Allergy, intolerance or sensitivity?
These three words get used as if they mean the same thing. They don’t, and the difference matters.
Food allergy: an immune reaction driven by an antibody called immunoglobulin E (IgE). It happens within minutes to a couple of hours of eating, every time, and ranges from hives and swollen lips to breathing problems and, at worst, anaphylaxis.
Food intolerance: no immune system involved. The classic example is lactose. If your gut produces little of the enzyme lactase, milk sugar passes on undigested and causes bloating or loose stools. Unpleasant, but not dangerous.
Food sensitivity: a popular term on test reports and social media, with no agreed medical definition. That makes it impossible to prove or rule out, which is part of the problem.
One in six believe, one in a hundred react
How big is the gap? A systematic review of European studies, carried out for the European Academy of Allergy and Clinical Immunology (EAACI), pooled data from over 50 studies to find out. The results:
- 17,3% of people said they had had a food allergy at some point in their lives.
- 5,9% said they had one now.
- 10,1% were sensitised to a food in specific IgE blood tests, and 2,7% in skin prick tests.
- Only 0,9% actually reacted when given the food in a food challenge.
A food challenge means eating the suspected food under medical supervision, ideally without knowing whether you’re getting the real thing or a placebo. It’s the gold standard for diagnosis.
Notice the middle step too. Being sensitised means your immune system recognises a food protein, but that doesn’t mean you’ll react to it.
Put another way: line up 100 riders at the start of a sportive, and around 17 will believe they’ve had a food allergy. About 1 could prove it.
Why the last meal gets the blame
So, what’s going on with the other 16? Part of the answer is that gut symptoms are really common. Bloating, cramps and loose stools come and go in perfectly healthy people. You eat several times a day, so there’s always a recent suspect. And memory plays tricks: the bad days that fit your theory stick, while the days you ate the same food and felt fine are forgotten.
Cyclists have extra variables. Hard efforts divert blood away from the gut, and what you eat and drink around training matters too. We’ll take a closer look at this in the next part of this series.
Some foods really do cause symptoms, just not through the immune system. Lactose is one. FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are another, found in foods such as wheat, onions, legumes and some fruits. They’re poorly absorbed in the small intestine, so your gut bacteria ferment them further down. The bacteria get a feast, and you get the gas.
The power of expectation
There’s another important factor. In a study from Monash University, 37 people with irritable bowel syndrome who believed they were sensitive to gluten first spent 2 weeks on a low-FODMAP diet. Their symptoms improved.
Then the researchers added either gluten or whey protein to their diets, without anyone knowing which they were getting. Symptoms worsened again, but to a similar degree with whey as with gluten. A gluten-specific effect showed up in only 8% of participants.
This is the nocebo effect, similar to placebo but negative. If you’re convinced a food will make you feel bad, eating it can genuinely produce symptoms, and avoiding it can bring genuine relief, whatever the food contains.
The message for cyclists is clear: Your symptoms are real. But feeling worse after a food doesn’t make you allergic to it. In the next article, we’ll look at the home blood tests that promise to identify your problem foods, and what they actually measure.