No single cause for osteoporosis has been identified. However, certain factors – called risk factors – do seem to play a role in the development of the disease. Women and men over 50 should be assessed to identify those at high risk.
Risk factors for low bone mineral density, future fractures and falls include:
Women are especially at risk because of the important role that estrogen plays in keeping their bones healthy. At menopause, there is a gradual decline in ovarian function and a consequent loss of estrogen production. As estrogen levels decline, loss of bone tissue begins. Rapid bone loss at a rate of two to five percent a year can occur for the first five to 10 years after menopause.
Although osteoporosis is more common in women, at least one in eight men over 50 also has the disease. In fact, in Canada 20-30% of osteoporotic fractures occur in men. As with the decline of estrogen levels in women, lower testosterone levels in men can lead to an increase in bone loss. The decline is more gradual in men and is not universal. A Canadian osteoporosis study (CaMOS) has found that 25% of Canadian men have vertebral fractures, similar to rates found in women.
Despite the fact that osteoporosis and osteoarthritis are completely different conditions, they are frequently confused because the names are similar. Osteoporosis is a bone disease. Osteoarthritis is a disease of the joints and surrounding tissue. Rheumatoid arthritis, an inflammatory disease of the lining of the joints, is another common form of arthritis.
Osteoarthritis is a degenerative joint disease, which leads to the thinning or destruction of the cartilage, causing painful irritation of the joints and adjacent bone tissue. Bony growths may occur because of the abnormal rubbing together of bones.
Individuals who suffer from both arthritis and osteoporosis should plan a program to manage both diseases. Specifically, they must pay attention to the advice they receive about exercising. Individuals in this situation should seek the advice of a healthcare professional.
Calcium is important for building strong bones in childhood, maintaining bone density in adulthood and reducing the risk of fracture as we age. In fact, every cell in our body needs calcium to function properly. Because calcium is so important, our body carefully regulates blood levels of calcium to ensure that calcium levels stay within the normal range. When blood levels of calcium are lower than the range allows, calcium is removed from bone to raise these levels back to normal range. Conversely, when blood calcium levels are above the range, as after a calcium-rich meal, calcium is deposited in the bone. Therefore, bones act as a “calcium bank” with deposits and withdrawals being made according to a strictly regimented system.
It is important to make sure you are getting the recommended amount of calcium every day – from food sources, if possible. Because Vitamin D is crucial to calcium absorption, it is also important to get the required amounts of Vitamin D. Osteoporosis Canada recommends the following intake of calcium and Vitamin D every day to maintain strong bones:
|Age||Calcium Requirement||Vitamin D Requirement|
|4-8||1000 mg||600 IU|
*Those with osteoporosis, recurrent fractures or with conditions affecting vitamin D absorption also require 800-2000 IU. Because there are few food sources of vitamin D, routine supplementation is recommended for adult Canadians.
Supplements are advisable for individuals who are not getting enough calcium from food sources and are unable to make changes in their diet. There are many types of calcium supplements on the market, with the most popular being calcium carbonate.
Look for a product where the label states the amount of elemental calcium per tablet, e.g., 1000 mg of calcium carbonate contains 400 mg of elemental calcium.
Look for products with a Drug Identification Number (DIN) or Natural Product Number (NPN). This indicates that the product meets the Canadian standards for lead content, quality and disintegration. The American equivalent is the United States Pharmacopoeia (USP) number.
Calcium carbonate is more slowly absorbed than other types of supplements. To be absorbed, it needs to be completely disintegrated. To determine how quickly a tablet disintegrates, place it in vinegar and, after 30 minutes, most of it should be disintegrated. When taking a chewable supplement, the chewing action disintegrates the tablet. To maximize the absorption of the calcium, keep these tips in mind:
Bioavailability refers to whether the calcium that is found in the food is available to the body. A major factor is how well it can be absorbed. For example, there are some vegetables that contain calcium, but they also contain oxalates that bind with the calcium and therefore make it unavailable for absorption. Such vegetables are spinach, rhubarb and beet greens. Although these are nutritious foods, they cannot be considered good sources of calcium.
Three factors are important in determining how much calcium we obtain from foods. We need to have enough vitamin D to promote absorption. The second factor is how much calcium is in the serving of food, and the third, whether the calcium is bioavailable. Dairy products such as milk, yogurt and cheese are less well absorbed (30%) than calcium-rich vegetables (50%), but have a much higher calcium content per serving. A cup of milk has about 300 mg of calcium, whereas a cup of cooked broccoli has about 65 mg. The calcium from fortified soy beverage is similar in amount but is absorbed at the rate of 75% of milk. If you take both calcium content and bioavailability into account, dairy products remain a good source.
High-fibre foods such as cereals and legumes contain phytates that hinder absorption by binding with calcium. As long as you are consuming sufficient calcium, this should not be a problem.
Another aspect of bioavailability has to do with retaining the calcium you have ingested and absorbed. There can be food components that interfere with how well one can hold on to the calcium. Excess salt (sodium chloride) and caffeine both cause more calcium to be lost in urine, thus reducing the overall bioavailability. Adding milk to coffee and cutting back on salt are two ways to prevent this.
Bioavailability is also a concern if you are relying on calcium supplementation to get the recommended daily intake. Calcium carbonate and calcium citrate are the most widely available calcium supplements. Calcium carbonate is not as easily absorbed (on an empty stomach) as calcium citrate. One can improve absorption of the carbonate form by taking it with a meal. However, both are effective and the deciding factor in choosing between these two forms is one of personal preference.
Physical activity helps to reduce the risk of falls and fractures and to prevent further bone loss. Physical activity to prevent osteoporosis includes both weight-bearing and strength-training exercise. Weight-bearing is any exercise where the entire weight of the body is supported by the legs, such as walking, line dancing, low-impact aerobics or racquet sports. Exercise programs for people at risk for or with osteoporosis should be aimed at increasing strength, coordination, balance and flexibility.
For those who are beginning physical activity, seeking advice from a physiotherapist or fitness instructor can be useful. If you are planning to attend an exercise class, make sure you ask whether the instructor has training in leading exercise for people with osteoporosis, and knows what is safe. For people who have recently fractured, a physiotherapist can help by developing and supervising a rehabilitation exercise plan.
With osteoporosis still a major and growing health concern for Canadians, new methods of assessment are always an important area of interest. Recent technology has developed an alternative technique- quantitative ultrasound (QUS) that measures bone mineral density (BMD) in the heel and other bones. Several companies in Canada are offering this service privately, outside the provincial medicare system, for payment by the patient or a sponsor, such as a pharmacy. Osteoporosis Canada recognizes QUS as a useful tool, especially in areas where dual x-ray absorptiometry (DXA) in not available: it is inexpensive, portable, easy to use and does not involve ionizing radiation (e.g. x-rays). But questions remain about how widespread a role it should play in assessing BMD.
The scientific community has raised concerns about the technological diversity, standards and instrument precision regarding these devices. Quality assurance is another issue: as yet, no formal training or accreditation process for commercial operators exists. Further, heel ultrasound detects fewer cases of osteoporosis than DXA and experts aren’t sure how to deal with the discrepancy between results from the two tests. Many people who undergo ultrasound testing require additional DXA test later, leading to more expense and inconvenience. At this time, DXA remains the diagnostic gold standard for identifying individuals with osteoporosis. Moreover, QUS is not sufficiently sensitive to changes in bone structure to be used to monitor ongoing therapy for the disease.