Table I.

Observational studies on the effect of glycemic index/load on acne

Source; country	Study design; no. of participants	Participant characteristics	Measures	Outcome summary	Strengths	Limitations	Quality of evidence
Bett et al,20 1967; United Kingdom	Case-control study; 16 patients with acne, 29 controls	15-27 y olds recruited from 2 clinics. Age/sex-matched controls recruited from a clinic and a factory/office.	Questionnaire on daily sugar intake. Physician-diagnosed acne.	No significant difference in daily sugar intake between patients with acne and controls.	Well-defined case selection. Appropriate control selection.	Low sample size. Potential bias in exposure classification	5
Kaymak et al,19 2007; Turkey	Case-control study; 49 patients with acne, 42 controls	19-34 y olds recruited from outpatient clinics.	Questionnaire on the frequency of food consumption and dietary intake. Dermatologist-assessed acne severity.	No significant difference in GI between patients with acne and controls. No significant difference in glycemic load between patients with acne and controls.	Well-defined case selection. Appropriate control selection.	Low sample size. Potential bias in exposure classification	7
Koku Aksu et al,21 2011; Turkey	Cross-sectional study; 2230	13-18-y-old adolescents from multiple schools.	Questionnaire on dietary intake and personal history of acne. Dermatologist-evaluated acne severity (Pillsbury diagnostic criteria).	Frequent sugar intake (aOR, 1.3 [1.06-1.82]) and frequent sweet consumption (aOR 1.2 [1.16-1.43]) associated with acne.	Appropriate sample size. Unbiased exposure classification.	Potential biases in outcome classification	7
Burris et al,22 2017; New York City	Cross-sectional study; 64	18-40 y olds with moderate/severe and no acne recruited by advertising.	Dietician-instructed 5-d food and beverage record. Dermatologist-evaluated acne severity. Bloodwork at study conclusion.	Moderate/severe acne group had a higher glucose load than participants without acne (137 ± 41 vs 117 ± 41, respectively; P < .001). No association between GI and acne.	Well-defined outcome classification. Unbiased exposure classification.	Low sample size. Potential bias in recruitment.	7
Huang et al,23 2019; China	Cross-sectional study; 8197	18-19-y-old students from 353 cities.	Questionnaire on dietary intake. Dermatologist-assessed acne history and severity (Pillsbury diagnostic criteria).	Soft drink sugar intake ≥100 g/d significantly associated with moderate-to-severe acne (aOR 3.12 [1.80-5.41]).	Appropriate sample size. Well-defined case selection.	Potential bias in exposure classification.	7

aOR, Adjusted odds ratio; GI, glycemic index.