Tea is one of the most popular drinks in the world and is believed to have many health benefits. In fact, tea has been used for over 5,000 years for medicinal purposes.
Green tea, in particular, offers many health benefits and this has now been supported by extensive research. Green tea consumption has been associated with a reduced cancer risk, may be able to protect us from heart disease, improves cognitive function, and has been shown to protect the brain. Some of the elements in green tea may also reduce anxiety and stress levels.
While tea has many important, health-promoting components, one nutrient found in green tea, known as l-theanine has significant health-enhancing effects. L-theanine, often simply referred to as theanine, is an amino acid primarily found in green tea that has received a lot of attention by researchers. [NOTE: the 'L' in 'L-theanine' refers to its molecular configuration. Most amino acids have two stereoisomers, an 'L' and a 'D' form. Only the 'L' forms are incorporated into body proteins, and it is the L-form that has the greatest health benefits]
Most of the research on l-theanine has investigated its neuroprotective effects and its ability to enhance mental well-being. This is because theanine has the ability to cross the blood-brain barrier, thereby contributing to its brain-protective effects. However, theanine also has many other health benefits and some of these are summarised below.
While theanine is contained in green tea, most clinical studies have used quite high amounts of theanine. The effects of approximately 100 to 400mg of l-theanine have been studied. This equates to 8 to 30 cups of green tea, which is impossible to consume on a daily basis. Therefore, most human studies have examined the effects of l-theanine delivered as a supplement. This may consist of theanine delivered on its own, or in conjunction with green tea. We believe the combination is best as green tea contains other components that have powerful health-enhancing effects.
L-theanine has been shown in numerous studies to have a positive effect on anxiety and stress levels. This is likely due to its ability to balance relaxing brain chemicals (neurotransmitters) such as serotonin, dopamine, and GABA. Theanine also has a calming effect on the brain by increasing alpha wave production. Alpha waves in the brain are increased during periods of focus and relaxation. In fact, alpha waves are often increased during meditation. This means that theanine intake can support a calm, relaxed mind, without causing drowsiness
Research has confirmed that l-theanine can improve sleep quality. It also has the ability to lower the perception of ‘unrefreshing’ sleep. In fact, in a Japanese study, many of the participants believed that they had slept longer than they actually did!
The effects of theanine in children suffering from attention deficit hyperactively disorder (ADHD) has also been investigated. In this study, theanine (or a placebo) was given to 8 to 12-year-old boys with ADHD for 6 weeks. Boys on theanine experienced greater sleep times and better sleep efficiency (the amount of time asleep while in bed). Theanine intake was well-tolerated at doses of 400mg a day.
Theanine has been shown in some studies to improve liver health. It does this by increasing glutathione levels (a powerful antioxidant) in hepatocytes (live cells). Glutathione production is important as it enhances our ability to detoxify ingested substances. This is particularly important for people who consume excess alcohol or take pharmaceutical drugs. Theanine was able to counteract the drug-induced losses of glutathione.
In a recent review paper, it was suggested that theanine’s liver-protective effects may be due to its ability to lower the body’s inflammatory response by inducing nitric oxide production and glutathione synthesis. These researchers suggested that theanine may be a natural therapeutic option for liver injury and chronic liver disease.
L-theanine may also have significant positive effects on memory, attention and cognitive ability. In a recent review paper, the researchers reported that evidence suggests that theanine and green tea supports mental and neurological health because of its ability to lower anxiety, improve memory and attention, and enhance brain function. While the researchers suggested that theanine is an important component of green tea, they argued that there were also many other components in green tea that likely contributed to its neurological benefits.
In some studies, the combination of l-theanine and small quantities of caffeine were shown to improve memory and attention. Theanine also had the ability to balance the stimulating effects of caffeine.
Theanine has been demonstrated in some studies to improve athletic performance. This may be due to its ability to relax the body and increase alertness and focus (possibly as a result of its effects on ‘alpha wave’ production in the brain). Being in an alpha wave state is often associated with being ‘in the zone’ or in a ‘flow state’.
In many experimental studies, theanine was able to lower the body’s response to stress. It does this by lowering levels of stress hormones such as cortisol. Excess circulating levels of cortisol can damage many of our organs. Our brain is particularly susceptible to chronic, high levels of cortisol.
The positive effects of theanine on psychological and physiological response to stress may also be due to its ability to block the binding of glutamic acid to glutamate receptors in the brain. Theanine can also reduce several markers of the stress response including blood pressure, heart rate, and salivary immunoglobulins (s-IgA).
As has been summarised in this article, l-theanine has the potential to offer a wide range of beneficial effects in the body. We recommend drinking green tea every day, however, for an increased therapeutic benefit, taking a theanine supplement (with green tea) may be particularly helpful for many people.