The Role of Cadmium in Breast Cancer

The association between breast cancer and cadmium, a heavy metal that can be found in food, cosmetics, water, and air, has been explored in several new studies with varied findings.

Consumption of cadmium may increase risk of breast cancer among women, according to results of a new study conducted in Sweden.¹ Among the first to focus on dietary cadmium and breast cancer risk, this study used data from questionnaires about food intake (55,987 respondents) and national estimates of cadmium levels in various foods. Women with the highest cadmium consumption were 21% more likely to develop breast cancer than women with the lowest cadmium intake. This risk increased to 27% for lean and normal-weight women. A diet rich in whole grains and vegetables seemed to provide a protective effect despite their cadmium content. The exact association between cadmium and breast cancer is not understood, but the favored hypothesis is that cadmium can mimic estrogen.

The study’s reliance on estimated values of cadmium was a major limitation.¹ This limitation was shared by a similar study conducted in Seattle, the results of which showed no evidence of associations between dietary cadmium and breast cancer risk factors, smoking habits, or total intake of calcium, iron, or zinc from diet, supplements, and multivitamins.² Researchers believe that their use of FDA estimates instead of actual values of cadmium content in food caused nondifferential measurement error and likely shrouded any associations.²

Preliminary findings from an unpublished study show that prolonged exposure to low levels of cadmium may cause some breast cancer cells to become increasingly aggressive and thus more likely to spread.3 This study, conducted at Dominican University of California, San Rafael, is among the first to analyze long-term exposure to low levels of the heavy metal. Researchers found that breast cancer cells with long-term exposure to cadmium express higher levels of SDF-1, a protein associated with tumor invasion and cancer spread. However, what happens in the laboratory is not always what happens in the real world, cautions Ken Spaeth, MD, MPH, director of Occupational and Environmental Medicine Center in Manhasset, NY.4 Further study of how specific proteins, including SDF-1, contribute to the aggressive characteristics of the cadmium-exposed cells is needed.

Pertinent Points:

- Dietary cadmium has a role in the development of breast cancer in postmenopausal women.¹
- Women who eat more whole grain and vegetables despite their cadmium content had a lower risk of breast cancer than women exposed to cadmium through other types of food.¹
- Long-term exposure to cadmium can contribute to the development of more malignant characteristics in breast cancer cells.³
- The high toxicity of cadmium is well known, but the specific relationship between cadmium and breast cancer, despite known associations, is poorly understood.

References:

References
1. Julin B, Wolk A, Bergkvist L, et al. Dietary cadmium exposure and risk of postmenopausal breast cancer: a population-based prospective cohort study. Cancer Res. 2012;72:1459-1466.
2. Adams SV, Newcomb PA, White E. Dietary cadmium and risk of invasive postmenopausal breast cancer in the VITAL cohort. Cancer Causes Control. 2012;Epub ahead of print.
3. Ponce E, Louie M, Aquino N. Chronic exposure to cadmium increases in the metastatic phenotype of breast cancer cells. Presented at: American Society for Biochemistry and Molecular Biology/Experimental Biology conference; April 23, 2012; San Diego. Abstract 7038. Program 782.10. Poster A291.
4. Mann D. Can heavy metal in foods, cosmetics spur breast cancer spread? Accessed April 23, 2012.