A study published in the American Journal of Clinical Nutrition examined the relationship between diet quality and epigenetic aging clocks .
This study used data from the Framingham Heart Study Offspring Cohort. This specific study noted the Dietary Approaches to Stop Hypertension (DASH) scores, which are derived from a food frequency questionnaire (FFQ), of 1,995 people with an average age of 67 years. The researchers also calculated a Mediterranean-style diet score (MDS) and used the Alternate Healthy Eating Index (AHEI).
DNA methylation status was described in a prior study . For participants who attended the eight-exam visit during 2005 and 2008, DNA was extracted from blood samples, and CpG methylation was assigned a value based on a proportion of methylation intensity. During this visit, participants completed an FFQ detailing their intake of each food item in the past year.
Epigenetic age acceleration was measured with the GrimAge , Phenoage , and DunedinPACE  clocks. Higher DASH scores indicate better diets [6,7], and these scores are based on a higher intake of vegetables, fruit, nuts and legumes, whole grains, low-fat dairy along with a lower intake of red and processed meat, sugar-sweetened beverages, and sodium.
Women had higher DASH scores
Participants with higher DASH scores were more likely to be women, had lower BMIs, had higher HDL cholesterol, were less likely to be current or past smokers, and were less likely to be on hypertension medication. The MDS and AHEI scores are extensively featured in the supplementary data, and both of these scores were found to be moderately and significantly correlated with the DASH score.
Higher DASH scores were correlated with decreased epigenetic age acceleration
After adjusting for age, sex, smoking status, physical activity score, BMI, and alcohol consumption, a higher DASH score was associated with less epigenetic age acceleration. For every standard deviation of increase in DASH score, DunedinPACE was decreased by 0.05, GrimAge was decreased by 0.09 and Phenoage was decreased by 0.07.
DASH score and smoking
The researchers conducted another set of analyses using a Bonferroni-corrected P-value threshold of 0.01. These results revealed significant interactions between DASH score and smoking status in their association with DunedinPACE and GrimAge; however, no significant interaction was found between diet quality, age, sex, BMI, and physical activity.
More specifically, the association between the DASH score and epigenetic age acceleration was stronger in the former and current smokers than the never-smokers. This result translates to the never-smokers having lower age acceleration and higher quality diet than the current smokers and former smokers.
Slower epigenetic aging is associated with a higher DASH score
When the researchers analyzed individual DASH components, higher intakes of vegetables, fruit, nuts and legumes, and whole grains were associated with a lower GrimAge. Higher intakes of sodium along with red and processed meat were associated with a higher GrimAge. A lower DunedinPACE and Phenoage were correlated with a higher intake of nuts and legumes.
These analyses also observed a more significant association between DASH score components and epigenetic age acceleration in participants with a history of smoking than in never-smokers. Additionally, in participants with a smoking history, 8 components of the DASH score were associated with GrimAge and 5 components were associated with DunedinPACE, whereas only 1 component was associated with GrimAge in never-smokers.
The investigators ran a sensitivity analysis including the blood cell counts of CD8+ cells, CD4+ T cells, natural killer cells, B cells and granulocytes. These measurements had a statistically significant correlation with DASH scores, MDS, and AHEI.
Finally, DASH scores and increased epigenetic age acceleration were significantly associated with increased all-cause mortality.
These results originate from one food frequency questionnaire that was given at one time point. People cannot always estimate how much food they ate in certain categories in the past year, especially since many people in the United States have varying diets by season. Additionally, the authors noted that this sample consisted of white middle-aged and older adults, so these results can not be generalized to other populations. They concluded with the statement:
Our findings demonstrate that better diet quality was associated with decelerated biological aging, providing a promising avenue to explore the beneficial effects of diet on prolonged lifespans. This effect seems to be more prominent for those who have a history of smoking. Further studies are warranted to validate our findings, including studies with larger sample sizes, studies with racially and ethnically diverse populations, and studies investigating the causal role of dietary factors on epigenetic regulations.
 Kim, Y., Huan, T., Joehanes, R., McKeown, N. M., Horvath, S., Levy, D., & Ma, J. (2022). Higher diet quality relates to decelerated epigenetic aging. The American journal of clinical nutrition, 115(1), 163–170. https://doi.org/10.1093/ajcn/nqab201
 Huan, T., Joehanes, R., Song, C., Peng, F., Guo, Y., Mendelson, M., Yao, C., Liu, C., Ma, J., Richard, M., Agha, G., Guan, W., Almli, L. M., Conneely, K. N., Keefe, J., Hwang, S. J., Johnson, A. D., Fornage, M., Liang, L., & Levy, D. (2019). Genome-wide identification of DNA methylation QTLs in whole blood highlights pathways for cardiovascular disease. Nature communications, 10(1), 4267. https://doi.org/10.1038/s41467-019-12228-z
 Lu, A. T., Quach, A., Wilson, J. G., Reiner, A. P., Aviv, A., Raj, K., Hou, L., Baccarelli, A. A., Li, Y., Stewart, J. D., Whitsel, E. A., Assimes, T. L., Ferrucci, L., & Horvath, S. (2019). DNA methylation GrimAge strongly predicts lifespan and healthspan. Aging, 11(2), 303–327. https://doi.org/10.18632/aging.101684
 Levine, M. E., Lu, A. T., Quach, A., Chen, B. H., Assimes, T. L., Bandinelli, S., Hou, L., Baccarelli, A. A., Stewart, J. D., Li, Y., Whitsel, E. A., Wilson, J. G., Reiner, A. P., Aviv, A., Lohman, K., Liu, Y., Ferrucci, L., & Horvath, S. (2018). An epigenetic biomarker of aging for lifespan and healthspan. Aging, 10(4), 573–591. https://doi.org/10.18632/aging.101414
 Belsky, D. W., Caspi, A., Arseneault, L., Baccarelli, A., Corcoran, D. L., Gao, X., Hannon, E., Harrington, H. L., Rasmussen, L. J., Houts, R., Huffman, K., Kraus, W. E., Kwon, D., Mill, J., Pieper, C. F., Prinz, J. A., Poulton, R., Schwartz, J., Sugden, K., Vokonas, P., … Moffitt, T. E. (2020). Quantification of the pace of biological aging in humans through a blood test, the DunedinPoAm DNA methylation algorithm. eLife, 9, e54870. https://doi.org/10.7554/eLife.54870
 Djoussé, L., Ho, Y. L., Nguyen, X. T., Gagnon, D. R., Wilson, P., Cho, K., Gaziano, J. M., & VA Million Veteran Program (2018). DASH Score and Subsequent Risk of Coronary Artery Disease: The Findings From Million Veteran Program. Journal of the American Heart Association, 7(9), e008089. https://doi.org/10.1161/JAHA.117.008089
 Fung, T. T., Chiuve, S. E., McCullough, M. L., Rexrode, K. M., Logroscino, G., & Hu, F. B. (2008). Adherence to a DASH-style diet and risk of coronary heart disease and stroke in women. Archives of internal medicine, 168(7), 713–720. https://doi.org/10.1001/archinte.168.7.713