In 2020, researchers at Johannes Gutenberg University in Mainz, Germany, published a laboratory study on sencha, and the sencha they used was ours. Their methods section says they bought certified organic sencha powder from Sei Mee Tea, the name our company went by until 2023 (Lu et al., Biomolecules, 2020). The study means a great deal to my family, because Yu Tea grew out of the years after my husband, Bill, was diagnosed with cancer in 2001, which I share in our story. Many of you have asked what it found, so here is what the researchers tested, what they saw, and what the study does not tell us.

What the researchers did

• They made three extracts from our sencha powder. About 3 g of powder was extracted with methanol, with a mix of methanol and water, and with plain water, and each extract was concentrated before testing.
• They tested the extracts on blood cancer cells grown in the lab. Two leukemia cell lines, one of them resistant to several chemotherapy drugs, and nine multiple myeloma cell lines, with normal white blood cells for comparison.
• No animals or people took part. Every experiment was done on cells in culture.

What the study found

• All three extracts reduced the number of living cancer cells. The concentration that cut the living leukemia cells in half was about 8 to 34 micrograms of extract per milliliter, and about 11 to 77 for the myeloma cells; the drug-resistant leukemia cells needed roughly two to three times as much as the ordinary ones.
• Normal white blood cells were affected less. The authors report that the extracts affected normal lymphocytes less than the leukemia cells.
• The extracts acted in several ways at once. In the cancer cells they stopped the cell cycle, triggered programmed cell death (apoptosis), raised reactive oxygen species and lowered the mitochondrial membrane potential; a gene analysis pointed to two signaling networks, PI3K/Akt and NF-κB.
• The methanol extract was the strongest. The authors link that to its higher catechin content. The water extract, which they note is the closest to how sencha is drunk, was the weakest of the three on the drug-resistant cells.

What the study does not tell us

This was a laboratory study. The cells sat in concentrated extract for three days, which is not what happens when you drink a cup of tea, and the authors write that the right dose of tea catechins has not been decided and that the next step is research in living animals. So it does not show that drinking sencha prevents or treats leukemia, myeloma or any other cancer, and I would never tell anyone it does. What it shows is why scientists keep studying green tea, and that our sencha was the tea these researchers chose to work with.

If you or someone you love is being treated for cancer, please talk with your oncology team before drinking green tea regularly or taking any green tea extract. Green tea is not always a harmless partner to treatment: a 2009 study in Blood found that EGCG and related green tea polyphenols blocked the effect of bortezomib, a common myeloma drug, in cell and mouse experiments, and its authors concluded that green tea products may be contraindicated during that treatment.

Why we still share it

The tea in the study is the same Organic Sencha powder we sell today, our signature tea since 2004: first-harvest leaves, steamed, rolled and stone-milled, so you drink the whole leaf rather than an infusion. It tastes bright and crisp, with notes of spring greens and a clean, citrusy finish, and its caffeine and L-theanine give a calm, steady energy. If you would like to know more about the tea itself, how it is grown and what is in it, start with my guide to what sencha is.