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Back to Cancer

Milk Products and Breast Cancer

According to the Third Expert Report by the World Cancer Research Fund and the American Institute for Cancer Research, there is suggestive evidence that dairy products and diets high in calcium may reduce the risk of premenopausal breast cancer.

Highlights

  • Consuming dairy products and diets high in calcium might decrease the risk of premenopausal breast cancer.
  • Consuming diets high in calcium might decrease the risk of postmenopausal breast cancer.
  • Components in milk products, namely calcium, vitamin D and lactoferrin appear to have anticarcinogenic effects.  

Basic Facts on Breast Cancer 

There is no single cause of breast cancer; however, there are many risk factors including the following among others:1

  • Personal history of breast cancer;
  • Family history of breast and other cancers;
  • BRCA gene mutations;
  • Hormone replacement therapy;
  • Oral contraceptives;
  • Obesity.

Breast cancer is the most common cancer among Canadian women (excluding non-melanoma skin cancers). About 1 in 8 Canadian women is expected to develop breast cancer during her lifetime.1

The Evidence

According to the Third Expert Report published in 2018 by the World Cancer Research Fund and the American Institute for Cancer Research, limited evidence suggests that consuming dairy products may decrease the risk of premenopausal breast cancer.2 For postmenopausal breast cancer, no significant associations were observed in studies on dairy products or on total milk. There is also limited evidence that consuming diets high in calcium may reduce the risk of breast cancer in both premenopausal and postmenopausal women. 

A 2015 meta-analysis of 22 prospective cohort studies (n = 1,566,940) evaluated the association between dairy intake and breast cancer risk.3

  • Higher dairy consumption (>600 g/d) was associated with a 10% lower risk of breast cancer, as compared to lower dairy consumption (<200 g/d);
  • Additionally, a dose-response relationship was found, indicating an inverse and linear association between dairy intake and the risk of breast cancer:
    • Per additional 250 g/d dairy intake, risk was reduced by 3%;
    • Per additional 500 g/d dairy intake, risk was reduced by 6%;
    • Per additional 750 g/d dairy intake, risk was reduced by 9%;
    • Higher yogurt and low-fat dairy intakes were associated with a risk reduction of 9% and 15%, respectively;
    • No association was observed between whole milk, low-fat/skim milk, cheese/butter or high-fat dairy and breast cancer risk.

Potential Mechanisms

The mechanisms by which the consumption of milk and milk products may influence the risk of breast cancer are not clear. Nevertheless, there are key components in milk products, namely calcium, vitamin D and lactoferrin, which appear to play important anticarcinogenic roles.

Calcium
A 2016 meta-analysis has shown that there is an inverse dose-response relationship between calcium intake and breast cancer risk among both pre-menopausal and post-menopausal women.4 Calcium participates in the regulation of apoptosis, cell proliferation and differentiation.

Animal studies have shown that a high calcium intake inhibits hyperproliferation of mammary glands and can inhibit mammary carcinogenesis. The anti-proliferation and pro-differentiation properties of calcium may also decrease benign proliferative epithelial disorders.5

Vitamin D
Vitamin D plays potential mechanistic roles through its anti-cancer and anti-inflammatory properties.

Calcitriol, the hormonally active form of vitamin D, exerts anti-proliferative, pro-apoptotic and pro-differentiating effects in many malignant cells.6-8 Vitamin D also opposes estrogen-driven proliferation in mammary glands by reducing progesterone and estradiol levels.7,9 A meta-analysis found an inverse association between circulating 25(OH)D and breast cancer risk among post-menopausal women.10

Lactoferrin
Bovine milk lactoferrin has also been found to be protective against breast cancer. It appears that lactoferrin has the ability to interact with certain receptors and modulate the genetic expression of molecules involved in the cell cycle and apoptosis machinery.11

Conjugated linoleic acid
Some experimental and in vitro studies have shown that conjugated linoleic acid, which is a naturally occurring fatty acid found in milk products, may protect against mammary carcinogenesis.12,13

Conclusion

The totality of the evidence to date suggests that the consumption of dairy products may reduce the risk of premenopausal breast cancer. Milk products are a major source of calcium and the available evidence suggests diets high in calcium may reduce the risk of breast cancer in both premenopausal and postmenopausal women. Vitamin D and lactoferrin may also be important anti-cancer milk components. More research is needed to elucidate the precise mechanisms by which dairy foods may reduce breast cancer risk.

References

  1. Canadian Cancer Society. 2018. Breast cancer. Available at www.cancer.ca Accessed September 27, 2018.
  2. World Cancer Research Fund / American Institute for Cancer Research. Diet, Nutrition, Physical Activity and Cancer: a Global Perspective, Continuous Update Project Expert Report 2018. Available at dietandcancerreport.org  Accessed September 27, 2018.
  3. Zang J et al. The association between dairy intake and breast cancer in Western and Asian populations: a systematic review and meta-analysisJ Breast Cancer 2015;18:313-322.
  4. Hidayat K et al. Calcium intake and breast cancer risk: meta-analysis of prospective cohort studiesBr J Nutr 2016;116:158-166.
  5. Chen P et al. Meta-analysis of vitamin D, calcium and the prevention of breast cancerBreast Cancer Res Treat 2010;121:469-477.
  6. Gandini S et al. Meta-analysis of observational studies of serum 25-hydroxyvitamin D levels and colorectal, breast and prostate cancer and colorectal adenomaInt J Cancer 2011;128:1414-1424.
  7. Krishnan AV and Feldman D. Mechanisms of the anti-cancer and anti-inflammatory actions of vitamin DAnnu Rev Pharmacol Toxicol 2011;51:311-336.
  8. Rohan TE et al. A randomized controlled trial of calcium plus vitamin D supplementation and risk of benign proliferative breast diseaseBreast Cancer Res Treat 2009;116:339-350.
  9. Knight JA et al. Vitamin D association with estradiol and progesterone in young womenCancer Causes Control 2010;21:479-483.
  10. Bauer SR et al. Plasma vitamin D levels, menopause, and risk of breast cancer: dose-response meta-analysis of prospective studiesMedicine (Baltimore) 2013;92:123-131.
  11. Duarte DC et al. The effect of bovine milk lactoferrin on human breast cancer cell linesJ Dairy Sci2011;94:66-76.
  12. McGowan MM et al. A proof of principle clinical trial to determine whether conjugated linoleic acid modulates the lipogenic pathway in human breast cancer tissueBreast Cancer Res Treat 2013;138:175-183.
  13. Arab A et al. The effects of conjugated linoleic acids on breast cancer: a systematic reviewAdv Biomed Res 2016;5:115.

Keywords: breast cancer , lactoferrin , milk , calcium


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