"The dietary fibre content in brewed coffee is higher than in other common beverages such as wine (0.14 per cent) or orange juice (0.19 per cent)," stated the researchers.
Coffee, one of the world's largest traded commodities produced in more than 60 countries and generating more than $70bn in retail sales a year, continues to spawn research and interest, and has been linked to improved cognitive performance and reduced risks of certain diseases, especially of the liver and diabetes.
Writing in the Journal of Agricultural and Food Chemistry , authors Elena Díaz-Rubio and Fulgencio Saura-Calixto from the Department of Metabolism and Nutrition at Madrid's Instituto del Frío, state that, while it is known that coffee beans contain dietary fibre, no study had ever investigated the presence of dietary fibre in coffee beverages.
Indeed, food composition tables list coffee as containing zero dietary fibre.
In the new study, the researchers used a special technique for measuring dietary fibre in beverages such as wine and beer, and reports that brewed coffee contains between 0.47 and 0.75 grams of soluble dietary fibre (SDF) per 100 millilitres of beverage, which would equate to between 2.54 and 20 per cent of the powdered coffee bean.
This is more dietary fibre than found in other common beverages such as wine (0.14 per cent) or orange juice (0.19 per cent).
Interestingly, instant coffee contained more SDF (0.752g/100mL) than espresso or filter coffee (0.65 and 0.47 g/100mL, respectively).
The main soluble dietary fibres in coffee are arabinogalactin type II (AGII), are galactomannan (GM).
"The average dietary fibre intake in Europe ranges from 16 to 21 grams per person per day; SDF in the Spanish diet is about seven grams per person per day," state the researchers.
"The contribution of brewed coffee to the dietary fibre intake in a common diet may be significant; a moderate daily consumption of three cups of espresso coffee is equivalent to 0.66 g of SDF, which accounts for about 10 per cent of SDF intake in Spain."
Díaz-Rubio and Saura-Calixto state that a significant part of the antioxidant activity of coffee (between 87 and 105 mg/100mL) is associated with the dietary fibre content.
"This suggests that a fraction of the antioxidant polyphenols from coffee is bioaccessible in the small intestine, whereas the part associated with dietary fibre (30-51 per cent) will be bioaccessible in only the large intestine after fermentation by colonic microflora," they said.
The researchers called for more research in the biological properties of the beverage's fibre.
The average worldwide daily coffee consumption is one and a half cups, while the US average is more than three and a half cups.
Source: Journal of Agricultural and Food Chemistry Published on-line ahead of print, ASAP Article, doi: 10.1021/jf062839p
"Dietary Fiber in Brewed Coffee" Authors: M.E. Díaz-Rubio, F. Saura-Calixto