22 Jan 2010 --- There is a lot of scientific interest in the antioxidants in coffee, and their potential benefits on human health. However, the bioavailability of coffee antioxidants, the extent to which they are available to the body, in the presence of milk, or sugar and nondairy creamer has not been studied until now. Scientists from the Nestlé Research Centre in Switzerland have just published a new study showing that these antioxidants are as bioavailable in coffee with or without milk.

The lead author, Dr Mathieu Renouf said, "Up until now there has been very little known about how proteins, especially from milk, influence the bioavailability and efficacy of coffee antioxidants. Our study is the first to show that coffee antioxidants are just as bioavailable in coffee with milk, as they are in black coffee."

The authors also found that the overall bioavailability of coffee antioxidants is not influenced by the addition of milk or of nondairy creamer and sugar. 

Chlorogenic acids (CGA) are antioxidants found in coffee. They are becoming of interest for their health-promoting effects, but bioavailability in humans is not well understood. The researchers hypothesized that adding whole milk or sugar and nondairy creamer to instant coffee might modulate the bioavailability of coffee phenolics.

Nine healthy participants were asked to randomly drink, in a crossover design, instant coffee (Coffee); instant coffee and 10% whole milk (Milk); or instant coffee, sugar, and nondairy creamer already premixed (Sugar/NDC). All 3 treatments provided the same amount of total CGA (332 mg). Blood was collected for 12 h after ingestion and plasma samples treated using a liquid-liquid extraction method that included a full enzymatic cleavage to hydrolyze all CGA and conjugates into phenolic acid equivalents. Hence, the researchers focused liquid chromatography-Electrospray ionization-tandem MS detection and quantification on caffeic acid (CA), ferulic acid (FA), and isoferulic acid (iFA) equivalents.

Compared with a regular black instant coffee, the addition of milk did not significantly alter the area under the curve (AUC), maximum plasma concentration (Cmax), or the time needed to reach Cmax (Tmax). The Cmax of CA and iFA were significantly lower and the Tmax of FA and iFA significantly longer for the Sugar/NDC group than for the Coffee group. However, the AUC did not significantly differ. As a conclusion, adding whole milk did not alter the overall bioavailability of coffee phenolic acids, whereas sugar and nondairy creamer affected the Tmax and Cmax but not the appearance of coffee phenolics in plasma.