Timing of Green Tea Intake Matters

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A new study is out that examines the impact of green tea on blood glucose levels after a meal.

As a little bit of background, green tea catechols are often promoted for reducing the risk of diabetes.  The results are sometimes tepid (very slight reduction in blood glucose levels [ref]) with other studies and reviews that were more positive [ref].

All in all, there are lots of general articles singing the praises of green tea for diabetes prevention.

Which is why this new study on green tea is so interesting…

The study participants were healthy Japanese males between the age of 21 and 30. The study used only men to avoid the differences in glucose metabolism that women have during different times of their menstrual cycle.

The trial measured blood glucose response in the participants after a specific breakfast and dinner both with a placebo drink and with green tea.  The meal was 70% carbs, 15% fat, and 15% protein. The high carbs were so that there would be a substantial postprandial glucose response.

The morning trials with a placebo drink (water) vs the green tea actually showed a slightly better blood glucose response after breakfast with the placebo (water) than the green tea. (This is the opposite of what all the articles on drinking green tea for diabetes prevention say.)

The evening meal trial, though, showed that green tea reduced the postprandial glucose levels (and increased insulin release).

Why is this interesting? It shows that the timing of interventions, such as consuming catechols in green tea, matter a lot. This may explain a lot of the opposing results in different studies — the timing of taking the supplement/food/drink may make a big difference in the results.

Specifically, tea polyphenols have been shown to affect the expression of the core circadian clock gene, BMAL1.  [ref]

This adds a bit more complexity to trying to decide on whether to take a supplement or not — now the question includes both whether the supplement is effective and when to take it.



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