Writing in the journal Food & Function, Crozier et al. from the University of Glasgow reported the results of a study of 20 commercially available espresso coffees, which showed that four exceeded upper limits for daily caffeine content recommended during pregnancy by the FSA.
The scientists did a HPLC analysis of a single espresso shot of 20 commercial espresso coffees – bought in outlets such as Café Nero and Starbucks.
This revealed a six-fold difference in caffeine levels, a 17-fold difference in caffeoylquinic (CQA) acid contents and four-fold differences in CQA to caffeine ratios.
“These variations reflect differences in batch-to-batch bean composition, possible blending of Arabica with robusta beans, as well as roasting and grinding procedures, but the predominant factor is likely to be the amount of beans used in the coffee making or barrista process,” Crozier et al. wrote.
Samples smashed upper limits
The most caffeine found in a single espresso was 322mg and a further 3 samples contained more than 200mg, which is the upper limit (200mg or four cups of ‘strong’ coffee per day) recommended for pregnant women by the FSA.
“This snapshot of high street espresso coffees suggests the published assumption that a cup of strong coffee contains 50mg caffeine may be misleading,” the authors wrote.
They added: “Consumers at risk of toxicity, including pregnant women, children and those with liver disease, may unknowingly ingest excessive caffeine from a single cup of espresso coffee.”
One of the study authors, Alan Crozier from the Schools of Medicine, College of Medical, Veterinary and Life Sciences at the University of Glasgow told BeverageDaily.com the research was “curiosity driven”.
Asked about the applicability of the research to shop bought espresso coffee, he said: “The main issue is how much coffee is used to make a cup of espresso. There may be some variation in the caffeine levels of certain packets of espresso coffee you get in the shops.
Difficult to regulate
“The amount of caffeine you get is determined by how you make it – how much coffee you use principally – rather than large inherent differences in the caffeine content of the coffees themselves.
“People say there should be regulations, but it’s very difficult to introduce regulations on this. You’ve also got the thing that people’s responses vary enormously, and most people have warning signals that tell them ‘look you’re having too much’, such as palpitations or other side-effects.”
“It’s people such as pregnant women who are at risk who don’t have any immediate symptoms to tell them they’ve gone over the limits.”
And Crozier suggested that regulatory bodies would be wise to examine their recommended upper limits for coffee consumption during pregnancy: “There is a problem with the ballpark figures that the FSA and other regulatory authorities in other countries put figures on their websites that bear very little relationship to reality, and the extremes that you can get.”
Asked whether he believed coffee sold in packaged form needed more information about caffeine levels, Crozier added: “It wouldn’t do any harm, but how much attention do people pay to what’s written on the backs of packets?
"Not much. And it tends to be hidden away, so it would just be another layer of bureaucracy that wouldn’t really improve things.”
Title: ‘Espresso coffees, caffeine and chlorogenic acid intake: potential health implications’
Authors: T.Crozier, A.Stalmach, M.E.J Lean, A.Crozier
Source: Food and Function 2012 (The Royal Society of Chemistry), advance article doi:10.1039/c1fo10240