Rae et al. 2003: Creatine Improves Brain Performance in Vegetarians — Study Summary

Study Overview

Rae et al. (2003) conducted a double-blind, placebo-controlled, crossover trial published in Proceedings of the Royal Society B.

The study enrolled 45 young adult vegetarians and vegans and tested whether 5g/day of creatine monohydrate for 6 weeks could improve cognitive performance (Rae et al., 2003) .

This was one of the first rigorous studies to examine creatine’s effects on brain function rather than muscle performance.

Key Findings

• Working memory improved significantly: Participants on creatine performed substantially better on backward digit span tests, a standard measure of working memory
• Intelligence and reasoning scores increased: Raven’s Advanced Progressive Matrices scores were higher during the creatine phase compared to placebo
• Vegetarians showed the greatest benefit: Because vegetarians and vegans have lower baseline creatine stores (creatine is found mainly in meat and fish), supplementation had a more pronounced effect on brain energy availability
• Effect was robust across the crossover design: The crossover methodology strengthened confidence in the findings, as each participant served as their own control

Practical Implications

This study provided early evidence that creatine is not just a muscle supplement — it is a brain supplement too.

For vegetarians, vegans, and anyone with low dietary creatine intake, supplementing with 5g/day may meaningfully improve working memory and mental processing speed.

The brain accounts for roughly 20% of total energy expenditure despite being only about 2% of body weight, making it highly sensitive to energy availability.

Creatine helps buffer ATP supply in the brain, supporting demanding cognitive tasks.

Study Limitations

• The sample consisted exclusively of vegetarians and vegans, so the magnitude of cognitive benefit in omnivores may differ
• The study lasted only 6 weeks, so longer-term cognitive effects were not assessed
• The sample size of 45 participants, while reasonable for a crossover design, is still relatively modest
• Only two cognitive tests were used, limiting the breadth of cognitive domains examined

Where This Fits in the Evidence

Rae et al. (2003) is often cited as the study that reframed creatine as a brain supplement and not only a muscle one, reporting roughly 20% gains in working memory and reasoning in vegetarians and vegans. Its crossover design, with each participant serving as their own control, gives the result more weight than the modest sample of 45 might suggest. Because it recruited only people with low dietary creatine intake, it leaves open how large the cognitive benefit is in omnivores — a question later vegetarian-cognition work picked up directly. The broader collection of brain and cognition studies sits in our research library.

Sources & References

This page summarizes Rae et al. (2003). Full citation: Rae C, Digney AL, McEwan SR, Bates TC.

Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial. Proceedings of the Royal Society B.

2003;270(1529):2147-2150. doi:10.1098/rspb.2003.2492

What This Means for You

If you are vegetarian or vegan, this is one of the most directly relevant studies on the list: in people like you, six weeks of daily creatine measurably improved working memory and reasoning. The practical implication is that the cognitive payoff comes from filling a dietary gap, so steady daily intake matters more than timing it around mental tasks. If you eat meat regularly your starting stores are higher, so expect a smaller effect than the vegetarians in this trial saw.

Further Reading

• creatine dosage guide
• creatine monohydrate
• creatine for muscle building
• creatine for brain health
• how creatine works
• creatine for teenagers