Around 6 million people in the US take glucosamine supplements, and yet their effects remain controversial. While glucosamine is essential for healthy joints and youthful skin, it has some other surprising benefits, too. But does it work? We reveal all potential benefits and side effects.
What Is Glucosamine?
Glucosamine is a naturally occurring substance in the body. It works to build connective tissue, cartilage, ligaments and other structures in our body. Plus, it lubricates and strengthens the joints, enabling smooth movement [1, 2].
Chemically speaking, glucosamine is a relatively simple substance. It’s classified as an amino sugar. Shellfish (lobsters, shrimp, crabs) are rich in chitin, a highly-resistant material made of long chains of glucosamine. Manufacturers use them as raw material for glucosamine supplements [3].
Animal bones and connective tissue are also decent food sources of glucosamine [3].
In the US, glucosamine is among the most popular dietary supplement for adults. Many professional athletes rely on it, especially those with joint issues [4, 5, 6].
Snapshot
Proponents:
- Helps with osteoarthritis
- Boosts cartilage and joint recovery
- May help with rheumatoid arthritis
- May relieve gut inflammation
- Hydrates the skin and removes dark spots
Skeptics:
- Beneficial joint effects are weak
- May cause digestive side effects
- Requires long-term treatment
- May raise blood glucose and eye pressure
- Interacts with blood thinners
How It Works
Glucosamine’s secret lies in its ability to boost the production of compounds that build connective tissue. For example, glucosamine builds complex molecules known as glycosaminoglycans, such as hyaluronic acid. They give strength and elasticity to our skin, joints, and ligaments [7, 8, 9].
Most skincare-savvy people have heard of hyaluronic acid — it’s extremely popular in serums… and for a good reason. It maintains skin moisture and offers powerful anti-aging benefits skin. Since glucosamine boosts hyaluronic acid, it’s also used in cosmetics [10].
Glucosamine also protects cartilage by maintaining collagen structure. Plus, it acts as an anti-inflammatory and antioxidant in the joints, intestines, and blood vessels. This effect may help protect the body against different chronic diseases [11, 12, 13, 14, 15, 16, 17].
Remember, glucosamine is no magic pill. Although scientists and practitioners are excited about its wide-ranging potential benefits, only a couple have sufficient evidence to back them up.
Health Benefits
Likely Effective:
1) Osteoarthritis
Osteoarthritis is the most common joint disease. Destruction of cartilage in the joints and bone deformation cause pain and restrict movement. It usually attacks large joints such as the knee and hip joints. Doctors are still looking for ways to slow or prevent its progression [18].
Knee Osteoarthritis
The majority of research examined the effects of glucosamine on the symptoms and progression of knee osteoarthritis.
According to a large review of 31 clinical trials, glucosamine improves the symptoms of osteoarthritis – such as pain, stiffness, and joint function – better than placebo [19].
In three studies with 1,800 knee osteoarthritis patients, glucosamine (alone or with chondroitin) reduced pain, stiffness, and joint swelling. In two studies, this combination was as effective as NSAID drugs, celecoxib and ibuprofen [20, 21, 22].
A cream with glucosamine also managed to relieve knee pain in 63 osteoarthritis patients. Other ingredients such as chondroitin and camphor may have contributed to the effects [23].
Other comprehensive reviews and meta-analyses (50+ clinical trials with 3,000+ patients) revealed mixed results. Glucosamine reduced knee pain better than placebo but failed to improve joint stiffness and function [24, 25, 26].
In a 2016 study of 164 patients with knee OA, a combination of glucosamine and chondroitin was even worse than placebo in reducing the symptoms. However, other authors have pointed out some flaws in the study design [27, 28].
Some scientific reviews found positive results only for specific formulations of glucosamine and its combinations with other supplements (more details in “Supplements and Dosage“) [26, 29, 30].
Jaw Osteoarthritis
In two clinical trials (105 patients, 3 months), glucosamine relieved pain and improved jaw mobility better than ibuprofen [31, 32].
