Why Calcium?:Calcium, for more than just Healthy Bones
-Dr. Anjan Rijal, Illustration: Afshan Pradhan
Consuming adequate amount of calcium during younger years of life may help create store for future when people loose calcium as they age.
The body needs various minerals, which serve vital functions. Among them, calcium is the most abundant in the body, with most of it (99%) stored in the bones and teeth. Apart from this, calcium is also present in muscles, blood, and the fluid inside our bodies. It helps in the contraction of muscles and blood vessels, along with being involved in the secretion of hormones and enzymes and the transmission of nerve impulses. Calcium is also involved in clotting of blood and regulation of the heart’s rhythm.
With so many roles, calcium is a very important mineral needed by the human body. It can be obtained from various sources, with one of the best sources being from dairy products, which contain highly absorbable calcium. Other sources include dark green leafy vegetables, dried beans, legumes, and soya. Calcium must be consumed in adequate amounts throughout life, because of the necessity of the body to keep on remodelling bone, with constant building and destruction of bone. It has been suggested that bones are built up till the age of 30 years, after which destruction of bone is more.
Generally, a balance of calcium reserves in the bone is maintained, but if the body does not get enough calcium from external sources, it ‘borrows’ or uses up calcium from the bones. Over time, this can lead to depletion of the calcium stores in the bone and affect the quality of bone. Although the supplies of calcium can be replenished, this does not always happen. Hence, it is imperative that this is prevented by adequate calcium intake.
However, consuming calcium alone may not solve the problem, and it should be taken along with vitamin D. This vitamin is important for calcium absorption from the gut and in preventing its loss from the kidneys. Vitamin D is found in milk, and is made in the body when the skin is exposed to sunlight. The sunlight in our part of the world is adequate to make vitamin D, but in certain latitudes, the winter sun may be too weak for adequate production of this vitamin. In these places, supplements of this vitamin are advised.
Recently, there has been a drive towards consumption of adequate amounts of calcium, because a lack of it causes a condition known as ‘osteoporosis’. Osteoporosis means ‘porous bone’, which causes the bone to be brittle and weak. This may lead to fractures, resulting in debilitating conditions affecting the quality of life. People tend to lose calcium in the bones as they age, although there are other factors that affect the degree of loss. Consuming adequate amount of calcium during the younger years of life, while bone is being built, may help create stores for the future. However, this may not prevent calcium loss from the bones in later life, which is also affected by other factors. These factors are genetic: lack of physical activity, and decrease in hormones (oestrogen in women and testosterone in men).
Postmenopausal women over the age of 50 years account for 80% of all the cases of osteoporosis. This is because oestrogen levels decrease rapidly after menopause, leading to increased loss of calcium from the bones. Men are also at risk of developing osteoporosis, but they tend to develop it 5 to 10 years later than women, because testosterone levels in men fall less rapidly than oestrogen in women. It has been estimated in countries like the United States that half of the women who have osteoporosis will suffer fractures of the hip, wrist, or vertebra.
Osteoporosis can have detrimental effects on our health, so the question is, how do we prevent this condition from developing? One important factor seems to be maintaining adequate amounts of calcium during the younger years (till 30 years of life) when bone is being formed. The other factor is to try and prevent the loss of bone during later adult life. This can be achieved by getting regular exercise in adult life, which should involve weight bearing and muscle strengthening exercises. People need to consume adequate amounts of calcium to replenish the loss, so that the body does not have to borrow calcium from the bones. Getting the required amount of vitamin D is also important for proper absorption of calcium. Another vitamin, vitamin K also seems to play an important role in bone formation, as shown by low bone density in people with low levels of this vitamin. A good source of vitamin K is green leafy vegetables.
Although it is clear that people must take adequate amounts of calcium to replenish the wear and tear in the bones, it is still not clear how much of calcium can be considered safe and healthy. Countries abroad recommend a fairly high amount of calcium on a daily basis:
1000 mg/day for those aged 19 to 50 years
1200 mg/day for people aged above 50 years
1000 mg/day for pregnant or lactating women
However, it is interesting to note that though these amounts are recommended in the United States, in countries like India, Japan, and Peru, far lesser amount of calcium (300 mg/day) are consumed, with lesser incidence of fractures reported.
Although the amount of calcium recommended is high, taking excessive amounts may lead to other problems. In men, a study has shown that increased calcium levels may be associated with a higher incidence of prostate cancer. Due to this, some centers recommend 500 mg/day as a safe amount for men. Similarly, dairy products, which though rich in calcium, can lead to other problems, as suggested by research. Full cream milk is rich in saturated fat, which can be a risk factor for heart disease. There also seems to be an association between galactose (a sugar released from digestion of lactose in milk) and possible damage to the ovaries, leading to ovarian cancer. However, this association is seen in women who consume relatively high amounts of lactose (more than 3 cups of milk/day).
There is some evidence to suggest that drinking too much of coffee (more than 4 cups a day) may lead to increased incidence of fractures. This occurs because caffeine tends to increase the excretion of calcium in the urine. Consuming high amounts of cola products may also lead to decreased bone density in older women. Increased phosphorous in cola may alter the natural balance between calcium and phosphorous in the body, leading to weakening of the bones. Some studies also suggest that a high protein diet over a long period of time may cause a decrease in calcium reserves. Digestion of protein releases acidic content into the blood stream that is neutralised by calcium, which may have to be drawn from the bones. Short-term consumption of high protein does not seem to make a difference, though. This field of research is still controversial and more studies are needed to verify these claims.
To conclude, calcium is the main mineral in our bones and has other vital functions. Our bone reserves are generally built up till the age of 30 years, so consuming adequate amounts of calcium is necessary. Even after that, calcium must be taken to replenish the loss due to bone wear and tear. Although the recommended daily amount of calcium is high in Western countries, no long-term study has been able to establish the actual amounts necessary. Dairy products have a naturally high source of absorbable calcium, and one glass of milk is equivalent to about 300 mg of calcium. However, drinking too much milk (more than 2-3 glasses/day) is also controversial, with the association of milk fat with heart disease; galactose with ovarian disease; and high calcium with prostate cancer. Other sources of calcium are green leafy vegetables, dried beans, and legumes.
It must be remembered that taking calcium alone may not help, and adequate amounts of vitamin D must also be taken. It has been suggested that taking 700 to 800 international units of vitamin D may help prevent osteoporosis. Exercising regularly with weight bearing and muscle building exercises are also important in preventing osteoporosis. Prevention, or slowing down, of osteoporosis seems to demand a holistic and balanced approach to life, with consumption of adequate amounts of calcium, vitamin D, and an active lifestyle. The importance of building adequate reserves of calcium must also be stressed in young adults for them to have a healthy adulthood later.