**Background:** Atherosclerotic cardiovascular disease is a leading cause of morbidity and mortality worldwide. Carotid plaque rupture accounts for approximately 15% of ischemic strokes. Plaque vulnerability, assessed by gray-scale median (GSM) on B-mode ultrasonography, reflects plaque composition—low GSM indicates echolucent, rupture-prone plaques with high lipid content, while high GSM indicates stable, calcified plaques. Dietary patterns such as the Mediterranean diet and DASH diet are known to influence cardiovascular risk, but their association with plaque vulnerability (GSM) had not been studied. Supplement intake is widespread, yet evidence linking supplements to plaque characteristics is lacking. This study aimed to examine associations between these dietary factors and both the presence and GSM of carotid plaques, with sex-stratified analyses.
**Methods:** This analysis used data from the first 10,000 participants of the Hamburg City Health Study (HCHS), a prospective population-based cohort. Participants aged 45–74 were randomly recruited from Hamburg, Germany, between February 2016 and November 2018. Carotid B-mode duplex sonography was performed using a Siemens SC2000 ultrasound system with a 7.5 MHz linear transducer. Plaques were defined as local cIMT ≥ 1.5 mm. GSM was measured in 2,163 participants with at least one plaque using custom software based on JS Paint. Plaques were manually segmented, and images were normalized using vessel lumen (GSM=0) and adventitia (GSM=190) as reference structures. Dietary intake was assessed via the EPIC food frequency questionnaire (FFQ2). Mediterranean diet adherence was measured using the validated German MEDAS score (0–14 points, grouped as 0–3, 4, 5, 6+). DASH adherence used a Folsom-adapted score (grouped as 0–3.5, 3.6–4.5, 4.6–5.0, 5.1+). Supplement use (multivitamins, multiminerals, calcium, magnesium, vitamin B complex, folic acid) was self-reported for at least one month in the prior year. Multiple linear regressions assessed associations with GSM (sex-stratified, adjusted for age, BMI, smoking, socioeconomic status, energy intake, comorbidities, medications). Multiple logistic regressions assessed associations with plaque presence (adjusted for age, sex, education, BMI, diabetes, hypertension, hyperlipidemia, smoking, cardiac conditions, stroke, physical activity). Missing data were handled by multivariate imputation with chained equations (20 copies, 10 iterations).
**Key Results:** In the GSM sub-cohort (n=2,163), median age was 68 years (IQR 62–73). Women had higher dietary adherence: 37.8% of women vs. 16.1% of men achieved MEDAS ≥6; 31.1% of women vs. 14.2% of men achieved DASH ≥5.1. Supplement use was higher in women (43.8%) than men (23.8%). Median GSM was 56.50 (IQR 46.00–68.50) for men and 55.80 (IQR 44.25–70.33) for women. In multivariate linear regression, the only significant association with GSM was folic acid intake in men (β=+9.12, 95% CI 1.37–16.86, p=0.021). A non-significant opposite trend was observed in women (β=−2.50, 95% CI −9.31 to 4.31, p=0.472). No significant associations were found between MEDAS, DASH, or other supplements and GSM. In logistic regression (full cohort, n=10,000), high DASH score (≥5.1) was associated with significantly increased odds of carotid plaque presence compared to intermediate scores (OR=1.18, 95% CI 1.02–1.36, p=0.027). Higher odds for plaque presence were also found for men, older age, low education, hypertension, hyperlipidemia, and smoking. No significant associations were found between MEDAS or any supplement and plaque presence.
**Clinical Implications:** This large population-based study found no clinically meaningful association between Mediterranean or DASH dietary patterns and carotid plaque vulnerability as measured by GSM. The isolated finding of higher GSM with folate intake in men (only 2.4% of men supplemented folic acid) requires cautious interpretation and replication. The unexpected finding that high DASH adherence was associated with higher odds of plaque presence may reflect reverse causation—individuals with known cardiovascular disease may adopt healthier diets. These results suggest that GSM may not be the optimal ultrasound parameter for detecting dietary influences on atherosclerosis; alternative measures such as juxtaluminal black area (JBA) may be more informative. The study reinforces that traditional cardiovascular risk factors (age, male sex, smoking, hypertension, hyperlipidemia) remain the strongest predictors of plaque presence. Future research should investigate whether folate intake causally affects plaque stability and whether dietary interventions can modify plaque composition in ways detectable by GSM or other imaging biomarkers.