FlexGuard Ingredients: What Is in Each Capsule

An amino sugar the body makes from glucose and uses to build the glycosaminoglycans in cartilage. As a supplement it is manufactured from crustacean shell, which is why the allergen line on this panel reads crayfish.

It is the most-studied single ingredient here, and the picture is mixed. The Cochrane review pooled twenty studies in 2,570 people and found the outcome depended on which preparation was tested: the Rotta glucosamine sulfate product beat placebo, pooled non-Rotta preparations did not. A three-year trial of 1,500 mg a day reported changes in symptoms and joint space, while GAIT, in 1,583 people, found no significant benefit over placebo at six months.

Every one of those trials used 1,500 mg a day. This row is 500 mg.

The gum resin of the frankincense tree, used in Ayurvedic medicine and studied for joint comfort on the strength of its boswellic acids, of which AKBA is the one most often standardised for.

Two trials set the amounts. A 2003 crossover study used 333 mg three times a day and reported less knee pain and greater walking distance. The 5-Loxin trial used a 30 per cent AKBA extract at 100 mg and 250 mg a day for ninety days, funded by that extract's maker. NCCIH calls the field small and uneven.

At 67 mg this is the closest row to a researched amount. No extract ratio and no AKBA percentage are printed, so the comparison is indicative.

A long-chain glycosaminoglycan found in cartilage, usually made from bovine trachea or fish cartilage. It is glucosamine's traditional partner and is proposed to help cartilage hold water.

The Cochrane review of chondroitin pooled forty-three randomised trials in 9,110 people. It found a small improvement in pain against placebo, graded low quality, and noted that the effect shrank in the larger and better-conducted studies. The amounts in that literature run from 800 to 1,200 mg a day.

This row is 50 mg, which is roughly a sixteenth of the lower end of that range.

The rhizome that colours curry, and the source of the curcuminoids that carry its research. The distinction that decides this row is between root powder and a standardised extract: curcuminoids are a few per cent of the root by weight and the great majority of a standardised extract.

A 2016 meta-analysis of the joint trials found the studies typically used around 1,000 mg a day of curcuminoids. A 367-person trial used 1,500 mg a day of a standardised extract and reported results comparable to ibuprofen. NCCIH adds the detail that decides it: curcumin is poorly absorbed alone.

The label names the root, and fifty milligrams of root is a different proposition from fifty of a standardised extract.

A flavonoid present in onions, apples, capers and tea, extracted for supplements from the flower bud of the Japanese pagoda tree. A normal mixed diet supplies somewhere in the tens of milligrams a day.

The German federal institute's safety review describes supplement intakes from 250 mg to 1,500 mg a day and concentrates its safety questions at the upper end. Work on absorption shows how little of an oral dose reaches circulation.

Eight milligrams sits below what a plate of onions supplies.

An essential sulfur-containing amino acid. The body cannot make it, so it comes from dietary protein: a single egg carries a few hundred milligrams and a chicken breast several times that.

Its place on joint labels is indirect: methionine is the precursor the body converts into S-adenosylmethionine, and it is SAMe that carries the joint evidence. A meta-analysis of the SAMe trials found it comparable to anti-inflammatories at around 1,200 mg a day.

No trial has tested methionine itself for joint comfort, and 8 mg of methionine is not 8 mg of SAMe.

An organic sulfur compound found in small amounts in food and made industrially for supplements. It is one of the two or three best-selling joint ingredients in the United States.

The unit is the whole story. A 2006 pilot trial gave fifty people 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 1.5 g to 6 g a day.

This row is 8 mg, in different units from its own research.

A mixture of protein-digesting enzymes extracted from pineapple stem, used in Europe for swelling after injury and surgery and sold in units of enzyme activity as often as in milligrams.

A review of its osteoarthritis studies found the trials small and the doses in the hundreds of milligrams a day. It is also the row most likely to matter to anyone on an anticoagulant.

The panel prints 8 mg and no enzyme activity figure.