(This write-up is optimized for not costing a lot of time. The graphs are ugly, I know…).
Disclaimer: This is obviously not medical advice, just a report of something we did.
Intro: Creatine might enhance cognitive performance in vegetarians (https://www.gwern.net/Creatine). Specifically; Rae 2003, and Benton 2011.
Methods: Participants: 2 people, 27/28 years, m/f, long-term ‘lacto-vegans’ (consume no animal products except sometimes dairy). Supplementation: Following Rae 2003, supplemented 5 mg creatine per day, in the evening. Supplemented for 41 days (should definitely be enough, Rae 2003 only used 2 weeks). Then washout-phase for 50 days (read in some paper that wash-out is guaranteed after 6 weeks). No placebo, participants were not blinded. Tests: Reverse number recall test (following Rae 2003; Raven’s Advance Matrix, which was additionally used in Rae 2003, was not available). We started with a 11 days training phase with tests every few days (to avoid overly strong training effect at the beginning). We had planned to the test once per week on a fixed day for the rest of the trial, but in practice we tested only roughly once a week, and varied the day depending on our schedules. We always tested in the morning, after exercising.
Results: See figures (https://imgur.com/a/21Rax). Both participants had increased performance under creatine vs base-line, and one participant had a bit of a decrease in performance upon wash-out.
Conclusion: The results are very equivocal (as expected), as it is hard to distinguish creatine effects from training effects. But if anything, the results hint rather in the direction of creatine being useful. In face of reports in the literature, and very low side-effects, we believe that the potential benefits of creatine supplementation outweigh the potential costs for us. We will continue supplementing 5g/d.