A recent study on the impact of tea drinking on the health of Europeans reported conflicting findings depending on the region where the data was collected, and when researchers dug deeper, it turned out that the discrepancies were related to whether tea was drunk with or without milk. This finding led to a subsequent study published in the European Journal of Nutrition that investigated the influence of protein on the bioavailability of catechins, the polyphenols found in high concentrations in green tea that are responsible for most of its health benefits.
In the study, 24 healthy participants consumed an experimental drink containing 1.75 grams of green-tea extract with or without the addition of casein protein, soy protein or skim milk. Blood samples measuring concentrations of catechins were taken before and several times after consumption of the experimental drink, and the authors reported that total catechins were significantly decreased if subjects took green-tea extract with any of the protein sources, with the most significant reduction being in the potent antioxidant epigallocatechin gallate.
Action Point: Research has shown that green-tea-extract supplements standardized for EGCG work synergistically with cardio for fat reduction. This study provides solid evidence that if you take green tea with a protein shake, you may not be getting what you bargained for. Thus, to circumvent protein’s effects on EGCG bioavailability, make sure you take green-tea supplements with water, on an empty stomach, 30 minutes before consuming protein.