The Case for IgG Testing
If you’re struggling with GI-related health concerns, food sensitivity testing might feel like a no-brainer. However, a little bit of research will show that there is some contention between healthcare providers about the validity of IgG testing. We’re here to help settle this debate and answer some of your most discerning questions.
Also known as immunoglobulin G (IgG) antibody testing, IgG tests measure the presence of IgG antibodies in your blood, signaling a reactivity to certain foods. For example, a high concentration of IgG antibodies to avocado suggests that you may have an avocado sensitivity or intolerance.
Many people consider IgG food sensitivity testing when they’re experiencing common, GI-related symptoms, but aren’t sure how to pinpoint adverse reactions to specific foods. It’s also a popular choice for those with gastrointestinal conditions such as IBS and Crohn’s disease.
And – chances are – one of your medical providers is already utilizing it.
“IgG is the most prevalent of all the antibodies in your body,” says Notch Medical Advisor Dr. Chris Meletis, N.D. For this reason, he says, it’s a critical tool for addressing gastrointestinal issues, depression, asthma, anxiety and more. “It’s the first step to understanding your body’s relationship to certain foods.”
Notch’s lab partner uses Enzyme-Linked Immunosorbent Assay (ELISA) technology – a widely recognized immunological testing platform that detects the presence of antibodies in a person’s blood.
Meletis says his preference for ELISA-modified technology stems from the fact that it has withstood the test of time and is offered by many reputable labs. There are also recent studies that examine the benefits of IgG testing over other methods, such as cell size variability.
In this particular study, researchers not only determined that the IgG ELISA method was more reliable, but also precise enough to reproduce. Tested across four different time points, 82 percent of the foods produced identical results and 17 percent differed by one reactivity level.
Because Notch’s lab utilizes duplicate testing and advanced automation, this level of accuracy is only reinforced.
“I want to have something that’s reproducible, reliable and very specific,” Meletis says. While some tests provide a lot of “background noise,” he says, IgG testing is more focused on specificity. “I simply want to know if a food is a problem or isn’t a problem.”
It’s important to note, however, that food sensitivity testing is not all-encompassing or absolute. Exposure, travel and other external factors can also play a role in your reactivity, which is why IgG food sensitivity testing is often conducted synchronously with an elimination diet.
“People think you’re only going to have a reaction if you’ve been exposed, but sometimes things that you don’t even eat will have a reactivity as well,” says Meletis. This is particularly prevalent for those who experience cross-reactivity, he says. “We need to have a competent immune system and it comes down to susceptibility.”
One of the biggest sources of confusion is surrounding the difference between IgG and IgE testing, Meletis says, which are often treated as though they’re interchangeable even though they aren't.
“The biggest difference between IgG and IgE testing is whether you’re looking to test for food allergies or food sensitivities,” he says. “When we do an IgG test, we're looking for sensitivities and intolerances. We really don’t want to have that misnomer that IgG tests are for food allergies.”
Because food allergies generally trigger an immediate immune response, they are often tested for and diagnosed earlier in a person’s life. Food sensitivities, however, are delayed, cell-mediated responses, which means they often go overlooked.
In this sense, IgG can be considered more “gradual” while IgE is more often associated with “emergencies,” Meletis says. The half-life of IgG is 21 days, which is what makes it particularly useful for recognizing late-onset reactions. Additionally, IgE-mediated allergies are generally permanent while IgG-mediated sensitivities may only be temporary, which is why Meletis recommends getting an IgG test every few years.
“Food sensitivities can be sneaky,” he says. “Simply think of IgG food sensitivity testing as a tool to understand how your immune system works.”
Having used IgG testing on his patients for the last 27 years, Meletis says it only becomes an issue if you treat it as a comprehensive diagnostic tool or act on your results without rhyme or reason. For example, eliminating every food or spice you’re sensitive to without a set plan can often cause more harm than good.
“The axe that chops your wood is great until it hits your foot,” he says. “Your results shouldn’t be a weapon against you.”
In summary, food sensitivities are complex, which is why it’s extremely useful to consult with a medical practitioner about your results. Only then can you come up with an intentional, personalized treatment plan that serves you and your specific needs.