Green tea extract and immune cell activity in people
What it found
In 20 healthy adults, taking 300 mg of green tea extract daily for 14 days increased the release of two substances from white blood cells and raised the blood's antioxidant capacity.
These changes returned to starting levels after 4 weeks without the extract.
What they found
Studies in people
White blood cell activity
After 14 days, white blood cells released more myeloperoxidase and lactoferrin when stimulated with a bacterial peptide. The increase was significant compared to the start of the study.
Antioxidant status
Total antioxidant status in the blood increased significantly after 14 days of taking the green tea extract. After the 4-week washout, it returned to levels similar to the start.
White cell count
There was a slight decrease in the number of circulating white blood cells after 14 days, but this was not statistically significant and counts stayed within the normal range.
Individual variation
The effect on myeloperoxidase and lactoferrin release varied between people, from a small increase to about double the starting response. In 15% of subjects, no increase was seen in either substance.
Washout period
After 4 weeks without the extract, all measured parameters returned to levels similar to those at the start of the trial.
What the authors conclude
“This study indicates that a green tea extract when taken as a dietary supplement for 14 days can increase the leukocyte activity and the total plasma antioxidant status and may have role to play in the prevention of inflammatory disease.”
Also in their conclusions
- They conclude that a green tea extract taken as a dietary supplement for 14 days can increase leukocyte activity and total plasma antioxidant status.
- They say it may have a role to play in the prevention of inflammatory disease.
- They call for further work to identify the components and mechanisms responsible for priming human leukocytes.
How it was done
The authors wanted to see if a green tea extract could boost the function of white blood cells in people, since these cells are important for defence against bacteria and for inflammation.
They gave 20 healthy adults (10 men and 10 women, aged 20 to 55) 300 mg of green tea extract daily for 14 days. They took blood samples at the start, after 14 days, and after a 4-week washout period, and measured the release of myeloperoxidase and lactoferrin from white blood cells, white cell counts, and total antioxidant status.
What it can’t tell you
- This was a small study with 20 people, so the results may not apply to everyone.
- The study did not test whether these changes in white blood cell activity actually prevent infections or inflammatory diseases.
The paper
- Title
- Dietary supplementation with green tea extract promotes enhanced human leukocyte activity
- Type
- Clinical trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Lowe GM, Gana K, Rahman K (2015). Dietary supplementation with green tea extract promotes enhanced human leukocyte activity. Journal of complementary & integrative medicine. doi:10.1515/jcim-2014-0042Free full textPubMed 26259232DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error