If you drink green tea or take capsules containing green-tea extract in the hope that they’ll make you healthier, fitter or slimmer, then do so on an empty stomach. Australian nutritionists offer this well-meaning advice in an article in Nutrients. The Australians discovered that the body doesn’t absorb EGCG – the main bioactive substance in green tea – so well in combination with food.
The researchers gave four healthy subjects 500 mg EGCG [structural formula on the right] on three different occasions. They used Teavigo, manufactured by DSM.
On one occasion, the subjects took their EGCG in the form of capsules in the morning on an empty stomach [Capsule without breakfast]. On another occasion, they took the capsules together with cornflakes and milk [Capsule with breakfast]. And on yet another occasion, the researchers mixed the EGCG into a shake containing strawberries, sugar and whey [Strawberry Sorbet], which the subjects drank as breakfast.
After the subjects had consumed the EGCG, the researchers monitored the EGCG level in the subjects’ blood for a period of eight hours. The subjects were given lunch by the researchers during this time.
The Australians discovered that the subjects’ blood EGCG level was three to four times higher when the subjects had consumed the EGCG on an empty stomach than under the other conditions.
When food enters it, the stomach produces acid to digest the food. Once the food enters the small intestine the pancreas neutralises the acid with bicarbonate. According to a 2001 study, that’s the moment at which much EGCG is lost. [Food Chem. 2001, 73, 481–486.]
“In conclusion, the systemic absorption was significantly higher for EGCG taken in capsules without food after an overnight fast than it was when it was taken in capsules with a light breakfast or imbedded in a strawberry sorbet”, the researchers summarised. “Therefore, based on these findings, ingesting EGCG with water on an empty stomach is the most appropriate method for the oral delivery of EGCG in future clinical trials where EGCG is to be investigated as a potential bioactive nutraceutical in humans.”
Food Inhibits the Oral Bioavailability of the Major Green Tea Antioxidant Epigallocatechin Gallate in Humans
The bioavailability of the most abundant and most active green tea antioxidant, epigallocatechin gallate (EGCG) remains uncertain. Therefore, the systemic absorption of EGCG was tested in healthy fasted humans. It was administered as capsules with water or with a light breakfast, or when incorporated within a strawberry sorbet. The results for plasma EGCG clearly revealed that taking EGCG capsules without food was better; the AUC was 2.7 and 3.9 times higher than when EGCG capsules were taken with a light breakfast (p = 0.044) or with EGCG imbedded in the strawberry sorbet (p = 0.019), respectively. This pattern was also observed for Cmax and Cav. Therefore, ingesting food at the same time as EGCG, whether it was imbedded or not in food, substantially inhibited the absorption of the catechin. As with some types of medications that are affected by food, it appears that EGCG should be taken without food in order to maximise its systemic absorption. Therefore, based on these findings, ingesting EGCG with water on an empty stomach is the most appropriate method for the oral delivery of EGCG in clinical trials where EGCG is to be investigated as a potential bioactive nutraceutical in humans.