests were two-sided, and statistical significance was defined as
Target-Disease Intersection for Cyanidin and Inflammation
Putative cyanidin targets were retrieved from SwissTargetPrediction (https://www.swisstargetprediction.ch/) and PharmMapper (https://www.lilab-ecust.cn/pharmmapper/). SwissTargetPrediction draws on known ligand–target associations and similarity-based inference, but its coverage is shaped by existing annotations and the chemical space represented in reference datasets. 39 PharmMapper enables structure-based target prediction via pharmacophore mapping, although performance depends on the breadth and quality of available pharmacophore and structural models. 40
Inflammation-associated genes were retrieved from GeneCards (https://www.genecards.org/) by querying “inflammation”, which integrates evidence across multiple multi-omics databases but can include heterogeneous and publication-influenced gene–phenotype links. After mapping to reviewed human proteins in UniProt, 41 overlapping targets were identified by Venn intersection to prioritize candidates for downstream network analyses. 42 This workflow is intended to nominate candidates and is inherently hypothesis-generating, requiring experimental validation.
Protein–Protein Interaction (PPI) Network Construction and Functional Enrichment
The intersecting gene set was input into the STRING database for Homo sapiens to develop the protein-protein interaction (PPI) network. 43 To emphasize reliable functional links and limit spurious connectivity, we applied a high-confidence interaction threshold of 0.70 and removed isolated nodes. Network visualization and topological analysis were conducted using Cytoscape (version 3.10.3). 44 Nodes exhibiting the highest degree centrality were defined as hub targets, representing potential key regulators within the interaction network.
Functional enrichment analyses for Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were conducted via the DAVID database (https://david.ncifcrf.gov/). 45 Enrichment was considered significant for P-values less than 0.05.
Molecular Docking Validation of Hub Targets
Three-dimensional structures of the identified hub proteins were sourced from the RCSB Protein Data Bank (https://www.rcsb.org/). 46 Before docking, bound ligands and water molecules were removed, and polar hydrogens were added using AutoDockTools (v1.5.7). 47 The 3D structure of cyanidin was obtained from PubChem (https://pubchem.ncbi.nlm.nih.gov/).
Molecular docking simulations utilized AutoDock Vina (v1.2.3) with grid boxes centered on the predicted active sites of each protein. 48 Binding affinities with docking energies ≤–5.0 kcal/mol were used as a screening criterion consistent with thermodynamically favorable binding in silico for small-molecule interactions. The docking conformations and intermolecular interaction patterns were visualized and analyzed using Discovery Studio.
Results
Baseline Characteristics of Participants
Baseline characteristics across quartiles of total flavonoid intake are summarized in Table 1. The final analysis included 12 681 participants (median age: 47.00 years), representing a weighted population of 174 994 071 US adults. Median total flavonoid intake was 70.59 mg/day (IQR, 25.36-265.61). Participants in higher intake quartiles reported greater total energy intake (
Weighted Baseline Characteristics of Participants.
Continuous variables are reported as weighted median (IQR); categorical variables are shown as weighted percentages. Abbreviation: WBC, white blood cell; NLR, neutrophil-to-lymphocyte ratio; SIRI, systemic inflammation response index; SII, systemic immune-inflammation index.
Detailed subclass and compound-level intakes stratified by total flavonoid quartiles are shown in Table 2. Differences across quartiles were largely driven by flavan-3-ols, which rose from 2.96 (IQR, 0.90-5.90) mg/day in Q1 to 474.64 (IQR, 307.03-790.47) mg/day in Q4 (
Flavonoid Intakes of Studied Participants.
Associations of Flavonoid Classes with Systemic Inflammation
To evaluate associations between flavonoid intake and systemic inflammation, we fit weighted regression models for total flavonoids and six subclasses, scaled per interquartile-range (IQR) increment. Estimates are reported from an unadjusted model (M1), an age and sex adjusted model (M2), and a fully adjusted model (M3) (Figure 2A).

