Glucosamine: Benefits, Dosage And Side Effects

Glucosamine is a naturally occurring compound in the body that helps build connective tissues, including tendons, ligaments and cartilage. It works as a building block alongside other substances in the body for tendon, ligament and cartilage health, says Robert Miller, M.D., a Florida-based internal medicine doctor who provides physician services for Vista Staffing.

Cartilage acts as a “bumper” around bones and joints, he explains. “Over time these bumpers rub against each other and erode until you have little to no bumper left, which is seen in osteoarthritis as the bony cartilage wears away. Then you have bone on bone.”

Many people with osteoarthritis and other forms of arthritis may seek pain relief and improved flexibility by taking glucosamine supplements. These supplements may help increase cartilage mass and fluid volume to cushion joints and slow or prevent cartilage breakdown.

The Food and Drug Administration (FDA) hasn’t approved glucosamine supplements for joint health specifically. It regulates them as general dietary supplements, ensuring companies meet safety and labeling standards. However, not all manufacturers follow those rules. Many dietary supplement companies produce and sell their products without notifying the FDA, according to the government agency. Therefore, when purchasing glucosamine supplements, it’s important to shop carefully, read labels closely and research the manufacturer before buying.

The three most common forms of glucosamine include:

• Glucosamine sulfate. Made from the shells of shellfish (chitin), glucosamine sulfate stimulates production of glycosaminoglycans (GAGs), which play a crucial role in cell signaling by chondrocytes, the cells that form cartilage. Glucosamine sulfate by itself is  highly unstable because it absorbs and retains moisture. Therefore, this form needs a compound salt stabilizer, such as potassium chloride or sodium chloride, resulting in 74% purity.
• Glucosamine hydrochloride. More highly concentrated than glucosamine sulfate, glucosamine hydrochloride is also made from shellfish and has a 99% purity.
• N-acetyl glucosamine. Also made from shellfish, this form of glucosamine helps form hyaluronic acid, a component of joint fluid that may have anti-inflammatory properties.

All three forms are different versions of the same glucosamine compound. “They all work in a similar fashion in which they all promote joint health,” says Dr. Miller, who adds that research has yet to prove that any one form works better than another.

Glucosamine supplements are taken orally. They’re available in capsule, tablet or powder forms These supplements often contain both glucosamine and chondroitin, another naturally produced component of cartilage. Many glucosamine supplements also contain methylsulfonylmethane (MSM), another naturally occurring compound in the body that can also be produced in a laboratory and used to treat arthritis.

People with arthritis or those trying to get ahead of cartilage wear and tear might benefit from glucosamine supplements. However, clinical research on glucosamine supplements is currently inconclusive regarding demonstrated joint improvement or the slowing of cartilage breakdown. The suggested benefits of glucosamine supplements are based largely on anecdotal evidence from people who noticed decreased pain or improved flexibility after taking them.

“Although some studies show benefits of using glucosamine in osteoarthritis, it’s unclear if this substance can reduce knee pain from osteoarthritis [specifically],” says Payam Vahedifar, M.D., a physician and pain management specialist in the greater Los Angeles area. “Some studies show a beneficial effect in short-term use but not long-term use.”

“In my opinion, which is backed by studies on rugby and soccer players, consumption of glucosamine can reduce the degradation of joints and only slightly increase collagen synthesis,” says Dr. Vahedifar. Younger patients tend to have the best results when using glucosamine both as a preventative measure and for reducing degradation of the joint, he adds.

It can take up to eight weeks to notice pain reduction and improvement in joint function with glucosamine supplements, says Dr. Vahedifar. If someone has no noticeable improvement after two months, glucosamine supplements are unlikely to help.

Glucosamine is considered a relatively safe supplement. However, glucosamine supplements do have potential side effects, including health risks for people taking certain medications.

Glucosamine side effects are typically mild, including:

• Bloating
• Upper abdominal pain
• Nausea
• Diarrhea
• Heartburn
• Constipation

People who take certain medications may also be at risk for health complications. Medications that can interact with glucosamine include:

• Warfarin (coumadin). Taking glucosamine and Warfarin can increase the pharmaceutical’s blood-thinning effects, potentially causing serious bleeding or bruising.
• Certain cancer medications (topoisomerase II inhibitors). Glucosamine may block the ability of some cancer medications designed to slow the rate at which cancer cells can copy themselves, thus reducing the treatment’s efficacy.
• Acetaminophen. Taking glucosamine sulfate with an acetaminophen product like Tylenol may make both compounds less effective. However, this interaction isn’t currently cause for great concern.

People with the following health conditions should also use caution when considering or taking glucosamine supplements.

• Pregnancy and breastfeeding: There isn’t enough research to confirm whether pregnant or breastfeeding people can consume glucosamine supplements safely.
• Asthma: People with asthma should use caution when considering taking glucosamine, since the supplement may worsen asthma symptoms.
• Glaucoma: Glucosamine supplements may worsen glaucoma by increasing pressure inside the eye. Talk with your health care provider before taking a glucosamine supplement if you have glaucoma.
• Shellfish allergy: Glucosamine supplements are produced from shellfish—mainly shrimp, lobster and crab. If you have a shellfish allergy, avoid taking glucosamine supplements or consult your health care provider prior to doing so.

Both glucosamine and chondroitin are building blocks of cartilage that cushions the joints and bones. For this reason, many glucosamine products also contain chondroitin with the goal of supporting joint health.

“Chondroitin helps retain water and is important in shock absorption and elasticity of joints,” says Dr. Vahedifar. “[Glucosamine and chondroitin] are used together to help maintain the structure and integrity of joints and help with inflammation and pain.”

As with glucosamine, clinical research is inconclusive regarding chondroitin’s potential benefits for joint health. Furthermore, because the FDA doesn’t regulate glucosamine and chondroitin supplements, products may be mislabeled regarding how much chondroitin they contain.

Although science shows mixed results and inconclusive evidence for glucosamine’s effectiveness in reducing pain and slowing cartilage wear and tear, glucosamine supplements remain highly popular products.

Dr. Miller recommends talking to your health care provider and reviewing which medications you currently take before adding glucosamine to your regimen. “This field of medicine is one we’re still exploring,” he says, citing the lack of conclusive evidence for glucosamine’s touted benefits. “Understand that when you take these supplements, the information we’re able to provide as physicians is limited outside common side effects and the fact that it does affect other medications that you can take.”

What to Look for in a Glucosamine Supplement

Since glucosamine supplements aren’t regulated by the FDA, it’s important to read product labels carefully and research the company that produces the supplements. Avoid purchasing glucosamine supplements online from unfamiliar sellers if possible.

“When you’re purchasing from online retailers, you don’t know who the reseller is,” says Dr. Miller. “The product you believe you’re getting and the product you actually receive can be two different things. You’re trusting that the reseller has your best interest at heart, and that may not be the case.”

In-person shopping at vitamin and supplement stores may be a better choice since staff tend to be more knowledgeable about each brand offering glucosamine supplements, he adds.

Safe Glucosamine Dosage

There’s no established effective dose of glucosamine since the supplement isn’t regulated or approved by the FDA and clinical research confirming its benefits is lacking. However, glucosamine supplements are typically consumed in 500-milligram doses three times a day for osteoarthritis.

Talk with your health care provider to determine the best dosage of glucosamine for you or a loved one.