Since opening NFM, I’ve repeatedly been asked about food sensitivity testing. And there seems to be a lot of buzz about it lately, too. So I thought I would set the record straight.
IgG blood panels are the most popular, and the ordering providers promise it will identify the foods “causing” your symptoms. But the science behind these tests is much weaker than the marketing—and in many cases, the results can be very misleading.
Here’s why.
Elevated IgG does not = intolerance. Most food sensitivity tests measure IgG antibodies to foods. Companies often interpret elevated IgG as a sign of sensitivity. When in fact, it can be elevated from normal exposure to those foods.
IgG may simply indicate that:
- You’ve eaten the food recently
- Your immune system recognizes it as familiar
- Your body tolerates it normally
A positive result doesn’t automatically mean that food is harming you. It is not uncommon for patients to bring me their results, and they lit up like a Christmas tree. “Sensitive” to things like broccoli, apples, zucchini, grapes, etc. It’s often a list of over 15 foods! And majority of the time it is things they consume on a regular basis.
And spoiler alert–they have been avoiding all of it, and their health hasn’t changed.
Why? Something called “leaky gut.” Also known as intestinal permeability in the scientific world.
Your gut lining has this really thin layer separating your gut from your bloodstream. Thinner than a hair on your head actually! And it is designed to let fully digested nutrients in, while keeping larger food proteins and bacteria out. When the gut lining becomes inflamed or disrupted (due to stress, infections, poor diet, dysbiosis, medications, etc.), those tight junctions can loosen.
When that happens:
- Larger food proteins can enter the bloodstream
- Your immune system reacts
- IgG antibodies are produced
- The test lights up positive
But here’s the key:
The issue may not be the food. The issue may be that leaky barrier.
If your gut is inflamed, almost any food you eat regularly could show up as “reactive.” That doesn’t mean you’re truly sensitive — it may just mean your gut needs some love. And even the healthiest of diets can’t outperform a disrupted microbiome.
If you test while your gut is inflamed or your microbiome is out of balance, you’re essentially measuring immune activity in a stressed system.
That often leads to:
- Long lists of “sensitivities”
- Unnecessary food elimination
- Increased anxiety around eating
- Reduced diet diversity (which can actually worsen gut health)
Many people eliminate 10–20 foods when the real issue was gut dysfunction all along. If food sensitivities are truly suspected, it makes more sense to:
- Support the microbiome
- Improve diet quality and fiber diversity
- Reduce inflammation
- Improve sleep and stress management
- Eliminate alcohol and ultra-processed foods
- Allow the gut lining to heal
Then—if symptoms persist—consider further evaluation. It’s not until I’ve worked with my patients for 3+ months on healing that I will be open to a food sensitivity test if they insist on one. And clinically, I see night and day results! They only react to maybe 1 or 2 foods, and everything else is normal. Magic, right??
Often, when gut health improves, many so-called sensitivities disappear. And even then, the gold standard is the good ol’ elimination diet with careful re-introduction and observation. I tell my patients all the time, if you eliminate “X” for just four weeks, it will be so obvious when you add it back in if your body tolerates it or not.
The bottom line? Save your money on testing! IgG food sensitivity testing often measures exposure, not intolerance. So before you cut out half your diet based on a faulty lab panel, focus on repairing your gut first.