Associations of flavonoid classes and monomers with systemic inflammatory indices. Anthocyanidins and selected anthocyanidin monomers show the most consistent inverse associations with SII and SIRI. (A) Weighted regression coefficients (β) and 95% confidence intervals for total flavonoids and six flavonoid classes in relation to NLR, SII, and SIRI, scaled per interquartile-range (IQR) increase in intake. (B) Corresponding associations for 29 individual flavonoid monomers grouped by subclass. Points denote β estimates and horizontal bars indicate 95% confidence intervals. Results are shown for three models: M1 (unadjusted), M2 (adjusted for age and sex), and M3 (fully adjusted for covariates).
Across outcomes, the most consistent inverse pattern was observed for anthocyanidins. In the fully adjusted model, an IQR higher anthocyanidin intake was associated with lower SII (β = −2.91, 95% CI: −5.05 to −0.76,
By contrast, evidence for associations with NLR was limited after full adjustment. Anthocyanidins were inversely associated with NLR in M2 (β = −0.008, 95% CI: −0.015 to −0.001,
Associations of Flavonoid Monomers with Systemic Inflammation
We next evaluated 29 flavonoid monomers in relation to NLR, SII, and SIRI (Figure 2B). In fully adjusted models, the most robust associations were observed for anthocyanidin monomers. For SII, higher intakes of peonidin and cyanidin were associated with lower values in M3 (peonidin: β = −0.73, 95% CI: −1.14 to −0.32,
Beyond these top associations, several monomers exhibited nominal inverse relations with SIRI after full adjustment, notably epicatechin, quercetin, and kaempferol (all
Dose–Response Relationships from Restricted Cubic Spline Analyses
To further delineate potential dose–response patterns, we fit weighted RCS models for monomers that were associated with the inflammatory indices or showed comparatively larger effect estimates in the primary regression analyses (Figure 3 and Table 3).

Restricted cubic spline (RCS) analyses for dose–response relationships between key flavonoid monomers and systemic inflammation indices. Spline models show limited evidence of association with NLR but clearer inverse patterns for SII and SIRI for several monomers, with nonlinearity most evident for luteolin. RCS models relate daily intake of catechin, cyanidin, epicatechin, isorhamnetin, kaempferol, luteolin, peonidin, and quercetin to (A) NLR, (B) SII, (C) SIRI. The weighted median intake of each flavonoid served as the reference point. Fitted values are presented as differences from this reference (ie, the predicted outcome at a given exposure minus the predicted outcome at the weighted median). Shaded areas represent 95% confidence intervals around the fitted curves.
RCS Tests for Overall Association and Nonlinearity Between Flavonoid Monomers and Inflammatory Indices.
For NLR (Figure 3A), RCS models provided limited evidence of dose–response relationships across the selected monomers (all
Subgroup Analysis of the Cyanidin–SII Association
Since cyanidin was the only monomer showing consistent associations with SII across the FDR-controlled primary regression models and the spline analyses, we next examined whether this relationship varied across prespecified population strata (Figure 4). Overall, a higher cyanidin intake (per IQR increase) was associated with a lower SII (adjusted β = −1.16, 95% CI: −1.99 to −0.33).

Subgroup analysis of the association between cyanidin intake and SII. Inverse associations are broadly consistent across strata, with evidence of heterogeneity by education and by histories of stroke and COPD. Forest plot showing the association between cyanidin intake (per IQR increase) and SII across prespecified subgroups. Points indicate fully adjusted β coefficients and horizontal bars denote 95% confidence intervals.
Across most subgroups, estimates were directionally consistent, and interaction tests did not support heterogeneity by age, sex, race/ethnicity, poverty–income ratio, marital status, smoking, alcohol use, physical activity, BMI category, HbA1c, or major cardiometabolic comorbidities (all
Network Pharmacology Analysis of Cyanidin in Inflammation
Given the epidemiologic consistency observed for cyanidin, we used a network-pharmacology framework to generate mechanistic hypotheses linking cyanidin exposure to systemic inflammation. Putative cyanidin targets were obtained from SwissTargetPrediction and PharmMapper, and inflammation-related genes were retrieved from GeneCards. The intersection yielded 334 overlapping genes (Figure 5B), representing candidate molecular mediators linking cyanidin exposure to inflammatory regulation.