However, 6-week treatment with glucosamine (1,200 mg a day) had no effects in 59 patients with jaw osteoarthritis [33].
Possibly Effective:
2) Joint Recovery
Glucosamine is often the go-to supplement for athletes who are prone to joint injuries. In one trial, it improved knee function in 106 athletes with an acute knee injury (1,500 mg daily for 4 weeks) [34].
In studies on professional athletes, glucosamine supplements (1,500 – 3,000 mg, up to 4 months) blocked collagen degradation and thus aided in cartilage recovery [35, 36, 37].
Lower doses of glucosamine (500 – 1,000 mg) showed the same effects in 75 healthy individuals [11].
However, glucosamine supplementation failed to improve post-surgery recovery in 30 athletes with ruptured knee ligaments. The daily dose in this study (1,000 mg) was lower than usual [38].
3) Rheumatoid Arthritis
Unlike osteoarthritis, rheumatoid arthritis (RA) is an autoimmune disease that leads to joint inflammation. It causes joint pain and stiffness but may even spread to the entire body [39].
According to preliminary research, glucosamine may reduce the pain from rheumatoid arthritis, while its effects on joint inflammation are less convincing [40].
In 51 patients, 3-month treatment with glucosamine notably improved RA symptoms [41].
On the other hand, a combination of glucosamine, chondroitin, and quercetin had no effect on 22 RA patients [42].
In mice with rheumatoid arthritis, both glucosamine and N-acetyl-glucosamine (NAG) suppressed joint inflammation and enhanced joint function [43].
Scientists tested if a combination of glucosamine and vitamin E could block oxidative damage and inflammation In rats with RA by [44]:
- Boosting the levels of zinc and antioxidants (glutathione and superoxide dismutase or SOD)
- Decreasing inflammatory enzymes (PGE2, iNOS) and uric acid
- Reducing inflammatory NF-kB
Insufficient Evidence:
No valid clinical evidence supports the use of glucosamine for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.
4) Gut Inflammation
In a clinical trial of 38 patients, glucosamine (3 g daily for 3 months) decreased gut inflammation and suppressed the growth of dangerous diarrhea-causing bacteria (Clostridia) [45].
One review pointed to the gut-healing potential of glucosamine and an intricate connection between digestive and joint disorders [46].
According to lab experiments on rats and mice with IBD, glucosamine could relieve gut inflammation and prolong animals’ survival time [47, 48, 49].
5) Cancer Prevention
The findings discussed below stem from preliminary research. They should guide further investigation but shouldn’t be interpreted as supportive of the anticancer effects until more research is done. Glucosamine supplements aren’t approved for cancer prevention or treatment.
In a large observational trial with over 75,000 patients, those who consumed glucosamine and chondroitin supplements had two times lower rates of lung cancer and colon cancer. According to the researchers, however, the reduction of colon cancer rates was not significant [50, 51].
Another observational trial (2,000 patients) showed significantly lower rates of colon cancer among glucosamine and chondroitin users. However, an even larger one (6,000+ patients) found no significant connection [52, 53].
Glucosamine inhibited the growth of breast cancer and lung cancer in mice [54, 55].
In test tubes, glucosamine could kill different types of cancer cells, but this doesn’t tell us anything about its potential anticancer effects in the human body [56, 57, 58, 59, 60].
Skin Anti-Aging Properties of Glucosamine
Since glucosamine builds hyaluronic acid and other components of the skin and connective tissues, it may reduce wrinkles and boost skin complexion when added to cosmetic products. Plus, it blocks the production of the skin pigment melanin and may thus removes dark skin spots [61, 8].
Researchers analyzed skin samples of eight women who took glucosamine (250 mg daily for 8 weeks). Glucosamine rejuvenated the skin by enhancing collagen and hyaluronic acid production [62].
Glucosamine’s “cousin”, N-acetyl-glucosamine or NAG, also helps maintain a youthful appearance of skin [7, 63, 64, 65].
