What is an elimination diet?
An "elimination diet" typically refers to a trial period in which you take out specific foods for a set period of time to ascertain how they might be affecting your body. They are often used to diagnose various food intolerances or "sensitivities" that may not be detectable through available blood tests or other diagnostic tools. Food challenges are typically done for a period of at least several weeks, as it takes a considerable period of time for all traces of the food to leave your blood stream and other parts of your body. In some cases, your physician may tell you to remove the foods for a period of months or even a year if s/he believes that your body needs time to heal before the foods can be reintroduced. Also, if you or your doctor suspects that more than one food may be causing your symptoms, all suspected foods will likely be eliminated at once, so your body can get to a "baseline" without any of the potentially offending foods before reintroducing them one at a time.
Elimination diets should only be done under the direction of a physician and with the guidance of a registered dietitian, as it is crucial to ensure that you maintain your nutritional intake despite the change to your diet, and there are some conditions, such as celiac disease, that can only be diagnosed while you are still eating the food in question. In addition, if there is any possibility that you may have a food allergy, as opposed to intolerance, it is critical that any food challenges be done at the direction and under the supervision of a licensed allergist.
What happens at the end of the elimination period?
That depends a lot on the purpose, and on what medical conditions your doctor is trying to help you rule out. In general, foods are reintroduced into the diet one at a time at the end of a food challenge - but it is critical that you do this only the supervision and with the approval of your doctor. If your doctor thinks there is a possibility that you may have a food allergy, the food should only be reintroduced in the safety of his or her office, and you should expect to wait there for several hours to ensure that no reaction ensues.
If on the other hand your doctor suspects that you have a food intolerance, you may be instructed to reintroduce the foods in small quantities and only one at a time, with a substantial period of time (typically at least a week) between reintroductions. This is important because for some people and with some foods, it can take several days of exposure before symptoms present themselves. Your goal is to keep as many variables in the dietary equation stable as possible so that you can better correlate your body's reactions to a particular food.
How can you tell if it worked?
Careful observation. This is the most important part of doing a food challenge: you have to pay very close attention to how your body is reacting both during the challenge and once you start reintroducing the foods. We strongly recommend that you use a food journal throughout the process to record everything that you eat, and all of your symptoms -- including digestive complaints, headaches, sinus troubles, rashes, dry skin or eczema, mood swings, "brain fog", etc.
If I don't feel any different during my food challenge, does it mean I can go back to eating my regular foods?
Maybe. As it turns out, the ways our bodies react to a food are as diverse as they are complicated. If you follow your elimination diet rules "to the T" and feel no different, it could mean that the foods you removed are not causing your symptoms. However, be aware that it could also mean that your body does have an adverse reaction to the foods you removed - but that those reactions are being masked by broader reactions to some other inputs (including food, pharmaceuticals and environmental exposures) that you have not yet identified. It is also possible that your body only reacts to the food when in certain combinations or conditions -- for instance, those with a mild form of oral allergy syndrome (an allergic, oral reaction to certain fresh fruits) may only have reactions during high pollen season for a particular tree. Finally, it is also important to note that it is possible to have a food allergy - even one that could result in a life-threatening reaction - without realizing it, so it is very important to consult your physician to confirm that it is safe to reintroduce foods about which you have any suspicions.
I'm breastfeeding my baby and his pediatrician told me to start an elimination diet. Why?
When you are breastfeeding, your body breaks down the foods that you eat and then converts them into molecules with a new chemical composition. Those molecules pass into your blood stream and end up in your breastmilk. Sounds menacing but this process makes breastmilk as nutritionally-diverse as your own diet (one of the many benefits of breastfeeding). However, if your pediatrician suspects that your baby may be having a hard time tolerating a particular food or group of foods, whether due to an allergy, an intolerance or otherwise, she may ask you to remove those foods from your diet long enough to see whether your baby's health improves. Check out our article on food challenges for the breastfeeding mom for 'battle-tested' tips and tricks, along with a special food journal to track both baby's symptoms and your own!
So how do I get started on an elimination diet - and how do I survive it?
Glad you asked. Check out our guides to starting common diet restrictions and poke around this section for worksheets you can use to map out your food challenge plan of attack. Good luck - and try to enjoy the ride!