Letter by Song et al Regarding Article, “Associations of Dietary Cholesterol, Serum Cholesterol, and Egg Consumption With Overall and Cause-Specific Mortality: Systematic Review and Updated Meta-Analysis”

HomeCirculationVol. 146, No. 23Letter by Song et al Regarding Article, "Associations of Dietary Cholesterol, Serum Cholesterol, and Egg Consumption With Overall and Cause-Specific Mortality: Systematic Review and Updated Meta-Analysis" Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBLetter by Song et al Regarding Article, "Associations of Dietary Cholesterol, Serum Cholesterol, and Egg Consumption With Overall and Cause-Specific Mortality: Systematic Review and Updated Meta-Analysis" Yuxuan Song, Congcong Ding and Tao Xu Yuxuan SongYuxuan Song https://orcid.org/0000-0001-8326-0948 Department of Urology, Peking University People's Hospital, Beijing, China (Y.S., T.X.). , Congcong DingCongcong Ding https://orcid.org/0000-0002-0066-9092 Department of Cardiology, the Second Affiliated Hospital of Nanchang University, Jiangxi, China (C.D.). and Tao XuTao Xu https://orcid.org/0000-0003-3899-1500 Department of Urology, Peking University People's Hospital, Beijing, China (Y.S., T.X.). Originally published5 Dec 2022https://doi.org/10.1161/CIRCULATIONAHA.122.060376Circulation. 2022;146:e326–e327To the Editor:We were interested to read the impressive study by Zhao et al1 and would like to congratulate the authors for their superb findings. Zhao et al systematically evaluated the effects of dietary cholesterol and egg consumption on overall and cardiovascular disease (CVD) mortality through the ATBC cohort (Alpha-Tocopherol, Beta-Carotene Cancer Prevention) and an updated meta-analysis. The authors found that greater dietary cholesterol and egg consumption were associated with increased risk of overall and CVD mortality. This particular topic is a critical clinical issue, and this meaningful research provides valuable evidence for dietary recommendations regarding egg intake and public health. However, we wish to discuss the following concerns.First, the present study did not explore the nonlinear relationship between egg consumption and mortality. When treated as a continuous variable, consumption of 1 additional egg (50 g/d) seemed to be associated with significantly increased adjusted overall (hazard ratio, 1.06 [95% CI, 1.04–1.09]) and CVD (hazard ratio, 1.09 [95% CI, 1.05–1.12]) mortality (Table 3).1 However, when egg consumption was treated as 5 categorical variables, and quintile 1 (<25.1 g) was deemed as reference, only quintile 4 (52.3–75.4 g) and quintile 5 (≥75.4 g) significantly increased overall and CVD mortality risk, whereas quintile 2 (25.1–37.7 g) and quintile 3 (37.7–52.3 g) did not (Table S11),1 which indicated that a nonlinear relationship might exist between egg consumption and mortality. In addition, another recent meta-analysis2 found that nonlinear dose-response associations were identified for egg consumption and mortality. When the total egg intake is ≤1 per day, higher intake will not increase the mortality risk, indicating that approximately ≤1 egg per day may be a suitable and safe intake mode.2 Nevertheless, the mortality risk significantly increased as higher intake only when intake was >1 egg per day.2 Therefore, we suggest that the authors perform restricted cubic splines3 and a piecewise regression model to examine the nonlinear relationship between egg consumption and mortality.Second, the food frequency questionnaire about egg consumption was examined and recorded only at the baseline survey of each participant's initial recruitment in the ATBC cohort. Because the follow-up time was up to 31 years, it is unclear whether the dietary habits about egg consumption would change or be maintained during such a long follow-up period.Third, eggs are cooked by different methods in different countries. For example, the most common cooking method for eggs is frying in the United States, whereas boiling is the most common method in China.4 It is notable that the nutrient content of eggs can be changed by different cooking methods,5 which could be used to explain the different effects of egg consumption on CVD risk in subgroup meta-analysis on the basis of geographical regions.Fourth, in the present ATBC cohort, all participants were Finnish male smokers,1 which is a rather special population, and significantly different from other cohort studies enrolled in the updated meta-analysis. In addition, the proportion with CVD history at baseline (approximately 40%) and the average daily egg consumption (53.3 g) were significantly higher than in other studies in the meta-analysis.1 We believe that the specificity of participants in the ATBC cohort contributed to the substantial heterogeneity in overall meta-analysis (I2=80.1%) and all subgroups (I2 of all subgroups >50%). Therefore, the results of this prospective cohort and updated meta-analysis should be interpreted with caution because of those special population differences.Finally, we truly thank authors for the excellent and important work.Article InformationDisclosures None.Footnotes*Y. Song and C. Ding contributed equally.Circulation is available at www.ahajournals.org/journal/circReferences1. Zhao B, Gan L, Graubard BI, Männistö S, Albanes D, Huang J. Associations of dietary cholesterol, serum cholesterol, and egg consumption with overall and cause-specific mortality: systematic review and updated meta-analysis.Circulation. 2022; 145:1506–1520. doi: 10.1161/CIRCULATIONAHA.121.057642LinkGoogle Scholar2. Yang P, Wang C, Hao F, Peng Y, Wu J, Sun W, Hu J, Zhong G. Egg consumption and risks of all-cause and cause-specific mortality: a dose-response meta-analysis of prospective cohort studies.Nutr Rev. 2022; 80:1739–1754. doi: 10.1093/nutrit/nuac002CrossrefMedlineGoogle Scholar3. Desquilbet L, Mariotti F. Dose-response analyses using restricted cubic spline functions in public health research.Stat Med. 2010; 29:1037–1057. doi: 10.1002/sim.3841CrossrefMedlineGoogle Scholar4. Xia PF, Pan XF, Chen C, Wang Y, Ye Y, Pan A. Dietary intakes of eggs and cholesterol in relation to all-cause and heart disease mortality: a prospective cohort study.J Am Heart Assoc. 2020; 9:e15743. doi: 10.1161/JAHA.119.015743LinkGoogle Scholar5. Tang D, Wang R, He X, Chen X, Huo X, Lü X, Shan Y. Comparison of the edible quality of liquid egg with different cooking methods and their antioxidant activity after in vitro digestion.Food Res Int. 2021; 140:110013. doi: 10.1016/j.foodres.2020.110013CrossrefMedlineGoogle Scholar eLetters(0)eLetters should relate to an article recently published in the journal and are not a forum for providing unpublished data. Comments are reviewed for appropriate use of tone and language. Comments are not peer-reviewed. Acceptable comments are posted to the journal website only. Comments are not published in an issue and are not indexed in PubMed. Comments should be no longer than 500 words and will only be posted online. References are limited to 10. Authors of the article cited in the comment will be invited to reply, as appropriate.Comments and feedback on AHA/ASA Scientific Statements and Guidelines should be directed to the AHA/ASA Manuscript Oversight Committee via its Correspondence page.Sign In to Submit a Response to This Article Previous Back to top Next FiguresReferencesRelatedDetails December 6, 2022Vol 146, Issue 23 Advertisement Article InformationMetrics © 2022 American Heart Association, Inc.https://doi.org/10.1161/CIRCULATIONAHA.122.060376PMID: 36469594 Originally publishedDecember 5, 2022 PDF download Advertisement SubjectsEthics and PolicyMortality/SurvivalQuality and Outcomes