Liver can regenerate by itself. It means that even if a person donates half a liver, it will grow back to normal size within few months. Liver is very resilinet and can develop new cells, but prolonged alcohol misuse (drinking too much) over many years can reduce its ability to regenerate.
Usually, the upper limit of ALT is 35 - 40 U/L. Moderate increase in ALT (such as 70 U/L) is seen in chronic hepatitis, chronic obstruction of bile ducts, heart damage, alcohol abuse, liver tumor, skeletal muscle damage. In any acute liver conditions, ALT is much more elevated.
Banana are good source of potassium, vitamin C, vitamin B6 and dietary fibers which is good for an over-all good health including liver. As banana is also a rich source of sugars and carbohydrates, it is better to consume in moderation.