The L-Theanine craze
What is L-Theanine and should we all be taking it?
L-Theanine is an amino acid that helps you feel calm & less anxious. It’s good for blood pressure and all sorts of other things.
I would always be cautious to take a supplement (especially as its a new 'fad' rather than a long term tried and tested thing), and as I always say, instead try and get it from food. In this case, tea! Things exist in nature in combinations on purpose, other items in the tea for example could be what you need to absorb the L-theanine properly.
Normal black and green tea are both remedies for diarrhoea. They help poor digestion from acute or inflammation in the digestive tract (like IBD), and also help clear herpes (cold sore) outbreaks when you apply soaked tea leaves to the affected area.
In general tea also helps with flatulence, is cooling, relieves thirst and acts as a diuretic. Tea also cuts the fats & oils from rich meals. For these uses, the tea should be slowly infused, for the aforementioned ailments, small sips of stronger tea is better.
Green and black tea have it and if you don't love the little bit of caffeine in black tea for the evening then oolong tea can be drunk in the late afternoon.
In summary, drink tea don't take supplements. When its new, always be cautious.