Side Effects & Precautions
Countless clinical trials tested glucosamine supplements, and they haven’t shown any major side effects. In some patients, they may cause digestive issues such as [29, 26, 21, 33]:
- Nausea
- Heartburn
- Bloating
- Diarrhea
Doctors reported one case of worsened asthma symptoms, probably caused by a supplement with glucosamine and chondroitin, but no other studies confirmed this effect [66].
Diabetes and Weight Gain
Glucosamine has a structure similar to glucose and may interfere with its metabolism. However, clinical studies haven’t found adverse effects in patients with controlled diabetes [67, 68, 69, 70].
It may raise blood glucose levels in patients with untreated diabetes or insulin resistance. It’s a good idea to closely monitor blood glucose while taking glucosamine supplements, especially if you have diabetes or at risk [71, 72].
If blood glucose and insulin are in check, glucosamine probably won’t cause weight gain and metabolic side effects.
Eye Pressure and Glaucoma
In a clinical trial on 88 patients with osteoarthritis, glucosamine increased eye pressure, especially in older patients. A small observational study (17 patients) came to the same conclusion [73, 74].
Due to this effect, glucosamine may raise the risk of glaucoma in the elderly [75].
Side Effects on the Liver
A few case reports indicated a potential of glucosamine to worsen chronic liver disease, but no clinical or safety trials confirmed this effect. In one case, the liver side effects of glucosamine were probably a consequence of an allergic reaction [76].
Sensitive Groups
Most supplement manufacturers derive glucosamine from shellfish so they may not be safe for people with shellfish/seafood allergy. There’s an alternative solution, however, and we’ll get there in a minute.
Pregnant women should avoid glucosamine until we know more about its safety during pregnancy. The same goes for women who are breastfeeding or children unless they are under medical supervision [77, 78].
Drug Interactions
Supplement-drug interactions can be dangerous and, in rare cases, even life-threatening. Always consult your doctor before supplementing and let him know about all drugs and supplements you are using or considering.
The only significant drug interaction of glucosamine is with blood thinners such as warfarin (Coumadin). In combination with these drugs, glucosamine may prolong bleeding time and increase the risk of bruising [79].
To stay on the safe side, stop taking glucosamine supplements two weeks prior to surgery.
Some health experts are warning about the potential interaction between glucosamine and a painkiller acetaminophen (Tylenol) which may reduce their effectiveness [40].
Contraindications
To sum it up, the following groups may want to avoid glucosamine supplements:
- People with uncontrolled diabetes
- People with seafood and shellfish allergy
- Children and pregnant women
- People on blood thinners
- Those with increased eye pressure and glaucoma
Glucosamine Supplements and Dosage
Glucosamine supplements have not been approved by the FDA for medical use. In general, regulatory bodies aren’t assuring the quality, safety, and efficacy of supplements. Speak with your doctor before supplementing.
Glucosamine sulfate and glucosamine hydrochloride are the two most common salts, and people mostly take them as pills (1,500 mg) or bulk powders (500 – 1,500 mg per serving). Other available forms include:
- Liquid glucosamine (750 – 2,000 mg of glucosamine hydrochloride per serving)
- Glucosamine gels and creams for joints and skin care
Most glucosamine supplements also contain chondroitin and other ingredients such as MSM, hyaluronic acid, and turmeric extract.
Vegan glucosamine, derived from fermented corn, is also available in the form of pills or bulk powder. It’s suitable for people with seafood allergy and those who avoid animal products.
Note: Some pills contain NAG or N-acetyl-glucosamine (500 – 750 mg). Although a close derivative of glucosamine, NAG is a different substance with distinct health benefits and side effects. The dosing guidelines will also vary. Most studies we reviewed in this article did not use NAG.
What is the Best Glucosamine Supplement?
At this point, you’re probably wondering how to choose the best glucosamine supplement so let’s see what the evidence says.
One trial with 600+ patients found higher efficacy of glucosamine sulfate for knee osteoarthritis compared with hydrochloride, although both forms showed mixed results [30].
