Table 1.

Characteristics of studies describing acne diet therapy.

n	Type of Acne	Type of Study	Intervention/Measurement	Duration	Effect	Year [Reference]
66	moderate to severe AV	randomised controlled trial	-group 1: n = 34–participants with low GI and GL diet -group 2: n = 32–participants with usual eating diet	2 weeks	-IGF-1 concentrations significantly decreased among the group with low GI and GL diets and control group -there were no significant differences in insulin, glucose, IGFBP-3 concentrations and insulin resistance	2018 [5]
168	mild to moderate AV	randomised, double-blind, placebo-controlled trial	-group A (n = 82): capsules containing lactoferrin (100 mg), vitamin E (11 IU, as alpha-tocopherol), and zinc (5 mg, as zinc gluconate), capsule twice a day -group B (n = 82): placebo, capsules containing starch, capsule twice a day	12 weeks	-in the lactoferrin group, compared to the control: significant reduction in the total number of lesions (already after 2 weeks, with a maximum: at week 10), reduction in comedones and inflammatory changes (at week 10), sebum (improvement by week 12)	2017 [6]
160	nd	case-control study with a randomised controlled trial	n = 80 patients n = 80 healthy controls 1st stage: 25 (OH) D deficiency in 48.8% of AV patients, but only 22.5% of healthy controls 2nd stage: supplementation of 1000 IU of cholecalciferol/day	2 months	-deficiency of vitamin D was more frequent in patents with AV, oral vitamin D supplementation significantly improved AV inflammation	2016 [7]
48	nodular acne	randomised controlled trial	n = 24 patients received isotretinoin therapy (20–30 mg/day) and dietary supplement (gamma linolenic acid, vitamin E, vitamin C, beta-carotene, coenzyme Q10 and Vitis vitifera, twice a day) n = 24 patients received only isotretinoin (20–30 mg/day)	6 months	-patients using a dietary supplement with antioxidant properties had fewer side effects resulting from the use of isotretinoin, less redness and dryness and a better degree of hydration	2014 [8]
45	mild to moderate AV	randomised controlled trial	-group I: 2000 mg of eicosapentaenoic acid and docosahexaenoic acid) -group II: borage oil containing 400 mg γ-linoleic acid),III: a control group	10 weeks	-subjective assessment of improvement -reduction in inflammation and non-inflammatory acne lesions	2014 [9]
45	mild to moderate AV	prospective, randomised, open-label trial	-group A: probiotic -group B: minocycline -group C: probiotic and minocycline	12 weeks	-a significant improvement in the total number of lesions 4 weeks after the start of treatment in all groups -after 8 and 12 weeks, group C had a significant decrease in the total number of lesions compared to groups A and B	2013 [10]
235	inflammatory AV	multi-centre, open-label, prospective study	-addition of 1 to 4 tablets NicAzel (nicotinamide, azelaic acid, zinc, pyridoxine, copper, folic acid) to the current acne treatment regimen	8 weeks	-visible reduction in inflammatory changes (88% of patients), and 81% of patients rated skin appearance as moderate or much better	2012 [11]
32	mild to moderate AV	randomised, controlled trial	n = 17–low-glycaemic-load diet n = 15–control group	10 weeks	-significant clinical improvement in the number of non-inflammatory and inflammatory AV lesions (in the low-glycaemic index group)	2012 [12]
43	mild to moderate	exploratory study	100 mg of lactoferrin-enriched (80%) whey milk protein powder, twice a day	8 weeks	-reduction in inflammatory lesions (20.2%), non-inflammatory lesions (23.5%) and total lesions (22.5%), reduction in total lesion count (76.9%)	2011 [13]
36	mild to moderate	double-blind, placebo-controlled study	n = 18–lactoferrin group (200 mg daily) n = 18–placebo group	12 weeks	-a significant reduction in acne severity (by 20.3%), number of inflammatory lesions (by 38.6%) and total lesions (by 23.1%) compared to the placebo group	2010 [14]
58	1 (mild), 2 (moderate), or 3 (severe)	controlled clinical trial	n = 23–low glycaemic index n = 20–high glycaemic index	8 weeks	-improvement in the appearance of the skin (but not statistically significant), change in insulin sensitivity (but not statistically significant)	2010 [15]
31	mild to moderate AV	dietary intervention trial	n = 16, LGL group n = 15–control group	12 weeks	-increases in the ratio of saturated to monounsaturated fatty acids of skin surface triglycerides compared to controls	2008 [16]
43	mild to moderate	randomised, investigator-masked, controlled trial	n = 23–LGL group, n = 20–control group	12 weeks	-decrease in the total number of lesions, body weight, free androgen index and increase in insulin-like growth factor-1 binding protein compared to the control group	2007 [17]
43	mild to moderate	non-randomised, parallel, controlled feeding trial	n = 23, patients: LGL diet (25% energy from proteins, 45% energy from carbohydrates) n = 20, control group: diet rich with carbohydrates, but without reference to the glycaemic index	12 weeks	-decrease in the total number of lesions, decrease in body weight and body mass index, greater improvement in insulin sensitivity-compared to the control group	2007 [18]
82	severe AV, moderate AV unresponsive to conventional therapy, scarring AV, and AV causing psychological disorder	investigator-blinded, randomised study	group 1: isotretinoin (1 mg/kg/day) group 2: isotretinoin (1 mg/kg/day) and vitamin E (800 IU/day)	16 weeks	-vitamin E did not reduce the side effects associated with the use of isotretinoin	2005 [19]

GI—glycaemic index, GL—glycaemic load and LGL—low glycaemic load.