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Original Investigation
January 21, 2020

Association of Low-Carbohydrate and Low-Fat Diets With Mortality Among US Adults

Author Affiliations
  • 1Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
  • 2Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
  • 3Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
  • 4Channing Division of Network Medicine, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
  • 5Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
  • 6MOE Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
  • 7Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York
JAMA Intern Med. Published online January 21, 2020. doi:10.1001/jamainternmed.2019.6980
Key Points

Question  What are the associations of types of low-carbohydrate and low-fat diets with mortality among US adults?

Findings  In this cohort study of 37 233 US adults 20 years or older, overall low-carbohydrate and low-fat diets were not associated with total mortality, but a healthy low-carbohydrate diet (lower amounts of low-quality carbohydrates and higher amounts of plant protein and unsaturated fat) and a healthy low-fat diet (lower amounts of saturated fat and higher amounts of high-quality carbohydrates and plant protein) were associated with lower total mortality.

Meaning  The associations of low-carbohydrate and low-fat diets with mortality may depend on the quality and food sources of macronutrients.

Abstract

Importance  It is crucial to incorporate quality and types of carbohydrate and fat when investigating the associations of low-fat and low-carbohydrate diets with mortality.

Objective  To investigate the associations of low-carbohydrate and low-fat diets with total and cause-specific mortality among US adults.

Design, Setting, and Participants  This prospective cohort study used data from the US National Health and Nutrition Examination Survey from 1999 to 2014 from 37 233 adults 20 years or older with 24-hour dietary recall data. Data were analyzed from July 5 to August 27, 2019.

Exposures  Overall, unhealthy, and healthy low-carbohydrate-diet and low-fat-diet scores based on the percentage of energy as total and subtypes of carbohydrate, fat, and protein.

Main Outcomes and Measures  All-cause mortality from baseline until December 31, 2015, linked to National Death Index mortality data.

Results  A total of 37 233 US adults (mean [SD] age, 49.7 [18.3] years; 19 598 [52.6%] female) were included in the present analysis. During 297 768 person-years of follow-up, 4866 total deaths occurred. Overall low-carbohydrate-diet and low-fat-diet scores were not associated with total mortality. The multivariable-adjusted hazard ratios for total mortality per 20-percentile increase in dietary scores were 1.07 (95% CI, 1.02-1.11; P = .01 for trend) for unhealthy low-carbohydrate-diet score, 0.91 (95% CI, 0.87-0.95; P < .001 for trend) for healthy low-carbohydrate-diet score, 1.06 (95% CI, 1.01-1.12; P = .04 for trend) for unhealthy low-fat-diet score, and 0.89 (95% CI, 0.85-0.93; P < .001 for trend) for healthy low-fat-diet score. The associations remained similar in the stratification and sensitivity analyses.

Conclusions and Relevance  In this study, overall low-carbohydrate-diet and low-fat-diet scores were not associated with total mortality. Unhealthy low-carbohydrate-diet and low-fat-diet scores were associated with higher total mortality, whereas healthy low-carbohydrate-diet and low-fat-diet scores were associated with lower total mortality. These findings suggest that the associations of low-carbohydrate and low-fat diets with mortality may depend on the quality and food sources of macronutrients.

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    1 Comment for this article
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    Is it possible to adjust for alcohol measurement error?
    George Henderson | Auckland University of Technology
    I congratulate these authors for revisiting the NHANES data previously interpreted by Mazidi et al and controlling for potential bias owing to underreporting of food consumption.
    However I wonder if it is also possible to control for potential bias owing to underreporting of alcohol consumption.
    The association of the LCD score with alcohol intake is the most significant association for LCD in this population, with alcohol intake across quantiles in Mazidi et al. resembling the distribution in studies of population alcohol intake.
    Alcohol is not just a confounder, it is a consistent driver of the LCD pattern in normal populations
    in an era when LCHF dieting has not been commonplace. Also from an NHANES paper - "Of all macronutrients, carbohydrate intake was the first to decrease with increasing alcohol consumption".[1] Although alcohol was adjusted for, alcohol is the macronutrient recorded with least accuracy, often under-reported by a factor of 2-3. Alcoholism and binge drinking, by their very nature, may not be reported or remembered accurately at all. "Heavy drinking and non-routine drinking patterns may be associated with greater under-reporting of alcohol consumption. Estimates of drinking above recommended levels are likely to be disproportionately under-estimated."[2]
    Alcohol is also a source of calories. which are not included as non-carbohydrate calories in the LCD score, and which will also subject to under-reporting.
    Alcohol may have stronger associations with mortality than any other macronutrient.[3]

    [1] Liangpunsakul S. Relationship between alcohol intake and dietary pattern: findings from NHANES III. World J Gastroenterol. 2010;16(32):4055–4060. doi:10.3748/wjg.v16.i32.4055 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2928459/

    [2] Boniface S, Kneale J, Shelton N. Drinking pattern is more strongly associated with under-reporting of alcohol consumption than socio-demographic factors: evidence from a mixed-methods study. BMC Public Health. 2014;14:1297. Published 2014 Dec 18. doi:10.1186/1471-2458-14-1297 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4320509/

    [3] Kunzmann AT, Coleman HG, Huang WY, Berndt SI. The association of lifetime alcohol use with mortality and cancer risk in older adults: A cohort study. PLoS Med. 2018;15(6):e1002585. Published 2018 Jun 19. doi:10.1371/journal.pmed.1002585
    CONFLICT OF INTEREST: I work with a clinical team which has used a low carbohydrate diet to reverse type 2 diabetes
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