Network pharmacology framework linking cyanidin to inflammation-related targets. In silico target intersection prioritizes oxidative-stress and kinase-related programs among candidate mediators. (A) Chemical structure of cyanidin. (B) Overlap between predicted cyanidin targets and inflammation-associated genes. (C) GO enrichment analysis of the shared targets. Bars indicate enrichment scores for the top GO terms across biological process (BP), cellular component (CC), and molecular function (MF) categories. (D–F) CNET plots illustrating gene–term relationships for top enriched GO terms in BP (D), CC (E), and MF (F).
GO enrichment of the 334 shared targets highlighted stress-adaptive programs centered on responses to xenobiotic and chemical stress, oxidative stress, and reactive oxygen species (ROS) metabolic processes (Figure 5C). The CNET plots (Figure 5D-F) further showed that multiple genes were mapped across these terms, suggesting convergence on a shared set of regulatory nodes. Consistent with redox-linked regulation of phosphorylation cascades, enriched terms also included positive regulation of kinase activity and related signaling functions. KEGG enrichment extended this by prioritizing interconnected kinase-centered pathways—FoxO, PI3K–Akt, Ras, and MAPK—alongside stress and survival programs such as mTOR and autophagy (Figure 6A and B). Importantly, the pathway–pathway network (Figure 6B), in which edges indicate shared genes between pathways, positioned PI3K–Akt/MAPK/Ras/FoxO as a densely connected core linking oxidative-stress programs with downstream inflammatory signaling modules. This network structure is compatible with a model in which changes in redox state may propagate through kinase cascades that coordinate cellular stress responses, survival, and inflammatory signaling.

KEGG pathway enrichment of cyanidin–inflammation shared targets. Enrichment highlights a kinase-centered core (PI3K–Akt/MAPK/Ras/FoxO) linked to stress-response and immune signaling pathways. (A) Sankey plot summarizing enriched KEGG pathways for shared targets; nodes represent genes and pathways, and the bubble plot indicates gene ratio and enrichment significance. (B) Pathway–pathway network derived from enriched KEGG terms; nodes are pathways and edges indicate shared genes. Node size reflects the number of mapped genes and node color indicates enrichment significance.
Downstream of these kinase-centered modules, KEGG terms also encompassed canonical immune and cytokine pathways, including TNF, IL-17, chemokine, JAK–STAT, and T cell receptor signaling (Figure 6B). The enrichment map indicates that these immune pathways share overlapping genes with the central PI3K–Akt/MAPK/Ras/FoxO cluster, suggesting potential crosstalk through shared mediators. Additional enrichment of AGE–RAGE signaling, lipid and atherosclerosis, cellular senescence, apoptosis, and platelet activation further supports integration of metabolic stress and vascular–immune interfaces, processes that can influence circulating neutrophil, lymphocyte, and platelet dynamics. Overall, these network patterns nominate a hypothesis that cyanidin exposure may relate to systemic inflammatory burden by modulating redox homeostasis, which in turn reprograms kinase signaling and downstream immune pathways, ultimately contributing to shifts in immune-cell and platelet compartments captured by SII.
Protein–Protein Interaction Network and Identification of Hub Targets
To prioritize candidate molecular mediators among the overlapping genes, we constructed a PPI network and ranked nodes using complementary topological metrics, including degree, betweenness centrality, and closeness centrality (Figure 7A and Table 4). This analysis highlighted a set of highly connected and centrally positioned hub targets, led by epidermal growth factor receptor (EGFR) (degree = 57), HSP90AA1 (degree = 56), AKT1 (degree = 54), SRC (degree = 47), PIK3R1 (degree = 41), and GRB2 (degree = 40), with additional hubs including ESR1, HSP90AB1, ALB, and PTPN11. These hubs map to signaling modules implicated by the enrichment analyses, consistent with a network structure in which kinase-driven pathways form major interaction backbones.

