For most people the immediate association of calcium with bone mineral density (BMD) is a spontaneous one. Calcium has many other uses though. It helps in muscle contractions, maintaining heart rhythm and even in nerve function.
We have more calcium in our body than any other mineral, and it is important to maintain just the right balance. The two ends of the calcium imbalance are called hypocalcemia (low calcium levels) and hypercalcemia (high calcium levels).
The human body tries to keep a steady amount of calcium in the blood and tissues. Ninety nine percent of our calcium is stored in the bones. When the plasma level drops, the parathyroid hormone signals the bones to release calcium into the bloodstream. When there is enough calcium in the bloodstream, the hormone calcitonin lowers calcium levels in the blood by inhibiting any further calcium release from the bones. It then signals the kidneys to filter out the excess.
Sources of calcium
This macro mineral can be derived from dairy as well as non-dairy sources like leafy greens, edamame, almonds, chia seeds, tofu, and fish, among others. Since calcium is not easily broken down by the body, it is important to choose sources with a higher calcium bioavailability.
For instance, a cup of milk has 30 percent bioavailability. This means that if a cup of milk yields 300 mg of calcium, only 100 mg will actually be absorbed by the body.
Plant sources have lesser calcium content compared to dairy, but have a higher bioavailability of 50 percent. So, a cup of pak choi with 160 mg of calcium will provide 80 mg of available calcium to the body. Its calcium content is, therefore, almost as much as a cup of milk.
However, this is not true for all green leafy vegetables. Take for instance spinach; a common misconception is that it is a calcium source because of its high calcium content. True, it has 260 mg of calcium for every cup. But since it is also high in anti-nutrients like phytates and oxalates that bind to calcium, it reduces its chances of absorption to just five percent. As such, spinach is not a dependable calcium source. It is still a great addition to the overall diet, loaded as it is, with many other nutrients.
Bone loss due to calcium deficiency
Gradual deficiency over the years leads to bone loss or osteopenia. It is a consequence of consuming too little calcium, leading to a drop in BMD. Osteoporosis causes the bones to thin and makes people vulnerable to fractures, pain and problems relating to posture. In women particularly, perimenopause and menopause lower oestrogen levels which, in turn, reduces calcium absorption.
Another mineral, phosphorus, plays a vital role in calcium homeostasis. It is found naturally in many foods and its deficiency is, therefore, rare. Excess phosphorus however, can lead to calcification in the heart, blood vessels and the lungs, raising the risk of a heart attack or stroke. The calcium phosphorus balance in the body is guided by vitamin D receptors in the kidneys that assist in controlling the absorption and regulation of the parathyroid hormone.
It is important to note that people, who are lactose intolerant may be more prone to calcium deficiency, if adequate amounts are not consumed from non-dairy sources.
Symptoms and cures
According to estimates, nearly four billion people worldwide are at a risk of calcium deficiency due to its relatively lower consumption. The best approach, of course, is to add more calcium to one’s regular diet.
So, the next time you have symptoms such as muscle cramps, tingling in the lips and fingers, confusion, numbness or pain in the thighs or arms while walking, consult a doctor immediately. He or she will prescribe supplements to increase the calcium levels in your body. In fact, doctors recommend that women over 50, and men over 70, should increase their calcium intake by a minimum of 20 percent, which is 1200 mg per day.
It is advisable to also contact a certified nutritionist who can suggest a suitable diet. It will support your health and fitness programme, and ensure successful outcomes.