Dr. Rev. Isabel Sharkar

Dr. Isabel Sharkar, NMD, is co-founder of Indigo Integrative Health Clinic in Washington, D.C., a thriving clinic that has been serving the local community in health restoration and body optimization for over a decade. Being in constant pursuit for truth and healing Dr. Isabel graduated in 2011 from Southwest College of Naturopathic Medicine as a Doctor of Naturopathic Medicine.

Author profile

By Caroline Hoeffgen, COO, BCHC, JD | Reviewed by Dr. Isabel Sharkar, NMD | May 2026

L-Theanine

L-theanine is an amino acid isolated from green tea leaves (Camilla sinensis) and some mushroom varieties. It has a neuroprotective effect which is important in today's world of ever-increasing Alzheimer/dementia patients. With stress being so high,this amino acid also supports a more balanced mood to face life's many challenges.It has also been shown to promote relaxation, improve mental focus, and reduce anxiety. It can also boost cognitive function and enhance sleep quality. It is considered safe and non-addictive, making it a popular natural supplement for stress relief and improved mental performance.Studies have shown L-theanine can help improve cognitive function including decision making and verbal fluency. Additionally, it can help you fall asleep faster. It also helps reduce overall stress and can increase attentiveness and supports a healthy mood by lowering anxiety and depression scores in a healthy adult population when compared to a placebo.According to human and animal toxicity studies, L-theanine is well-tolerated. It is found in single supplements or in formula blends supportive of overall mood, mental health, or improved sleep. Green tea also contains this amino acid. Gyokuro and matcha green teas have been shown to contain more L-theanine than sencha, so if you are looking to add green tea to your diet you may find more benefit from choosing one with more of beneficial amino acid.

REFERENCES
  • Baba, Yoshitake, et al. 2021. "Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study." Journal of Medicinal Food, 24(4); 333-341. doi:10.1089/jmf.2020.4803.
  • Hidese, Shinsuke, et al. 2019. "Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial." Nutrients, Oct. 3, 2019, 11(10); 2362. doi:10.3390/nu11102362.

Medical Disclaimer

This content is provided by Indigo Integrative Health Clinic for educational purposes only. It does not constitute medical advice, a diagnosis, or a treatment recommendation, and does not establish a provider-patient relationship. Individual health conditions vary — information presented here may not apply to your specific situation. Always consult a qualified, licensed healthcare provider before making decisions about your health, medications, supplements, or treatment plan.

Featured in
Related articles

Continue reading

View all articles

Hashimoto's is diagnosed by combining findings, not one test: thyroid antibodies (TPO, sometimes thyroglobulin), thyroid function (TSH and free T4), symptoms, and often an ultrasound. A normal TSH does not rule it out, and a low-positive antibody is not always disease. Found early, before the gland is damaged, there is the best chance to protect it and feel better.

There is no single Hashimoto's diet, but a few moves have real evidence. Correct the nutrient gaps you can measure, like iron, selenium, and vitamin D. Get your iodine to the right level, which takes an assessment, not one test. And cut a food only for a real reason, like a positive celiac test or too much iodine. Assess first, then personalize.

Lyme disease shares key symptoms with fibromyalgia, multiple sclerosis, and chronic fatigue syndrome, so it can be mistaken for any of them. It is also over-diagnosed in people who do have one of those conditions. The honest answer is that Lyme is worth confirming or ruling out with a knowledgeable clinician, not assumed in either direction.