Understanding Blood Calcium Levels

Mallorca (Majorca) is one of Spain's Islands in the Mediterranean. (Dr. Noorali Bharwani)
Mallorca (Majorca) is one of Spain's Islands in the Mediterranean. (Dr. Noorali Bharwani)

Calcium and vitamin D are the two most important nutrients for bone health. Calcium has many other important functions in the body.

Calcium is necessary for life.

In addition to building bones and keeping them healthy, calcium helps our blood clot, helps nerves send messages and helps muscles contract. About 99 percent of the calcium in our bodies is in bones and teeth.

Each day, we lose calcium through our skin, nails, hair, sweat, urine and feaces. But our bodies cannot produce new calcium. That is why it is important to get calcium from the food we eat. When we do not get enough calcium for our body’s needs, it is taken from our bones. This makes bones weak.

A natural source of calcium in our diet comes from milk and milk alternatives. It is important to drink milk everyday. Calcium is also found in dark leafy greens, legumes and canned salmon.

Role of parathyroid hormone

Excessive calcium (hypercalcemia) most commonly results from overactive parathyroid glands. These four tiny glands are each about the size of a grain of rice and are located on or near the thyroid gland. Certain types of cancer, other medical disorders, some medications, and excessive use of calcium and vitamin D supplements can also cause hypercalcemia.

Overactive parathyroid gland (hyperparathyroidism) can raise calcium levels. The role of the parathyroid hormone is to help maintain an appropriate balance of calcium in the bloodstream and in tissues that depend on calcium for proper function.

Hyperparathyroidism is often diagnosed before signs or symptoms of the disorder are apparent. When symptoms do occur it is because of damage or dysfunction in other organs due to high calcium levels in the blood, urine, or too little calcium in bones.

Hyperparathyroidism can cause a wide variety of symptoms. It can make bones fragile (osteoporosis), create kidney stones, increase urination, cause abdominal pain, weakness, depression and forgetfulness. It can also cause aches and pains, nausea, vomiting or loss of appetite.

When your calcium levels are low, your parathyroid glands secrete parathyroid hormone to restore the balance. Parathyroid hormone raises calcium levels by releasing calcium from your bones and increasing the amount of calcium absorbed from your small intestine. Parathyroid hormone also acts on the kidneys, resulting in decreased excretion of calcium.

The physiology and balancing acts of calcium, phosphorus, vitamin D and parathyroid hormone is very interesting and not easy to comprehend.

To summarize:

Bones play an important role in blood calcium levels, which must be maintained within narrow limits to maintain bodily functions.

Bones are the major storage site for calcium. The movement of calcium into and out of bone helps to maintain blood calcium levels.

Parathyroid hormone and calcitonin also help regulate blood calcium levels.

Parathyroid hormone promotes the absorption of calcium by the small intestines, which also increases blood calcium levels.

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How much vitamin D do you need daily to prevent fractures?

A vitamin capsule. (iStockphoto/Thinkstock)
A vitamin capsule. (iStockphoto/Thinkstock)

Basking in the sun is one way to obtain vitamin D

Basking in the sun is one way to obtain vitamin D although the risk of skin cancer increases. Other sources of vitamin D are fortified dairy products, fatty fish and egg yolks.

Answer to this question appears in an article in the New England Journal of Medicine (NEJM) published in July, 2012. The authors examined the relationship between vitamin D supplementation and fracture reduction.

They looked at 11 double-blind, randomized, controlled trials of oral vitamin D supplementation (daily, weekly, or every 4 months), with or without calcium, in persons 65 years of age or older. The goal was to look for the incidence of hip and any nonspinal fractures.

The study included 31,022 persons (mean age, 76 years; 91 per cent women) with 1111 incident hip fractures and 3770 nonspinal fractures.

When they looked at a subgroup of participants by actual intake of vitamin D, they found reduction in the risk of fracture was shown only at the highest intake level (median, 800 IU daily; range, 792 to 2000), with a 30 per cent reduction in the risk of hip fracture and a 14 per cent reduction in the risk of any nonspinal fracture.

“Benefits at the highest level of vitamin D intake were fairly consistent across subgroups defined by age group, type of dwelling, baseline 25-hydroxyvitamin D level, and additional calcium intake,” says the NEJM paper.

The conclusion of the study was that high-dose vitamin D supplementation (≥800 IU daily) was somewhat favorable in the prevention of hip fracture and any nonspinal fracture in persons 65 years of age or older.

As we know, vitamin D is a nutrient that helps the body use calcium and phosphorous to build and maintain strong bones and teeth. Vitamin D is unique in that it can be synthesized by the body after exposure to ultraviolet rays from sunlight.

Too much vitamin D can cause too much calcium to be deposited in the body, which can lead to calcification of the kidney and other soft tissues including the heart, lungs and blood vessels. But it is hard to define what is too much. Some expert recommend daily intake of 1000 to 2000 IU of vitamin D to prevent certain types of cancers.

Health Canada’s recommendation for daily dietary intake of vitamin D in adults age 70 and over is 800 IU (20 mcg). This is based on the assumption that there is minimum of exposure to sunlight. The major sources of vitamin D are fortified foods. In Canada, cow’s milk and margarine must be fortified with vitamin D. The only natural sources of vitamin D in the Canadian food supply are fatty fish and egg yolks.

Many people meet at least some of their vitamin D needs through exposure to sunlight. Although there is some risk of skin cancer. But you never know how much vitamin D you are getting through sun exposure. It all depends on the season, time of day, cloud cover, smog, skin pigmentation, and sunscreen use.

Daily intake of vitamin D recommendation depends on a person’s age. Talk to your doctor or see Health Canada website for more details. But do not forget to drink your milk everyday.

