FlexGuard Ingredients: All Eight Actives and Amounts

An amino sugar that the body uses in building cartilage and joint fluid. Commercially it is made from shellfish shell, which is why the carton carries an allergen line, and it is sold in two salt forms that the evidence treats differently.

The three-year trial of glucosamine sulphate used 1,500 mg once a day and reported less joint space narrowing than placebo. The GAIT trial used 500 mg of the hydrochloride three times a day and found no benefit over placebo in its main analysis. A 2018 meta-analysis of the sulfate form specifically is the fairest reading of the split.

Sources: Cochrane, 2005 · NCCIH

The resin of the Indian frankincense tree. Its boswellic acids inhibit 5-lipoxygenase, an enzyme in one of the inflammatory pathways, and it is the one plant in this category whose recent record has improved rather than faded.

The 2025 network meta-analysis of 39 trials ranked it first among the supplements it compared for pain and stiffness. The dose-ranging trial used 100 mg and 250 mg a day of an extract standardised to 30 per cent AKBA; an earlier trial used 333 mg three times a day of crude extract. This row gives a weight and no standardisation, so it can be compared with neither figure cleanly.

Sources: meta-analysis, 2020

A long sugar chain found in cartilage, usually sold alongside glucosamine and almost never alone. The Cochrane review pooled 43 trials and 9,110 people and found a small improvement in pain in the shorter studies, with the effect shrinking as trial quality rose.

The two-year STOPP trial used 800 mg a day. A 2024 meta-analysis of the pair looked at whether combining the two beats either alone. Fifty milligrams is a sixteenth of the STOPP amount, which is the widest single gap on this panel in proportional terms after the four 8 mg rows.

The most-trialled botanical in joint research. An umbrella review of eleven meta-analyses found consistent improvement in pain scores, and a 367-patient trial put 1,500 mg a day of extract against ibuprofen 1,200 mg a day for four weeks.

Absorption is the known problem: curcumin taken alone reaches the blood poorly, which is why most products add something to raise it. This row names the root, gives 50 mg, and names no absorption aid. A liver-injury case series is worth knowing about for high-dose turmeric products, though not at this amount.

Sources: NCCIH turmeric

A flavonoid, here sourced from the Japanese pagoda tree rather than from onions or apples where most dietary quercetin comes from. It has attracted recent interest as a senolytic, meaning a compound that clears worn-out cells.

The pooled osteoarthritis evidence is preclinical: animal models and laboratory work. There is no randomised trial of quercetin in human joints at any amount, which makes 8 mg a number with nothing to compare it to rather than a small version of something larger.

An essential sulfur-containing amino acid, present in every protein-rich food. It is the body's raw material for S-adenosylmethionine.

That distinction is the whole of this row. The joint evidence belongs to S-adenosylmethionine, which was studied at 600 to 1,200 mg a day and compared with anti-inflammatories. Methionine is the precursor, not the compound, and a normal day's food supplies well over a gram of it.

An organosulfur compound, sold on the idea that it supplies usable sulfur. The 2017 review sets out how it is normally used: 1.5 to 6 grams a day.

A 2023 trial in mild knee pain used 2 grams a day for twelve weeks, and an earlier systematic review called the evidence promising and thin in the same sentence. Eight milligrams is roughly a two-hundred-and-fiftieth of that 2 gram amount.

A mixture of protein-digesting enzymes from pineapple stem, used in Europe in enzyme preparations for swelling after injury.

An open dose-ranging study gave 200 mg and 400 mg a day and saw more at the higher amount. A placebo-controlled pilot at 800 mg a day did not beat placebo, and a 16-week WOMAC trial used 1,890 mg a day of a bromelain preparation. The honest summary is that the evidence is mixed at hundreds of milligrams and absent at eight.