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.