Higher levels of vitamin D and iron were inversely related to alopecia, while higher intake of alcoholic and sugary beverages was positively correlated with hair loss, according to a systematic review of 17 studies involving 61,332 patients.
The analysis, conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, examined data from Medline, Web of Science, and Scopus databases between March and June 2024. The study population was predominantly female (97%) with ages ranging from 7 to 77 years.
Vitamin D emerged as the most frequently studied nutrient across five investigations. Three studies identified an inverse correlation between vitamin D levels and alopecia areata severity, while two studies also found an inverse relationship between vitamin D levels and disease duration. One study reported a correlation between serum vitamin D levels and the severity of androgenetic alopecia.
Iron supplementation (100 mg/tablet) was associated with improved hair growth. Iron functions as a cofactor for enzymes involved in DNA synthesis and cellular proliferation, making it essential for rapidly dividing cells in hair follicles.
Two studies found alcohol consumption negatively impacted hair health, contributing to increased hair loss and premature depigmentation. Another study linked excessive sugary beverage intake to greater hair loss.
A protein-deficient diet was linked to reduced hair bulb diameter and pigmentation. Because the hair shaft is composed primarily of keratin, sufficient amino acids are required for synthesis and follicle function.
Studies comprised seven cross-sectional investigations, four case-control studies, three randomized clinical trials, two clinical trials, and one cohort study. Eleven studies were conducted in Asia, five in America, and one in Europe.
The most extensively studied hair outcome was alopecia occurrence and severity (eight studies), followed by hair loss assessment (five studies). Four studies relied on clinical history, while four used the Severity of Alopecia Score.
Four studies examining complex dietary supplements yielded evidence of improvements in hair parameters. The consumption of soy products (24.0 g or more a day) and cruciferous vegetables (70.8 g or more a day) were associated with reduced hair loss.
Most studies were cross-sectional in design, preventing establishment of cause-and-effect relationships. Heterogeneity in age groups, nutrients studied, health outcomes, and assessment methods precluded meta-analysis.
"Further research is needed to deepen our understanding of these associations and to develop evidence-based recommendations for promoting hair health through nutrition," the researchers concluded.
The researchers declared no potential conflicts of interest.
Source: Nutrition and Health