PPI network and molecular docking of cyanidin–inflammation hub targets. Network topology highlights central kinase-related hubs, and docking supports plausible binding of cyanidin to selected targets in silico. (A) PPI network for the shared target set, visualized in Cytoscape; node size and color reflect degree (connectivity). (B–G) Representative docking poses of cyanidin with the six prioritized hub targets: AKT1 (B), EGFR (C), GRB2 (D), HSP90AA1 (E), PIK3R1 (F), and SRC (G).
PPI Network Metrics of Hub Targets.
We then performed molecular docking to assess whether cyanidin could plausibly engage the top-ranked hubs at the protein level (Figure 7B-G and Table 5). Across the six proteins prioritized for docking (AKT1, EGFR, GRB2, HSP90AA1, PIK3R1, and SRC), predicted binding energies ranged from −5.9 to −9.3 kcal/mol. The most favorable energies were observed for HSP90AA1 (−9.3 kcal/mol) and SRC (−8.8 kcal/mol), followed by EGFR (−8.4 kcal/mol) and AKT1 (−7.8 kcal/mol). Energies in this range are consistent with thermodynamically favorable binding in silico and support the plausibility of target engagement, but in vivo potency still requires further experimental confirmation. Docked poses were characterized by multiple noncovalent contacts within the predicted binding pockets (Figure 7B-G). Collectively, these in silico results nominate a hub-centered axis as a mechanistic interface through which cyanidin could influence inflammatory regulation.
Predicted Binding Affinities of Cyanidin with Top Six Hub Targets.
Discussion
In this nationally representative cross-sectional study of U.S. adults, associations between dietary flavonoid intake and blood count derived inflammatory indices differed across subclasses and individual compounds. After multivariable adjustment, total flavonoids and most subclasses showed little evidence of association with NLR, SII, or SIRI. In contrast, at the monomer level, cyanidin and peonidin were inversely associated with SII in fully adjusted models after FDR control, and peonidin was also inversely associated with SIRI. Cyanidin was the only monomer for which the inverse association with SII remained consistent in both the primary regression analyses and the restricted cubic spline models.
A plausible biochemical rationale for cyanidin begins with its structure (Figure 5A). Cyanidin contains multiple hydroxyl groups, including a catechol motif on the B ring (3′,4′-dihydroxylation), which enhances electron-donating capacity and can facilitate interactions with ROS and redox-sensitive signaling pathways.49,50 More broadly, the number and position of hydroxyl substituents, together with the extent of conjugation, shape antioxidant behavior and anti-inflammatory potential across polyphenol classes.51,52 In vivo, however, anthocyanidins and other flavonoids can be metabolized through phase II conjugation and microbiome-dependent biotransformation.53,54 Circulating forms are typically glycosylated, glucuronidated, sulfated, or methylated conjugates and smaller phenolic metabolites.55–58 Some conjugated metabolites retain signaling activity, 59 and inflammatory microenvironments may promote local deconjugation (eg, via β-glucuronidase), potentially increasing the local availability of more reactive aglycone-like species where immune cells are activated.60,61 These processes may help explain why associations are detectable in population data even when reported intakes are modest and right-skewed, as observed for most monomers in this dataset.
