What is a heavy metal and how often are you exposed to them? Should you be concerned? Though its definition varies, “heavy metals” is the general term given to a group of elements with metallic properties. Some of these metals are nutritionally essential to support life though they are needed in very small quantities. These are referred to as “trace minerals” and they include: Iron, copper, chromium, cobalt, manganese, molybdenum and zinc.
Ample evidence has established the importance of trace minerals in the human body for normal functioning. For example, Iron is required for the transport of oxygen needed for our cells to "breathe". Copper is used to create red blood cells and to scavenge free radicals, substances linked to increased risk of cancer or heart disease. Zinc is needed to heal wounds and to ensure that proteins are formed properly to carry out their vital roles.
Other metals like vanadium, strontium, arsenic, nickel, tin, aluminum, boron, arsenic and cadmium have unknown or inconclusive roles in human processes. However, some evidence has tied medical benefit to small dosages of these types of metals. For example, vanadium has been examined for its comparable role to insulin, or increasing effect of insulin in the body. Nickel is medically prescribed for increasing iron absorption and treating porous bones (osteoporosis).
Too little of any trace mineral in the body can affect normal functioning, but too much of any metal (essential or not) can become a health hazard as well. When heavy metals are not properly metabolized by the body they can accumulate in soft tissues and become toxic. The nervous system is a major and very crippling target.
Accumulation may also occur due to increased exposure of these metals which may enter the body through the diet, medications, inhaled in the air or through direct contact on the skin. Exposure can and probably occurs more often than you realize.
These elements, or some form of them occur naturally on the Earth’s crust which can leech onto fruits, vegetables, or any plant-based food grown directly in soil. This environmental exposure includes organic and conventionally grown crops. Consequently, if these plants are used to feed livestock then the metals will leech into many animal or animal based products as well. In a similar manner, water obtained from natural springs would contain some of these heavy metals. In fact, a 2011 study in California found 14 heavy metals in six different sources of bottled natural spring water1. All concentrations were within federal and state maximum contaminant levels, except for arsenic which exceeded California public health goal levels in all six sources1. Seafood like tuna, obtain mercury from the ocean. Cooking foods in iron or aluminum-made cookware might also leech trace amounts onto the food being cooked in them.
Some metals are even used therapeutically in medications such as (but not limited to) gold, gallium and lithium. Moreover, dental amalgams made from silver and mercury and prosthetics made from metal alloys may further contribute to exposure. Common household items containing some of these metals include fertilizers, fungicides, batteries, household cleaning agents and lead-based paints. Industrial exposure is more common in adults working in facilities handling metals or near hazardous waste sites and accounts for the majority of heavy metal poisonings throughout human history2.
Metal toxicity depends on a few factors however. First of all, some metals are more hazardous than others. The total dose absorbed and whether the exposure was chronic or acute will determine the severity of the resulting toxicity. The route of exposure is also important. For example, mercury is more injurious when inhaled rather than consumed via GI tract. In general, the overall health of the individual will dictate the toxic effects although children rather than adults tend to be more susceptible to toxicities since growing bodies absorb nutrients (and non-nutrients) more efficiently.
As often as exposure seems to occur, a healthy individual will rarely get near toxic levels. Through proper diet, your body has natural ways of eliminating and/or reducing the toxic effects of heavy metals. Antioxidants like vitamin A, C, E, alpha-lipoic acid (commonly found in meat), glutathione, lactoferrin (iron from milk protein) will increase protection from oxidative stress attributed to the presence of metals in the body. Even the trace minerals zinc and selenium have antioxidant properties to aid in this capacity. The amino acids cysteine, glycine and glutamine are also important detoxifying agents as they help to form glutathione in the presence of magnesium. Glutathione combines with many toxic substances and converts them into harmless forms that are then excreted from the body. Also, metallothionein is a cysteine rich, metal-binding protein produced in the body that works closely with zinc and has been shown to protect against cadmium toxicity3. Certain plants, most notably in the micro-algae family have been studied as heavy-metal “scavengers” though most research has shown these properties to occur within the plant itself, in test-tubes, or in animal studies. Chlorella and spirulina are popular micro-algae purported and sold by many natural product companies for their metal-binding capabilities, though studies on the effects in humans remain limited. Ultimately, these natural and biologic remedies should not replace the immediate medical attention required should an actual toxicity exist.
By: Scarlett Full, in-house Dietitian/Nutrition Scientist
1. Sullivan MJ, Leavey S. Heavy metals in natural bottled spring water. J Environ Health. 2011 Jun; 73(10):8-13.
2. Soghoian S, Tarabar A. Heavy metal toxicity. Medscape Reference. 2011. Available at: http://emedicine.medscape.com/article/814960-overview
3. Klaassen CD, Liu J, Chouhuri S. Metallothionein: An intracellular protein to protect against cadmium toxicity. Annu Rev Pharmacol Toxicol. 1999. 39: 267–94.