Internal cleansing is one of the best things you can do for your body. People don't realize how many poisons are ingested everyday. Even healthy fruits and vegetables have chemical poisons in them.
It builds up in our bodies over time which I believe is the cause of many cancers.
The best thing you can do for yourself is to get a cleansing and start eating organically grown foods. Eat a high fiber diet full of grains, fruits, veggies, etc...
From my own experience on the rare occasion that I splurge on something junky (like fast food) it makes me feel really tired and I can literally feel the poisons in my body.
Anyways, you'd be mighty surprised how well or terrible the body works from the diet alone. Oh yes and the liver is one of the most important organs. Well, they're all important, but the liver filters all your blood and cleanses it. Look into some herbs/vitamins that are good for the liver. I know of some, but I forgot what they were called. Also there are some excellent herb teas for the liver. You'd also be surprised at how much herbs and vitamins are over-looked and how much people turn to medicines instead which most of the time help destroy other organs/parts of the body, when it just needs to get the correct nourishment. Just my experience and opinion.
Hope this helps in some way.