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Thursday, Aug. 14, 2003

NATURAL SELECTIONS

Fleshing out your memory


The French novelist Marcel Proust wrote his seven-volume epic, "Remembrance of Things Past," mainly from his bed, shut away in a soundproof apartment. The 3,000-page work is a stream-of-consciousness masterpiece, produced by intense introspection and exhaustive recall of the tiniest details of his past.

The key scene in the first volume occurs when the narrator eats a madeleine cake: "And suddenly the memory revealed itself: The taste was that of the little piece of madeleine which on Sunday mornings at Combray when I went to say good morning to her in her bedroom, my aunt Leonie used to give me, dipping it first in her own cup of tea or tisane."

The madeleine triggers in Proust's narrator a cascade of memories.

We all have experience of how memories may be tied to a taste, but now Australian scientists have shown that a dietary supplement of creatine, an amino acid found in muscle tissue, can give a significant and measurable boost to memory. Moreover, it also boosts general intelligence levels.

Athletes and fitness enthusiasts have known for some time that creatine supplementation can increase sports performance. The compound has also been trialed successfully in the treatment of neurological, neuromuscular and atherosclerotic disease.

Caroline Rae and colleagues at the University of Sydney and Macquarie University, New South Wales, gave creatine to 45 young adult subjects in a double-blind, placebo-controlled experiment. The work is published in a forthcoming issue of Proceedings B, a journal published by the Royal Society.

"The level of creatine supplementation chosen was 5 grams per day as this is a level that has previously been shown to increase brain creatine levels. This level is comparable to that taken to boost sports fitness," said Rae, adding that the subjects for the study were all vegetarian.

"Vegetarians or vegans were chosen for the study as carnivores and omnivores obtain a variable level of creatine depending on the amount and type of meat they eat -- although to reach the level of supplementation in this experiment would involve eating around 2 kg of meat a day!"

Creatine is found naturally in meat (the word comes from the Greek kreas, meaning flesh). So where do vegetarians get their creatine from?

"Vegetarians synthesize more creatine than omnivores as a rule," said Rae in an e-mail interview, "because the enzymes adjust to make more to compensate for them getting little in the diet."

Creatine plays a pivotal role in maintaining energy levels in the brain, Rae added. "So it was a reasonable hypothesis that supplementing a diet with creatine could assist brain function."

The experiment tested this hypothesis by giving the one group of subjects a creatine supplement and a second group a placebo for six weeks, followed by a six-week period with no intake and a final six-week period when the control and placebo group were swapped. Intelligence and memory were tested at four points: the start of the trial; the end of the first six-week period; and the start and endpoint of the final six-week period.

The effect on working memory was tested using a backward digit-span test in which the subject has to repeat in reverse order progressively longer random number sequences. Intelligence was tested using Ravens Advanced Progressive Matrices. The Ravens test is commonly used for IQ assessment and requires the subject to complete pattern sequences. It doesn't use letters or figures, so is considered a good measure of general ability that has minimal dependence on cultural factors.

"The results were clear with both our experimental groups and in both test scenarios," said Rae. "Creatine supplementation gave a significant measurable boost to brain power. For example, in the digit-span test, subjects' ability to remember long numbers, like telephone numbers, improved from a number length of about 7 to an average of 8.5 digits."

The study shows that increased creatine intake results in improved brain function, similar to effects shown previously in muscles, including the heart.

"It increases the 'energy supply' that the brain has," said Rae. "The brain burns glucose to make an energy storage compound called ATP, which contains a high-energy phosphate bond."

This energy can also be stored in a form of creatine called phosphocreatine.

"Eating and increasing your creatine supply also increases the amount of phosphocreatine you have. This in turn gives you a higher residual store of ATP. When you think, you initially use up the ATP much faster than you can replace it by burning glucose, so increasing the amount of ATP in reserve basically increases your thinking capacity."

However, we shouldn't all go out and gorge ourselves on creatine just yet: Long-term supplementation has yet to be declared completely safe. There have been reported effects on glucose homeostasis (the regulation of blood-sugar levels) and therefore potential subjects with a medical history of diabetes were excluded from the experiment.

In addition, the supplement can have some antisocial effects. "To be frank, taking the supplement can make you a considerably less 'fragrant' person," said Rae. "You may get smelly breath and flatulence. However, creatine supplementation may be of use to those requiring boosted mental performance in the short term -- for example, university students."

Taking creatine may do for them what eating a madeleine did for Proust.

Rowan Hooper is a researcher at Trinity College, Dublin. He welcomes comments at rowan.hooper@tcd.ie


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