Beta-Carotene

Won't reliably improve cognition in people without the APOE ε4 gene variant — the association was only significant in that subgroup. Eating more fruits and vegetables doesn't reliably raise blood beta-carotene levels, as one food voucher trial showed no significant change in beta-carotene despite increased self-reported produce intake. Not a proven cancer preventive on its own — combination regimens showed uncertain long-term results. Won't give you a natural-looking tan — oral carotenoids produce a yellow-orange skin hue, not a sun-bronzed look.

• High-dose beta-carotene supplements are associated with increased lung cancer risk in smokers — a well-known safety concern not contradicted by any provided study
• One large observational study in the provided data found food colouring additives including carotenoid-class compounds associated with higher cancer incidence, though causality is unclear
• Oral beta-carotene causes yellow-orange skin discoloration (carotenodermia), which is cosmetically undesirable and often mistaken for jaundice
• Cognitive benefit was only observed in a specific genetic subgroup (APOE ε4 carriers); generalizing this to the broader population is not supported by the provided data
• No specific supplemental dose was studied in any of the provided clinical trials — dosing guidance from supplements is not evidence-based per this data set