Understanding Food Sensitivities
by Dr. Evan McCarvill, ND
PO Box 3343
Melfort, Saskatchewan, S0E1A0
In my line of work, many patients come with chronic conditions that affect their quality of life, for which there has been little to no “standard” solution. Symptoms such as slowly worsening fatigue, weight gain, skin rashes, headaches, and joint pain are common complaints. Often, these symptoms are unexplained in conventional circles in terms of their root causes, and are either unmanageable or are inadequately managed by drug treatments. While drug treatments are essential in many circumstances, all too often for these chronic symptoms, they are not the final or even the best answer.
In my experience, a significant proportion of these cases are helped by investigating and addressing the possibility of chronic low-level reactions to certain foods in their diet, which may have gone unrecognized for years. These reactions may have developed into a set of symptoms that often have been accepted as normal, until it gets bad enough to complain about. These are hidden food sensitivities, often mistakenly referred to as “hidden food allergies.”
Different Kinds of Food Reactions
Firstly, there are a couple of different kinds of food reactions that can be mistaken for genuine hidden food sensitivities. The first is what I will call simply a “food intolerance.” Sorry if this feels like too many distinctions to keep track of, but this is why there is so often confusion. A food intolerance is simply a food reaction that is not actually mediated by the immune system. Rather, it is the result of a chemical, enzymatic, or functional digestive problem. A good example of this is lactose intolerance, where people can react with bloating and discomfort when consuming milk and other dairy products. This is due to a lack of the enzyme lactase, which normally properly digests lactose, a sugar found in dairy. There can be similar reactions to other poorly digested carbohydrates that ferment in the gut, such as from certain fruit, beans, and wheat.  While these may be mistaken for hidden food sensitivities, they would not result in any immune or antibody response.
The second kind of food reaction that can be mistaken for a hidden food sensitivity is a true food allergy, which is a well-established phenomenon in medicine and is distinct in how it manifests. For example, food allergies to dairy or to peanuts trigger an immediate reaction, resulting in sudden symptoms such as swollen throat, mucous production, rashes, puffy eyes, etc. In severe cases, it can even result in anaphylactic shock, which can be life-threatening. Individuals with true food allergies need to be especially careful to avoid exposure, to prevent these acute symptoms, and it is usually not difficult to discern early on in life just what the food allergy is. A food allergy occurs by means of the IgE antibody, which triggers the release of histamines from white blood cells called basophils. This is called a type 1 immune reaction.
True Hidden Food Sensitivities
Hidden food sensitivities are different. They tend to manifest more slowly over a period of days or even weeks, due to exposure to foods you may be eating repeatedly in that period, with no apparent problem in the moment. This is why they are “hidden,” because they are more difficult to discern, due to their slower-to-manifest, and more systemic and nonspecific symptoms. These reactions are mediated by a different antibody, the IgG antibody, which is more typically involved in the immune system’s response to pathogens such as viruses and bacteria. This is called a type 3 immune reaction. Many people experience digestive symptoms, such as irritable bowel; others experience arthritic joint pain, migraines, skin rashes, or even just general unexplained fatigue.
This occurs because IgG antibodies in the blood bind with antigenic (reactive) food molecules and create large clumpy hybrid molecules called complexes. These are normally detected by white blood cells, called macrophages, which swallow them up and break them down. However, if there are too many complexes for the macrophages to dispose of, these excess particles can settle in certain tissues, causing inflammation.  For example, they can settle in the joint capsules of one’s hands or knees, and the resulting inflammation can contribute to joint pain. Alternatively, the skin might end up serving as an alternative “detox” organ for these complexes to be expelled through, and the resulting inflammation in the skin can manifest as dermatitis; acne, rashes, or even psoriasis.
