Men and women exposed to cadmium (Cd) via their diet showed an increased risk of osteoporosis when compared with a population of people who were not exposed to it, according to a recent study published in the Journal of Bone and Mineral Research.
Yang Xinfen, PhD, and colleagues from the School of Public Health and Tropical Medicine at the Southern Medical University, Guangdong Provincial Center for Disease Control and Prevention in Guangzhou, China, evaluated 832 subjects from 7 towns were residents for at least 15 years and ate a diet of rice and vegetables grown in an area polluted by Cd. The researchers measured the bone mineral density (BMD) and urinary Cd concentrations of these patients against 284 subjects from 2 neighboring towns with similar dietary, lifestyle, and socioeconomic status whose residents lived and ate a diet of rice and vegetables in a non-Cd polluted area. Urinary concentrations were grouped into 4 quartiles based on concentration level, with subjects showing a median concentration of 3.97 µg/g creatinine and a range of 0.21 to 87.31 µg/g creatinine across both groups. The subjects were age 40 to 79, and there were no significant differences in either group regarding age, body mass index (BMI), gender ratio, anemia, cardiovascular disease prevalence, and menopause prevalence.
Dr Xinfen and colleagues also measured markers of early renal impairment, such as urinary N-acetyl-β-D-glucosaminidase (NAG), urinary albumin (U-Alb), α1-microglobulin, and β2-microglobulin, as well as the T-score of each subject using peripheral dual energy x-ray absorptiometry (DXA).
There was a significant association between categorical and continuous Cd concentrations and osteoporosis, while urinary Cd concentration and BMD shared a significant negative association. A higher Cd concentration was associated with a greater increased risk for osteoporosis, with subjects grouped in the second (odds ratio [OR] 3.07; 95% CI, 1.77-5.33), third (OR 4.63; 95% CI, 2.68-7.98), and fourth quartile (OR 9.15; 95% CI, 5.26-15.94) of urinary Cd concentration having the greatest risk for osteoporosis compared with subjects in the first quartile.
While there was a significant negative correlation between urinary Cd concentration and factors such as BMI, T-score, BMD, and serum albumin, Dr Xinfen and colleagues found a significant positive association for factors such as calcium, U-Alb, NAG, α1-microglobulin, and β2-microglobulin.
Men and women living in Cd-polluted areas had a median urinary concentration of 5.53 μg/g creatinine, while the control group had a median urinary Cd concentration of 1.70 μg/g creatinine.
High Yield Data Summary
- Men and women living in Cd-polluted areas had a median urinary concentration of 5.53 μg/g creatinine, while the control group had a median urinary Cd concentration of 1.70 μg/g creatinine.
“Urinary Cd concentrations at upper quartiles were found to be more common among women, indicating that women had a higher body burden of Cd compared with men,” the researchers wrote. “Women may be more affected than men because they are more prone to iron deficiency, which causes a higher fraction of dietary Cd to be absorbed in the gastrointestinal tract.”
The researchers also studied a subgroup of smokers and subjects exposed to secondhand smoke, but these variables did not significantly affect the results.
“Despite the high Cd content in cigarette smoke, the exposure to Cd from passive smoking was not significant,” Dr Xinfen and colleagues wrote.
Summary & Clinical Applicability
Using a T-score of –2.5 as a marker for osteoporosis, the benchmark dose was 1.14 μg/g creatinine — with a benchmark dose of 5% — and the lower bound benchmark dose was 2.73 μg/g creatinine — with a benchmark dose of 10% — in all subjects. Women in the study had an overall lower benchmark dose of urinary Cd concentration compared with men.
Dr Xinfen and colleagues noted that nephrotoxicity could occur in addition to subjects developing osteoporosis and reduced BMD. Recommendations included lowering the levels of Cd exposed in the environment.
“The findings support efforts to reduce environmental Cd exposure and reassess the maximum permitted level for foods that are naturally enriched in Cd,” the researchers wrote in their study.
The researchers noted the cross-sectional design of the study, use of peripheral DXA, and lack of central DXA testing could potentially limit their results.
Yingjian L, Ping W, Rui H, et al. Cadmium exposure and osteoporosis: a population-based study and benchmark dose estimation in southern China [published online April 13, 2017]. J Bone Miner Res. doi:10.1002/jbmr.3151