FIT Testing vs The Elimination Diet

The FIT Test Compared to IgG Food Sensitivity Tests

The goal of eliminating foods from the diet is to identify non-IgE mediated sensitivities or intolerances to foods that are triggering unpleasant symptoms. Symptoms like skin rashes, headaches, asthma, and IBS type symptoms can be related to sensitivities or intolerances, to name a few.

Really, an intolerance is due to a lack of an enzyme. Lactose intolerance is an example. In someone who is lactose intolerant, the body is not producing enough lactase, the enzyme that breaks down the milk sugar lactose. This leads to symptoms like bloating and diarrhea.

A sensitivity can create more general inflammation that may manifest as rashes, headaches, IBS symptoms, acne or others. Identifying sensitivities can help decrease inflammation. These sensitivities may have developed when the gut barrier was inflamed and compromised, allowing undigested food particles to cross the gut barrier.

On the other side of your gut wall, your immune system is strategically placed, protecting you from bacterial pathogens and other potential invaders. A healthy gut barrier does not allow this to happen. But this is how these food sensitivities may develop. If the gut wall is ‘leaky’, it can allow undigested foods to cross the gut barrier, and the immune system may begin to develop and immune response to that food.

When looking for guidance about eliminating foods, you generally have 2 options. You can follow an elimination diet, or you may choose to take a test that measures markers of inflammation linked to foods. While elimination diets aim to eliminate foods that more commonly cause sensitivity or intolerance reactions in people, it is possible that the foods that are not initially eliminated could be causing a problem. The elimination diet may also be a little more overwhelming to take on compared to elimination based on testing.

One of the benefits to an elimination diet is that it eliminates processed junk foods, which has health benefits in and of itself. This alone is beneficial to our health. But because even healthy foods can end up triggering a response in the setting of leaky gut, a food sensitivity test can help identify even healthy foods that may usually be included in an elimination diet.

Food Sensitivity Tests

Food sensitivity tests are designed to identify potential adverse reactions or sensitivities to specific foods or food components. There are several different types of food sensitivity tests, and they are a topic of debate within the medical community.

The FIT Test aims to detect IgG antibodies that are linked to complement protein, a marker of the immune system that is sometimes associated with inflammatory reactions to food. The FIT test is different than other IgG antibody food tests, which may just be reflective of exposure to foods, but not inflammation. The presence of IgG antibodies to a particular food does not necessarily indicate a clinical inflammatory reaction or intolerance.

An important distinction of the FIT test compared to an elimination diet that I see is that even healthy foods like fruits, vegetables, lean proteins, healthy fats, or supplements you may be taking to combat your inflammatory issues could actually be creating inflammation in your body. While the elimination diet seeks to eliminate commonly allergic and inflammatory foods, really any food could end up causing inflammation if it crosses a gut barrier that is leaky and inflamed.

Getting to the root of problems often comes back to our gut.  An inflamed gut will be a poor barrier between you and the outside word, impact digestion, and allow things (like the foods you eat, and bacteria that enter the GI tract) to cross into the body that were never meant to. 

This triggers the immune system, The best way to deal with this fast and effectively is to test so you can see what needs to be pulled out to reduce the inflammatory response while you work on healing the gut.  Any other form of elimination diet is really just a guessing game.  ​

A Sample FIT Test Report

This is what a report looks like (only bigger so you can read it of course). You can see the degree of reaction to different foods there is. Using this, you could eat off of the ‘green’ foods to allow inflammation to go down and hopefully see a resolution of inflammatory symptoms.

During this time, you could work on taking steps to heal the gut barrier. This is best done with the guidance of a health care provider.

You may then choose to slowly add back yellow foods in small amounts to see how you tolerate them.

The nice thing about testing is it removes the guesswork of an elimination diet. Many healthy foods are tested for, foods that though healthy, could still cause inflammation for you.

The Elimination Diet

Keeping an elimination diet and food journal is a method that involves removing specific foods or food groups from your diet for a period of time and then reintroducing them one at a time while carefully monitoring symptoms. This method allows you to observe any adverse reactions firsthand. Keeping a food journal can be helpful in identifying patterns between the foods you consume and any symptoms you experience. This approach is considered the gold standard for diagnosing food sensitivities.

This can be a very difficult process, as the timeframe for removal is generally 1-3 months. During this time, your symtoms of inflammation would in theory calm down. As you reintroduce foods, you watch for a return of symptoms.

A drawback of this method is that you will still be eating foods that could potentially be causing inflammation and contributing to symptoms. The foods that are not eliminated can vary depending on the source of information. The Institute of Functional Medicine’s Elimination Diet is a 3 week version (you could go longer of course) of elimination diet designed to help you identify food triggers of inflammatory reactions or intolerances.

The Institute for Functional Medicine (IFM) elimination diet is a comprehensive approach to identify and manage food sensitivities. It involves temporarily removing specific foods from your diet and then systematically reintroducing them to determine if they trigger any adverse reactions or symptoms. The IFM elimination diet focuses on removing common allergic and inflammatory foods.

