Dietary supplements for osteoarthritis

by Richard Glickman-Simon, MD

Richard.gifOsteoarthritis (OA) is by far the most common form of arthritis. So common, in fact, that if you are over 40, there is a 90% chance you already show signs, though you probably dont know it. Its not until later in life that OA becomes one of the leading causes of chronic pain and disability. Geriatric physicians say it is the most common diagnosis they make.

Although the term osteoarthritis technically means "inflammation of bones in a joint," OA is associated with minimal inflammation compared with rheumatoid arthritis. Degenerative joint disease, another term for OA, is a better description of the process of wear and tear that gradually softens and breaks down the joint cartilage that normally prevents bones from rubbing together. X-rays of osteoarthritic joints often show narrowing of the joint space and destructive changes in the adjacent bone.

Patients with OA generally complain of joint pain and stiffness, particularly after physical activity. The hips, knees, and spine are most susceptible to OA, since they absorb the brunt of gravitational forces. The distal interphalangeal joints (second knuckles) and cervical spine (neck bones) are also commonly affected.

Joint cartilage is made up of cells, called chondrocytes, embedded in a substance called the extracellular matrix. One of the primary components of this matrix is a material called proteoglycan. This material helps cartilage absorb the forces of friction.

With normal aging, the proteoglycan content of the matrix decreases. This decrease can be accelerated by injury, excessive mechanical force, or joint deformity. This explains why certain occupations, like dockworkers and professional football players, become disabled from OA sooner than the rest of us. It also explains why obesity, which adds considerable stress to joints of the lower extremities, greatly increases the risk of OA, particularly of the knees.

Even after OA begins to set in, there is evidence that regular exercise can delay or prevent the onset of pain and disability. Aerobic activity protects against obesity, while weight training enhances the strength and flexibility of the muscles, tendons, and ligaments around the joints, which improves joint stability and resilience. Keep in mind that acute injuries and repetitive strain increase the risk of OA. Therefore, exercise is only beneficial to joint health if it is done gradually, and with proper preparation (stretching) and equipment (quality footwear).

Standard treatments for symptomatic OA include:

• Physical therapy to increase the strength and flexibility of affected joints
• Prescription or non-prescription pain medication, most commonly non-steroidal anti-inflammatory drugs (NSAIDs)
• Injections of more powerful anti-inflammatory steroid medication into the joint
• Joint replacement surgery

Although often effective at relieving pain, these interventions do nothing to slow or reverse the deterioration of cartilage. Therefore, researches have recently turned their attention to two natural constituents of human cartilage that may preserve, or even enhance, cartilage integrity—glucosamine and chondroitin.

Glucosamine and chondroitin are thought to stimulate the production of proteoglycan and inhibit its breakdown. The forms used in dietary supplements to treat OA are extracted from cow cartilage.

Numerous clinical studies have evaluated the effectiveness of these supplements in treating OA of the knee and hip. These studies show glucosamine and/or chondroitin to be moderately more effective than a placebo, with no significant side effects. In a recent long-term investigation, for example, researchers gave glucosamine or a placebo to 212 subjects with knee OA for three years. Subjects taking glucosamine showed the following promising results:

• Less narrowing of the joint space on x-ray
• Significant reduction in symptoms
• No more adverse effects than subjects in the placebo group

How much to take

A safe and effective dose of glucosamine appears to be 1500 mg per day, taken in three doses of 500 mg. It is available as:

• A sulfate
• A hydrochloride
• N-acetylglucosamine

Chondroitin is available as a sulfate. The daily dose believed to be safe is 1200 mg, taken in three, 400 mg doses.

Until it becomes clear if the combination of glucosamine and chondroitin is superior to either supplement alone, it is reasonable to take the two together as a single product. Some of these products contain other ingredients, such as the mineral manganese. Manganese is believed to play a role in proteoglycan metabolism. However, it has not been established if this mineral or any other ingredients provide additional benefit.
Buyer beware

Since there is little government regulation of dietary supplements, the products you buy over-the-counter may not contain exactly what the label indicates. You may need to do a little homework to find out about the dose and purity of the supplement you plan to buy. A good place to start is http://www.consumerlab.com/, an online service that conducts independent tests on a variety of products, including glucosamine and chondroitin.

Many other dietary supplements are purported to benefit OA patients. While most appear to be safe, and some may be quite effective, there is not enough evidence to recommend them over glucosamine or chondroitin. These supplements include:

• S-adenosylmethionine (SAMe) – an analgesic/anti-inflammatory
• Vitamins C and E, and beta-carotene – antioxidants
• Vitamin D – essential to normal bone and cartilage metabolism
• Avocado/soybean oil extracts – may stimulate chondrocyte activity

There is no cure for osteoarthritis, short of replacing the entire joint. Exercise and weight control may delay its onset and progression. Most patients who develop symptoms usually try NSAIDs first, even though they do nothing to address the underlying problem and can cause serious adverse effects, particularly in the elderly.

Glucosamine and chondroitin, on the other hand, may actually help preserve cartilage integrity as they safely and effectively relieve symptoms—it may be time for a new first line treatment.