Dietary vitamin C is linked to reduced breast cancer incidence, mortality: meta-analysis

  • Zhang D & al.
  • Aging (Albany NY)
  • 29 Sep 2020

  • curated by Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • Intake of dietary vitamin C is associated with reduced breast cancer incidence and mortality, according to a meta-analysis of 69 studies.
  • The effect was observed only with dietary vitamin C, not vitamin C supplements.

Why this matters

  • Previous meta-analyses have yielded mixed findings.
  • This first meta-analysis compared dietary vitamin C with vitamin C supplements.

Study design

  • Meta-analysis of 69 observational studies of breast cancer risk (54 studies) and survival (15 studies).
  • Funding: None.

Key results

  • Relative risks were lower in the highest vs lowest quintiles of vitamin C exposure for:
    • Breast cancer incidence:
      • 0.86 (0.81-0.92).
    • Breast cancer-specific mortality:
      • 0.78 (0.69-0.88).
    • All-cause mortality:
      • 0.82 (0.74-0.91).
    • Breast cancer recurrence:
      • 0.81 (0.67-0.99).
  • Lower relative risk for breast cancer seen with dietary vitamin C:
    • 0.89 (0.82-0.96).
  • No relative risk decrease seen with vitamin C supplements:
    • 1.02 (P=.678).

Limitations

  • All studies were observational.