There's no reason to ever think of needing a "cleansing" procedure. Colon "cleansing" can be fatal.
Detoxification is a normal body process.
There is no magic diet.
Dietary problems have simply arisen from the proliferation of too much processed food -- that which is pre-prepared, full of sodium-based preservatives, and may contain fillers and other ingredients which are superfluous and possibly problematic.
The proper diet should include 9 servings of green vegetables per day , only 3 servings of starch (corn, beans, rice, potatoes, bread, & pasta),
4 servings of fresh fruit, and 3 servings of nuts and/or whole grains.
Only those patients diagnosed with Celiac Sprue have a definitive gluten intolerance.
Lactose deficiency is common, and may prohibit many people from tolerating dairy products.
Odd dietary intolerances may include such things as Red Dye #3, or other additives.
Good luck.
Eat healthy.