I need a natural growth and appetite supplement or drink for my 8year old whos slightly underweight?

It doesn't come in: Doesn't come in a pill. It's called happiness, and is created inside the child or passed to the child by those around him... assuming happiness is contagious. Kids will eat as much as they will eat if they are happy and hungry. Kids who "don't eat" either don't need the extra food, have tummy disorders such as reflux, have psychological issues such as stress or anxiety, etc... His doctor can help.