Hidden food sensitivities are not a disease, but may play a role in causing disease or worsening existing symptoms. If hidden food sensitivities can be identified, and the offending foods eliminated from the diet, severeal different conditions can improve, including:
- Irritable Bowel Syndrome
- Migraine Headaches
- Excessive weight
- Joint pain
- Skin conditions
A large study was conducted by the British Allergy Foundation in 2007.  It looked at patients who had received IgG-sensitivity blood tests within the previous three months. The goal of the study was to find out whether removing certain foods from their diets, that had been highlighted as “reactive” by the IgG blood test, would improve these patients’ symptoms. Of the more than 5,000 participants, over 70% rigorously followed the test results and eliminated their reactive foods. Among these patients, improvements in a variety of symptoms were reported, mostly within the first three weeks. Furthermore, symptoms would reliably return upon reintroduction of the foods afterwards.
The improved symptoms varied by body system and included joint pain, breathing issues, digestion, skin conditions, neurological conditions, and even psychological conditions. Interestingly, the symptoms that showed the greatest improvement were digestive issues, such as irritable bowel syndrome, as well as psychological conditions, such as anxiety and depression.
Other published research provides evidence for the benefit of removing certain IgGreactive foods from the diet, in cases of heartburn/indigestion,  Sjögren’s syndrome,  and Crohn’s disease. 
There are a couple of ways to identify whether your symptoms may be related to a hidden food sensitivity. The first is the cheaper, but the longer and more disciplined method. It is called the “elimination diet,” where a substantial list of commonly reactive foods are simultaneously eliminated from the diet for a period of at least six weeks. During this time, only those foods most unlikely to cause a reaction, from each food group, should be consumed. Consult with your naturopathic doctor or other health-care provider to ensure adequate nutrition during these six weeks. During this time, there should be a radical improvement, if not a complete resolution of symptoms. Once the six weeks have passed, return to the list of foods you eliminated, and reintroduce them one at a time. For example, if you are reintroducing potatoes, eat potatoes for two out of your three meals a day, for three days in a row. If there is no return of symptoms in this time, potatoes can be safely reincluded in your diet, and you can move on to the next food. If there is a reaction, then remove the food again, give a few days to recover, keep it removed from the diet as a positive result, and move on to the next food. Through this rather slow but methodical process of elimination, one or multiple hidden food sensitivities can be identified.
The advantage of the elimination diet approach is that it relies not on antibody titers on a lab report, which can sometimes reflect physical reactions or not, but rather on direct observation of clinical symptoms. Some clinicians consider this to be the superior approach for this reason. In addition, food reactions that are not necessarily immunemediated will also be picked up by this method. This method is best applied when symptoms can respond fairly quickly to changes in antigen stimuli, such as digestive symptoms, energy levels, joint pains, or skin reactions. However, some people may have food-sensitivity connections to such symptoms as high blood pressure or bimonthly migraine attacks. It may not be easy to tell if these symptoms are returning or not, in a matter of only three short days of reintroduction. This is where direct measurement of IgG titers can be useful.
IgG Blood Test
The second way to identify potential hidden food sensitivities is the more expensive, but much quicker and more convenient method. It involves providing a sample of capillary blood to be sent to a laboratory, where the IgG antibodies in the sample are combined with dozens of different food antigens; usually, a much wider variety than can usually be covered by an elimination diet. Foods that demonstrate an IgG reaction above a certain threshold are highlighted as potential hidden food sensitivities. This can significantly reduce the list of potential food culprits, and a more reasonable elimination diet can then be employed to more concretely define what foods need to be avoided. There is some individual variability in terms of the kind of foods that react, and the severity and nature of the resulting symptoms. So there is usually some experimentation to do, on a case-by-case basis. But an IgG blood test can be a very helpful starting point.
Try it Yourself
If you have been struggling with some chronic unexplained symptom, that you may have learned to live with until now, or which you need ongoing drug treatment to manage, and would like to change that, then perhaps the possibility of a hidden food sensitivity is worth exploring. Talk to your naturopathic doctor about the appropriateness of an elimination diet for your case, and how to execute it safely and effectively. Discuss the feasibility of an IgG blood test to detect your likely sensitivities, or to at least narrow the list of possibilities. You may gain new insights for your diet that will enhance your quality of life for the long-term afterward.