What Are the Dangers of Theanine?

Theanine, also called L-theanine, is an amino acid found in tea and mushrooms, according to the Memorial Sloan-Kettering Cancer Center. Theanine, which is available as a dietary supplement, contains antioxidants, promotes weight-loss and is used as an alternative anxiety treatment due to its relaxant properties.

Sedative Interaction

• Theanine is sometimes used as an herbal sedative. However, it should not be taken in conjunction with other sedatives to avoid potentially dangerous increased sedative effects, according to Sloan-Kettering.

Stimulant Interaction

• Theanine should not be taken with stimulant drugs such as diethylpropion, epinephrine, phentermine and pseudoephedrine, according to WebMD. Stimulant drugs speed up the nervous system. Theanine's relaxant effects counter the effects of stimulant medications.

Lowers Good Cholesterol

• Theanine lowers overall cholesterol, meaning it lowers both low-density lipoprotein (bad cholesterol) and high-density lipoprotein (good cholesterol), according to Sloan-Kettering. Although lowering low-density lipoprotein is beneficial, some high-density lipoprotein is needed to carry cholesterol away from the arteries to the liver where it is passed through body, according to the American Heart Association.

Low Blood Pressure

• Theanine is shown to lower blood pressure and should not be taken with antihypertensive drugs, according to WebMD. Taking theanine with drugs that decrease blood pressure can result in dangerously low blood pressure.

Possible Pregnancy Complications

• Although the risk to infants is unknown, WebMD suggests that pregnant and breast feeding women avoid theanine. Theanine is one of the few dietary supplements that crosses the blood-brain barrier, according to Life Extension Magazine. This factor may increase potential risks to fetuses, infants and small children.