Journal Title (Medline/Pubmed accepted abbreviation): Br. J. Nutr.
Page numbers: 1100-1105
doi (if applicable): 10.1017/S0007114510004733
Summary of Background and Research Design
Background: Creatine and creatine phosphate are in dynamic equilibrium in the body. This system provides a readily available phosphate group to ADP to regenerate ATP energy. Muscle houses 95% of creatine, and the other 5% is mostly in the brain, heart, and testes (if applicable). Meats are one source of dietary creatine, but creatine is not essential in the diet; it can be synthesized in the body from glycine, arginine, and methionine. However, dietary creatine supplementation has been shown to increase creatine concentrations in various tissues. Vegetarians typically have lower levels of blood and muscle creatine, and therefore may benefit the most from supplements in regard to exercise performance and cognitive abilities.
Hypothesis: Vegetarians will benefit more from a creatine supplement than omnivores while performing cognitive tests.
Subjects: Females age 20.3 ± 2.1 yrs. who were meat-eaters (n = 51) or vegan/vegetarian (n = 70)
Experimental design: double-blind, placebo-controlled, randomized design
Treatments: The treatments ( 20 g placebo (glucose) or 20 g creatine monohydrate) were consumed on an empty stomach as 4 × 5 g tablets, spread out throughout the day. Supplementation lasted 5 days.
Protocol: Subjects participated in a variety of cognitive tests before and after creatine supplementation. The tests included tasks such as memory recall, reaction time, a rapid information processing task (measures the ability to maintain attention), and verbal fluency.
Summary of research findings
- After supplementation, the vegetarians performed better on the word recall (memory) exercise than meat-eaters. However, unexpectedly (and for unknown reasons), the meat-eaters performed more poorly on the memory task after creatine supplementation than before.
- Neither dietary style nor creatine supplementation affected performance on the reaction time task (decision time or movement time). Interestingly, after supplementation, the placebo group had much higher intra-individual variability in the reaction times versus before supplementation; this effect was not seen in the creatine group.
- Performance on the rapid information processing task was the same regardless of diet or supplementation.
- Neither supplementation nor diet affected word fluency.
- Most participants could not correctly identify which supplement they were taking, indicating few side effects. Those that were reported were sparse and minor and included bloated feelings or headaches.
Interpretation of findings/Key practice applications
The results of the study suggest that ones’ habitual diet can affect creatine status in the brain and that creatine status is capable of influencing cognitive abilities, specifically memory and the variability of reaction times.
It is interesting that there were statistically significant results showing 1) both placebo groups and the meat-eater/creatine group performed worse on the memory task after supplementation and 2) the placebo increased the variability of reaction times. Perhaps the tests were conducted slightly differently before vs. after supplementation, in which case it would not be appropriate to compare before vs. after. However, because the authors did not have a reasonable explanation for these phenomena, it is troublesome to make any comparisons or draw any substantial conclusions. There may have been confounding factors could have biased the data in unknown ways.