Cadmium has become a more prevalent cause for concern in recent years. Like lead, it is an underground mineral that did not enter our air, food, and water in significant amounts until it was mined as part of zinc deposits. Now there is widespread environmental contamination with cadmium.
As cadmium and zinc are found together in natural deposits, so are they similar in structure and function in the human body. Cadmium may actually displace zinc in some of its important enzymatic and organ functions; thus, it interferes with these functions or prevents them from being completed. The zinc-cadmium ratio is very important, as cadmium toxicity and storage are greatly increased with zinc deficiency, and good levels of zinc protect against tissue damage by cadmium. The refinement of grains reduces the zinc-cadmium ratio, so zinc deficiency and cadmium toxicity are more likely when the diet is high in refined grains and flours.
Cadmium levels in humans tend to increase with age (probably because of chronic subtle exposure), usually peaking at around age 50 and then levelling off. No cadmium is present in newborns. Interestingly, cadmium does not cross the placenta-fetal barrier nor the blood-brain barrier as lead and mercury do, so it is not toxic to fetuses, nor does it cause the mental and brain symptoms of lead and mercury.
We may have as much as 40 mg. of cadmium in our body and probably consume at least 40 mcg. daily. Levels vary according to region, as we get most of it from soil by way of our food. There may be some in water from contamination and water pipes, and cigarette smoke plus industrial burning of metals puts some cadmium into the air. Cadmium levels in the atmosphere are much higher in industrial cities.
Cadmium is not very well absorbed, with a rate of about 20 percent, but this is still a higher rate than that of many other minerals. Cadmium is not particularly well eliminated. Besides fecal losses, it is excreted mainly by the kidneys. This mineral is stored primarily in the liver and kidneys. As zinc has an affinity for the testes, cadmium is also stored there in higher concentrations than in other tissues. With zinc deficiency, more cadmium is stored. With aging, cadmium accumulates in the kidneys and may predispose to hypertension. As I stated, it does not get into the brain, nor does it pass into the fetus during pregnancy or the breast milk with lactation.
Sources: There are many sources from which our environment and our bodies can be contaminated with cadmium. Cigarette smoke, refined foods, water pipes, coffee and tea, coal burning, and shellfish are all definite sources. Cadmium is also a component of alloys, used in electrical materials, and is present in ceramics, dental materials, and storage batteries.
During the growth of grains such as wheat and rice, cadmium (from the soil) is concentrated in the core of the kernel, while zinc is found mostly in the germ and bran coverings. With refinement, zinc is lost, increasing the cadmium ratio. Refined flours, rice, and sugar all have relatively higher ratios of cadmium to zinc than do the whole foods.
One pack of cigarettes contains about 20 mcg. of cadmium, or about 1 mcg. per cigarette. About 30 percent of that goes into the lungs and is absorbed, and the remaining 70 percent goes into the atmosphere to be inhaled by others or to contaminate the environment. With long-term smoking, the risk of cadmium toxicity is increased. Though most of it is eliminated, a little bit is stored every day. Marijuana may also concentrate cadmium, so regular smoking of cannabis may also be a risk factor for toxicity from this metal.
Water pipes can be a source of cadmium concentration. Cadmium is often used to protect metals from corrosion. Galvanized (zinc) pipes usually contain some cadmium, as does the solder used to hold them together. Soft or acid water is corrosive and causes the metals in the pipes to break down, releasing cadmium and other minerals from them. Hard water containing calcium and magnesium salts actually coats the pipes and protects against the leaching of other minerals.
Air pollution of cadmium comes from zinc mining and refining, and from the burning of coal. Cadmium is also an industrial contaminant from the steel-making process.
Soil levels of cadmium are increased by cadmium in water, by sewage contamination, by cadmium in the air, and by high-phosphate fertilizers. Coffee and tea may contain significant cadmium levels. Root vegetables such as potatoes may pick up more cadmium, and the grains can concentrate cadmium. Seafood, particularly crustaceans, such as crab and lobster, and mollusks, such as clams and oysters, have higher cadmium levels, though many are also higher in zinc, balancing the cadmium.
