By Adrienne Dellwo
Medically reviewed by Shaheen Lakhan, MD, PhD 
January 16, 2020

Theanine is an antioxidant that's found naturally in tea leaves. So far, it hasn't been studied specifically for fibromyalgia and chronic fatigue syndrome, but we do have studies suggesting that it may be effective in treating many symptoms of these conditions.

Research shows theanine may:

  • Increase alertness
  • Boost energy
  • Relieve anxiety
  • Aid relaxation without causing drowsiness
  • Protect brain cells
  • Increase the availability of dopamine and norepinephrine
  • Lower activity of the neurotransmitter glutamate, which can overstimulate brain cells
  • Balance glutathione levels
  • Boost production of T cells by your immune system
  • Prevent memory impairment due to improper blood flow (ischemia) in the brain

Theanine may also lower blood pressure and bad cholesterol, increase anti-tumor activity, and help regulate the sleep-wake cycle.

Those are a lot of benefits from a single substance, and especially from one that appears to be quite safe.

Typical Dosage

Theanine is available in supplement form, frequently under the name l-theanine or under the brand name suntheanine. Some formulations may have other ingredients as well, so be sure to check the label so you know exactly what you're taking.

Because it hasn't been studied for these conditions, we don't have standard dosage recommendations for treating fibromyalgia or chronic fatigue syndrome. However, for other conditions, the typical recommended dosage is 100 to 200 mg per day. Some studies, though, have used up to 600 mg per day.

Getting Theanine via Your Diet

If you prefer to get theanine through your diet rather than from supplements, there's the good news: Studies have shown that theanine does cross the blood-brain barrier. That's not the case with a lot of things, including substances that your brain needs.