RCS analyses provided further insight into dose–response shape. For several monomers, the associations were approximately linear across the observed intake range (cyanidin and isorhamnetin with SII; cyanidin, kaempferol, and quercetin with SIRI). One interpretation is that, within this range, incremental increases in intake correspond to roughly proportional increases in circulating metabolites and downstream biological exposure. For quercetin, human pharmacokinetic studies indicate relatively slow elimination, with half-lives on the order of ∼1 day, 62 supporting the possibility of sustained exposure under habitual intake and may favor monotonic associations in observational settings. For isorhamnetin, O-methylation relative to quercetin may increase metabolic stability and cellular persistence, potentially extending the range over which intake differences remain biologically relevant.63,64 For kaempferol, available evidence suggests that circulating exposure is dominated by glucuronidated and sulfated conjugates rather than the aglycone following phase I and phase II metabolism. 58 Under usual dietary patterns, an approximately linear spline could therefore reflect dose-proportional variation in these conjugated pools across mid-range intakes, even when absolute bioavailability is limited. 65
In contrast, luteolin exhibited a tendency toward plateauing for SII and SIRI, which may reflect a combination of biology and data distribution. Its disposition involves glucuronidation and methylation (UGTs/COMTs), 66 processes that could limit further increases in circulating bioactive pools once metabolic or transport capacity becomes rate-limiting at higher intakes. In addition, monomer intakes are right-skewed and are more susceptible to day-to-day variability and measurement error inherent to 24-h recalls. These features can visually compress the upper tail and flatten apparent dose–response curves. We also notice that peonidin showed inverse associations in the primary regression models but did not retain a concordant pattern in spline analyses. This may be due to sparse exposure with many near-zero intakes destabilizing flexible spline fits and reducing the power to detect nonlinearity or even preserve directionality. Moreover, peonidin intake is is also correlated with other anthocyanidins and shared food sources, increasing sensitivity to multivariable adjustment and to exposure misclassification from 24-h recalls. Under these conditions, a conventional linear term may capture an average contrast, while spline estimates fluctuate when data density is low in higher intake regions.
In the primary regression analyses, effect estimates often attenuated, and in some cases changed direction, after full adjustment, consistent with nonrandom patterning of flavonoid intake. In NHANES, higher flavonoid consumption tends to cluster with socioeconomic position, smoking, adiposity, and overall diet quality, factors that are independently related to systemic inflammation and can inflate associations in minimally adjusted models. 67 Age is also a major source of confounding. Ageing is accompanied by chronic low-grade inflammation and coordinated shifts in immune cell compartments that influence hematologic indices even in the absence of acute illness. 68 Adjusting for age, health behaviors, and comorbidities may therefore separate associations from correlated lifestyle and disease profiles. This interpretation is consistent with epidemiologic work showing that diet quality and inflammatory potential relate to inflammatory markers. 69 Subgroup analyses further suggest context dependance for the cyanidin and SII association. The interaction by education may reflect differences in dietary access and patterns, health literacy, and correlated behaviors that shape inflammatory status.70,71 We also observed modification by history of stroke and COPD. The estimate among participants with prior stroke was positive but imprecise, consistent with limited stability in this smaller stratum (n = 499) and possible post-event changes in diet, medication use, or blood counts. The stronger inverse association in COPD could align with higher baseline inflammatory and oxidative-stress burden, which may widen the dynamic range of SII, although residual confounding remains possible in a cross-sectional design. 72
The network-pharmacology enrichment results align with a mechanistic path that is coherent with blood count derived inflammatory indices. Enriched processes centered on reactive oxygen species handling and kinase signaling (PI3K–Akt, MAPK, Ras, and FoxO), with links to AGE–RAGE and VEGF-related programs. These pathways regulate neutrophil survival, lymphocyte homeostasis, and platelet reactivity, key determinants of SII and SIRI. PI3K–Akt signaling has well-established roles in regulating neutrophil survival, 73 and MAPK pathways intersect with oxidative burst and inflammatory activation. 74 FoxO transcription factors integrate oxidative stress signals with apoptosis and cell-cycle control, influencing lymphocyte turnover and stress resilience.75,76 AGE–RAGE signaling, particularly relevant in metabolic stress contexts, can amplify oxidative stress and inflammatory cascades which also promote myeloid activation and platelet responsiveness,77,78 biologic components directly reflected in SII and SIRI. Importantly, platelets are integral to SII, and experimental work shows that cyanidin-3-glucoside can inhibit platelet activation and thrombus formation via GPVI-linked signaling, 79 supporting a biological route by which cyanidin-related exposures could relate to a platelet-weighted inflammation index. Together, these links support a model in which cyanidin associated redox modulation engages kinase networks that shape innate immune activation and platelet activity, which is then captured by composite hematologic indices.
