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.