Overview

• Colorectal cancer rates among 25- to 49-year-olds in Britain have risen by 52% since the early 1990s, with unclear causes behind the increase.
• Observational studies suggest higher vitamin D levels may reduce colorectal cancer risk by up to 58%, but randomized controlled trials (RCTs) show inconsistent prevention outcomes.
• The VITAL trial involving over 25,000 participants found no significant reduction in cancer incidence with vitamin D supplementation at 2,000 IU/day.
• A meta-analysis of seven RCTs reported a 30% improvement in survival rates for colorectal cancer patients taking vitamin D supplements, suggesting benefits during later stages of the disease.
• Public health guidance recommends maintaining sufficient vitamin D levels through sun exposure, diet, or supplements, though it stops short of endorsing supplementation as a standalone cancer prevention strategy.