The Joint Supplement Guide: What Is Actually In These Bottles

Glucosamine and chondroitin sulfate are the oldest idea in this category and the most tested. Both are constituents of cartilage, and the proposition is that supplying them supports the tissue that carries load.

The evidence is large and genuinely disputed. The NIH-funded GAIT trial randomised 1,583 people to glucosamine at 1,500 mg a day, chondroitin at 1,200 mg, both, an anti-inflammatory or placebo, and neither supplement arm separated significantly from placebo overall. The Cochrane review of glucosamine found the result depended on which preparation was tested, and the Cochrane review of chondroitin found a small pain benefit at low quality of evidence across forty-three trials.

Two clinical guidelines have since looked at the whole pile. The 2019 American College of Rheumatology guideline recommends against glucosamine for knee, hip and hand osteoarthritis, and the 2019 OARSI guidelines decline to endorse it for symptom relief.

What that means for a label: if a bottle carries glucosamine, the amount to look for is 1,500 mg a day, and if it carries chondroitin, 800 to 1,200 mg. Anything far below those is untested rather than tested and found wanting.

Boswellia, turmeric, bromelain, quercetin and ginger turn up across this category on the strength of their effects on inflammatory signalling rather than on cartilage structure.

Boswellia has the most direct joint trial record of the group. A 2003 crossover trial used 333 mg three times a day and reported less knee pain and greater walking distance, and a 90-day trial of an extract standardised to 30 per cent AKBA reported improvements at 100 mg and 250 mg a day. NCCIH describes the field as small and uneven, which is fair.

Turmeric is the one most often mis-sold, and the mis-selling is mechanical rather than dishonest. Curcuminoids are a few per cent of turmeric root by weight and the great majority of a standardised extract, so 500 mg of root and 500 mg of extract are different products. The joint meta-analysis drew on trials using around 1,000 mg a day of curcuminoids, and a 367-person trial used 1,500 mg a day of a standardised extract.

Bromelain's clinical work, collected in a review of the osteoarthritis studies, runs in the hundreds of milligrams a day, and quercetin's supplement literature, surveyed in a German federal safety review, runs from 250 mg upward.

The right-hand column is the useful one. Every row in it describes a way a label can name a researched ingredient while supplying an amount nobody studied.

MSM is the sulfur compound that actually appears in joint trials, always in grams. A 2006 pilot used 3 g twice a day, a 2011 randomised study used 1.125 g three times a day, and a 2017 review describes a literature running from about 1.5 g to 6 g a day. A joint capsule carrying MSM in milligrams is carrying a name rather than a dose.

Methionine is the one that causes confusion. It is an essential amino acid, supplied in hundreds of milligrams by ordinary dietary protein, and it is the precursor the body converts into SAMe. It is SAMe that has a joint meta-analysis behind it, at around 1,200 mg a day, and SAMe is a different compound sold separately and at a different price.

Collagen is the fourth family and it sits slightly outside this guide's evidence set, because most joint collagen trials use type II collagen at 40 mg a day and the products sold most heavily are hydrolysed type I and III at ten grams. Those are different propositions with the same word on the front.

1. Serving size first. Every figure on a panel is per serving, and a serving is often two or three capsules. Multiply before comparing anything.
2. Look for a blend. A row reading proprietary blend with one total means the individual amounts are undisclosed and no comparison is possible.
3. Find the largest row. On most joint capsules it is glucosamine, and whether it reaches 1,500 mg a day tells you most of what you need.
4. Check the plant rows for a ratio. An extract with no ratio and no standardisation figure cannot be matched to any trial.
5. Check the units. Anything in single-figure milligrams that the research ran in grams is decoration.
6. Read the allergen line. Shellfish on a glucosamine product is expected, and it also settles the vegan question.
7. Read the caution. Age limits, pregnancy and the medication line are all there, and they are the same on almost every bottle.
8. Then read the front. In that order, because the front is marketing and the panel is a legal document. The labelling rule governs the second and not the first.

That sequence works on any bottle in this category, including the one sold on this website. The FlexGuard panel is reproduced in full so it can be run through the same eight steps as anything else on a shelf.

A guide to joint supplements that does not say this is not worth reading. The Cochrane review of exercise pooled fifty-four trials of land-based exercise for knee osteoarthritis and found improvements in both pain and physical function. No ingredient in this whole category has a result of that size and that consistency behind it.

Weight is the second. Load through a knee is a multiple of body weight, and the arithmetic of that is not controversial. The NIAMS overview and MedlinePlus both put exercise and weight at the top of what actually helps.

Neither of those makes a supplement pointless. Both make it a supplement: something added to the things that work rather than something bought instead of them. Anybody selling a capsule as a replacement for either is selling something else.

NCCIH's short guide to using supplements sensibly is the best five minutes available to somebody about to buy their first joint product, and it costs nothing.