Research
Mixed
Higher baseline serum 25-hydroxyvitamin D levels are not independently associated with a lower risk of breast cancer after adjusting for BMI and physical activity.
Having higher blood levels of Vitamin D does not appear to lower breast cancer risk on its own, especially when accounting for body weight and exercise levels. Focus on maintaining a healthy weight and staying active rather than solely targeting Vitamin D levels for cancer prevention.
GoodRefutesHIGH confidence
Baseline 25-hydroxyvitamin D levels were not associated with breast cancer risk in analyses that were adjusted for BMI and physical activity (P trend = .20).
Why this rating
Nested case-control study within a large RCT, but observational in nature regarding the biomarker level.
Source
Calcium Plus Vitamin D Supplementation and the Risk of Breast Cancer
Rowan T. Chlebowski et al. · JNCI Journal of the National Cancer Institute · 2008
DOI 10.1093/jnci/djn360
rct · n=36282Cited 424×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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