You, Illuminated

Commonsense explanations of neuroscience

Does Vegetarianism Make You Dumber?

Creatine supplements may improve memory for vegetarians.

I heard about a study several years ago that still has me perplexed.  In short summary, the study tested the memory of vegetarians and vegans after taking either creatine supplements or inactive placebo pills; those who had taken creatine performed better.   The result was surprising, but rather than provide a definitive answer to the question, "does creatine improve memory," it raised more questions.  The study only addressed vegetarians and vegans, but would the results hold up in omnivores?  Should vegetarians take creatine supplements to keep their minds sharp?  Most importantly, if vegetarians are lacking creatine, does it impair their memory?

Creatine, a naturally-occurring chemical that can provide quick energy to cells throughout your body, is present in meat, but not vegetables.  Accordingly, vegetarians and vegans have lower levels of it.  Creatine doesn't have to be consumed, however, because some creatine can be produced by your liver and kidneys.  For omnivores, about half of creatine is consumed and the other half is self-made.  Unless they take supplements, vegetarians produce all the creatine in their bodies. 

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Most creatine is stored in muscle tissue for bursts of high-intensity exercise. Some athletes, such as weight-lifters and sprinters, take creatine supplements to boost their performance.  But what about our mental muscle?  If creatine can power our biceps, could it similarly add brawn to our brain

Several research groups have addressed this question, but the results provide room for debate.   The answer may depend on who is taking creatine.  

The study regarding vegans and vegetarians came from a group led by Caroline Rae at the University of Sydney.  Rae gave all participants a memory test and then divided them into two groups, both blinded to which condition they were in.  One received placebo, the other received creatine.  After a few weeks, the group taking creatine had improved memory scores, whereas the placebo group languished at their original mark.  To make sure that the effects were not due to some difference between the groups, the participants continued taking pills, but with one change: the group previously taking creatine was now switched to placebo and vice versa.  Several weeks later, the group who started on creatine but now taking placebo nose-dived off their high marks.  The placebo-first, creatine-second group, who were lagging behind, now significantly outperformed their counterparts.  The only difference between the two tests was which pill the participants were taking.  Creatine supplements seemed to improve memory for vegetarians and vegans.

Similarly, a British group headed by Terry McMorris tested cognition in a group of elderly volunteers with and without creatine supplements.   Creatine acted as a small fountain of mental youth; creatine supplements aided cognitive performance for those over 60 irrespective of diet.  McMorris also tested the effects of creatine on young omnivores who were sleep-deprived for 24 hours.  Not only did creatine improve cognition, it also put participants in a better mood.  Who would object to that side-effect?  

Yet, a recent study by physiologist Eric Rawson, whose bailiwick is creatine, found that for young, healthy, well-rested omnivores, creatine supplements didn't produce any change in smarts. 

The brain, at roughly three pounds, only accounts for 2-3% of your total weight, yet it consumes 20% of your calories at rest, and more when deep in thought.  The brain gets most of its energy from a form of sugar called glucose, but converting sugar to fuel takes time.  Much faster than glucose, creatine can provide a short swell in energy to cells that are working overtime, like accessing a high-powered processor in your brain that only boots up for big files.  You might think that anyone would benefit from having more creatine, but that's not what Rawson found. 

Supplements may only benefit individuals who have impaired memory function or have low levels of creatine.  Similar to caffeine, which provides the most revitalization to weary minds, supplements may be unnecessary for high-functioning, fresh, healthy adults who are already well-stocked with creatine.   So what about vegetarians, who lack dietary creatine? 

This past year, David Benton, a psychology professor in Wales who studies the relationship between diet and behavior, examined the memory of vegetarians and omnivores before and after taking either placebo or creatine supplements.  Prior to taking pills, vegetarians and omnivores performed similarly on a memory test.  Both the vegetarians and omnivores were divided into two groups, one receiving placebo, the other creatine.  After a week, the omnivores scored the same whether or not they had taken placebo or creatine, and the vegetarians who had taken placebo still matched the omnivores' performance.  However, the vegetarians who took creatine leapt ahead.   Initially, all groups were roughly even, but the creatine-enriched vegetarians now had better memories. 

So what do the results of Benton's study mean?  Vegetarians didn't have a memory deficit prior to taking creatine, so they don't seem to be at a cognitive disadvantage.  However, after taking creatine they did top omnivores and vegetarians not taking supplements.  Could it be that vegetarians would have better memories than omnivores, but they impair themselves through diet? 

That would corroborate evidence from the National Child Development Study, described in a post by The Scientific Fundamentalist, that vegetarians are smarter than omnivores.  The study found that children with higher IQs were more likely to grow up to be vegetarians.  IQ was not reported again after these people became vegetarians, but perhaps a later test would reveal that the IQ gap had been closed.  So does vegetarianism make you dumber?  Like so many questions in our world, this one will remain unanswered today, but it's nothing that a clever, curious mind of any dietary persuasion couldn't crack. 

Notes: 

Benton and Donohoe (2010) The influence of creatine supplementation on the cognitive functioning of vegetarians and omnivores.  Brit J Nutrition

McMorris, Mielcarz et al. (2007) Creatine supplementation and cognitive performance in elderly individuals.  Aging Neuropsycol Cogn 14

McMorris, Harris et al. (2006) Effect of creatine supplementation and sleep deprivation, with mild exercise, on cognitive and psychomotor performance, mood state, and plasma concentrations of catecholamines and cortisol.  Psychopharmacology 185

Rae, Digney et al. (2003) Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled cross-over trial.  Proc Biol Sci 270

Rawson, Lieberman et al. (2008) Creatine supplementation does not improve cognitive function in young adults. Physiol Behav 95

 

Joshua Gowin, Ph.D., earned his doctorate in behavioral neuroscience at the University of Texas Health Science Center in Houston.

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