Does zinc remove heavy metals from the body?

Introduction

Heavy metal toxicity is a common health concern. Heavy metals like lead, mercury, arsenic, and cadmium can accumulate in the body over time and cause a variety of health problems. This has led many people to look for ways to remove heavy metals from their bodies. One method that has gained popularity is using zinc supplements to chelate (bind to) heavy metals in the body, allowing them to be excreted more easily. But does the science actually support using zinc for heavy metal detoxification? Let’s take a detailed look at the evidence.

How Zinc Is Thought to Remove Heavy Metals

Zinc is an essential dietary mineral that plays crucial roles in immune function, protein synthesis, DNA synthesis, and cell division. It interacts with and influences the absorption of other minerals like iron and copper.

Some functional and integrative medicine practitioners believe that zinc can also bind to heavy metals in the body, creating stable compounds that are then excreted in the urine or feces. The proposed mechanisms are:

1. Zinc has a higher affinity for binding to metal transport proteins like metallothionein than other heavy metals like cadmium and lead. So in theory, supplemental zinc could occupy those proteins, displace bound toxins, and allow the heavy metals to be eliminated from the body more easily.

2. Zinc supplementation increases levels of metallothionein, a protein that binds to heavy metals like cadmium, mercury, and lead and assists with their removal.

3. Zinc competes with heavy metals for absorption in the gastrointestinal tract. So supplemental zinc may help block absorption of ingested heavy metals from food or water.

Based on these mechanisms, some integrative health practitioners recommend zinc supplementation as part of heavy metal detoxification protocols. Zinc is considered a relatively safe and affordable supplement. But what does the current research actually tell us about its effectiveness?

Studies on Zinc and Heavy Metal Removal in Animals

A number of studies in animals have found that supplemental zinc can reduce heavy metal burden and toxicity under certain conditions:

– Rats fed zinc supplements were found to have decreased lead accumulation in tissues like the liver, kidneys, and bones after lead exposure. Zinc was thought to compete with lead for absorption in the intestines.

– In lead-exposed mice, zinc supplementation lowered lead levels in the liver, kidneys, and bones and reversed some of the biochemical effects of lead toxicity.

– Zinc has been shown to induce synthesis of metallothionein in liver and kidney cells of rats. Metallothionein bound to cadmium, mercury, and other heavy metals in these studies, facilitating their removal.

– Ducklings exposed to arsenic and lead absorbed lower amounts of these metals when they were also supplemented with zinc.

These results suggest that zinc can reduce heavy metal bioaccumulation and toxicity in animals by stimulating metallothionein production, competing for absorption with toxic metals, and possibly displacing heavy metals already stored in tissues. However, effects vary based on the specific metal, animal species, dosage, and duration of exposure.

Human Studies on Zinc for Heavy Metal Detoxification

While the animal research is intriguing, what about studies in humans? Several small human studies have investigated whether zinc supplementation can lower levels of toxic metals like lead, cadmium, and arsenic:

– In a study of 15 lead workers, taking zinc supplements for 4 weeks (50 mg zinc sulfate, 3 times per day) increased urinary lead excretion. However, zinc did not affect blood lead levels.

– Zinc supplementation for 6 weeks (22 mg/day) in cadmium-exposed workers resulted in significantly increased urinary cadmium excretion without affecting cadmium blood levels.

– In Bangladeshi children chronically exposed to arsenic via contaminated drinking water, 6 months of zinc supplementation slightly lowered urinary arsenic levels compared to a placebo. However, total arsenic elimination in urine was not increased.

– A small study in pregnant women found that zinc supplementation (25 mg/day) for 6 months increased urinarylead excretion during pregnancy but did not lower maternal or neonatal blood lead levels.

Although these human trials show some increase in urinary heavy metal excretion with zinc supplementation, they provide limited evidence that zinc significantly reduces total body levels of heavy metals like lead, cadmium, and arsenic. Lowering blood levels is considered the most accurate measure of reducing heavy metal body burden.

Larger, longer-term trials directly measuring effects on blood heavy metal levels are still needed. There are also no studies assessing whether zinc affects body levels of other toxic metals like aluminum and nickel.

Other Considerations on Zinc and Heavy Metal Detox

It’s important to consider that high doses of zinc over 50 mg per day taken long-term can negatively impact copper absorption. Copper helps form red blood cells, maintain nerve cells, and support immune function, so over-supplementing zinc could lead to copper deficiency.

There are also mixed findings on whether taking zinc on an empty stomach versus with food impacts absorption and efficacy for heavy metal detox. Some functional medicine doctors advise taking zinc supplements on an empty stomach away from food to increase absorption. But human studies showing benefits have not consistently followed an empty stomach protocol.

Finally, evidence does not support using zinc alone as a heavy metal “cure-all.” For individuals with significant heavy metal burden, zinc supplementation may need to be part of a more comprehensive detoxification program under a practitioner’s supervision.

Conclusion

Based on current evidence, zinc may provide some benefits for enhancing heavy metal excretion – primarily in urine. Findings from animal studies and limited human trials suggest zinc can stimulate metallothionein production to bind toxic heavy metals and modestly increase urinary elimination of metals like lead, cadmium, and arsenic.

However, there is still minimal research showing zinc supplementation dramatically reduces total body levels of heavy metals by increasing blood excretion or redistributing tissue stores. Many of the studies had small sample sizes, short durations, and other limitations as well. Larger, more rigorous human trials are still needed.

Zinc is considered safe when not over-dosed, so it may have a role as an adjunct therapy for heavy metal detoxification. But the science does not clearly establish zinc as a stand-alone, highly effective treatment for removing stored heavy metals from the human body at this time. For people with significant heavy metal toxicity, zinc supplementation should be considered part of a more comprehensive detoxification regimen under medical supervision.