Calcium is no stranger to controversy, and its important role is often tarnished by unfounded contradiction. Its silent participation in troubled waters put its reputation in jeorpardy, wrongly accused of misdeeds it has not committed.
The guilty verdict dished out is often based on circumstantial evidence of its presence at the "crime scene". The most common type of kidney stone is composed of calcium oxalate. A senior citizen who has seen some miles often has opaque calcification of the artery leaving the heart (aorta) in a chest x-ray. In cardiovascular disease, the underlying fires of inflammation within the artery walls instigates deposition of calcium, making it an indirect predictor of the No.1 killer.
None of the above is the direct result of calcium causing mischief, but merely its response to disease and injury.
Calcium101
Calcium is the most abundant mineral in the body, and if it were possible to gather it all in a bag, it will weigh about a kilogram. About 99% is banked in the bones and teeth, and only 1% circulates freely in the blood, within cells, and the fluid between cells.
Calcium has an undeniable role in building up bone density, giving strength and integrity to our supporting framework. What many are unaware of is the myriad other cellular functions of calcium that keep us alive.
It plays a constant role in controlling traffic of incoming supplies of nutrients and the exit of biochemical wastes from the cells, the making of hormones, and the transmission of messages from one nerve cell (neurons) to another.
Last, but not least, is its involvement in muscle contractions, working in concert with another important player, magnesium, in the cellular "see-saw" where one comes in and the other goes out, alternating between muscle contractions and relaxation.
The daily movement of calcium commences with ingestion, where after dispersion and absorption in the gut, it meanders its way to the bones to build up "hardness", while a small portion is utilised for metabolic functions.
When demand exceeds supply, the mineral is withdrawn from the bone bank, the bones.
Installed within us is an automatic alarm system that keeps calcium levels within a physiologic range. Failure of this hardware will lead to disease if the calcium levels swing too high or drops too low.
Behind the thyroid in the neck is a gland (parathyroid) that secretes parathyroid hormones, which elevates blood calcium when its level drops, mobilising the shift from the bones into the circulation. Calcitonin is another regulatory hormone that moves calcium back into the bones.
Active vitamin D is the gatekeeper to the entrance of calcium, its presence being a prerequisite for effective absorption of the mineral. The dietary precursor of vitamin D is activated in a three-step process, with the initial ignition in the skin, aided by sun exposure, thus earning the label "sunshine vitamin".
A second process occurs in the liver, and the final step of activation is effected by the kidneys. Lack of sun exposure, liver or kidney disease will lead to poor calcium absorption, auguring the development of porous bones (osteoporosis).
Consumption matters
The average daily diet confers 350mg to 400mg of calcium. Gulping down a glass of milk adds another 250mg of calcium. However, absorption of dietary calcium is only about 40%. Infants to children aged five years require 300mg to 600mg calcium daily; those six to 10 years old require 800mg; those 11 to 18 years require 1,300mg; 19- to 50-year-olds require 1,000mg; those above 50 years/pregnant/lactating require 1,200mg; while perimenopausal women require 1,500mg. (The safe upper limit for children and adults is 2,500mg per day).
Calcium rich foods include dairy products (milk, cheese, yoghurt, eggs), tofu, sardines, and vegetables like cabbages, kale, and broccoli. One may also choose a "good" calcium supplement in the right dosage and right form to meet the dietary shortfall.
Calcium supplements are the most widely used and prescribed mineral supplement, and confusion abounds in choosing the right type, based on dose, form, and combination.
The capacity to absorb calcium from the gut is limited to 500mg at one pass. The most common and cheapest form is calcium carbonate (inorganic salt), and the absorption rate is about 30%, whereas calcium citrate is said to be better absorbed.
As the former enters the cavernous stomach, it drops into a pit of acid juices (hydrochloric acid), which react with the carbonate to form a "champagne-like" foam. Calcium carbonate has the notorious tendency to cause heartburn.
Subsequently, the partly dissolved tablet exits the stomach into the first part of the small intestines, where further down is a short segment that acts as the window of absorption. The activated form of vitamin D brokers the entry of calcium into the cells by a process called active transport, akin to an electrical pump.
Even as the remnants of calcium leave the site of active absorption, some still manage to gain entry by a different manner, called passive diffusion, and the rest makes its way to the rear exit.
If much of the calcium is poorly absorbed, the result is unpleasant constipation.
Other forms of calcium tablets include calcium gluconate and lactate.
There is such a complex interplay of factors that scientists are not in total agreement about calcium requirements. Even if adequate calcium is made available to the body, there is no guarantee that it will be incorporated into the scaffolding of the bone’s architecture.
The combination of activated vitamin D, magnesium, boron, silicon, copper, zinc and other trace minerals are required for calcium to be translated into improved bone density. Calcium is like the brick, but to cement them together, we need at least 20 other known nutrients to form the mortar to glue it together.
Unfortunately, how many of us are cellular scientists, and how many supplement makers understand the science?
Amidst all this scientific jargon brews confused hearsay, misconceptions and myths. Perhaps this is the forum to address some common issues.
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