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What You Should Know About
L-Theanine
Benefits and uses
Risks and side effects
Dosage
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L-theanine is an amino acid found primarily in green and black tea and some mushrooms. It’s also available in pill or tablet form.
It’s said to help ease anxiety, stress, and reduce insomnia.
Before trying it out yourself, learn more about the potential health benefits, as well as any possible risks or complications.
L-theanine benefits and uses
Most known for helping people relax, L-theanine has other potential health benefits, including:
Anxiety and stress relief
Sipping on a hot cup of tea can help you feel at ease, and research suggests that it not only relaxes the mind, but it also does so without causing drowsiness (1).
In a review of five randomized controlled trials that included 104 participants, four trials linked L-theanine with reduced stress and anxiety in people experiencing stressful situations (2).
Another study published in the Journal of Clinical Psychiatry focused on people living with schizophrenia or schizoaffective disorder. Researchers found that L-theanine decreased anxiety and improved symptoms (3).
Increased focus
Paired with caffeine, L-theanine may help increase focus and attention.
A small study found that a combination of L-theanine (97 milligrams, or mg) and caffeine (40 mg) helped a group of young adults focus better during demanding tasks. A typical cup of coffee contains 95 mg of caffeine (4Trusted Source, 5).
The study’s participants also felt more alert and less tired in general.
Better immunity
Some research suggests that L-theanine may improve the function of the body’s immune system. One study published in the journal Beverages found that L-theanine could help decrease upper respiratory tract infections (6).
Another one found that green tea catechins— antioxidants— and theanine could be effective at preventing the flu (7Trusted Source, 8Trusted Source).
Another studyTrusted Source found that L-theanine could help improve inflammation in the intestinal tract. However, more research is needed to confirm and expand on these findings (6, 9).
Tumor and cancer treatment
L-theanine has also been associated with amplifying the anti-tumor effects of certain chemotherapy drugs. Because of these promising findings, researchers expect that L-theanine could also help improve chemotherapy’s ability to fight cancer (10).
Although there’s no definitive evidence to show that tea prevents cancer, a number of studies suggest that people who regularly drink tea have lower rates of cancer (10, 11Trusted Source, 12Trusted Source).
Researchers of one study in China found that women diagnosed with ovarian cancer who drank at least one cup of green tea a day lived longer than those who didn’t (13Trusted Source).
Another study that looked at tea drinkers compared to nondrinkers found that women who drank green tea were 32 percent less likely to develop pancreatic cancer (14).
Blood pressure management
L-theanine has also been associated with amplifying the anti-tumor effects of certain chemotherapy drugs. Because of these promising findings, researchers expect that L-theanine could also help improve chemotherapy’s ability to fight cancer (10).
Although there’s no definitive evidence to show that tea prevents cancer, a number of studies suggest that people who regularly drink tea have lower rates of cancer (10, 11Trusted Source, 12Trusted Source).
Researchers of one study in China found that women diagnosed with ovarian cancer who drank at least one cup of green tea a day lived longer than those who didn’t (13Trusted Source).
Another study that looked at tea drinkers compared to nondrinkers found that women who drank green tea were 32 percent less likely to develop pancreatic cancer (14).
L-theanine risks and side effects
There are no confirmed or direct side effects of consuming L-theanine. Generally speaking, it’s safe to drink teas and take supplements that contain L-theanine.
But it’s important to note that the Food and Drug Administration (FDA) doesn’t regulate supplement. Manufacturers of those products bear the weight of the responsibility to make sure their products are safe (19).
However, though some research shows promising results for L-theanine’s anti-tumor properties, teas that contain amino acids can have other ingredients that could be harmful to people being treated for cancer.
According to Memorial Sloan Kettering Cancer Center, the polyphenol EGCG found in green tea can reduce some chemotherapy drugs’ efficacy, such as bortezomib (20, 21Trusted Source).
For that reason, it’s crucial for those taking chemotherapy drugs to talk with their healthcare provider before drinking green tea as part of their treatment plan.
While there haven’t been reported side effects from taking L-theanine, because of the caffeine content, consuming large amounts of green tea can lead to:
- nausea
- upset stomach
- irritability
Women who are pregnant or breastfeeding should also limit how much tea they drink to avoid over-caffeinating.
It’s best to ask your healthcare provider about what’s safe for you. The same advice applies to children as well.
Safe dosage recommendations for L-theanine
Because there’s been no conclusive research, a safe L-theanine dosage recommendation isn’t known. But following general caffeine consumption guidelines can be helpful if you’re drinking tea.
It’s best for those taking an L-theanine supplement to consult a medical provider for guidance on dosage.
Last medically reviewed on January 13, 2021
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5 Proven Benefits of BCAAs (Branched-Chain Amino Acids)
Studies show that BCAAs may increase muscle growth, reduce soreness and fatigue, prevent muscle wasting, and support liver health. They are also found in a variety of food sources, including meat, eggs, and dairy products.
There are 20 different amino acids that make up the thousands of different proteins in the human body.
Nine of the 20 are considered essential amino acids, meaning they cannot be made by your body and must be obtained through your diet.
Of the nine essential amino acids, three are considered branched-chain amino acids (BCAAs): leucine, isoleucine, and valine.
“Branched-chain” refers to the chemical structure of BCAAs, which are found in protein-rich foods such as eggs, meat, and dairy products. They are also a popular dietary supplement sold primarily in powder form.
Here are 5 proven benefits of BCAAs.
1. Increase muscle growth
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One of the most popular uses of BCAAs is to increase muscle growth.
