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Saturday, October 10, 2009

"Food Detective" Home Allergy Test Flunks

Intolerances are not the same as allergies. Lactose intolerance is defined as having symptoms because of the body's inability to digest the lactose sugar in milk. A milk allergy is caused by antibodies that react to the proteins in dairy products. They are totally different. I know that. If you've been reading this blog from more than about five minutes you know that.

And the makers of the "Food Detective™, the world’s first food intolerance self test" kit know that. They have a whole page devoted to the difference.

And yet they keep calling the Food Detective a food intolerance kit. It isn't. It tests for protein antibody reactions. Not the same.

Why make a big deal of this? Many people, especially in the UK where the Food Detective is based, confuse the terms or even use them interchangeably. But I'm cynical. And as their own food intolerance page says, as many as 45% of the population of the UK may have food intolerances, but only 2.5% have food allergies. Now which set would you rather your marketing department pitch your product to?

And that's assuming that the product can possibly work as claimed. You take a mere pinprick of blood and put it into the tiny test tube in the kit. Pour on some developer and in 40 minutes you'll know if you have allergies to any of the following:

Corn, Durum Wheat, Gluten, Oats, Rice, Rye, Wheat.

Nuts & Beans
Almond, Brazil Nut, Cashew, Cocoa Bean, Peanut, Legume Mix (pea, lentil, haricot),
Soya Bean, Walnut.

Beef, Chicken, Lamb, Pork.

Freshwater Fish Mix (salmon, trout), Shellfish Mix (shrimp, prawn, crab, lobster, mussel), Tuna, White Fish Mix (haddock, cod, plaice)

Broccoli, Cabbage, Carrot, Celery, Cucumber, Leek, Peppers (red, green, yellow), Potato.

Apple, Blackcurrant, Grapefruit, Melon Mix (cantaloupe, water melon), Olive, Orange & Lemon, Strawberry, Tomato

Egg (whole), Cow's Milk, Garlic, Ginger, Mushroom, Tea, Yeast

That's amazing. Too good to be true? Well, I'm always a skeptic.

You see, the makers of Food Detective are Cambridge Nutritional Sciences CNS), which has done this testing for several years if you mail them a sample of your blood. And the British newspapers have not been kind to CNS.

In You and Yours on Which? Investigation into Food Intolerance Tests, Dr. Mike Walker of CNS reveals that the tests don't test for IgE, the antibody that causes true allergies. It tests for IgG, an antibody which causes hypersensitivities. Some researchers do lump the various antibody reactions together as allergies, some don't. All, to my knowledge, agree that only IgE reactions cause the anaphylactic reactions that are the ones to take most seriously.

Tests on similar testing kits have a large fail sign pasted on them. As Jenny Hope reported in The Daily Mail:
The tests found a total of 183 intolerances, even though the researchers had just one medically confirmed allergy and one already recognized food intolerance between them.

Different test results were produced from identical blood and hair samples sent to the same company under different names. There was little or no overlap of test results from different companies for the same researcher.

A panel of medical specialists and a dietician concluded that none of the tests, which cost between £45 and £275, had ' diagnostic value' for genuine allergies or intolerances.

It's nice to think that one tiny pinprick of blood can tell you what foods not to eat. It's also too good to be true.

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PeteConry said...

Your point about the confusion of IgE and IgG is reasonable, but the conclusion that it's down to marketing people probably isn't. Because IgG antibodies are usually helpful - they are our defence against infection - the medical convention is that the word "allergy" shouln't be used in this context.

Instead, the general (and indequate) term "food intolerance" is normally used. Which, as you say, also includes lactose intolerance or fructose intolerance. In Northern Europe, lactose intolerance is only about 2% of the population (versus the majority of people in most parts of the world), so the group of intolerances - or "IgG-mediated allergic reactions" if you prefer - measured by the Food Detective is much bigger, and a lot closer to the 40% figure you mention, than lactose intolerance.

Anonymous said...

Anaphylactic reactions are caused by IgM antibodies, not IgE or IgG.

Steve Carper said...

That's simply wrong. Anaphylactic reactions are caused by the IgE antibodies. That is, in fact, their usual definition.

Of the nine different immunoglobulins (Ig) in man --- IgM, IgG1 to IgG4, IgE, IgA1 and IgA2, and IgD --- only IgE is associated with atopy and anaphylaxis. It's a very special molecule.

That definition may be overly broad for technical use, but it is what is current.

Anaphylaxis has no universally accepted clinical definition. The traditional nomenclature for anaphylaxis reserves the term anaphylactic for IgE-dependent reactions and the term anaphylactoid for IgE-independent events, which are clinically indistinguishable. The World Allergy Organization, which is an international umbrella organization representing more than 70 national and regional professional societies dedicated to allergy and clinical immunology, has recommended replacing this terminology with immunologic (IgE-mediated and non-IgE-mediated [eg, IgG and immune complex complement-mediated]) and non-immunologic anaphylaxis.

Whatever term the profession decides for technical usage, it's clear that it will involve IgE-mediated reactions, and not IgM.