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Head-to-head evidence comparison — which supplement is right for you?
Probiotics wins 3 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
29 of 38 studies with measurable effects showed benefit.
Top outcomes
Verdict
Mostly mechanism / observational
Top outcomes
10-20 billion CFU
With or without food (strain-dependent), Same time daily for consistency
Capsules with multiple strains
Prescription topical: a pea-sized amount of 0.025%-0.1% cream or gel applied to clean, dry skin once nightly. Start low-strength and every-other-night to build tolerance. A prescription drug used under clinician direction — not a supplement regimen.
before-bed
Topical cream or gel, 0.025%-0.1% (prescription)
2-4 weeks
4-8 weeks
4-8 weeks
First 1-2 weeks
12-24 weeks
12-24 weeks
Months
8-12 weeks
Preventive Effect of Probiotics on Oral Mucositis Induced by Cancer Treatment: A Systematic Review and Meta-Analysis
International journal of molecular sciences (2022) · Meta analysis · n=708
Three trials using Lactobacilli-based probiotics reported that the incidence of oral mucositis in the probiotic group was significantly low (risk ratio [RR] = 0.84, 95% confidence interval [CI] = 0.77−0.93, p = 0.0004).
Probiotics for treating acute infectious diarrhoea
The Cochrane database of systematic reviews (2020) · Meta analysis · n=12127
Effect size was similar in the sensitivity analysis and marked heterogeneity persisted.
Probiotics for the prevention of Clostridium difficile-associated diarrhea in adults and children
The Cochrane database of systematic reviews (2017) · Meta analysis · n=9955
A complete case analysis (i.e. participants who completed the study) among trials investigating CDAD (31 trials, 8672 participants) suggests that probiotics reduce the risk of CDAD by 60%.
Topical tretinoin improves photoaged skin. A double-blind vehicle-controlled study.
JAMA (1988) · Rct
Randomized, double-blind, vehicle-controlled trial of topical tretinoin for photoaged forearm and facial skin
Tretinoin emollient cream: a new therapy for photodamaged skin.
J Am Acad Dermatol (1992) · Rct
Multicenter double-blind vehicle-controlled trial of tretinoin emollient cream for photodamaged skin
Long-term treatment of photoaged human skin with topical retinoic acid improves epidermal cell atypia and thickens the collagen band in papillary dermis.
J Am Acad Dermatol (2005) · Open label
Long-term topical retinoic acid on photoaged human skin assessed histologically
Based on meta-analyses showing benefits for IBS and digestive symptoms. Effect sizes varied considerably between studies with low to very low certainty of evidence. Initial GI symptoms common when starting but typically resolve within 1-2 weeks.
AI-estimated from published studies. Interpret as directional guidance.
Probiotics has a higher evidence score (9/10 vs 8/10) and wins in 3 of 3 categories.
No known interactions between Probiotics and Tretinoin (Retin-A) have been documented in our database. However, always consult a healthcare provider before combining supplements.