L-theanine is a nutrient found in some herbs and supplements. It has gained popularity for its potential health benefits, particularly related to stress relief and improved sleep. We spoke with registered dietitians to get the full details on L-theanine, its benefits and side effects, plus who should take it and who should avoid it.
What is L-theanine?
L-Theanine is a water-soluble, non-protein amino acid known for its potential to promote relaxation and relieve stress without causing drowsiness. It is found naturally in plants such as matcha, green, black and white teas and in mushrooms such as certain mushrooms. It is also available in supplement form, usually in pill or powder form.
Potential Health Benefits of L-Theanine
Although L-theanine is best known for helping people relax, it may also have other potential health benefits.
Promotes relaxation and relieves stress
According to Kelsey Costa, registered dietitian nutritionist and founder of Dietitian Insights, “L-theanine may have important therapeutic effects on mental health, such as reduced depression and stress and improved emotional and cognitive function. »
Studies show that L-theanine helps reduce stress-related symptoms, improve sleep quality, and promote cognitive function in healthy individuals and those with major depressive disorder. Athletes and other stressed people have also reported improved performance and reduced stress responses when using L-theanine.
May increase concentration and attention
L-theanine may improve attention, concentration and cognitive performance. It may be even more effective when combined with caffeine, which can help improve memory and executive functions, and reduce distractions and mind wandering. L-theanine might also benefit people with ADHD because it promotes sustained attention and impulse control. However, further research on this topic is needed to clarify this relationship, particularly for children and young adults.
Supports the immune system
L-theanine has antioxidant, immunoregulatory and anti-inflammatory properties. Studies suggest that it may reduce cases of respiratory infections, help prevent the flu and reduce inflammation of the digestive tract.
“It is important to note that many of the available studies on potential health benefits have small sample sizes, show limited improvements, and often involve healthy individuals rather than people with chronic health conditions” , says Emily Haddock, RD, LDN, registered dietitian and owner of Music City Nutrition and Wellness. Additional research is needed in more diverse populations to further clarify and support these benefits.
Potential Side Effects of Taking L-Theanine
“With the limited research currently available, there are not many confirmed side effects or direct risks associated with taking L-theanine,” says performance nutrition specialist Gabbie Ricky, MS, RDN. Eat well.
“As with any supplement you are considering, however, be sure to purchase from a reputable manufacturer. Look for supplements that are Good Manufacturing Practices (GMP) certified and have been rigorously third-party tested for product quality and purity,” she adds.
Some side effects associated with L-theanine are often due to overconsumption of caffeine by those who increase their L-theanine intake by drinking tea. These side effects may include:
- Headache
- Nausea
- Nervousness
- Irritability.
The recommended daily intake of caffeine is 400 milligrams or less.
Who should take L-theanine?
“People who regularly work in high-risk environments or under high stress conditions may benefit from the potential cognitive benefits of L-theanine, such as improved concentration, especially when combined with caffeine,” Ricky explains. “Some examples of these populations could include professional athletes, tactical athletes (like firefighters, military personnel, etc.), and healthcare workers,” she adds.
People suffering from poor sleep quality, depression, and anxiety might also benefit from L-theanine, but it’s important to speak with a healthcare professional before adding new supplements to your routine.
Who should avoid it?
Although L-theanine is safe for most people, some should avoid it. “People who are pregnant or breastfeeding should avoid L-theanine because it has not been adequately tested in these populations,” adds Haddock.
People who take blood pressure medications may need to avoid L-theanine because it can further reduce blood pressure.
Additionally, anyone receiving chemotherapy for cancer treatment should avoid L-theanine supplements until their treatment is complete. “In additional doses, the powerful antioxidant function of L-theanine may reduce the effectiveness of certain chemotherapy drugs,” explains Ricky. Eat well.
It is always recommended to speak with a healthcare professional before adding new supplements to your routine, especially if you are undergoing treatment for cancer or high blood pressure.
The essential
L-theanine is a non-protein amino acid found in certain foods like tea and mushrooms. It is also available in supplement form. Many people can take L-theanine safely without negative side effects, but some people (such as those who are pregnant or undergoing cancer treatment) should avoid it. Although L-theanine appears promising in terms of potential health benefits, further research is needed in larger, more diverse populations to confirm this.
Frequently asked questions
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Is it safe to take L-theanine every day?Based on currently available information, most healthy adults can take L-theanine daily without negative health consequences or side effects. Generally, it is safe to drink tea and take supplements containing L-theanine daily. However, talk to your doctor before starting to make sure it is safe for you.
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Does L-theanine make you sleepy?L-theanine may improve sleep quality by reducing stress and promoting a feeling of calm. This is not usually associated with daytime sleepiness or sleepiness, but may contribute to better sleep at night.
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What are the negative side effects of L-theanine?No major side effects have been reported, and L-theanine is generally considered safe for most people. Some people may experience side effects like nervousness, headaches, and irritability when they drink too much of the caffeine in tea.