Some medications that suppress the immune system's attack on the transplanted organ also attack and damage the kidney, which is especially unfortunate since the kidney is the organ most frequently transplanted. But green tea and green tea extract in pill form have been found to offer some protection against the toxic effects of immunosuppressives on the kidney. Unfortunately green tea extract is toxic if taken in overdose, so patients are advised to take no more than 300 mg a day of it, or 5 cups of green tea.
Green-Tea Post-Transplant: Some... - Kidney Transplant...
Green-Tea Post-Transplant
Please do NOT drink five cups of green tea a day. That is extremely dangerous.
Due to competitive enzyme catalytic actions green tea is known to alter tacrolimus trough levels. Transplant centers do not recommend green tea consumption in daily basis. Please consult your doctor before taking any green tea supplement.
Ref: ajkd.org/article/S0272-6386...
It is beneficial for diminishing cyclosporine toxicity, however. See: "Meanwhile, Green tea extract administration improved renal function, by bringing about a significant decrease in peroxidative levels and increase in antioxidant status. These results indicate the renoprotective potential and usefulness of green tea extract, as an excellent source of antioxidants, in modulating CsA-induced nephrotoxicity."
Samy Ali Hussein, Omayma A. Ragab and Mohammed A. El-Eshmawy, 2014. Protective Effect of Green Tea Extract on Cyclosporine A: Induced Nephrotoxicity in Rats. Journal of Biological Sciences, 14: 248-257.
A lot of other peer-reviewed scientific research supports this benefit.
The interaction effect is medication-dependant. This is why we should never recommend a compound under the assumption that it is safe for everyone. ALWAYS check with your doctor before starting any supplement.
I found similar studies about green tea; therefore, I’ve been putting two tablespoons of matcha in vegan smoothies daily for the last 7 years. Excellent plant for renal protection. I go with science.
From NKF:
"
Q: What supplements or herbal products should I avoid after receiving a transplant?
A: Some of the more popular herbal products that can have adverse interactions (with transplant medications) include:
Vitamin C
St. John’s Wort
Herbal teas: green tea, chamomile, peppermint, dandelion
Echinacea
Ginseng
Feverfew"
This article will give you a broader perspective on why green tea is not appropriate for a majority of transplant patients. I hope it helps to bring attention to the danger of green tea consumption while on those medications.