I replied to your question in the spirituality section. I'll repeat it here:
I think you have to be careful with the claims of some of these herbal teas. The UK has laws prohibiting claims of efficacy unless they're proven in conventional clinical trials which, since many act as tonics would take too long. LOL - doesn't seem to matter than herbalists have been observing the effects for many centuries (including the Japanese with this one for at least a millenium!)
I've had some interest in phytotherapy (herbal medicine) in the past and notice that while these teas are obliged to list contents they rarely list the proportions in comprehensible ways. So you never know quite what's there. Serious medical herbalists would consider dose, frequency, time of day and on. But I can tell you that a couple of teas marketed as "helping you sleep" won't and if they seem to work it's the placebo at work.
You also have to know that these fancy herbal teas are a marketing extravaganza. They're big business and in the absence of regulation are often a con. There's a brilliant article in today's Guardian about a certain sandwich shop being an utter con. (Can't mention the company name without infringing forum rules but it's obvious when you look at the site/newspaper. It's in the "Opinion" section.)
My b/f drinks Matcha Green Tea but goes with the Sainsbury's brand. I'd have serious doubts that the prettily packaged Pukka brand actually does enhance or restore magical powers. They certainly haven't with him!! if he had any in the first instance. Then again he has a somewhat bigoted block against "magick" or "magick". That's his business. However, a guy at the local magic shop drinks it and believes it keeps his blood pressure down.
One chemical thing is for certain - it contains catechins, powerful anti-oxydents that fight cancer and heart disease. It also contains caffein so if you have sleep troubles don't drink it late in the evening. There was a good article about it in The Telegraph
a couple of years ago. I bookmarked it so here it is if you're interested. It briefly goes into its Japanese history and a warning about pollution.
As for posology, there seems a general opinion that one cup or one shot per day is enough. For sure, none of these teas can do harm (other than through pollution) so drink away and enjoy!