One group was given a drink containing a green tea extract, while a second group was given a placebo drink without the extract.
Then, using an MRI machine, scientists studied the effects of the two drinks on the men's brains while they performed a memory test.
Compared to the placebo group, the green tea drinkers experienced an increase in the activation of the dorsolateral prefrontal cortex, an area of the brain associated with working memory, which you need for problem solving and focus.
The results of the new study are reported in the European Journal of Clinical Nutrition.
Green tea is full of polyphenols, which widen blood vessels, speeding the supply of blood to the brain, like EGCG, a strong anti-cancer chemical.
Researchers have found these health giving chemicals might be behind green tea's benefits.
Study co-author Stefan Borgwardt, of the University Hospital Basel, in Switzerland, said: 'Green tea may help prevent neurotransmitters involved in brain functioning, like dopamine and epinephrine, from degrading.
'It may also inhibit senile plaques from depositing in the brain, which impairs cognition.'
The Many Benefits of Ancient Green Tea
Green tea helps burn fat by speeding up the metabolic rate
It can help lower blood pressure by tackling an enzyme which triggers hypertension
Green tea can help protect against diabetes, as it contains polyphenols which inhibit starch, and so can help lower blood sugar levels.
It can help also prevent food poisoning as it can kill harmful bacteria
The tea can also prevent bad breath by killing oral bacteria that cause cavities and bad breath.
Green tea guards against hepatitis by decreasing iron levels throughout the body, including those in the liver - the cause of viral hepatitis.
The tea can protect against cancer as it contains a compound called epigallocatechin-3-gallate (EGCG), which helps inhibit blood vessel growth.
It can help prevent arthritis, working in much the same way as anti-inflammatory drugs.
Gargling with the tea boosts immunity to influenza and flu, according to a study in Japan.
A study also found 96 percent of those who drank ten cups of green tea a day showed no signs of the cognitive impairment linked to Alzheimer's, compared to only 12 percent who didn't drink green tea.
April McCarthy is a community journalist playing an active role reporting and analyzing world events to advance our health and eco-friendly initiatives.