Diet Quality Scores are Positively Associated with Whole Blood-derived Mitochondrial DNA Copy Number in the Framingham Heart Study

Background Association between diet quality and mitochondrial DNA copy number (mtDNA-CN) remains to be examined. Objectives We aimed to study the relationship between diet quality and mtDNA-CN. Methods We analyzed data from 2,931 Framingham Heart Study (FHS) participants with mean age of 57 years and 55% females. Whole genome sequencing was used to calculate mtDNA-CN from whole blood samples. We examined the cross-sectional associations between three diet quality scores, the Dietary Approaches to Stop Hypertension (DASH) score, the Alternative Healthy Eating Index (AHEI), and the Mediterranean diet-style score (MDS), and mtDNA-CN. Linear mixed models were used to account for maternal lineage. Results We observed that a higher DASH score was positively associated with mtDNA-CN after adjusting for sex, age, energy intake, smoking status, alcohol intake, and physical activity level. One standard deviation (SD) increase in the DASH score was associated with a 0.042 SD greater mtDNA-CN (95% CI: 0.007, 0.077; P = 0.02). Similarly, for each SD increase in AHEI and MDS, mtDNA-CN increased by 0.056 (95% CI: 0.019, 0.092; P = 0.003) and 0.047 (95% CI: 0.01, 0.083; P = 0.01), respectively. Diet quality scores were associated with neutrophil and lymphocyte counts but not platelet counts, e.g., for one SD increase in the DASH, neutrophils decreased by 0.8% (95% CI: 0.5%, 1.1%; P = 4.1 × 10–6), lymphocytes increased by 0.7% (95% CI: 0.4%, 1%, P = 1.2 × 10–5), and there was no significant change in platelet, 0.1 thousands/μL (95% CI: –1.6, 1.9; P = 0.89). Further adjustment for neutrophil, lymphocyte, and platelet counts, the associations between diet quality scores and mtDNA-CN were completely attenuated to nonsignificant (P = 0.95, 0.54, and 0.91, respectively). Conclusions We observed that higher diet quality is associated with a greater whole blood derived mtDNA-CN in middle aged to older adults in FHS participants, and that blood cell composition, particularly neutrophil counts, attenuated the association between diet quality and mtDNA-CN.