Systematically reintroducing foods from one food group at a time is a great way to see if they cause any problems.
Continue a daily eating plan similar to the 21-Day Cleanse (days 11-21). You will reintroduce one food from a food group at a time and then decide how it makes you feel and if there is a reaction.
If choosing to reintroduce some foods/food groups eliminated during 21-Day Cleanse, here are some guidelines to follow:
Choose whole grains, instead of refined grains, which have most of their nutrients removed. Eat a healthy range of whole grains that includes quinoa, spelt, bulgur, steel-cut oatmeal, brown rice, and barley.
These foods are nutritionally dense and provide a host of nutrient components like calcium and protein. Note: Dairy foods can be very mucus producing.
Nuts & Seeds (Raw)
Nuts and seeds can supply necessary oils. Nuts are concentrated sources of fuel, so portion control is important. A handful a day does the trick for most people.
Shellfish, like shrimp and mussels, can add important nutrients like protein and iodine.
Eggs provide an important source of protein, iron, and B vitamins. Possibly reintroduce eggs after grains. Hard boil an egg and eat it at breakfast or as a snack.
A note about allergies and food intolerances.
An allergic reaction happens when the body's immune system mistakes a part of a food for something harmful. Foods that cause the most problems for adults are peanuts, tree nuts (like walnuts or almonds), fish, and shellfish. Any food can cause an allergy but some other "highly" allergenic foods are: milk, eggs, soy products, and wheat. Allergic reactions usually happen fast—minutes to hours after eating the allergen.
Food intolerance is the digestive system's response to the part of a food or additive that it can't process, or that causes irritation. This could be from a biological cause, or it could be from an additive that is poorly absorbed by the gut. The body's response to food intolerance is usually based on portion: a small amount provokes a small reaction; a large portion provokes a larger reaction. The time frame for problems is longer too. The body's reaction to food intolerance can take place immediately, or over a few days.