Glucosamine sulfate probably owes its advantage to better absorption. Sulfur from this form may also help build and protect the cartilage [80, 81].
On the other hand, both the sulfate and hydrate were equally effective in one clinical trial [82].
The strongest evidence comes from a series of comprehensive reviews in which a specific crystalline form of glucosamine sulfate was superior to others [26, 83, 84].
The fact that one pharmaceutical company owns a patent for this formulation may indicate a potential conflict of interests.
Retailers claim better absorption of liquid glucosamine supplements, but no clinical trials have confirmed this yet. When it comes to other ingredients, chondroitin and MSM may boost the effects of glucosamine on knee pain and joint recovery, but there’s not enough clinical evidence to confirm this [85, 29, 86].
Dosage
The below doses used in clinical trials may not apply to you personally. If your doctor suggests using a glucosamine supplement, work with them to find the optimal dosage according to your health condition and other factors.
The following doses gave positive results in clinical trials:
- Osteoarthritis and rheumatoid arthritis: 1,500 mg daily for 3+ months
- Cartilage regeneration: 1,500 – 3,000 mg (athletes) or 1,000 mg daily for 4 months
- Knee injury recovery: 1,500 mg daily for 1 month
- Gut inflammation: 3,000 mg daily for 3 months
User Reviews
The opinions expressed in this section are solely from the users who may or may not have medical background. Their reviews do not represent the opinions of SelfHacked. SelfHacked does not endorse any specific product, service, or treatment.
Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice from your doctor or another qualified healthcare provider because of something you have read on SelfHacked.
Looks like users did their research since most of them are taking glucosamine sulfate in combination with chondroitin and MSM. Although the majority of products deliver 1,500 mg of glucosamine per serving, the content of other ingredients varies a lot.
Most reviews are positive: people managed to ease the pain in their knees, but also in elbows, spine, and hips. Some users reported skin benefits as a plus.
Glucosamine is quite popular among dog owners and they also report positive results. They are usually giving human glucosamine supplements to their “best friends”.
On the other hand, some users have reported a lack of effects or even worsened symptoms in a few cases. Digestive issues and dizziness are common side effects while some people reported high blood pressure and kidney pain.
For Dogs
Chews, capsules, and powders with glucosamine for dogs are all over the market. They claim to have the same beneficial effects on aging dog joints.
Just like in humans, glucosamine showed some beneficial effects in dogs, but they are mostly limited to mild pain relief. Given that most dogs tolerated the treatment well, glucosamine supplements might be worth a try if your dog has joint issues [87, 88, 89].
Glucosamine dosage for dogs in the quoted studies was 2,000 mg daily, but it may vary depending on your buddy’s weight. Some vets recommend 500 mg per 10 lbs of body weight.
Despite all the products explicitly marketed for dogs, they are fine using the human ones, too.
For Cats
Glucosamine for joint disorders in cats doesn’t seem to have any notable effects, but the studies are sparse. Some vets reported clinical success in using glucosamine and chondroitin for joint issues in cats, though.
Due to the lack of data, it’s best to consult your vet first if you’re considering glucosamine for your feline friend [90, 91].
Takeaway
Glucosamine gives structure and elasticity to your skin, joints, and connective tissue. As we age, the lack of glucosamine may lead to joint pain and wrinkled skin. Food sources of glucosamine include shellfish, animal bones, skin, and cartilage.
Glucosamine is the most popular nutritional supplement for joint support. It can relieve the pain and improve joint function in mild-to-moderate osteoarthritis. Glucosamine may also help with rheumatoid arthritis and gut inflammation, but the evidence is limited. Cosmetics with glucosamine can remove dark spots and improve skin complexion.
Crystalline glucosamine sulfate in a daily dose of 1,500 mg has shown the best results. Chondroitin and MSM may boost its effects, but the evidence is limited.
Skip glucosamine if you are pregnant; have untreated diabetes, have increased eye pressure or glaucoma; take warfarin or other blood thinners; have a seafood/shellfish allergy. Make sure to consult your doctor before supplementing.
