Calcium is the most abundant mineral in our bodies, as it plays an essential structural role , with Phosphorous and vitamin d in our bones and teeth, it is really a mineral of dynamite.
What is its importance , and what are the hormones that regulate it?.
Calcium: the mineral of dynamite
Calcium forms hydroxyapatite crystals , which strengthen the protein matrix in our skeleton. Actually, from 1200 grams of calcium the average human body contains 99% is found in our bones and teeth.
The remaining one percent is found primarily, in our bloodstream and outside of our cells. While the amount of calcium within our cells is very limited, and it is controlled very carefully.
This trace amount of calcium is extremely powerful, and it acts a bit like dynamite. It is very powerful and can be very useful if used in a controlled manner. But if it gets out of control, it results in disasters.
One of the first symptoms of suboptimal calcium deficiency is our nervous system. We become irritable, anxious and have difficulty sleeping. Give us some calcium and we’ll calm down.
However, the real consequences of suboptimal calcium deficiency , are far more serious than just anxiety and irritability.
The importance of calcium
Calcium is necessary for muscle contraction, because it activates troponin in muscle cells.
Calcium is also necessary for the transmission of nerve impulses, because it allows the release of A neurotransmitter in the synaptic cleft.
Calcium is involved in blood clotting. As an adjunct to prothrombin.
Calcium is involved in regulating blood pressure. To the extent that calcium deficiency is a risk factor for high blood pressure. And these are just a few of the many functions of calcium in our bodies.
If we don’t have the required calcium, our muscles cannot contract , and our nerves cannot transmit the signals. This condition is called “tetany.” It can even lead to death.
On the other hand, if we had a large excess of calcium, this would also lead to tetany and death as we shall see.
Calcium regulating hormones
Calcium is no laughing matter, it is not in vain that calcium is the only mineral whose levels are controlled in the bloodstream. Not with one or two, but with three different hormones.
To maintain the stability of calcium in the blood. These hormones can increase or decrease the absorption of calcium from food. It can either increase or decrease the excretion of calcium by the kidneys. Calcium can be deposited or withdrawn From our bones, the calcium in our bones is in dynamic equilibrium with our bones and blood.
If dietary calcium is chronically unsuitable. These hormones are still able to maintain adequate levels of calcium in the blood. By stealing it from our bones, but our bones end up paying a heavy price when the calcium in them is depleted. They lose density and become more susceptible to fractures.
The three hormones involved in calcium homeostasis are:
1- parathyroid hormone, which is produced by the parathyroid glands.
2- Calcitriol, which is the hormonally active form of Vitamin D , after it is activated in the kidneys.
3- Calcitonin, which is produced by the thyroid gland, is excreted when calcium in the blood is low, and tells the kidneys its role in activate vitamin D to calcitriol.
The hormones of parathyroid gland and calcitrol raise calcium levels in the blood. By increasing its absorption into the intestine and reducing its excretion in the urine. And some taken some from our bones if necessary.
In contrast, calcitonin is excreted when calcium in the blood is too high. It does the exact opposite: it reduces the level of calcium in the blood by increasing its excretion and promoting its deposition in our bones.
So how much calcium do we need?
The recommended adult calcium intake is 1 gram.
For women after age 50 and for men after age 70, the RDA is 1.2 grams.
The average absorption of calcium from food is 25% but can go up to 60%. If the body needs more, it is absorbed better in an acidic environment for example with gastric secretions during the meal. Or with citric acid from lemon juice.
However, calcium absorption decreases with age, which is part of the reason, The daily allowance recommended for the elderly is a little higher. Certain dietary factors can affect calcium absorption or increase excretion.
Factors affecting calcium absorption and excretion
If there is a sudden increase in dietary fiber vitamins from whole grains. Or oxalate from some vegetables. Or tannins of tea and red wine. Or chocolate will decrease calcium absorption.
In contrast, if these substances are a regular part of our diet, the body is able to regulate calcium absorption.
Excess dietary phosphorous will also interfere with calcium metabolism. By reducing its absorption. In a few other ways, other dietary factors can interfere with calcium this time, increasing its excretion.
The two main risk factors are diets high in protein and diets high in salt. Especially if the consumption of fruits and vegetables is low. Undermining excess protein and chloride from salt, both creates acids that need to be buffered quickly.
To keep the pH stable in the bloodstream, the kidneys usually take care of this but when their ability to homeostatically is exceeded. Calcium is stolen from our bones to isolate these acids, and is then excreted in the urine.
This is also the very likely reason why a very high consumption of milk and dairy products was associated not with a decrease but with an increase in bone fractures to a slight extent. Caffeine abuse also increases calcium excretion.
The most important sources of calcium
Everyone also knows that milk, yogurt and cheese are good sources of calcium. as long as they are not consumed in large quantities.
But there are equally good sources of calcium. Among them, most green leafy plant foods are excellent sources of calcium.
Among these foods are green cabbage, broccoli, green turnip , mustard greens, cauliflower, head cabbage, ratabaga and watercress.
Calcium from all of these vegetables is absorbed very well between 50 and 60 , in fact it is absorbed more efficiently than calcium from dairy products. Whose absorption is about 30.
There are other vegetables that, although rich in calcium, are not good sources of calcium, as absorption is limited by the presence of oxalate. For example spinach, latex and Swiss wagon, it has a lot of Calcium. But the absorption is less than five percent.
Chocolate is also a source of oxide, so think twice before drinking chocolate and flavored milk, you aren’t just getting too much added sugar. But it also hinders calcium absorption.
The nori seaweed used in sushi is a good source of calcium. Whole grains can also contribute significantly to our calcium requirements. As well as almonds and sesame seeds.
Fish eaten with bones is a good source of calcium. Think, for example, of small fish like sardines, and some water is rich in calcium.
Well-established tofu contains a lot of calcium, because calcium carbonate is used in its manufacture. Finally, an increasing number of foods fortified with calcium, for example some orange juices, soy milk, and breakfast cereals.
Calcium also has an unbearable top level of 2.5 grams per day for adults. If insufficient calcium is undoubtedly a problem, the important excess calcium is not a good thing either. Once the calcium starts to increase.
The first result is a reduced activation of vitamin D, as we said before. The primary function of active Vitamin D is to increase calcium absorption.
So it stands to reason that if calcium intake is high then less vitamin D will be activated. Because we do not need to increase calcium absorption. It’s really high and that would be totally fine.
But as you know that the only function of Vitamin D is not to increase calcium absorption. But it has also been shown to be active vitamin D. It does a lot of other important things that are potentially very helpful. An example that regulates the expression of many genes. It may play important roles in preventing a variety of diseases.
If we take too much calcium supplements. We suppress the activation of vitamin D and end up losing these secondary health-promoting effects of active vitamin D. Which is potentially very important when you eat higher amounts of calcium, it interferes with the absorption of other minerals such as zinc and iron.
If you eat larger amounts, it increases your risk of developing kidney stones and leads to soft tissue calcification. This leads to severe calcium poisoning, to tetany and death.