Harvard study suggests we seek maximum caffeine bang from coffee buck

Lead author Marilyn Cornelis, who is research associate at the Department of Nutrition at Harvard School of Public Health, said: “Coffee and caffeine have been linked to beneficial and adverse health effects. ​

"Our findings may allow us to identify sub-groups of people most likely to benefit from increasing or decreasing coffee consumption for optimal health,”​ she added.

One interesting question – which BeverageDaily.com has put to Cornelis, is whether similar results could apply to other caffeine-containing drinks – including sodas and energy drinks.

"Since our genetic findings point to ‘caffeine’ our conclusions may potentially generalize to other caffeine containing products. In 2011, we conducted a genome-wide analysis of total caffeine and identified two genetic variants. These were confirmed in the recent larger effort for coffee. Coffee is the primary source of caffeine for many populations and data pertaining to coffee intake has been collected in numerous on-going studies (i.e. the ones included in our current report)," ​Cornelis said.

"Other dietary products containing high amounts of caffeine (>100 mg)  are relatively new and less commonly consumed and so we were unable to examine whether our genetic variants of coffee consumption were also related to non-coffee sources of caffeine. These will be important studies to conduct in the future since many of these novel products target younger individuals and also contain many other ingredients that potentially impact health (i.e. sugar!)," ​she added.

The study – ‘Genome-wide meta-analysis identifies six novel loci associated with habitual coffee consumption’ – appeared online yesterday in the journal Molecular Psychiatry.​

By identifying six new genetic variants – resulting from mutations in the chemical structure of genes – associated with habitual coffee drinking, the researchers said their work provides a genetic basis for future research probing the links between coffee and health.

New genes linked to coffee metabolism​

They write that genetics have long been suspected of contributing to individual differences in response to coffee and caffeine – with given amounts having different effects on different people – but that pinpointing specific genetic variants has been difficult.

Lead author Marilyn Cornelis and her team undertook a genome-wide meta-analysis of 120,000+ regular coffee drinkers of European and African American ancestry, and found two genetic variants that mapped to genes POR and ABCG2, which are involved in caffeine metabolism.

Two other variants were identified near genes BDNF and SLC6A4 – which potentially influence the rewarding effects of caffeine – while the remaining two variants were sited near genes GCKR and MLXIPL (involved with glucose and lipid metabolism), which had not previously been linked to the metabolism or neurological effects of coffee.

‘Important step forward in coffee research’​

Harvard School of Public Health said in a release that these findings suggest people naturally modulate coffee intake to experience the optimal effects of caffeine, and that the strongest genetic factors linked to increased coffee intake likely work by directly increasing caffeine metabolism.

Cornelis said identifying these ‘candidate genes’ was an “important step forward in coffee research”.​

Given the genetic predisposition that Cornelis and her team identified in some towards higher consumption of caffeine (and increased metabolism) we asked how quickly can this develop? For instance, could it develop within the course of one person’s lifetime?

"There are reports of tolerance to the stimulating effects of caffeine and the  need to increase the amount consumed to maintain optimal caffeine effects. The current study includes coffee consumption habits measured at  a single time point and so cannot address the question of tolerance development. A few of the contributing studies do have multiple data collections over the span of several years and might be used to answer your question,"​ she replied.

"Since most were adults at the time of study enrolment, however, we may have missed the critical stage for  ‘developing tolerance’. Clinical studies might answer your questions specifically and I would highly suspect that the development of tolerance will vary by genotype,"​ Cornelis added.

Senior author, Daniel Chasman, associate professor at Brigham and Women’s Hospital, said that, like previous genetic analyses of smoking and alcohol consumption, “this research serves as an example of how genetics can influence some types of habitual behaviour”.​

Title: ​’Genome-wide meta-analysis identifies six novel loci associated with habitual coffee consumption’

Authors:​ Cornelis M, Chasman, D.I et al.

Source:​ Molecular Psychiatry​, Available online October 7, doi:10.1038/mp.2014.107​

*Article updated with answers to questions put to Marilyn Cornelis (13/10/14).