Toxic heavy metals in our environment

Article Highlights

  • Heavy metals are toxic and come from insidious sources in our modern environment.
  • Their health effects are widespread and can be serious if exposure is left unchecked.
  • Several nutrients and herbs may help with the detoxification of these heavy metals.

Heavy metals are ubiquitous in our environment, food and water sources with some having potentially toxic effects. But what are heavy metals and which ones should we be concerned about in our clients’ and own daily lives?

The classification for heavy metals (HMs) is not standardised but is generally referred to as ‘naturally occurring elements with high atomic weight and density at least five times that of water.’1-2 This includes nutritionally essential heavy metals such as iron, cobalt, zinc, copper, chromium, molybdenum, selenium and manganese, which are needed at low concentrations for metabolic activities. However, some of the HMs are classed as non-essential, non-threshold, toxic metals with no established biological functions in the body, and potentially serious health effects at very low concentrations.1-3

Toxic, non-essential heavy metals, listed in priority based on their toxicological profile, include:2-3

• Aluminium
• Arsenic
• Cadmium
• Lead
• Mercury

HMs are naturally occurring, non-degradable, persistent and accumulative elements, with urbanisation, industrialisation and technological advances increasing widespread distribution and deposition in the air, soil and water.1-4

Table 1: Potential environmental, commercial and ingestive sources of toxic heavy metals5-10

These toxic HMs have acute and chronic health effects on most organ systems, including potential neurotoxicity, carcinogen status and renal and liver toxicity.1,3 They can also directly impact the gut microbiota and overall gut physiology.

Toxic HMs interact and affect cellular organelles and components leading to DNA, cellular protein, phospholipid and nucleic acid damage and cell death. They do this by increasing reactive oxygen species (ROS) or nitrogen-based free radical production and activity, or through the depletion of cellular thiols.2,6 Toxic heavy metals may also interact and impair the function of essential nutrients, such as iron, calcium, zinc and selenium.1,13

Several nutrients and plant extracts have been identified that may support the body’s antioxidant status, chelate heavy metals (bind and eliminate the HMs through the bile and urine) and protect against HM toxicity and nutrient depletion.

Nutritional and plant extract support for heavy metal toxicity and clearance

Garlic has been shown in preclinical and clinical studies to reduce toxicity, accumulation and oxidative effects, and impact uptake and elimination of HMs, including cadmium, lead, mercury, aluminium and arsenic.1,14-16 Garlic has potent antioxidant effects with its sulfurous compounds, including allicin and alliin, binding to HMs and promoting excretion through the bile to the faeces.1,17 In a prospective, double-blinded, randomised clinical trial, low doses (3.6 mgs) of allicin were clinically safer and as effective as D-penicillamine in reducing blood lead concentrations and symptoms in mild to moderate lead poisoning.16

Multiple human clinical trials show the benefits of zinc supplementation in heavy metal toxicity. This research in diverse population groups, showed zinc reduced cadmium, lead and aluminium levels, improved antioxidant capacity and selenium status, and significantly increased metallothionein (a naturally produced potent heavy metal chelator) mRNA by 2-fold in leukocytes and up to 4-fold in blood. 18-22

Glutathione (GSH) is the master antioxidant in the body, with its reduced form a crucial chelator and protector against heavy metal-induced free radical damage. GSH is required to produce GSH peroxidase and GSH S-transferase – two enzymes involved in numerous antioxidant and detoxification processes. Although bioavailability of GSH has been questioned, one clinical trial using Opitac™ reduced glutathione showed ‘the GSH contents in the protein-bound fraction of plasma significantly (P<0.01) increased from 60 to 120 min after GSH supplementation.23-26

Another important cellular antioxidant for heavy metal clearance is alpha lipoic acid. This fat- and water-soluble nutrient is readily absorbed and utilised by the body and helps to regenerate other antioxidants and increase the body’s natural antioxidant capacity. Preclinical trials show this nutrient not only protects against heavy metal free radical-induced damage but also chelates and removes heavy metals and protects mitochondrial function. 23,25,27-30

Vitamin C protects against mercury, arsenic and lead toxicity through its antioxidant effects. It also reduces lead levels. In a randomised, placebo-controlled clinical trial, blood lead levels were reduced by 81% in cigarette smoking males aged 20 to 30 years, when given 1000 mg of vitamin C daily for one week. The authors stated this could be due to a reduction in lead intestinal absorption.17,31-33

Mercury causes selenium deficiency due to its high affinity to this antioxidant mineral. It binds to selenium, permanently affecting its ability to function and disrupting the intracellular redox status. In a clinical trial, selenium supplementation, as yeast-based selenium, reduced pubic hair mercury levels by 34% and elevated serum and blood selenium levels by 73% and 59%, respectively, when study participants were given 100 mcg per day for four months. 13,33-35

The elimination of arsenic through the renal system requires this toxin to be methylated and relies on folate-dependent one-carbon metabolism. Research, including a double-blind, placebo-controlled trial, shows that folic acid supplementation rapidly increases arsenic methylation, lowers blood arsenic levels and reduces the risk of arsenic-induced toxicity effects.36 

Table 2 outlines the mechanisms of action, and approximate dosages if available from clinical trials, of these nutrients.

Table 2: Specific nutrients for HM toxicity and clearance

*References available on request