Methods of toxicity: Though cadmium has no known useful biological functions, it competes with zinc for binding sites and can therefore interfere with some of zinc’s essential functions. In this way, it may inhibit enzyme reactions and utilization of nutrients. Cadmium may be a catalyst to oxidation reactions, which can generate free-radical tissue damage.
Symptoms of Toxicity: In his book Trace Elements and Man, the late expert in trace and toxic elements Henry Schroeder, M.D., described in detail cadmium’s involvement in generating, or at least contributing to, high blood pressure. Cadmium concentrates in the kidney and can generate kidney tissue damage and hypertension, as well as an increased incidence of calcium kidney stones. Initially, protein and sugar may be spilled in the urine. Some patients with high blood pressure show elevated urine cadmium levels. This hypertension is likely related to the reduced zinc-cadmium ratio. The cadmium effect may contribute not only to hypertension but to heart disease as well. In rat studies, higher levels of cadmium are associated with an increase in heart size, higher blood pressure, progressive atherosclerosis, and reduced kidney function. And in rats as well as in humans, cadmium toxicity is worse with zinc deficiency and reduced with higher zinc intake.
Cadmium appears to depress some immune functions, mainly by reducing host resistance to bacteria and viruses. It may also increase cancer risk, possibly for the lungs and prostate. Cadmium toxicity has been implicated in generating prostate enlargement, possibly by interfering with zinc support.
Cadmium also affects the bones. It has been known to cause bone and joint aches and pains. This syndrome, first described in Japan, where it was termed the itai-itai (“ouch-ouch”) disease, was caused by cadmium pollution there. It was also associated with weak bones that lead to deformities, especially of the spine, or to more easily broken bones. This disease was fatal in many cases.
We may be seeing an increase in emphysema due to cadmium exposure. Anemia also seems to be a problem. Most of these potential cadmium toxicity problems, including its immunosuppressant actions and its role in cancer, hypertension, and heart and kidney disease, need to be substantiated by more research.
Amounts leading to toxicity: What level of cadmium causes toxicity is not clear; zinc levels in the body play a role in determining this. Estimates of daily cadmium exposure range from 25 to more than 200 mcg., mostly from food. About 40-50 mcg. daily is probably a safe guess. This should be handled fairly well by a normally functioning body. Below 2 ppm in hair and .015 ppm in whole blood are considered current normal ranges for body cadmium levels.
Who is susceptible? People who have higher exposure to cadmium are at higher risk. Industrial workers, metal workers, zinc miners, and anyone who works with zinc galvanization may accumulate more cadmium. Those who drink soft water; those who smoke or whose friends, roommates, or coworkers smoke; coffee and tea drinkers; and those who eat refined flours, sugars, and white rice are also likely to receive greater exposure to cadmium.
Treatment: Intravenous EDTA chelation is effective in increasing cadmium elimination, though this is probably indicated only at more toxic levels. Avoiding further cadmium exposure is emphasized. High intake of zinc as well as of calcium and selenium will protect against further cadmium absorption, and adequate body levels of zinc may displace some tissue cadmium. Iron, copper, selenium, and vitamin C have been shown to increase cadmium elimination as well, as can be measured by urine levels. Hair analysis is a good way to follow cadmium levels.
Prevention: With good health, cadmium is probably not a problem unless there is increased exposure, zinc deficiency, or weakened kidney function. Cadmium toxicity also seems to be a little worse with lead intoxication. There are two good ways to protect against cadmium toxicity. The first is to avoid cadmium exposure and intake-primarily by minimizing smoking and exposure to cigarette smoke, avoiding refined foods, shellfish, coffee, tea, and soft water. Air contamination is usually minimal compared to that from food and water. The second way to protect against cadmium toxicity is to maintain good zinc levels by eating high-zinc foods, such as whole grains, legumes, and nuts (oysters are high in zinc but also high in cadmium). Taking additional zinc, 15-30 mg. daily in a supplement, will offer further protection against cadmium problems.