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Associations of dairy intake with risk of mortality in women and men: three prospective cohort studies

BMJ 2019; 367 doi: https://doi.org/10.1136/bmj.l6204 (Published 27 November 2019) Cite this as: BMJ 2019;367:l6204
  1. Ming Ding, research associate1,
  2. Jun Li, research associate1 2,
  3. Lu Qi, professor1 3,
  4. Christina Ellervik, assistant professor4 5 6,
  5. Xuehong Zhang, assistant professor7,
  6. JoAnn E Manson, professor2 6 7,
  7. Meir Stampfer, professor2 7,
  8. Jorge E Chavarro, associate professor1 2 7,
  9. Kathryn M Rexrode, associate professor8,
  10. Peter Kraft, professor2,
  11. Daniel Chasman, associate professor6 9 10,
  12. Walter C Willett, professor1 2 7,
  13. Frank B Hu, professor1 2 7
  1. 1Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA
  2. 2Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA
  3. 3Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA
  4. 4Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
  5. 5Department of Laboratory Medicine, Boston Children’s Hospital, Boston, MA, USA
  6. 6Division of Preventive Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
  7. 7Channing Division of Network Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
  8. 8Division of Women’s Health, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
  9. 9Division of Genetics, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
  10. 10Broad Institute of MIT and Harvard, Cambridge, MA, USA
  1. Correspondence to: M Ding mid829{at}mail.harvard.edu
  • Accepted 17 October 2019

Abstract

Objective To examine the association of consumption of dairy foods with risk of total and cause specific mortality in women and men.

Design Three prospective cohort studies with repeated measures of diet and lifestyle factors.

Setting Nurses’ Health Study, Nurses’ Health Study II, and the Health Professionals Follow-up Study, in the United States.

Participants 168 153 women and 49 602 men without cardiovascular disease or cancer at baseline.

Main outcome measure Death confirmed by state vital records, the national death index, or reported by families and the postal system. During up to 32 years of follow-up, 51 438 deaths were documented, including 12 143 cardiovascular deaths and 15 120 cancer deaths. Multivariable analysis further adjusted for family history of cardiovascular disease and cancer, physical activity, overall dietary pattern (alternate healthy eating index 2010), total energy intake, smoking status, alcohol consumption, menopausal status (women only), and postmenopausal hormone use (women only).

Results Compared to the lowest category of total dairy consumption (average 0.8 servings/day), the multivariate pooled hazard ratio for total mortality was 0.98 (95% confidence interval 0.96 to 1.01) for the second category of dairy consumption (average 1.5 servings/day), 1.00 (0.97 to 1.03) for the third (average 2.0 servings/day), 1.02 (0.99 to 1.05) for the fourth (average 2.8 servings/day), and 1.07 (1.04 to 1.10) for highest category (average 4.2 servings/day; P for trend <0.001). For the highest compared to the lowest category of total dairy consumption, the hazard ratio was 1.02 (0.95 to 1.08) for cardiovascular mortality and 1.05 (0.99 to 1.11) for cancer mortality. For subtypes of dairy products, whole milk intake was significantly associated with higher risks of total mortality (hazard ratio per 0.5 additional serving/day 1.11, 1.09 to 1.14), cardiovascular mortality (1.09, 1.03 to 1.15), and cancer mortality (1.11, 1.06 to 1.17). In food substitution analyses, consumption of nuts, legumes, or whole grains instead of dairy foods was associated with a lower mortality, whereas consumption of red and processed meat instead of dairy foods was associated with higher mortality.

Conclusion These data from large cohorts do not support an inverse association between high amount of total dairy consumption and risk of mortality. The health effects of dairy could depend on the comparison foods used to replace dairy. Slightly higher cancer mortality was non-significantly associated with dairy consumption, but warrants further investigation.

Footnotes

  • Contributors: MD, JL, LQ, CE, XZ, JEM, MS, JEC, KMR, PK, DC, WCW, and FBH designed the study and collected data. MD mainly conducted analyses and wrote the manuscript. FBH supervised the data analysis and reviewed and edited the manuscript. All authors contributed substantially to the interpretation of data and the drafting or critical revision of the manuscript for important intellectual content. The authors assume full responsibility for analyses and interpretation of these data. MD and FBH are the guarantors. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.

  • Funding: The NHS, NHSII, and HPFS are supported by grants (UM1 CA186107, P01 CA87969, R01 CA49449, R01 HL034594, R01 HL088521, UM1 CA176726, R01 CA67262, UM1 CA167552, R01 HL35464, R01 HL60712) from the National Institutes of Health. The funding sources did not participate in the design or conduct of the study; collection, management, analysis or interpretation of the data; or preparation, review, or approval of the manuscript.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: support from the National Institutes of Health for the submitted work; FBH reports support from grants HL60712, HL118264, and DK112940 from the National Institutes of Health, research support from the California Walnut Commission, honorariums for lectures from Metagenics and Standard Process, and honorariums from Diet Quality Photo Navigation, outside the submitted work; the remaining authors report no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: The study protocol was approved by the institutional review boards of the Brigham and Women’s Hospital and the Harvard T H Chan School of Public Health. The completion of the self administered questionnaire was considered to imply informed consent.

  • Data sharing: No additional data available.

  • The lead authors affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

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