Vitamin D had a strong protective effect against developing cancer, concluded an analysis of 63 studies which compared people's vitamin D levels to their medical histories. The researchers noted that:

• average vitamin D3 blood serum levels differed by latitude and race, with residents of the north eastern United States and individuals with darker skin pigmentation being at the highest risk of deficiency
• people with dark skins are more likely to die of breast, colon, prostate and ovarian cancer than white people of the same age
• vitamin D3 supplements could “reduce cancer incidence and mortality at low cost, with few or no adverse effects”
• supplementing with at least 1,000iu a day was necessary to produce an anti-cancer effect
• the American National Academy of Sciences has set a safe upper supplementation limit of 2,000iu a day

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The 63 studies analysed included 30 studies comparing vitamin D3 levels to risk of developing colon cancer, 13 examining the relationship with breast cancer, 26 the relationship with prostate cancer and seven the relationship with ovarian cancer.

Study leader Cedric Garland feared that vitamin D3 deficiency might be responsible for several thousand premature deaths from cancer each year in the US alone.