-50% 4,000 IU/day of vitamin D3 vs. breast cancer incidence
[Garland 2007 Journal of Steroid Biochemistry & Molecular Biology]
The study concluded that a 50% reduction in incidence of breast cancer was possible from high vitamin D supplementation. A blood level of vitamin D at or above 52 ng/ml was need to achieve that level of risk reduction. The study also related intake of vitamin D to blood levels and to decrease in risk of breast cancer:
1000 IU (22 ng/ml) 21% reduction in cases [53 nmol/L]
2000 IU (32 ng/ml) 31% reduction in cases [77 nmol/L]
2400 IU (36 ng/ml) 35% reduction in cases [87 nmol/L]
3000 IU (42 ng/ml) 40% reduction in cases [102 nmol/L]
3800 IU (50 ng/ml) 48% reduction in cases [121 nmol/L]
4000 IU (52 ng/ml) 50% reduction in cases [126 nmol/L]
-50% highest blood levels of vitamin D reduced risk of death after diagnosis of breast cancer by approximately 50%.
[Mohr 2014 Anticancer Research]
This study combined and analyzed data from 5 previous studies. Women in the highest fifth of vitamin D blood levels (≥30 ng/ml or ≥75 mmol/l) had about half the risk of death after diagnosis as compared to women in the lower fifth.
Vitamin D supplements reduce risk of Breast Cancer incidence and mortality. The tolerable upper limit for Vitamin D is 4000 IU/day.