The science-based food intolerance resource since 2013

Expert Q&A with Dr. Rob Loblay – Misconceptions about food intolerance

The Allergy Unit at the Royal Prince Alfred Hospital in Australia has been a pioneer in food intolerance research. The unit is directed by Dr. Robert Loblay, a clinical immunologist who has spent the better part of his career helping patients suffering from food allergy, food intolerance, and celiac disease. Working with Head Dietitian Anne Swain (whose doctoral thesis documents the research behind the well-known RPAH Elimination Diet) and a team of doctors and dietitians, Dr. Loblay has laid out the basic ideas of food intolerance, namely that reactions are dose dependent, not limited to one type of food, and most easily diagnosed after a suitably restrictive elimination diet.

Today we’ll ask Dr. Loblay some questions that address common misconceptions about food intolerance.

Q: Thank you, Dr. Loblay, for spending time with us. Let’s start with a few quick questions. First off, does food intolerance cause weight gain?

A: No.

Q: Can you become intolerant to a food if you eat it too often?

A: No. But reactions are dose-dependent, so if you have a tendency to intolerances, eating them more often might provoke symptoms and bring them to attention.

For foods eaten at subthreshold levels, we generally advise: “Not too much…Not too often…”

Q: Is there a cure for food intolerance? Are there any supplements or enzymes that people can take to prevent food intolerance reactions?

A: No, and No.

Q: As both an immunologist and a food intolerance expert, what is your opinion on the ‘delayed allergies’ (sometimes referred to as food intolerance) that are supposed to be picked up by IgG blood tests? Do these tests provide any meaningful results?

A: We have not found any correlation between challenge results and IgG blood tests, so we don’t think they’re helpful. IgG antibodies to food are simply a marker of exposure, and IgG4 subclass levels correlate with the development of clinical tolerance in people who have outgrown their IgE mediated food allergies. This has nothing to do with intolerances, in my opinion.

Q: In the time since the RPAH Allergy Clinic began looking at food intolerance, histamine intolerance has become a hot topic. Do you test for histamine intolerance specifically? In real-life meal planning, does the distinction between histamine and other biogenic amines make a difference?

A: ‘Histamine intolerance’ is a misnomer, popularized in Europe, used to describe people who get certain symptoms in response to foods containing biogenic amines. They fail to recognize that (1) such people are usually also sensitive to one of more other substances, and (2) that their skin responses to a standard prick test with histamine (the positive control used in allergy skin tests) are perfectly normal.

We find that our standard challenge tests with tyramine and phenyl ethylamine (done with purified chemicals and/or selected foods) are sufficient for identifying people with intolerance to biogenic amines and to guide real-life meal planning.

Q: In your experience, do people with food intolerance usually have some inkling that their symptoms are related to food? How many are truly surprised to find that they have food intolerance?

A: About half the people we see have an ‘inkling’ that food is involved. The rest are unaware and many are ‘truly surprised’. There are 2 likely reasons: (1) natural chemical intake accumulates from many different food sources which vary from day-to-day, so individual foods do not stand out; (2) reactions can be delayed by many hours or a day or more, so the cause-effect relationship is often not obvious. When people on the elimination diet are tested with carefully selected foods (grouped according to chemical content), some only begin reacting after 4-5 days – for that reason our open food challenge protocol goes for up to 7 days for each group.

And in those who do suspect foods or ingredients, they often incriminate the wrong ones.

Q: A lot of Internet advice tells people that they can check for food intolerance by avoiding a food for a week or two – most often, the ‘food’ in question is gluten. Are there any problems with doing this?

A: People who eliminate gluten usually also unknowingly cut back on their intake of other things in their diet which are high in natural chemicals, e.g. ham, cheese, tomato and spreads on sandwiches, burgers, etc; tomato-based sauces and spices with pasta; and all the things that go on top of a pizza base. As a result they can mistakenly attribute any clinical improvement to the elimination of gluten, overlooking all the other changes they’ve made. Proof of the pudding is always in the eating – systematic challenges – but it needs to be done on a suitable low-chemical baseline diet to get reliable answers.

People can be misled in much the same way when they go on other diets such as ‘sugar-free’, ‘dairy-free’, ‘yeast-free’ etc. Hence the popularity of any number of other diet approaches, as well as various dodgy testing methods. Any major change in one aspect of a person’s diet inevitably alters their intake of various food chemicals to which they may be sensitive, so a degree of clinical improvement is common. In other words, some people can get the right answer for the wrong reasons. For people with mild intolerances, such changes may be sufficient to get their symptoms under control. However for the more severe/persistent intolerances, improvement is usually temporary, and more rigorous investigation is needed to get to the bottom of their problem.

Q: Many adults claim to be soy intolerant, and there is some talk on the Internet that people with gluten sensitivity will also be sensitive to soy. Is there anything behind this?

A: Some people with celiac disease and persistent symptoms despite sticking to their gluten free diet don’t tolerate soy. [These findings were published by Dr. Loblay and colleagues in 1999.].

Q: But outside of celiac disease and perhaps gluten intolerance, do you find that soy intolerance is something common in adults?

A: In people with irritable bowel symptoms, we eliminate wheat, soy, and milk in addition to natural and added chemicals initially; then we challenge with each in turn. People vary in their pattern of sensitivities, so at the end of the process each is prescribed an individualized diet based on their challenge responses. There is no single diet that suits everybody.

Soy is not really an issue in people with non-GI symptoms.

Thank you, Dr. Loblay.

If that you suspect that you have food intolerance, first see your doctor to rule out food allergies and other potential causes for your symptoms. Food intolerance is diagnosed through an elimination diet and food challenges, and it is best done with the help of a registered dietitian. Contact the professional dietitics association in your country to find a dietitian who is familiar with food intolerance or visit the directory of member dietitians on their website.