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Safety of calcium supplements questioned – how much is enough?

One thing is beyond dispute – whatever the age, we all need calcium to make our teeth and bones strong. Calcium is also required to make our muscles and nerves function. Calcium is also a necessary factor for blood clotting.

Although these facts are well known, many people continue to be deficient in their calcium intake and hence in their body’s total calcium requirement. This leads to bad teeth and osteoporosis, bone fractures and its nasty complications.

On the other hand, studies have shown that too much calcium is not good for your health. But how much is enough? There is no agreement on that.

-In Britain, women over 50 are urged to consume 700 milligrams a day.
-In Scandinavia the level is set at 800 mg.
-In the United States and Canada it’s 1,200 mg.

-In Australia and New Zealand top the list with 1,300 mg.

A Swedish study published in the British Medical Journal found that women who consumed less than 700 mg of calcium a day had a higher risk of fractures than those who took in larger amounts. But an intake of more than 700 mg per day didn’t seem to provide any additional protection. The results suggest that there are no further benefits to taking more than 700 mg. of calcium every day.

Some studies have suggested that taking calcium supplements (but not calcium from food) may increase a woman’s chances of developing heart disease. Other studies have suggest that calcium may play an important role in the development of prostate cancer but evidence also shows calcium may lower the risk of colon cancer and age-related thinning of the bones.

Men are also prone to getting osteoporosis. In women, bone loss begins before menopause and is accelerated in old age. So prevention is better than cure.

One glass of milk contains 300 mg of calcium. About 175 ml of plain yogurt and 42 grams of cheese each contain about 300 mg of calcium. You can get enough calcium on a daily basis just by drinking milk and enjoying natural yogurt and cheese.

And don’t forget your vitamin D 1000 to 2000 IU per day especially in winter months. Vitamin D has an important role in preventing prostate cancer and other cancers.

A report published in the Journal of the American Geriatrics Society says vitamin D, taken in a high dose, may help prevent falls in the elderly. The study shows that nursing home residents who took a daily dose of 800 international units (IU) of vitamin D for five months were less likely to fall than those who took either lower doses or no vitamin D.

Another paper reviewed 29 observational studies and concluded that in North America, a projected 50 per cent reduction in colon and breast cancer incidence would require a universal intake of 2,000 to 3,500 IU per day of vitamin D.

A third report came out in the Archives of Internal Medicine. This review paper analyzed the results of 18 vitamin D studies says that taking vitamin D supplements may help people live longer. But it’s not yet clear exactly how vitamin D does that. But it appears to be a life extender.

Don’t be confused now. Eat a healthy balanced diet, take vitamin D and do regular exercise. Talk to your doctor to find out what is the best dose of calcium and vitamin D for you. Then sit on a recliner and enjoy a cold or hot glass of milk. Sounds like a good idea to me.

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Fractures in Osteoporotic Men and Women

Osteoporosis is a condition in which there is a gradual softening of the bones which makes them fragile. It is caused by the loss of calcium. Our current understanding has been that osteoporosis occurs most often in women after the age of menopause. Men can suffer from osteoporosis as well when they experience low levels of testosterone.

Bone fracture is a common complication of osteoporosis. One in two women and one in five men over the age of 50 will have a fracture. A person may lose height if the vertebra collapses due to osteoporosis. One may develop a hump if several vertebrae collapse.

Other causes of osteoporosis for men and women are: long-term use of corticosteroid medication, maternal osteoporosis, smoking, heavy drinking, sedentary lifestyle, low body weight and medical conditions that affect absorption, such as celiac disease. Diagnosis of osteoporosis is made by measuring bone mineral density.

A recent article in the CMAJ says that our understanding of and approach to osteoporosis is in the middle of a revolution. Research now shows the bone loss begins before menopause and involves other hormones in addition to estrogen, and that measuring bone mineral density alone is an inefficient way of addressing the clinical burden of osteoporosis.

The ongoing Canadian Multicentre Osteoporosis Study also shows that both men and women experienced an additional phase of accelerated bone loss from age 70 onward. Hormone replacement therapy with estrogen in women does protect against bone loss over time.

The finding that bone loss began before menopause indicates that estrogen loss alone cannot account for the changes. Therefore, interest has focused on other hormones whose levels change in early menopause such as follicle-stimulating hormone and the activins and inhibins. The role of steroid produced in the body and the size of the body composition is being determined.

The current national guidelines recommend that the test for osteoporosis (measuring bone mineral density) should be done every 2-3 years. In one of the CMAJ articles, Berger and colleagues suggest that densitometry for most women can be repeated every five years rather than every 2–3 years because the average changes in bone density over 2–3 years is small and comparable to the measurement error in the scanning technique.

There is also a question whether women who are already receiving treatment for osteoporosis should have follow-up assessments of bone density at all, since changes in density as a result of therapy account for only a small component of the effectiveness of these medications, says the CMAJ article.

There are four key points in the CMAJ articles: bone loss in women begins before menopause and is accelerated in old age, medications which reduce the loss of calcium from the bone helps preserve bone density, the interval between bone density assessments can safely be increased to 5 years for many untreated women and finally, decisions about when to test and treat will increasingly focus on estimates of absolute fracture risk as indicated by the bone density test.

Osteoporosis is treated with calcium and vitamin D supplements, a variety of hormone treatments (hormone replacement therapy like estrogen) and Bisphosphonates, a group of drugs that prevent bone breakdown and can be very effective in osteoporosis. But prevention is better than cure. So, increase calcium and vitamin D in your diet, increase the amount of weight-bearing exercise you do, reduce your alcohol intake and quit smoking.

The reduction in risk was greatest among elderly individuals who were most adherent to therapy and among those who received at least 1200 mg of calcium and 800 IU of vitamin D daily.

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