Citrulline malate does nothing for strength in trained lifters

Citrulline malate is a fixture of pre-workout supplements, and the mechanisms by which it is supposed to help performance are well described in the literature. Yet the actual trial results on muscle strength have been inconsistent, with some studies suggesting a benefit and others finding nothing. That confusion matters for athletes and recreational lifters who buy these products specifically to optimise strength gains. The authors argued that a properly conducted pooled analysis was needed to cut through the mixed findings and give a clearer answer.

The researchers ran a systematic search of Medline and SciELO, completed in August 2020, looking for randomised controlled trials that tested citrulline malate supplementation against placebo for muscle strength in resistance-trained adults. Four studies met the criteria and were pooled in a meta-analysis covering 138 assessments, 69 in the citrulline malate groups and 69 in the placebo groups. The analysis looked at overall strength outcomes and also split results by upper and lower limbs to see whether the supplement worked differently depending on the muscles tested. The review was registered in advance on the PROSPERO database.

There was no overall effect favouring citrulline malate over placebo on muscle strength. Breaking the results down by body region did not change the picture: neither lower limb nor upper limb outcomes showed a significant effect, and the mean effects for upper and lower limbs were statistically similar to each other. In short, every way the data were cut, the supplement failed to separate itself from placebo. The authors concluded that citrulline malate supplementation does not improve muscle strength in healthy, resistance-trained individuals.

This pooled analysis addresses a literature the authors themselves describe as unclear, where individual trials pointed in different directions. By combining them, it lands firmly on the null side for strength in trained lifters. The main limitation is the small evidence base: four trials is thin, which leaves room for a small effect to have gone undetected, and it leaves open questions about other outcomes, doses and populations that these trials did not cover. It also says nothing about untrained people, who were outside the scope of this review.

For anyone who lifts and reads supplement labels, this is a reason to treat strength claims attached to citrulline malate with scepticism. The pooled evidence in trained adults shows no strength advantage over placebo, in either the upper or lower body. That does not prove the ingredient is useless for every purpose, since this review only examined strength, but it does mean the specific promise of stronger lifts is not backed by the trials conducted so far.