If you don’t think that osteoporosis is a disease that you should be concerned about, think again. While most women are concerned about their risk for breast cancer and many men are concerned about prostate cancer, they really should be concerned about their risk for developing osteoporosis later in life. Why? Because the lifetime risk of hip fracture in white women is 15 percent as great as that of breast, endometrial, and ovarian cancer combined. For men, the lifetime risk of hip fracture (5 percent) is as great as the risk of developing prostate cancer. For men and women alike, promoting and maintaining optimal bone health is an important consideration at any age.
Osteoporosis, which literally means “porous bones,” occurs when the amount of mineral in the bones drops to a level low enough to permit fractures to occur after minimal trauma. The mineral content of the bones (called bone mineral density or BMD) drops gradually throughout life as a normal process of aging. In women, who are at a higher risk for osteoporosis, BMD begins to decline slowly around age thirty five. For three to five years before and three to five years after menopause (which occurs, on average, around age fifty) bone loss speeds up dramatically due to the loss of estrogen production by the ovaries. Bone continues to be lost at a slower rate after this rapid phase and continues to be lost slowly as we age. If the BMD drops too fast or gets too low, however, the risk for fractures is increased.
Although more than 25 million Americans suffer from osteoporosis, the stereotypical osteoporotic patient is a postmenopausal white female, often with a history of low body weight, low calcium intake, and a sedentary lifestyle. Each of these factors (gender, age, hormonal status, nutritional intake, and physical activity) can influence the risk for developing osteoporosis. As such, osteoporosis is considered a multifactorial disease meaning that it is caused by a number of factors and cannot be “cured” by changing any single factor.
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Bone Health Nutrition
The primary role of adequate nutrition for skeletal health is that it allows development of the largest possible skeleton during growth, thus protecting against calcium loss in old age. Large population studies have shown that if we could ensure a fully adequate intake of calcium and vitamin D for every member of the North American and European populations, we could eradicate as much as 50 percent of the worldwide osteoporosis burden.
When calcium intake is restricted during growth, the body tries to spread the inadequate amount of calcium over as much of the skeleton as possible. The result is not stunted growth, but normal growth accompanied by a reduced amount of bone tissue overall. The bone is normal in every way, but it tends to be flimsy, thin, and weak. Such bone will not only not serve the structural needs under conditions of high mechanical stress, but will also not serve as much of a calcium reservoir in later years, when calcium stores are drawn upon with greater frequency.
Chronically low calcium intake results in a chronic drain on the body’s calcium reserve. There is an old analogy about your skeleton being a bank vault for calcium storage. When you are getting enough calcium in your diet, you are able to store some of it to make “deposits” in the vault. During times of low calcium intake, you can draw on these savings to pay your “bills” which in this case are the other functions for which the body uses calcium (electrolyte balance, nerve conduction, muscle contraction).
Bone Health Hormonal Status
Whenever women lose ovarian hormones (menopause), or men lose testosterone (andropause), the skeleton seems to sense that it has more bone than it needs. The result is an increase in bone resorption (breakdown) to get rid of what the body thinks it doesn’t need. A woman can expect to lose approximately 15 percent of her peak bone mass during menopause. No amount of increased calcium intake or increased exercise will substantially influence this change due to hormones.
Bone Health Exercise
Bones have the unique ability to adjust their mass in response to stress. Normal deformation of living bones is in the range of 0.1 percent to 0.15 percent. This means that when a force is applied to a bone say, by exercise the bone will bend slightly. When a bone encounters a force that causes a deformation greater than this range (more bending than it wants to do), the skeleton responds by depositing more bone to the area. When less deformation is “sensed” by the skeleton, bone is removed from the area. Thus, the more stress is delivered to the skeleton, the more bone is deposited to maintain a set level of deformation. The less exercise, the less strain, and the less bone that is needed, so the body gets rid of the excess bone by increasing the rate of bone resorption.
Body weight is a strong predictor of bone mass and density. Overweight women are known to have more bone and less bone loss at menopause and have been shown to absorb calcium with greater efficiency. Each of these factors may be due to somewhat higher estrogen levels in heavier women. Thin women tend to have a greater risk of osteoporotic fractures. This increased fracture risk in thin women is partly due to lower bone mass and also partly due to having less soft tissue around their bones to absorb the shock of a fall.
