I have not tried this but the logic holds good.
Blend 1 tablespoon cumin and put in saucepan,skin ginger and grate a tablespoon and put into the same saucepan, add a litre of water and bring to boil, cook for 5 minutes, let cool then strain into a glass jar, add to the mix the juice of one lemon and stir. 30 minutes before each meal consume 50 ml of this mix.