The skeleton, made up of all the body’s bones, provides strength, stability, and a frame for muscles to work within to produce movement. Bones come together to form joints, most of which are in constant motion. The ends of bones are covered with cartilage, a smooth, tough, protective tissue that acts as a shock absorber and reduces friction. The skin acts as a protective barrier to the outside world. Skin also helps to regulate body temperature, senses painful and pleasant stimuli, and shields us from the sun’s harmful effects.

Today, we are seeing increasing incidences of problems with the musculoskeletal system. We can help ourselves maintain our "body frame" health through nutrition and supplements. One of the most powerful musculoskeletal supplements is glucosamine.

Glucosamine
Glucosamine is an aminosugar. It is made in the body from the simple carbohydrate glucose (sugar) and the amino acid glutamine. Although our bodies generally use glucose to produce energy, the aminosugars found in glucosamine are incorporated into the structure of body tissue. Glucosamine is involved in the formation of cartilage, nails, tendons, skin, eyes, bones, ligaments, and heart valves. It also plays a role in the mucous secretions of the digestive, respiratory, and urinary tracts. Of particular interest is its role in cartilage.

Cartilage
Cartilage is connective tissue at the ends of bones (where it is known as articular cartilage). It separates bones so that they do not grind together, causing stiffness and pain. Cartilage also serves as a shock absorber. Briefly put, cartilage protects our bones from the wear and tear of movement.

One way to think of cartilage is as a super sponge. It soaks up water (more accurately, synovial fluid) when a joint is at rest, and squeezes out the water when a joint moves. As the joint rests again, it again soaks up water. This spongelike effect of cartilage makes it a shock absorber, buffering our bones and body from the wear and tear of making thousands of movements per day. Cartilage is also slippery—five to eight times more slippery than ice. Thus, when two bones do meet, the cartilage at the ends of each bone allows them to slide off each other, adding to the buffering effect.

The cartilage matrix
Cartilage is made up of three main components: Water (70 to 80 percent), collagen (10 to 15 percent), and proteoglycans (10 to 15 percent). Combined, these are called the cartilage matrix. The cartilage matrix is where new cartilage is born.

As we have seen, water provides cartilage with buffering qualities, and also helps shape the "cartilage" sponge. It also feeds the cartilage. Cartilage contains no blood vessels, so the soaking up and squeezing out of water is what provides cartilage with nutrients.

Collagen also plays a role in giving cartilage its shape and resiliency, and it also absorbs shock. Think of collagen as super strong threads that create the framework to hold the third component of cartilage: proteoglycans.

Proteoglycans are large water-soluble molecules. They are woven in among the collagen threads, forming a kind of netting. This netting traps the water. Proteoglycans also act like magnets. The individual molecules push away from each other, again allowing for space and a buffering effect.

Finally, tiny factories called chondrocytes are located throughout this netting. They produce new collagen and proteoglycans, as well as enzymes that dispose of older, past-their-prime collagen and proteoglycans.

The role of Glucosamine
Glucosamine stimulates chondrocytes to produce more collagen and proteoglycans. The more glucosamine there is, the more collagen and proteoglycans there are, and the more water can be absorbed. The end result is healthier cartilage. Because of these properties, glucosamine can help the body help itself repair damaged or eroded cartilage. It works at the cellular level to reinforce our natural "repair" ability.

When things go wrong
As we age, the millions of movements we have made in our lives begin to wear and tear on cartilage. Catilage begins to deteriorate, and our bones begin to rub together. This becomes noticeable around age 45, and often happens in the fingers, knees, hips, neck, and lower back. Cartilage can also be destroyed through trauma, injury, and repetitive actions.

When cartilage is damaged, the chondrocytes go into high gear, manufacturing more proteoglycans and collagen. Unfortunately, these replacements may be of inferior quality, or be overproduced, resulting in bumpy joint surfaces. Chondrocytes also produce more of the enyzmes that "eat away" old matter. These enzymes may begin attacking the new, inferior cartilage, with an end result of diminished cartilage, not more cartilage. This also may result in fewer proteoglycans, which means the cartilage cannot hold water well. The cartilage can then dry out and wear out more quickly.

The result is that we begin to feel our bones rubbing together during movement. We experience pain and stiffness.

What to do
One way to counter the deterioration and destruction of cartilage is to increase the amount of glucosamine your body has—remember, glucosamine helps the body build and repair damaged cartilage. Glucosamine is not only a "builder" but also a painkiller. In sum, it improves joint function and reduces pain. It makes no difference whether it comes from foods we eat or from supplements.

Proof positive
Many clinical trials have demonstrated that glucosamine results in less pain due to cartilage deterioration and a wider range of movement.

The first studies were performed in the 1960s, using injectable forms of glucosamine sulfate. When glucosamine sulfate became available in pill form, research switched to this.

Up to the present, most glucosamine studies have been performed outside of North America. In all of these studies, glucosamine sulfate proves to maintain joint health.

• An early study in Italy found that 20 percent of those using glucosamine sulfate became "symptom-free." Nearly 25 percent had no restriction of active or passive movement. The researchers concluded that glucosamine sulfate rebuilt damaged cartilage. Clinical Therapeutics 3, no. 4 (1980): 226-272.

• A large-scale study looked at over 1,200 patients with osteoarthritis. Results show that pain decreased throughout the trial, that both active and passive movement improved, and that glucosamine proved to work for six to 12 weeks after treatment had stopped. Pharmatherapeutica 3, no. 3 (1982): 157-168.

• In a study comparing glucosamine sulfate to the pain reliever ibuprofen, the ibuprofen proved more effective the first two weeks, but then faded. After eight weeks, the glucosamine sulfate group reported better results. Current Medical Research and Opinioin 8, no. 3 (1982): 145-149.

• More recently, Italian researchers found glucosamine to be more effective than placebos or traditional NSAIDs (nonsteroidal anti-inflammatory drugs) in treating osteoarthritis. Osteoarthritis and Cartliage 5, supplement A (1997): 82.

It should be noted that although there are positive results in all of these studies, not all participants experience them. Thus, although glucosamine works for many people, it does not necessarily work for all people.