For centuries, Chinese and Japanese monks drank tea before their meditations. Tea helped them stay alert and focused for extended time periods. Recently, scientists started examining tea’s chemical structure, looking for a logical explanation. Researchers found 
that drinking 1-4 cups of tea throughout the day improves alertness, focus, and mental performance. These benefits are attributed to two chemicals – caffeine and l’theanine. Multiple studies have explored the effects of l’theanine and caffeine on the mind and body. But what is l’theanine?
L’theanine is an amino acid found almost exclusively in tea leaves. It is 1-2% of the leaf’s dry weight, which is about 25-60 mg per 200 ml of liquid tea. According to WebMD.com, “People use theanine for treating anxiety and high blood pressure, for preventing Alzheimer’s disease, and for making cancer drugs more effective.” l’theanine has been shown to increase alpha-wave activity, implying increased tranquility. A study published in Nutrition Reviews 1998 stated that it takes about 30 minutes for l’theanine to cross the blood / brain barrier, reaching maximal levels five hours after ingestion. Another study investigated the effects of l’theanine and caffeine interactions.
Unilever, Lipton Tea’s brand distributor, commissioned a study at the Nathan S. Kline Institute for Psychiatric Research, investigating the connection between caffeine and l’theanine. The study had 16 participants. Participants drank one of the four: plain water, water with 100 mg of l’theanine, water with 60 mg of caffeine, or water with both. Participants completed an activity that tested their alertness and attentiveness. Researchers found accuracy improved dramatically when the participants ingested both additives as opposed to a single additive. Participants tended to focus throughout the three hours of testing. Caffeine alone will give you a brief burst of energy, but you will crash.
Jane Bryan, of the University of South Australia, compared over 10 psychological studies, which looked at the effects of l’theanine and caffeine on brain activity. Each study used human participants and experimental trials that administered caffeine, L’theanine, or both additives. Bryan explained that you begin to feel the effects of caffeine and l’theanine after about 30 minutes, but it takes about 5 hours to feel the maximium effects. Each cup of tea contains about 35 mg of caffeine and 25-60 mg of L’theanine. Bryan concluded, “The authors suggest that the combination of both caffeine and L’theanine at low doses interact to produce a better ability to focus attention, with improvement of both speed and accuracy.” This conclusion confirms what Buddhist monks have known for centuries.
Now we know the unique combination of L’theanine and caffeine is responsible for the alertness and focus monks feel during meditation. Their alertness is on an upward trend for up to 5 hours, which explains the prolonged ability to focus. Caffeine stimulates the mind and body, while L’theanine stimulates alpha brain activity. Drinking a few cups of green tea throughout the day will help you maintain your alertness and focus.
This is such an important message for people to understand. It’s what makes tea drinking so much superior to coffee. As you point out – NO crash just long, sustained, calm alertness.
This is *exactly* why I switched from coffee to tea all those years ago.. The ‘wired’ feeling one gets from coffee may be useful in the short-term… but over time the stress on your body just isn’t worth it.
I’ll take a relaxed, focused state over a mad rush of energy any day!
Fascinating article, Tiffany!
Does green tea have an effect on coumadin meds ?
I would encourage you to speak with your medical doctor about this question. I’m not a physican and I don’t know about the impact that green tea would have on blood thinning, if any. Best to always be safe. If your doctor is uncertain, then I could seek information from a medical herbalist. Please let us know what you’ve found out.