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. 2022 Mar 29;7:95–112. doi: 10.1016/j.jdin.2022.02.012

Table II.

Observational studies on the effect of dairy on acne

Source; country Study design; no. of participants Participant characteristics Measures Outcome summary Strengths Limitations Quality of evidence
Adebamowo et al,24 2005; United States Retrospective cohort study; 47,355 25-42-y-old women enrolled in the Nurses’ Health Study II. Questionnaire on “physician-diagnosed severe teenage acne” (1989) and high school diet (1998). Total milk (PR 1.22 [1.03-1.44]), skim milk (PR 1.44 [1.21-1.72]), and cottage cheese (PR 1.63 [1.22-2.20]) consumption associated with severe acne. Whole milk and low-fat milk not associated. Appropriate sample size. Generalized exposure classification. Potential bias in exposure and outcome classification. 4
Adebamowo et al,25 2006; United States Retrospective cohort study; 6094 9-15-y-old girls from GUTS. Questionnaires on food consumption frequency and the self-assessment of the presence and severity of acne. Whole, low-fat, skim, or chocolate milk associated with acne in 1996. PRs ranged from 1.17 (1.04-1.31) to 1.29 (1.08-1.53). Appropriate sample size. Longitudinal, generalized exposure classification. Potential bias in outcome classification. 5
Adebamowo et al,26 2008; United States Retrospective cohort study; 4273 9-15-y-old boys from GUTS. Questionnaires on food consumption frequency and the self-assessment of the presence and severity of acne. Skim milk associated with acne (PR 1.19 [1.01-1.40]). Total milk, whole milk, 2% milk, and low-fat milk not associated. Appropriate sample size. Longitudinal, generalized exposure classification. Potential bias in outcome classification. Multiple testing bias. 4
Di Landro et al,27 2012; Italy Case-control study; 205 patients with acne, 358 controls 10-24 y olds from 15 different outpatient hospital clinics. Questionnaire on the frequency of dietary intake. Dermatologist-evaluated acne severity (global acne assessment scale). Milk consumption (>3 portions per wk) associated with moderate-to-severe acne (OR 1.78 [1.22-2.59]). Appropriate sample size. Multiple institutions. Well-defined outcome classification. Unbiased study recruitment. Generalized exposure classification. None. 9
Pontes et al,28 2013; Brazil Longitudinal cohort study; 30 18-30 y olds with recent protein calorie supplementation use from dermatology clinics and gyms. Dermatologist-assessed acne (Leeds) before, after 30 d, and after 60 d of protein-calorie supplementation. Protein calorie supplementation significantly increased comedo and acne lesion count. Well-defined exposure and outcome classification. Low sample size. Potential recruitment bias. 6
Semedo et al,29 2016; Portugal Cross-sectional study; 1055 20-60 y olds from 5 different clinics. Questionnaire on dietary intake. Dermatologist-evaluated acne (Pillsbury). Reduced-fat milk and whole milk consumption associated with acne (OR 1.33 [1.03-1.70]). Appropriate sample size. Multiple institutions. Well-defined outcome classification. Unbiased study recruitment. Generalized exposure classification. None. 8
Duquia et al,30 2017; Brazil Cross-sectional study; 2201 18-y-old enlisted men. Questionnaire (Y/N) on daily cheese, whole milk, low-fat milk, and yogurt consumption. Dermatologist-evaluated acne. No significant association between acne and milk was found. Appropriate sample size. Unbiased recruitment. Generalizability. Limited exposure classification in Y/N format. No severity grading. 6
Ulvestad et al,31 2017; Norway Longitudinal cohort study; 2489 15-16-y-old (10th grade) Norwegian students. Questionnaire on dairy consumption at baseline and the presence of acne after 3 y. High intake of full-fat dairy associated with acne (OR 1.56 [1.02-2.39]). Total milk intake in girls only associated with acne (OR 1.80 [1.02-3.16]). Appropriate sample size. Unbiased recruitment. Potential bias in exposure and outcome classification. Generalizability. 6
Heng et al,32 2022; Singapore Cross-sectional study; 2090 cases and 1798 controls 17-71 y olds from a clinic. Questionnaire on diet. Trained personnel evaluated the presence, severity, and scarring of acne lesions. Frequent milk consumption associated with a lower likelihood of moderate-to-severe acne (OR 0.572 [0.360-0.910]). Appropriate sample size. Well-defined outcome classification. Potential bias in exposure classification. 7
Say et al,33 2021; Singapore Cross-sectional study; 1117 patients with acne and 723 controls 17-77 y olds from 2 different hospital sites. Questionnaire on diet. Medical staff evaluated the presence, severity, and scarring of acne lesions. No association between the frequency of milk consumption and acne severity. Increased milk consumption associated with a lower risk of scarring. Appropriate sample size. Well-defined outcome classification. Potential bias in exposure classification. 7

GUTS, Growing Up Today Study; OR, odds ratio; PR, prevalence ratio.

Negative studies - Say et al58 and Heng et al56 specifically asked about dairy and, therefore, had a potential bias in exposure classification. However, their results appear well supported, with hints that different populations and cultural attitudes toward food consumption influence the role of diet and acne.