Two factors that interact to help determine body weight dietary intake and physical activity also have a strong influence on overall bone mass. For example, a thin woman may be at a higher risk for osteoporosis because of low body weight, but if her low weight was achieved through a program of rigorous exercise, then perhaps her risk is not as high as we would expect based on body weight alone. On the other hand, suppose another woman achieves her low body weight through chronic dietary restriction. Chances are that her diet is also lacking in important nutrients such as calcium, phosphorous, magnesium, vitamin K, boron, and zinc, which are needed to support proper bone health.
Bone Health – Other Factors
When most people think of bone health and nutrition, they immediately think of calcium. Although calcium intake is certainly a critical component of achieving and maintaining healthy bones, there is much more to the optimal nutrition of bones than just calcium. Many nutritional factors can interact to influence calcium absorption, bone breakdown, and bone formation. For example, high levels of both sodium and protein in the diet can increase the amount of calcium lost each day in the urine, while both fiber and caffeine slightly reduce the absorption of calcium from the diet. For example, because of dietary fiber content, the calcium in beans is only abo
available as the calcium found in milk, while calcium from spinach is almost totally unavailable to the body.
Major Risk Factors for Osteoporosis
• White or Asian ethnicity
• Family history (genetic causes)
• Small body frame/low body weight (less than 130 lb)
• Low dietary calcium intake
• Amenorrhea, irregular menstrual cycles, or early natural menopause
• Sedentary lifestyle
• Cigarette smoking
• Medications that increase bone loss (corticosteroids)
Bone Health Supplements
Calcium supplements are the king (queen) of the hill when it comes to bone health but it’s important to remember that bones are a lot more than just sticks of calcium (that’s what chalk is). Although calcium supplements have been clearly shown to help reduce bone loss and increase bone density at doses of 500 to 1,500 mg per day, a number of additional nutrients are crucial for the optimal utilization of calcium. For example, vitamin D is needed for optimal absorption of calcium from the intestines as well as for proper maintenance of calcium levels within the blood and bone tissue. Elderly people are most at risk for vitamin D deficiency because production is reduced as we age. Vitamin D supplements of 200 to 400 lU can help maintain calcium absorption. Vitamin K status has been linked to overall bone health in elderly subjects, with those having low vitamin K levels also showing reduced bone density. Because vitamin K functions in coordinating the proper deposition of calcium crystals in bone tissue, it works in conjunction with vitamin D to get calcium from the gastrointestinal tract into the blood and then into the bones in a coordinated fashion. Likewise, the absorption of calcium is also tied to adequate levels of magnesium and zinc in the diet. As with calcium, both minerals are found at high concentrations in bones and are thought to help maintain optimal bone metabolism. Supplemental intakes of 15 to 30 mg of zinc and 200 to 400 mg of magnesium are often combined with calcium preparations.
Occasionally, bone supplements also contain varying levels of trace minerals involved in bone metabolism. For example, copper is involved in the synthesis of a protein called collagen, which forms the major nonmineral structural portion of bones. Levels of copper up to 1 to 3 mg per day seem to be well tolerated and may help maintain bone health by supporting collagen production. Other minerals such as boron, silicon, and manganese may play a supporting role in bone metabolism, but isolated supplements are generally not needed as most are available in multivitamin/mineral supplements.
Last, but certainly not least, are dietary supplements containing isoflavones usually from soybeans, red clover, or another plant source (also called “phytoestrogens”). The chemical structure of isoflavone compounds is similar enough to estrogen to permit some of the good effects of estrogen (such as bone building) without many of the bad side effects (such as increased breast cancer risk). Most of the time, the isoflavones in dietary supplements area mixture of the primary soy extracts genistein and daidzein, but synthetic isoflavones, such as ipriflavone, are also available in many dietary supplements. The isoflavones appear to be safe and effective in reducing bone loss during menopause, so much so that they are frequently included in mainstream calcium supplements.
Ingredient Dose (per day) Primary claims
Boron 1 2 mg Builds bone
Calcium 500 1,500 mg Slows bone loss and builds bone
Isoflavones 25 50 mg Slows bone loss
Magnesium 250 750 mg Promotes calcium absorption
Vitamin D 200 500 IU Increases calcium absorption
Vitamin K 10 120 mcg Promotes bone formation