Overview

• The review synthesized 17 studies with more than 61,332 participants under PRISMA guidelines and a PROSPERO registration.
• A Chinese cross-sectional study found higher hair loss among people consuming over 3,500 ml of sugary drinks per week, with a stronger signal in men.
• Multiple studies associated lower serum vitamin D with greater severity of androgenetic alopecia and alopecia areata, though one large cohort found no link.
• Additional findings tied alcohol intake to increased hair loss and premature hair depigmentation.
• Small trials and nutrient studies signaled potential benefits from iron, adequate protein and select supplements, but high bias, heterogeneity and a predominantly female sample (~97%) precluded firm conclusions or meta-analysis.