Also known as: Apple peel extract, Urson, Malol, Prunol
Muscle & RecoveryEarly evidence
A compound from apple peel with striking results in mice and very little to show in people. A clear example of promising preclinical work that has not yet translated.
Typical dose
150.0–450.0 mg per day
With fat-containing meals, split across the day
What it is
Ursolic acid is a triterpene found in the waxy coating of apple peel, and also in rosemary, holy basil, thyme and other herbs.
It attracted attention after research identified it as a compound that produced the opposite gene expression pattern to muscle wasting, and mice given it gained muscle and lost fat.
Those findings were genuinely striking and drove a wave of supplement launches. The human research has not kept pace, and poor absorption is the likely reason.
How it works
Ursolic acid is proposed to increase signalling through the insulin and IGF-1 pathways in muscle, which promotes protein synthesis and suppresses the pathways driving breakdown.
In animal models it also increased brown fat, raising energy expenditure, which is how the same compound came to be associated with both muscle gain and fat loss.
The obstacle is bioavailability. Ursolic acid is poorly water-soluble and poorly absorbed orally, and blood levels achieved from a capsule are far below the concentrations used in the laboratory work.
What the evidence shows
The preclinical work is substantial and consistent, with clear effects on muscle mass, fat mass and metabolic markers in animal models.
Human trials are few and small. A trial in resistance-trained men reported some favourable changes in body composition and irisin levels without meaningful differences in strength.
The pattern is familiar in this field: impressive mouse data, an appealing story, and human results that have not followed. Formulations addressing the absorption problem may change that, and they have not yet.
Dosing
Products typically supply 150 to 450 mg daily, often split across three doses. These figures come from product convention rather than human dose-finding work.
Take with a meal containing fat, since it is fat-soluble and poorly absorbed. This is one of the few things you can do to improve your odds with it.
Set expectations from the human evidence rather than the mouse data. The gap between the two is the whole story of this ingredient, and anyone selling it on the animal findings is describing research done in a different species.
At a glance
Common forms
Ursolic acid extract, Apple peel extract, Combined with fat for absorption, Within muscle-building formulas
Half-life / duration
Poorly absorbed; not well characterised in humans
Timing
With fat-containing meals, split across the day
Competition status
Permitted — not on the WADA Prohibited List
Category
Muscle & Recovery
Safety and side effects
Ursolic acid has been well tolerated in the limited human research conducted, with few adverse effects reported. It has extensive dietary exposure through fruit and herbs.
Human safety data at supplemental doses is limited to a small number of short studies.
Because it influences insulin signalling, take care if your blood sugar is being managed. Speak to your doctor before use if you take regular medication.
Who should avoid it
Take care if your blood sugar is being managed, given the effects on insulin signalling. Speak to your doctor before use if you take regular medication or are under medical care. Human safety data at supplemental doses is limited. Not established in pregnancy or breastfeeding.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
