Drinking green tea can affect our response to stress. (Photos.com)

Probably all of us know that life events and stress can change our mood, but there’s less acknowledgement that what we can have impact as well. One example relates to blood sugar imbalance: If blood sugar levels plummet, it can switch on the body’s stress response, which in turn can induce feelings of tension and anxiety. Of course, it’s always possible that foodstuffs may have the opposite effect, and help us regain or retain a state of calm.

One foodstuff that is reputed to do this is tea. Interestingly, a recent study published in the American Journal of Clinical Nutrition [1] found that Japanese adults drinking at least five cups of green tea a day were at a 20 percent reduced risk of “psychological distress,” compared to those consuming one cup a day or less. Epidemiological studies of this nature do not prove that green tea has an anti-stress effect; just that green tea drinking is associated with improved mental well-being.

However, there is at least some evidence that suggests that tea can have genuine mood-enhancing effects.

In a study published in 2007, the effects of tea on the stress response were tested in a group of men [2]. The study subjects were all taken off caffeinated beverages and put on to a caffeinated placebo drink for a period of 4 weeks.

After this, the men were put through a challenging task; measures of the stress response were made before, during, and after the task. After this, men were given either tea or placebo drink to consume for a period of 6 weeks, at which point their responses to stress were rechecked.

Some measures, including heart rate and blood pressure, were not different between the two groups. However, some were.

Compared to those drinking the placebo drink, tea drinkers had reduced platelet activation. (Platelet activation makes the blood more likely to clot and is activated during the stress response.)

Tea drinkers also had lower cortisol levels after the challenging task. Cortisol is a major hormone secreted in response to stress.

And finally, tea-drinkers also felt more relaxed after completing the challenging task.

These findings suggest that tea drinking may have at least some capacity to mitigate the negative effects of stress.

References:

1. Hozawa A, et al. Green tea consumption is associated with lower psychological distress in a general population: the Ohsaki Cohort 2006 Study. American Journal of Clinical Nutrition 2009; 90(5): 1390–6

2. Steptoe A, et al. The effects of tea on psychophysiological stress responsivity and post-stress recovery: a randomized double-blind trial. Psychopharmacology (Berlin) 2007; 190(1): 81–9

Dr. John Briffa is a London-based physician and health writer with an interest in nutrition and natural medicine. His Web site is DrBriffa.com