Consuming three cups of instant coffee a day for three weeks resulted in increased populations of Bifidobacterium spp., according to findings published in this month’s issue of the International Journal of Food Microbiology.
“Our results show that the consumption of the coffee preparation resulting from water co-extraction of green and roasted coffee beans produce an increase in the metabolic activity and/or numbers of the Bifidobacterium spp. population, a bacterial group of reputed beneficial effects, without major impact on the dominant microbiota,” wrote the researchers, led by Rodrigo Bibiloni from the NRC in Lausanne, Switzerland.
Study details
Dr Bibiloni and his co-workers recruited 16 healthy adult volunteers aged between 21 and 57 and a BMI of between 20 and 30 kg/m2 (nine women), and assigned them to drink three cups of coffee per day for three weeks. The volunteers consumed a restricted diet for three weeks prior to the coffee period, during which they did not consume any yoghurts, probiotic or others, fermented milk, or whole grain products.
Faecal samples collected before and after the coffee consumption period showed that the populations of dominant bacteria were not significantly affected. However, numbers of Bifidobacterium spp. increased, with the greatest increases amongst people with lower initial bifidobacterial populations.
Some of the participants also showed an increased metabolic activity for bifidobacterial species after consuming the coffee for three weeks.
"Our study has not been tailored to address a particular health condition, but may sway future strategies to identify a specific population with low bifidobacterial numbers in their gastrointestinal tract where coffee consumption may have an important impact,” wrote the researchers.
“Although these results cannot be directly related to the consumption of the product, it suggests that the consumption of coffee may prove useful for increasing bifidobacterial numbers or metabolic activity of those individuals with lowered colonic bifidobacterial numbers,” they added.
“The health benefits or the biological relevance associated with these findings have still to be assessed.”
Prebiotic coffee?
Dr Bibiloni told NutraIngredients.com that coffee or its constituents could only be considered as a prebiotic if there is a health benefit associated to its consumption.
Prebiotics are defined as "nondigestible substances that provide a beneficial physiological effect on the host by selectively stimulating the favourable growth or activity of a limited number of indigenous bacteria".
“Our study found that coffee consumption increased Bifidobacterium in the gut, but it remains to be proven which components of coffee are responsible for this increase.
“Since our study did not evaluate the potential health benefit linked to these findings, we can only suggest that coffee has a bifidogenic effect, rather than identifying it or its respective components as a prebiotic,” he said.
The NRC researchers state, however, that is not currently known which of the components of coffee may be responsible for the effect, but note that both fibre and chlorogenic acids may be metabolised by the gut microbiota.
Furthermore, instant coffee does contain soluble polysaccharides, said the researchers, of which 20 per cent is in the form of arabinogalactan proteins.
Future study
Dr Bibiloni told this website that coffee, and the caffeine it contains, is associated with beneficial effects on mental and physical performance.
“Several human epidemiological studies showed an inverse association between coffee consumption and the risk of developing diseases such as specific types of cancer, like liver and colon, steatosis, cirrhosis, Parkinson’s disease and type-2 diabetes,” he said.
“Nestlé research scientists extensively study the bioavailability, absorption and protective effects of coffee polyphenols. Through in vitro studies, pre-clinical and human intervention studies, it was shown that coffee polyphenols exhibit strong antioxidant activity and are well absorbed by the human body.”
Source: International Journal of Food Microbiology March 2009, Volume 130, Issue 2, Pages 117-121“Impact of coffee consumption on the gut microbiota: A human volunteer study” Authors: M. Jaquet, I. Rochat, J. Moulin, C. Cavin, R. Bibiloni