For many, cof­fee is an elixir of life, with­out which they would hard­ly be able to start the day in the morn­ing. But its caf­feine not on­ly seems to wake peo­ple up, it al­so caus­es mea­sur­able changes in the struc­ture of the brain — at least tem­porar­i­ly. We can now show that reg­u­lar caf­feine con­sump­tion caus­es the gray mat­ter in the brain to shrink temporarily.

Cof­fee is known as a stim­u­lant. For many, it is part of the morn­ing rou­tine at the break­fast ta­ble. How­ev­er, its caf­feine be­comes a curse if it is con­sumed short­ly be­fore go­ing to bed. Then there is the threat of sleep prob­lems — and with them a loss of mem­o­ry per­for­mance. Var­i­ous stud­ies have al­ready shown that sleep de­pri­va­tion af­fects the gray mat­ter of the brain.

So can reg­u­lar caf­feine con­sump­tion change brain struc­tures through poor­er sleep? We in­ves­ti­gat­ed this ques­tion. Our study in­volved 20 young, healthy peo­ple who al­so reg­u­lar­ly drink cof­fee in every­day life. They were giv­en tablets to take twice for ten days and were asked to ab­stain from any oth­er caf­feine in­take dur­ing this time. In one study pe­ri­od they re­ceived tablets with caf­feine, in the oth­er pe­ri­od tablets with­out ac­tive in­gre­di­ent (place­bo). At the end of each ten-day pe­ri­od, we mea­sured the sub­jects’ gray mat­ter vol­ume and ob­served their sleep qual­i­ty in the laboratory.

SAME SLEEP, BUT LESS GRAY MATTER

To our sur­prise, com­par­i­son of the da­ta showed that the caf­feine sup­ple­ments did not lead to worse sleep: Par­tic­i­pants slept equal­ly deeply whether they took caf­feine tablets or the place­bo. How­ev­er, there was a clear dif­fer­ence in the gray mat­ter: af­ter ten days of place­bo — i.e. ab­sti­nence from caf­feine — its vol­ume was greater than af­ter the same pe­ri­od of time with the caf­feine tablets — gray mat­ter is the term used to de­scribe parts of the cen­tral ner­vous sys­tem that con­sist main­ly of the cell bod­ies of the nerve cells, while white mat­ter con­sists main­ly of the con­duc­tion path­ways, the long process­es of the nerve cells.

CAF­FEINE EF­FECT IS NOT NEC­ES­SAR­I­LY NEG­A­TIVE FOR THE BRAIN

The dif­fer­ence was par­tic­u­lar­ly clear in the right me­di­al tem­po­ral lobe of the brain, in­clud­ing the hip­pocam­pus, a brain re­gion cen­tral to mem­o­ry. Al­though the re­searchers found low­er mem­o­ry per­for­mance in cor­re­spond­ing tests af­ter the caf­feine pe­ri­od. How­ev­er, the change in gray mat­ter could not be cor­re­lat­ed with the loss of func­tion. Our re­sults do not nec­es­sar­i­ly mean that caf­feine con­sump­tion has neg­a­tive ef­fects on the brain. But every­day caf­feine con­sump­tion does al­ter our cog­ni­tive hard­ware, which should at least give rise to fur­ther studies.

The health ef­fects of caf­feine have so far been in­ves­ti­gat­ed main­ly in pa­tient stud­ies. More re­search is need­ed on the ef­fects on healthy in­di­vid­u­als. It should be em­pha­sized that al­though caf­feine ap­pears to re­duce gray mat­ter vol­ume, it re­gen­er­at­ed sig­nif­i­cant­ly in sub­jects af­ter on­ly ten days of caf­feine with­draw­al. Thus, the changes in brain mor­phol­o­gy ap­pear to be tem­po­rary. But sys­tem­at­ic com­par­isons be­tween cof­fee drinkers and peo­ple who usu­al­ly con­sume lit­tle or no caf­feine are lack­ing so far.