I think it's time we talk a little bit about basic liver anatomy and physiology.
Here's your basic diagram of the liver pulled from the internet:
Blood from the digestive organs flows through that portal vein and carries nutrients, by-products of medications/vitamins/herbal supplements, and by-products of metabolism that would be toxic if allowed to remain in the bloodstream. Once these substances reach the liver cells they are altered/detoxified and then either stored or passed back into the blood or released to the bowel to be eliminated. For example, whenever we eat a protein-rich food like an egg, the protein is broken down into amino acids in the stomach and intestine, then those amino acids flow down the portal vein to the liver, then in the liver the amino acids are further broken down and either stored in the liver as glycogen or sent out to the bloodstream. That whole process then forms ammonia (toxic) which the
liver converts to urea (less toxic) to be eliminated by the kidneys.
And that is a really, really basic overview. For a more extensive review on the liver's role in blood clotting, breaking down damaged blood cells, bile production for fat breakdown/absorption, blood glucose regulation, vitamin storage, cholesterol synthesis, hormonal modification, etc you can go here: National Liver Foundation.
So, your liver is performing it's many, many important functions, including detoxification, 24/7. It will do this without you eating brocolli or drinking green tea. To say that these foods/beverages cleanse the liver implies that there are substances just hanging around in between the liver cells just waiting for a person to eat cauliflower or drink green tea so that the liver can actually do its job. Fortunately your liver will keep working just fine whether or not you drink green tea, etc. Of course, these foods provide other vitamins, minerals, that are important for our body to function, but they are not "liver sweepers."
Unfortunately, the liver, like any other organ, can become diseased, in my practice I usually see alcoholic liver disease and hepatitis C, but those are only two of the many different diseases out there. When someone has a diseased liver, the only things that can be done to preserve liver function is to remove the offending agent (e.g. stopping all alcohol), possibly starting anti-inflammatories like prednisone or other agents, and in some cases a liver transplant a la Larry Hagman. I would love to tell you that drinking green tea, etc would help the remaining part of the liver "work harder," but that simply isn't true.
Take home message--Eat your fruits and vegetables to get your vitamins without loading up on calories. Don't expect cleansing from an organ doing just fine though (or get redemption from your years of drinking too much).