The results of a new study have revealed that having higher levels of cadmium may raise a woman's risk of developing endometrial, or uterine, cancer.
In the United States, endometrial cancer - also known as uterine cancer - is the most common cancer of the reproductive organs in women.
The disease, which mainly affects postmenopausal women, arises when cells in the endometrium, or the inner lining of the uterus, grow out of control.
Endometrial cancer accounts for 92 percent of cases of cancers of the body of the uterus, which estimates suggests will total around 61,380 in the U.S. in 2017. Another type of cancer of the uterus, called uterine sarcoma, accounts for the other 8 percent of cases.
Lead author Jane McElroy, an associate professor in the University of Missouri Medical School's Department of Family and Community Medicine, and colleagues explain in their study report that cadmium is a "highly persistent" toxic metal that builds up in the body over time.
They refer to evidence that links cadmium exposure to a "variety of adverse health effects," including kidney damage, disruption to calcium balance, and raised risk of pancreatic, breast, and endometrial cancer.
Sources of cadmium exposure
The main route through which cadmium enters the body for people who are not routinely exposed to it in their jobs is from eating foods that contain the metal. These foods include liver, kidneys, crustacean shellfish - such as shrimp, lobster, and crab - and cereals.
Smoking tobacco is the second main non-occupational source of cadmium exposure due to the fact that tobacco plants absorb it readily from soil.
Urine samples from heavy smokers have been found to contain twice as much cadmium as samples from non-smokers, note the authors.
In the body, cadmium has similar effects to that of estrogen, which may explain its link to hormone-dependent cancers.
"Endometrial cancer has been associated with estrogen exposure. Because cadmium mimics estrogen, it may lead to an increased growth of the endometrium, contributing to an increased risk of endometrial cancer."
Prof. Jane McElroy
However, the researchers report that the evidence linking cadmium and endometrial cancer is "sparse," which is why they chose to investigate it further.
From the cancer registries of three mid-western states - Arkansas, Iowa, and Missouri - the team obtained details of women who had been diagnosed with endometrial cancer and had expressed willingness to take part in the research.
The study was designed as a case-control study - that is, one wherein the subjects with disease are matched to counterparts of the same age and sex who do not have the disease (or the controls). In this study, the team used voter registration lists to randomly select the controls.
From 35-minute comprehensive telephone interviews with participants, researchers obtained information about their general health, lifestyle, diet, and known and suspected risk factors for endometrial cancer.
Following the interviews, the participants also received kits for collecting and returning urine and saliva samples for analysis of cadmium levels.
Altogether, 631 women who had been diagnosed with endometrial cancer between January 2010 and October 2012, as well as 879 age-matched female controls, took part in the study. Their ages ranged from 18 to 81 years and the average age was 65.
'Significant increased risk'
Prof. McElroy says that when they compared the cadmium levels of the women who had been diagnosed with endometrial cancer with those of the controls, they "found a statistically significant increased risk of the cancer associated with a woman's cadmium levels."
"We found the rate of endometrial cancer incidence increased by 22 percent in individuals with increased cadmium levels," she adds.
The researchers point out that more research is now needed to better understand the link between cadmium exposure and endometrial cancer. However, in the meantime, there are things that people can do to limit their exposure, they add.
Smoking is an obvious area to address, and they also recommend paying attention to dietary sources, such as crustacean shellfish, kidney, and liver.
"You don't necessarily need to cut these from your diet," explains Prof. McElroy, "but eat them in moderation. This is especially true if women have a predisposition to endometrial cancer, such as a family history, diabetes or obesity."