Here is my 2 cents worth on this subject of diet.
Dont' overeat. Ones stomach can easily digest the amount of food that one can have in ones hands when you keep them together cupped. .. more food then fitting in your cupped hands will make the stomach have not enough room for the juices to flow and thus congestion is started.
Eat lots of (fresh) fruits and veggies and little oil and nuts and seeds and grains and lecumes. Stay away from meat and minimize dairy especially cheese (hard to digest).
A great tasting liver loving drink: Fresh applejuice with mint leaved juiced along and a teaspoon of olive oil mixed into it and have it on empty stomach either as breakfast or before bed when dinner has been digested... This drink tastes the best and will keep your liver fit.