To test, whether people with depression have a higher levels of food-specific antibodies and therefore, presumably an increased gut permeability, researchers recruited three different groups of people:

Patients suffering from major depressive disorders (MDD)

Patients suffering from irritable bowel syndrome (IBS)

Healthy control subjects

There is growing evidence that one of the clearest manifestations of gut permeability is IBS. Therefore, the researchers speculated to find high IgG levels in the blood of those people.

The scientist looked for 39 selected food compounds and found that IgG hyperactivity (average of levels of IgG antibodies above 7.5 µl/mL) was detected in 64% of patients with MDD, 46% of people with IBS and in only 19% of healthy control subjects.

This is a clear indication that people with MDD have an increased gut permeability, allowing undigested food into the blood circulation and thereby, causing an immune reaction.

What is more?

The researchers also identified the major food items that showed a significant IgG hypersensitivity in patients with MDD and IBS compared to healthy individuals.

The table below shows the differences in serum IgG levels. For instance, patients with MDD or IBD had more than three times higher IgG levels for milk products, compared to healthy people. The IgG levels for wheat and rye were also double as high in patients with MDD compared to healthy individuals but there was no difference between IBS patients and healthy people.