“And this is just the sort of thing the internet is going to have a lot of misinformation about.” - Joel Hammond, Santa Clarita Diet
Now, before you all go running to watch Santa Clarita Diet thinking it’s a documentary or something, it’s a Netflix show about, well, finding yourself unable to eat pretty much anything except a very specific food group - people. So be forewarned, it can be graphic. But awesome. And it highlights what I want to say about the difference between a food allergy and a food intolerance quite well. Drew Barrymore’s character, Sheila Hammond, doesn’t become allergic to eating food, she becomes intolerant to eating anything other than people. She won’t die if she eats a snail or raw hamburger, but she doesn’t thrive unless she’s eating people. It’s a subtle difference, but a necessary one for the best health and wellbeing of the character. One that becomes so overwhelmingly important that she and her husband buy a dedicated ‘meat freezer’ to store her new dietary staples in.
A food allergy is a specific immune system response to a food. It can be immunoglobulin E (IgE) mediated (produce your typical food allergy symptoms - anaphylaxis, hives, wheezing), or non-IgE mediated (less well understood, tend to cause gastrointestinal, respiratory and cutaneous symptoms on oral challenge, but don’t produce a positive result on the skin prick allergy test). IgA-mediated and IgG-mediated reactions are typically included in the non-IgE mediated category, but there’s a lot still unknown about these reactions as they are typically delayed onset - often hours to days after the ingestion of the offending food. Either way, it’s the immune system responding to an antigen from the food.
A food intolerance is something different. It’s typically a metabolic disorder and causes a reaction due to a lack of an appropriate enzyme required to digest a particular component of a food at the proper stage of the digestive process. For instance, lactose intolerance - it’s not an immune system reaction. It’s a reaction caused by the inability of the body to break down lactose, a sugar found in milk because that individual doesn’t have the required enzyme, lactase. Because this sugar doesn’t get broken down in the small intestine, it makes its way to the colon in an undigested form, where the bacteria in the colon have a feeding frenzy and produce all kinds of methane gas as a byproduct of that feeding frenzy. The result of this process produces uncomfortable symptoms of gas, bloating, diarrhea, etc., for the person who ate the dairy product.
Food intolerances are all the rage right now, and rightly so, but people need to understand the difference between the immune reaction of an allergy and the missing enzyme causing digestive havoc of an intolerance. Because there is an unfortunate lack of understanding, even among specialists, about the underlying mechanisms between the two types of conditions, leading to many genuine complaints of food intolerances being ignored or dismissed.
What’s unfortunate about that is that a missing enzyme is relatively easy to fix symptomatically, given that if you can figure out what the missing enzyme is and introduce it to the system in a way that supplements the digestion at the proper phase - like the commercially available lactase products, which supply the individuals who are missing the proper enzyme an exogenous version of it to digest lactose - you can often get complete relief from the condition. Many people find relief from intolerances simply by including digestive enzymes in their daily routines. Or, if you can figure out what the food that corresponds to the missing enzyme is, you can simply avoid that food. The problem with that is that figuring out the offending food(s) can be incredibly complicated. It can often lead to nutritional imbalances if you have to avoid whole groups of foods, and the diagnostics for determining them are still rudimentary at best.
One of the reasons people tend to scoff at intolerances is that they can seem confusing: they can come on seemingly out of nowhere (like in Santa Clarita Diet), be transient (lots of things can cause short term intolerances - microbiome imbalance, inflammation of the intestinal lining which can be caused by ingested microbes, viral infection, ingested toxins, or allergic reaction - that can go away on their own or may require treatment), are often difficult to diagnose (there are typically genetic components involved in intolerances but a lot of the research characterizing them hasn’t been done yet leading to a ‘if the science doesn’t exist confirming a problem yet, then the problem doesn’t exist either’ mentality a lot of times), and ‘aren’t as serious as allergies’ (which, yes, can be life threatening and terrible - food allergies deserve respect - but have you ever been around someone who’s severely lactose intolerant who accidentally eats cheese at a potluck because someone forgot to mention it was in the dish and they have a reaction? It’s unpleasant for everyone involved.) Now, not every intolerance is as dramatic as all that, but it’s worth pointing out for the folks who dismiss and poo poo the suffering of someone with an intolerance because it’s not a medical emergency. Suffering is suffering. Both things deserve respect and research.
Where things get fuzzy and where a lot of the controversy around food intolerances comes in has to do with leaky gut syndrome and the systemic inflammation that can result. Leaky gut is a condition where the lining of the gut becomes more permeable, allowing substances into the bloodstream that normally wouldn’t be there. This can produce an immune reaction to the foreign matter (this is typically where IgG testing comes in - it can detect the immune response to those not-fully-digested protein molecules which can indicate leaky gut and the foods that may be contributing to it) and cause pain in areas of the body distant from the gut - typically joints, headaches, the spine, etc. This is a newer area of research, so we really don’t know exactly what’s happening or the best treatments for it. A lot of the current treatments are best guesses at this point, as the supporting evidence on the effectiveness of those treatments is still accumulating, so always seek the advice of a qualified healthcare practitioner who specializes in gut health or allergies for individualized advice on which type you have and how best to treat it. But be aware - doctors who specialize in allergies don’t always know anything about intolerances. That’s a gastroenterologist specialization, and even then, finding someone who specializes in intolerances can be tricky because they often aren’t considered all that important medically. Medicine cares about base level health, so allergies fall more on that side of healthcare. Eliminating and treating intolerances tends to be more of a wellness concern, so seeing an integrative medicine specialist is usually more helpful.
You can read up on both things here and here, and find recommendations for practitioners here.
(Disclaimer: In no way am I endorsing the eating of people as a cure for food related intolerances. Though there is research suggesting that vampirism is good for your health, the research on the health benefits of zombism is still inconclusive…)