IFM’s General Guidelines for Foods to Eliminate During the Initial Phase:

  1. Gluten-containing grains: Wheat, barley, rye, and products made from them, such as bread, pasta, and baked goods.
  2. Dairy products: Milk, cheese, yogurt, and other dairy-based products.
  3. Eggs: Both the egg white and egg yolk.
  4. Soy: Soybeans and soy-based products, including tofu, tempeh, and soy sauce.
  5. Corn: Corn and corn-derived ingredients, such as corn syrup and cornstarch.
  6. Processed and refined sugars: This includes table sugar, high-fructose corn syrup, and other added sugars commonly found in sweets, desserts, and processed foods.
  7. Peanuts: Peanuts and peanut products.
  8. Nightshade vegetables: Tomatoes, potatoes, eggplant, peppers (bell peppers, chili peppers, paprika), and spices derived from peppers.
  9. Shellfish: Shrimp, crab, lobster, and other shellfish.
  10. Citrus fruits: Oranges, lemons, limes, and grapefruits.
  11. Other potential allergenic foods: Tree nuts (such as almonds, walnuts, and cashews), beef, pork, chicken, and processed meats.

During the elimination phase, it is important to carefully read food labels to avoid hidden sources of these ingredients. It is also recommended to focus on whole, unprocessed foods that are less likely to contain hidden allergens or additives.

After a period of elimination, foods are systematically reintroduced one at a time in intervals of ~3 days, while closely monitoring for any adverse reactions or symptoms. This helps identify specific trigger foods and determine individual sensitivities. Inflammatory responses can be delayed, so the timing of reintroduction of foods is spread out.

Foods on the “Can Eat” List of IFM’s Elimination Diet

During the elimination phase, the following foods are suggested to eat:

Animal Proteins:
  • Fish: Halibut, herring, mackerel, salmon, sardines, tuna, etc.
  • Meat: All wild game, buffalo, elk, lamb, venison
  • Poultry: Chicken (skinless), Cornish hen, turkey
Plant Proteins:
  • Bean or mushroom burgers
  • Protein Powders: Hemp, pea, rice protein
  • Bean soups, Dried beans, peas, or lentils (cooked), Vegetarian Refried beans
  • Legume flours
  • Green peas
  • Hummus or other bean dip
Milk Alternatives:
  • Coconut yogurt (cultured coconut milk) and kefir, Almond milk, coconut milk, flaxseed milk, hazelnut, hemp,
Nuts and Seeds:
  • Almonds, Brazil nuts, Cashews, Chia seeds, Coconut, Flaxseed, Hazelnut, Hemp seeds, Nut and seed butters, Pecan Halves, Pine nuts, Pistachios, Pumpkin seeds, Sesame seeds, Sunflower seeds, Walnuts
Fats and Oils:
  • Avocado, Coconut milk, , Olives, black or green, Prepared salad dressing with acceptable oils, Coconut, grapeseed, olive (extra virgin), rice bran, sesame, Almond, avocado, flaxseed, grapeseed, hempseed, high oleic safflower and sunflower, pumpkin, walnut
Non-Starchy Vegetables:
  • Artichoke, Arugula, Asparagus, Bamboo shoots, Bok choy, Broccoli flower, Broccoli, Brussels sprouts, Cabbage, Carrots, Cauliflower, Celeriac root, Celery, Chard/Swiss chard, Chervil, Chives, Cilantro, Cucumbers, Daikon radishes, Eggplant, Endive, Escarole, Fennel, Garlic, Green beans, Greens (beet, collard, dandelion, kale, mustard,turnip), Horseradish, Jicama, Kohlrabi, Leeks, Lettuce – all types, Microgreens, Mushrooms, Okra, Onions, Parsley, Peppers – all types, Radicchio, Radishes, Salsa, Sea vegetables, Scallions, Shallots, Snap peas/snow peas, Spinach, Sprouts – all, Squash (delicata), pumpkin, spaghetti squash, zucchini, Tomat0, Tomato juice, Turnips, Vegetable juice, Vegetables- fermented, Water chestnuts, Watercress
Starchy Vegetables:
  • Acorn squash, Beets, Butternut squash, Plantain,
  • Potato: Purple, red, sweet, white, yellow, Potatoes, mashed (made with non dairy milk)–½ c
  • Root vegetables: Parsnip, rutabaga, Yam
  • Apple, Applesauce, Apricots, Banana, Blackberries, Blueberries, Dried fruit (no sulfites), Figs, Grapes, Grapefruit, Juices – diluted, Kiwi, Kumquats, Lemon, Lime, Melon – all types, Mango, Nectarine, Orange, Papaya, Peach, Pear, Persimmon, Pineapple, Plums, Pomegranate seeds,Prunes, Raisins, Raspberries, Tangerines
  • Amaranth, Brown rice cakes, Buckwheat/Kasha, Crackers (nut, seed, rice)
  • Flours for baking: arrowroot, sorghum, tapioca, Millet, Oats, , Quinoa, Rice, Teff
  • Eliminate: Barley, corn, emmer, farro, kamut, rye, spelt, triticale, wheat
  • Filtered water (with lemon or lime juice), Sparkling/mineral water, Green tea, Fresh juiced fruits/vegetables, Unsweetened nut/seed milks, Unsweetened coconut water

If you suspect that you have a food sensitivity or intolerance, it is best to consult with a healthcare professional who can guide you through the appropriate diagnostic process and help you develop a suitable dietary plan.

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Anne Marie Berggren RDN, MS, CDN, CNSC is a Registered Dietitian with a Master's Degree in Nutrition, training in integrative and functional nutrition, nutrition for mental health, obesity and weight management, is a board certified nutrition support clinician, and an adjunct professor for the Stony Brook Graduate Nutrition Program teaching advanced clinical nutrition.

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