Nutritional Multitasking? Exploring Calcium Supplementation to Reduce Toxic Metal Effects

Abstract

Metals and metalloids are widespread in soil, air, and drinking water around the world,^1,2 with other sources, such as tobacco smoke,² adding to people’s total exposure. The effects of metal(loid)s on the body are widespread, too: Exposure can affect the nervous system, kidney function, and bone development; disrupt metabolic functions; interfere with DNA replication and repair; and perturb protein and enzyme activity.^2–4 In a new mouse study published in Environmental Health Perspectives,⁵ investigators explored whether a nutritional supplement might help avert some of this damage.

Household dust is one major route by which young children are exposed to potentially toxic metal(loid)s. The results of a new experimental study in mice suggest certain calcium supplements may help protect against the damage these elements cause. Image © iStock.com/Tanja Ristic.

The study was conducted by an interdisciplinary team of researchers from China, the United States, and Australia. One of the scientists was inspired by his own experience after his daughter was diagnosed with low bone density at 1 year of age. While considering which calcium supplement would be most helpful, first author Hong-Bo Li, an associate professor in the School of Environment at Nanjing University, wondered whether different calcium compounds might vary in their ability to decrease people’s uptake of metals.

Although some previous studies have suggested that calcium supplementation may decrease uptake of lead in the intestine, other research cautions against viewing dietary supplements as a magic bullet against lead exposure.⁶ Nevertheless, Li says, “I was curious to test whether the strategy can achieve a win–win: reducing toxic metal exposure and improving calcium nutrition.” Recent studies reported “substantial variability in calcium intake worldwide”⁷ and that nutritional rickets—a health outcome influenced by calcium and vitamin D intake—is the most frequent cause of pediatric bone disease⁸ worldwide.

For the new study, the researchers spiked the animals’ feed with real-world indoor dust samples to assess relative bioavailability of lead, cadmium, and arsenic in the presence of six calcium compounds: calcium hydrogen phosphate, calcium carbonate, calcium gluconate, calcium lactate, calcium aspartate, and calcium citrate. “We selected house dust as the exposure medium because children have hand-to-mouth behaviors and have a great chance of ingesting house dust particles when playing on the floor,” Li explains.

The team measured lead, cadmium, and arsenic levels in tissue (liver, kidney, bone) and blood; examined the calcium and phosphate transporters in the mouse small intestine; and characterized the metal(loid) compounds present in the feces. They also assessed metal(loid) solubility using an in vitro assay with simulated gastrointestinal fluid.

The results showed that the mice receiving calcium compounds had lower tissue levels of lead, cadmium, and arsenic than control animals, but the extent of decrease varied by calcium compound. Lead and cadmium levels were lowest in mice consuming calcium hydrogen phosphate, whereas arsenic levels were lowest in mice consuming calcium aspartate. These findings suggest that lead and cadmium may be metabolized by mechanisms different from those involved in arsenic metabolism.

Allison Kupsco, an assistant professor of environmental health sciences at Columbia University, appreciates that the study used real-world household dust. “Metals exposure is an urgent health risk for children,⁹ who are particularly vulnerable to metals effects, and public health policies to reduce source emissions may be difficult to implement,” says Kupsco, who was not involved in the study. “The authors’ focus on personal interventions via dietary supplements could be an important step toward reducing metals exposure in children.” She adds that exploring the efficacy of different calcium formulations is “hugely helpful” in determining which—if any—supplements would be an appropriate intervention.

Kupsco notes two limitations of the study. First, the complex biological interactions that take place involving essential and toxic metals are affected by the proportions of those elements, so knowing the specifics of the exposure mixture (as was known in this experiment) would be essential to determining appropriate interventions in an actual setting. Second, only female rodents were used. Not only do metabolic processes differ by sex for many toxicants, but rodents have different metabolism and uptake processes than humans, so confirmation of these findings in a human population, preferably in the form of a randomized controlled trial, would be a necessary next step of the research. The study authors acknowledge that conducting a follow-up cohort intervention study is a priority.

“Remediation of exposure should always remain the top priority,” says Mary Gamble, a professor of environmental health sciences at Columbia University who was also not involved in the study. She points to recent work on nutritional interventions to lower exposures by enhancing urinary elimination.^10,11 She says such interventions may offer “very promising complementary approaches that may reduce both nutritional deficiencies and their associated adverse health outcomes in exposed populations.”

Biography

Kelley Christensen is a science writer and editor in Eugene, Oregon.