Tea: adding milk negate the beneficial effect on cardiovascular function

If it is found that tea consumption protects against cardiovascular risk, adding milk negate this beneficial effect , suggesting published in the journal " European Heart Journal " German study .
Many previous experimental and clinical studies have shown that tea has a protective effect against cardiovascular disease. However, some have suggested that adding milk could alter the biological activities of tea.

To determine the vascular effect of tea with or without milk , Verena Stangl , University of Medicine charity in Berlin, and colleagues conducted a study of 16 healthy women divided into three distinct groups depending on the drink that was assigned to them : 500 ml of black tea, 500 ml of black tea with 10 % milk or 500 ml of hot water (control group) . The researchers then measured the dilation of the arteries of each volunteer with a high-resolution ultrasound before and two hours after drinking the beverage .

According to their results , the consumption of black tea has improved significantly dilated arteries compared to the hot water consumption. In contrast, the addition of milk completely abolished the effects of tea.

To confirm this experiment, the researchers conducted a laboratory study on both cultures of endothelial cells and vessels of isolated rat aorta . They showed that tea induced vasorelaxation of rat aorta and increased production capacity of nitric oxide in endothelial cells, a molecule causing vasodilation . Both effects were totally inhibited by the addition of milk in tea.

Casein , a type of protein found in milk, are at the origin of this inhibitory effect , probably due to the formation of complexes with tea catechins ( flavonoids family ) , responsible for the antioxidant effect and cardioprotective this drink .

Milk seems to inhibit the beneficial effects of tea on vascular function . This result demonstrates the need for increased vigilance for the interpretation and design of studies evaluating the effects of flavonoids on various diseases (cancer, cardiovascular disease) , the authors conclude.