Several limitations warrant caution in causal interpretation. First, the cross-sectional design precludes establishing temporality, and reverse causation is possible (eg, diet changes after illness). Second, flavonoid intake derived from 24-h recalls is vulnerable to measurement error and within-person variability, particularly for episodically consumed, anthocyanin-rich foods. Third, although we adjusted for a broad covariate set and applied within-outcome FDR control, residual confounding remains plausible because flavonoid intake is closely correlated with socioeconomic position and health behaviors. Fourth, the complete-case approach excluded participants with missing exposure, outcome, or covariate data. Selection related to sociodemographic characteristics (eg, age, race/ethnicity, PIR, education, and marital status) may affect generalizability and could influence effect estimates. Finally, the mechanistic analyses are in silico and are intended to prioritize hypotheses rather than demonstrate target engagement or biological effects in vivo.
Despite these constraints, the results motivate follow-up work focused on anthocyanidin composition and selected monomers, together with targeted testing of cyanidin-linked redox and kinase pathways in immune and platelet biology. Prospective cohorts with repeated dietary assessment and metabolomic profiling, complemented by experimental studies of cyanidin and its metabolites, will be needed to determine whether the observed associations reflect causal modulation of systemic inflammatory burden.
Conclusion
In this nationally representative cross-sectional analysis of US adults, higher anthocyanidins intake was associated with lower systemic inflammatory burden as indexed by SII and SIRI, while associations with NLR were weak. Cyanidin showed the most consistent inverse association with SII. Complementary in silico network pharmacology and docking analyses prioritized redox and kinase linked pathways, including PI3K–Akt/MAPK related hubs, as plausible mechanistic candidates. These findings link dietary anthocyanidins, particularly cyanidin, to variation in composite blood count derived inflammatory indices and motivate follow-up studies integrating longitudinal dietary assessment, metabolomics, and targeted experimentation to test causal mechanisms and translational relevance.
Footnotes
Abbreviations
Ethical Approval
The present study is a secondary analysis of publicly available data from the U.S. National Health and Nutrition Examination Survey (NHANES). NHANES protocols are reviewed and approved annually by the NCHS Ethics Review Board, and all procedures comply with the U.S. Department of Health and Human Services ethical standards. Because this research uses de-identified, publicly accessible data, no additional institutional ethical approval was required, and no approval number applies to the secondary analysis.
Statement of Informed Consent
NHANES obtains written informed consent from all participating individuals prior to data collection. Detailed consent procedures, including permission for future research use of de-identified data, are conducted by trained NCHS personnel. Because the present work uses only anonymized NHANES data released for public research purposes, no additional informed consent was required for this analysis.
Statement of Human and Animal Rights
This study involved no direct interaction with human participants, no collection of new biological specimens, and no animal experiments. All analyses were performed on de-identified NHANES datasets released by the NCHS. The study therefore adheres fully to the ethical principles outlined in the U.S. Federal Regulations for research using existing, anonymized data, and poses no risk to human or animal subjects.
Author Contributions
H.P. and H.W.: conceptualization, data curation, formal analysis, visualization, writing–original draft, writing–review and editing. J.G. and Y.C.: methodology, formal analysis, writing–review and editing. H.J.: conceptualization, writing–original draft, writing–review and editing. X.Y. and Y.Z.: supervision, project administration, resources, writing–review and editing.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was funded by the National Natural Science Foundation of China (No. 82073539) and the Natural Science Foundation of Sichuan Province (No. 2023NSFSC0682).
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
