Elsevier

European Journal of Cancer

Volume 50, Issue 7, May 2014, Pages 1223-1231
European Journal of Cancer

Vitamin C and survival among women with breast cancer: A Meta-analysis

https://doi.org/10.1016/j.ejca.2014.02.013 Get rights and content

Abstract

Background

The association between dietary vitamin C intake and breast cancer survival is inconsistent and few studies have specifically examined vitamin C supplement use among women with breast cancer. The purpose of this study was to summarise results from prospective studies on the association between vitamin C supplement use and dietary vitamin C intake and breast cancer-specific mortality and total mortality.

Methods

Studies were identified using the PubMed database through February 6, 2014 and by examining the references of retrieved articles. Prospective studies were included if they reported relative risks (RR) with 95% confidence intervals (95% CIs) for at least two categories or as a continuous exposure. Random-effects models were used to combine study-specific results.

Results

The ten identified studies examined vitamin C supplement use (n = 6) and dietary vitamin C intake (n = 7) and included 17,696 breast cancer cases, 2791 total deaths, and 1558 breast cancer-specific deaths. The summary RR (95% CI) for post-diagnosis vitamin C supplement use was 0.81 (95% CI 0.72–0.91) for total mortality and 0.85 (95% CI 0.74–0.99) for breast cancer-specific mortality. The summary RR for a 100 mg per day increase in dietary vitamin C intake was 0.73 (95% CI 0.59–0.89) for total mortality and 0.78 (95% CI 0.64–0.94) for breast cancer-specific mortality.

Conclusion

Results from this meta-analysis suggest that post-diagnosis vitamin C supplement use may be associated with a reduced risk of mortality. Dietary vitamin C intake was also statistically significantly associated with a reduced risk of total mortality and breast cancer-specific mortality.

Introduction

Breast cancer is the most commonly diagnosed cancer in women worldwide [1] and in the United States (US) alone there are approximately 2.9 million breast cancer survivors [2]. Multivitamin and supplement use is common among cancer patients with a prevalence reported to range from 75% to 87% among breast cancer survivors [3]. Vitamin C is one of the most commonly consumed supplements [4], however, the safety and benefits of oral vitamin C supplement use among cancer survivors has not been established [5], [6], and few studies have specifically examined vitamin C supplement use among women with breast cancer [7], [8], [9], [10], [11]. The association between dietary vitamin C intake and breast cancer survival is inconsistent, with some studies reporting a reduced risk of mortality with increasing intake [6], [7], [9], [12], [13], [14], [15], [16], and others reporting no association [17], [18], [19], [20], [21]. The purpose of this study was to summarise results from prospective studies on the association between vitamin C supplement use and dietary vitamin C intake and breast cancer survival.

Section snippets

Search strategy and study selection

We conducted a literature search through February 6, 2014 using the PubMed database (http://www.ncbi.nlm.nih.gov/pubmed ) without restrictions on language. The following search terms were used: ‘vitamin C’ or ‘vitamin C supplements’ or ‘supplements’ and ‘breast cancer’ or ‘breast cancer mortality’ or ‘breast cancer survival.’ In addition, we reviewed the reference lists from retrieved articles to identify additional studies.

To be included in the meta-analysis the following criteria had to be

Study characteristics

We identified 15 papers with data from 11 prospective observational studies that were potentially eligible for inclusion into the meta-analysis [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21]. Two were excluded because they did not report RRs or CIs for vitamin C intake [12], [21], three were excluded because they only reported results for total vitamin C intake (food + supplements) [13], [16], [19], and one had more recent results available within the

Discussion

In this meta-analysis, dietary vitamin C intake and post-diagnosis oral vitamin C supplement use were statistically significantly associated with a reduced risk of total mortality and breast cancer-specific mortality.

There are several mechanisms through which intake of vitamin C may influence mortality among women with breast cancer. Vitamin C exhibits antioxidant actions including the neutralisation of free radicals which may impact cancer progression [29], [30]. At higher doses it may also

Role of the funding source

The funding source had no role in the study design, collection, analysis, and interpretation of data, in the writing of the manuscript or in the decision to submit the manuscript for publication.

Conflict of interest statement

None declared.

Acknowledgement

This work was supported by the Swedish Cancer Foundation.

References (36)

  • R. DerSimonian et al.

    Meta-analysis in clinical trials

    Control Clin Trials

    (1986)
  • S. Osganian et al.

    Vitamin C and risk of coronary heart disease in women

    J Am Coll Cardiol

    (2003)
  • B. Frei

    Reactive oxygen species and antioxidant vitamins: Mechanisms of action

    Am J Med

    (1994)
  • World cancer factsheet. Cancer Research UK, London;...
  • Society AC. Breast cancer overview....
  • C.M. Velicer et al.

    Vitamin and mineral supplement use among US adults after cancer diagnosis: a systematic review

    J Clin Oncol

    (2008)
  • K. Radimer et al.

    Dietary supplement use by US adults: data from the National Health and Nutrition Examination Survey, 1999–2000

    Am J Epidemiol

    (2004)
  • AICR

    Food, nutrition, physical activity, and the prevention of cancer: a global perspective

    (2007)
  • P. Shekelle et al.

    Effect of the supplemental use of antioxidants vitamin C, vitamin E, and doenzyme Q10 for the prevention and treatment of cancer

    Evid Rep Technol Asses (Summ)

    (2003)
  • A.T. Fleischauer et al.

    Antioxidant supplements and risk of breast cancer recurrence and breast cancer-related mortality among postmenopausal women

    Nutr Cancer

    (2003)
  • H. Greenlee et al.

    Antioxidant supplement use after breast cancer diagnosis and mortality in the Life After Cancer Epidemiology (LACE) cohort

    Cancer

    (2012)
  • H. Harris et al.

    Vitamin C intake and breast cancer mortality in a cohort of Swedish women

    Br J Cancer

    (2012)
  • S. Nechuta et al.

    Vitamin supplement use during breast cancer treatment and survival: a prospective cohort study

    Cancer Epidemiol Biomarkers Prev

    (2011)
  • E. Poole et al.

    Postdiagnosis supplement use and breast cancer prognosis in the After Breast Cancer Pooling Project

    Breast Cancer Res Treat

    (2013)
  • D. Ingram

    Diet and subsequent survival in women with breast cancer

    Br J Cancer

    (1994)
  • M. Jain et al.

    Premorbid diet and the prognosis of women with breast cancer

    J Natl Cancer Inst

    (1994)
  • A. McEligot et al.

    Dietary fat, fiber, vegetable, and micronutrients are associated with overall survival in postmenopausal women diagnosed with breast cancer

    Nutr Cancer

    (2006)
  • T. Rohan et al.

    Dietary factors and survival from breast cancer

    Nutr Cancer

    (1993)
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