The BCAA leucine activates a certain pathway in the body that stimulates muscle protein synthesis, which is the process of making muscle (1Trusted Source).
In one study, people who consumed a drink with 5.6 grams (g) of BCAAs after their resistance workout had a 22% greater increase in muscle protein synthesis compared to those who consumed a placebo drink (2Trusted Source).
That being said, this increase in muscle protein synthesis is approximately 50% less than what was observed in other older studies where people consumed a whey protein shake containing a similar amount of BCAAs (3Trusted Source, 4Trusted Source).
Whey protein contains all of the essential amino acids needed to build muscle.
Therefore, while BCAAs can increase muscle protein synthesis, they can’t do so maximally without the other essential amino acids, such as those found in whey protein or other complete protein sources (5Trusted Source, 6Trusted Source).
summary
BCAAs play an important role in building muscle. However, your muscles require all of the essential amino acids for the best results.
2. Decrease muscle soreness
Some research suggests BCAAs can help decrease muscle soreness after a workout.
It’s not uncommon to feel sore a day or two after a workout, especially if your exercise routine is new.
This soreness is called delayed onset muscle soreness (DOMS), which develops 12 to 24 hours after exercise and can last up to 72 hours (7Trusted Source).
While the exact cause of DOMS is not clearly understood, one theory is that it’s the result of tiny tears in the muscles after exercise (8Trusted Source).
Meanwhile, other research suggests that it may actually be related to the connective tissue associated with the muscle rather than the actual muscle itself (8Trusted Source).
BCAAs have been shown to decrease muscle damage, which may help reduce the length and severity of DOMS.
Several studies show that BCAAs decrease protein breakdown during exercise and decrease levels of creatine kinase, which is an indicator of muscle damage (9Trusted Source, 10Trusted Source).
In one 2010 study, people who supplemented with BCAAs before a squat exercise experienced reduced DOMS and muscle fatigue compared to the placebo group (11Trusted Source).
Therefore, supplementing with BCAAs, especially before exercise, may speed up recovery time (12Trusted Source).
summary
Supplementing with BCAAs may decrease muscle soreness by reducing damage in exercised muscles.
3. Reduce exercise fatigue
Just as BCAAs may help decrease muscle soreness from exercise, they may also help reduce exercise-induced fatigue.
Everyone experiences fatigue and exhaustion from exercise at some point. How quickly you tire depends on several factors, including exercise intensity and duration, environmental conditions, and your nutrition and fitness level (13Trusted Source).
Your muscles use BCAAs during exercise, causing levels in your blood to decrease. When blood levels of BCAAs decline, levels of the essential amino acid tryptophan in your brain increase (14Trusted Source).
In your brain, tryptophan is converted to serotonin, a brain chemical that is thought to contribute to the development of fatigue during exercise (14Trusted Source, 15Trusted Source).
In two studies, participants who supplemented with BCAAs experienced a reduction in central fatigue, resulting in improved athletic performance (16Trusted Source, 17Trusted Source).
summary
BCAAs can alter levels of certain chemicals in the brain, such as serotonin, which may be useful in decreasing exercise-induced fatigue.
4. Prevent muscle wasting
BCAAs can help prevent muscle wasting or breakdown.
Muscle proteins are constantly broken down and rebuilt (synthesized). The balance between muscle protein breakdown and synthesis determines the amount of protein in muscle (18Trusted Source).
Muscle wasting or breakdown occurs when protein breakdown exceeds muscle protein synthesis.
Muscle wasting is a sign of malnutrition and occurs with chronic infections, cancer, periods of fasting, and as a natural part of the aging process (19Trusted Source, 20Trusted Source).
In humans, BCAAs account for 35% of the essential amino acids found in muscle proteins. They account for 40% to 45% of the total amino acids required by your body (21Trusted Source, 22Trusted Source).
Therefore, it’s important that the BCAAs and other essential amino acids are replaced during times of muscle wasting to halt it or to slow its progression.
Several studies support the use of BCAA supplements for inhibiting muscle protein breakdown. This may improve health outcomes and quality of living in certain populations, such as older adults and those with conditions like cancer (23Trusted Source, 24Trusted Source).
summary
Taking BCAA supplements can prevent the breakdown of protein in certain populations with muscle wasting.
5. Benefit people with liver disease
BCAAs may offer health benefits for people with cirrhosis, a chronic disease in which the liver does not function properly.
It’s estimated that 50% of people with cirrhosis will develop hepatic encephalopathy, which is the loss of brain function that occurs when the liver is unable to remove toxins from the blood (25Trusted Source).
While certain sugars and antibiotics are the mainstays of treatment for hepatic encephalopathy, BCAAs may also benefit people with this condition (26Trusted Source).
One review of 16 studies including 827 people with hepatic encephalopathy found that taking BCAA supplements had a beneficial effect on the symptoms and signs of the disease, but had no effect on mortality (27Trusted Source).
Liver cirrhosis is also a major risk factor for the development of hepatocellular carcinoma, the most common form of liver cancer, for which BCAA supplements may also be useful (28Trusted Source, 29Trusted Source, 30Trusted Source).
Several older studies have shown that taking BCAA supplements may offer protection against liver cancer in people with liver cirrhosis (31Trusted Source, 32Trusted Source).
As such, scientific authorities recommend these supplements as a nutritional intervention for liver disease to prevent complications (33).
summary
BCAA supplements may improve the health outcomes of people with liver disease, while also possibly protecting against liver cancer.
