I grew up with British grandparents who probably averaged 5-7 cups of tea a day- a routine I picked up sometime around the age of 10. I never considered though that tea could be good for me! We’ve written quite extensively on tea and it’s many proposed benefits, but despite all the pseudoscience about tea curing cancer or keeping you young, it is worth it to note the compounds that are found in teas, that are truly helpful to humans.
L-theanine is an amino acid analogue to glutamate, the most abundant excitatory neurotransmitter in the brain, and is also responsible for the umami taste found in green tea. Some studies have found that it favourably affects stress responses, memory and attention span, with special research attention being payed to the positive effects on cognition that substances containing both theanine and caffeine have. The catechins can be found in tea and are antioxidants, and have been found to help lower blood pressure (especially when systolic pressure are over 130 mm Hg), and may help regulate blood flow in humans. A recent study found that catechins may favourably effect cholesterol as well.
As with everything however, it doesn’t matter how helpful a compound is if there isn’t a relevant dose of it present. A 2011 study looked at the L-theanine in teas, and found black teas to contain the most, ~24 mg/200 ml, and green tea the least, ~8 mg/200 ml. This study also found that adding milk to tea caused a noticeably decrease in theanine content, and that in general, the longer you brewed your tea, the more theanine it contained. Most supplement bottles seem to recommend taking 200-400 mg per day, or the equivalent of about 8-16 cups of black tea, or 25-50 cups of green tea. That’s a lot of tea, even for me
If you do want to get the most out of your tea however, you’re in luck! A lot of research has looked at the most effective way to extracting theanine and catechins from tea leaves, but the results are… interesting. A 2011 study found that steeping quite a fine grind of green tea leaves in 80 °C water for 30 minutes, using a 20:1 ml/g water to tea ratio yielded the best results. For reference, most cups of tea are made with about 200 ml of water to 2 g of tea- a 100:1 ml/g ratio. I just don’t know that I want to drink a cup of tea that strong, even for nutritional benefits.
A 2012 study suggested a slightly different method for tea compounds- microwaving. By placing a tea bag in boiling water for 30 seconds, then microwaving it for 1 minute, the authors were able to improve the extraction of catechins by 18%, though the theanine extraction was not affected. If you’re anything like me however, your heart skipped a beat when I mentioned microwaving tea. Let me assure you however, having tried the described brewing method, it’s not so bad. Not as good an old-fashioned steeping, but not terrible. Keep in mind though, that even in this improved method, only 61 mg of catechins per g of tea, and 10 mg of theanine per g of tea are being extracted. In cup of tea made with 2 g of leaves, that’s ~ 122 mg of catechins and 20 mg of theanine per cup. So if you’re hoping to use tea instead of supplements, I’d still recommend black varieties, and maybe sticking close to a bathroom (my Nana always said, tea goes right through you).