From the FDA Drug Label
CONTRAINDICATIONS This solution should not be used in patients in hepatic coma, severe renal failure, metabolic disorders involving impaired nitrogen utilization or hypersensitivity to one or more amino acids. WARNINGS Administration of amino acids solutions at excessive rates or to patients with hepatic insufficiency may result in plasma amino acid imbalances, hyperammonemia, prerenal azotemia, stupor and coma.
L-theanine is not safe for individuals with hepatic insufficiency or hepatitis. The drug label warns against administering amino acid solutions, including L-theanine, to patients with hepatic insufficiency as it may result in plasma amino acid imbalances, hyperammonemia, and other complications.
- If a person has elevated liver enzymes and hepatitis and is taking L-theanine, it is required to stop or consult a doctor to re-evaluate the treatment plan 1 1.
From the Research
L-theanine can be safely taken in individuals with elevated liver enzymes or hepatitis, but it is recommended to consult with a healthcare provider before taking the supplement, as they may advise monitoring liver enzymes or adjusting the dose. The most recent and highest quality study, published in 2024 2, found that L-theanine has a protective effect on acute alcoholic liver injury in mice, mitigating liver tissue damage and reducing serum levels of liver enzymes. Additionally, a 2022 study 3 found that L-theanine prevents nonalcoholic hepatic steatosis by regulating hepatocyte lipid metabolic pathways, and a 2018 study 4 found that L-theanine prevents ETEC-induced liver damage by reducing intrinsic apoptotic response and inhibiting ERK1/2 and JNK1/2 signaling pathways. However, a 2012 study 5 found that L-theanine prevents alcoholic liver injury through enhancing the antioxidant capability of hepatocytes. It is essential to note that while these studies suggest a potential benefit of L-theanine in liver health, the safety profile in liver disease has not been well-established, and medical supervision is crucial. Some key points to consider include:
- L-theanine is an amino acid found naturally in tea that has calming effects
- The liver processes most supplements, so any substance that requires liver metabolism could potentially add stress to an already compromised liver
- Medical supervision is important, especially in individuals with liver conditions, to monitor liver enzymes and adjust the dose as needed
- The severity of the liver condition and overall health status should be taken into account when deciding whether to take L-theanine supplements.