Osteoporosis refers to a loss of bone mass in which the bones become porous and fragile. The body is constantly building up and breaking down bone tissue; that's normal. Bone density (the degree of mineralization of the bone matrix) usually increases until about the age of 30. But after that, trouble can begin. Osteoporosis sets in when more bone is lost than can be rebuilt. Eventually, bones become brittle and easily fractured.
Two types of bones in your body
There are actually two different types of bone - both of which lose bone mass, but at different times in life.
- Trabecular bone refers to the inner portion of bone that contains calcium in lattice crystal-like structures. The years of childhood through young adulthood are critical years for depositing calcium inside the trabecular bone, which can provide a reserve of this mineral in later life. Trabecular bone is sensitive to the hormones that control the amount of calcium deposited and withdrawn. The calcium in trabecular bone is called upon when the blood calcium level is low. After age 30, a gradual loss in trabecular bone begins to occur.
- Cortical bone, the other type, is the dense bone that forms the outer shell. Both types of bone are crucial to bone strength and both contain calcium, but cortical bone does not give up its reserves as readily as trabecular bone does. It begins to decline in mass from age 40 on.
What is estrogen's role in bone health?
Estrogen plays an important role in maintaining bone mass. Once women reach menopause and estrogen levels decline, bone loss escalates. Rapid bone loss continues for about five years during menopause, and can reach three to four percent of total bone mass. This surge of bone loss eventually tapers off after a few years, and is about equal to the amount of bone loss in men of the same age. But the loss of bone minerals continues throughout the rest of a person's life.
Consequences of Osteoporosis
About one out of every three postmenopausal women has osteoporosis. Osteoporosis leads to fractures, particularly of the hip, vertebrae and wrists. Fractures can have serious consequences as well. About 20 percent of women who undergo hip replacement surgery due to a hip fracture die within one year. And half of those who survive will require full time nursing care.
What are the risk factors?
- Genetics - Women are more at risk, but anyone of thin build and of Northern European or Asian descent are at higher risk. Studies of mothers and daughters have shown that heredity plays a role in bone density.
- Post-menopausal women -- particularly those not taking hormone replacement therapy
- Poor intake of calcium -- Calcium intake in the diet plays a vital role in bone mineralization during the growth years in order to deposit an abundant supply of calcium into the bones. Even after maximum bone mass has been achieved, calcium intake continues to be important to help slow down bone loss later in life. Dairy products are one of the best sources of calcium, but many people choose not to eat them or can't tolerate them because of lactose intolerance or allergy. Other food sources of calcium are canned sardines, dark green vegetables like collard greens and bok choy, tofu, broccoli, and calcium-fortified juices and soy milk. However, a supplement is recommended to ensure you are getting enough.
- Lack of Vitamin D - Vitamin D plays a pivotal role in allowing the body to absorb calcium. Vitamin D can be formed in the skin when it is exposed to sunlight. It is also added to milk. However, many people do not produce enough vitamin D or get enough from food. Vitamin D deficiency can be a problem for older people and those who are home-bound or bed-ridden.
- Inactivity - Weight-bearing activities such as walking, jogging and weight training help to maintain bone density. A sedentary lifestyle promotes bone loss similar as well as muscle loss. Conversely, muscle use promotes bone use. Physical activity strengthens both muscles and bones, slowing down bone loss and decreasing the risk of injury from falls.
- Smoking - Bone loss from cigarette smoke has been confirmed by numerous studies. However, once you quit smoking, even later in life, bone loss can be arrested.
- Excessive alcohol - People who drink too much alcohol are more prone to fractures. This may be due to the diuretic effect of alcohol, which induces excess calcium losses through the urine. Alcohol can decrease the absorption of calcium from the intestines and cause deficiencies in vitamin D and magnesium - both of which are important to bone health.
- High sodium intake - Several studies have demonstrated the harmful effects of too much dietary sodium on bone integrity. Reducing sodium intake can reduce bone loss considerably, a study with 124 postmenopausal women found (Am J Clin Nutr, 1995).
- Coffee - Coffee consumption of more than two cups a day may cause bone loss, however this can be offset by drinking one glass of milk a day, according to a study at the University of California at San Diego (JAMA, 1994).
- High consumption of animal protein - Some studies have shown that a diet high in animal protein actually promotes bone loss by leaching calcium from the bones, although the verdict is still out on this issue.
- A high acid-ash diet - Recently researchers have suggested that an acid-ash producing diet (high in animal protein and grains, low in vegetables and fruit) may cause an increase in urinary excretion of calcium, leading to bone loss.
- Medications - Certain medications, such as steroids and anticonvulsants, may contribute to bone demineralization.
Are men at risk for Osteoporosis?
Certainly men are not immune to osteoporosis. Bone loss is more gradual in men, but once they reach 70 their risk for osteoporosis increases significantly. Men in this age group are at increased risk for fractures, particularly if they are sedentary and have a diet low in calcium.
What tests are used to diagnose osteoporosis?
The most accurate testing method to measure bone density and diagnose osteoporosis or osteopenia is the DEXA (Dual Energy X-ray Absorptiometry), which uses a computer to scan an image of the hip and spine. Less accurate screening methods are now available in pharmacies and health fairs. X -rays, which were used in the past, are not sensitive. At least 25% of bone loss has to occur before osteoporosis can be diagnosed from a routine X-ray.
What can I do to prevent Osteoporosis?
- Get enough calcium. Choose non-fat dairy products such as yogurt and non-fat milk. Eat more sardines, dark green vegetables like collard greens, bok choy and broccoli, soy products like tofu, and calcium-fortified soy milk and orange juice. Consider taking a calcium supplement if you are not eating at least three servings of dairy per day and/or calcium fortified foods, if you are postmenopausal or if you have a family history of osteoporosis.
- Make sure you get enough Vitamin D. The 400 IUs generally found in a multivitamin is adequate for most people. Individuals with osteoporosis or taking steroids should take 800 IU/day.
- Decrease your sodium intake. Avoid salty processed foods and fast food. Don't salt your food before tasting it.
- Eat plenty of vegetables and fruit. Potassium, magnesium, vitamin C and beta carotene (found in fruits and vegetables) have been associated with higher total bone mass. A diet rich in vegetables and fruit and moderate in animal protein and grains may minimize the acid-ash residue of the diet.
- Limit caffeine intake.
- Avoid alcohol or drink only in moderation.
- Increase weight-bearing activities, such as walking, weight training and calisthenics. Try to do at least 30 minutes of exercise most days of the week.
What should I look for in a calcium supplement?
There are many different forms of calcium. Although most of them are similar, there appears to be some increase in absorption of calcium citrate, especially in older adults.
What is the best way to take calcium?
To ensure maximum absorption, take with meals and limit to 500 mg per dosage.
Are there any other nutrients that I should be concerned about for bone health?
There are additional vitamins and minerals that play an important role in bone health. The ones we suggest adding include:
- Vitamin K - Recently identified as an important nutrient in bone health, vitamin K helps activate certain proteins that are involved in the structuring of bone mass.
- Magnesium is also an important mineral in the bone matrix.