Are Holidays with the In-laws a Pain in the Gut?

If Christmas feels more like Festivus, it may unbalance your microbiome.

Posted Dec 11, 2019

 A roll of toilet paper with Christmas decorations.  I By Iuliia Karnaushenko
The truth is in the poop
Source: Royalty-free stock photo: A roll of toilet paper with Christmas decorations. I By Iuliia Karnaushenko

They may call it “the most wonderful time of the year,” but after a few days of festivities with your in-laws, you may feel like your guts are in an uproar, and not just metaphorically.

Maybe it’s because your father-in-law, without fail, points out that you’ve gained a few pounds since last year. Or perhaps it’s your mother-in-law who, bless her heart, inevitably (and unfavorably) compares you to her child’s previous partners. If not the reliably re-gifting cousin, perhaps the resident Grinch is Grandpa, who invariably has one too many eggnogs and turns Christmas into Festivus.

If your complaints of in-law-generated indigestion have been met with skepticism, know that in a novel study, researchers hypothesized that the stress associated with spending Christmas with in-laws could negatively impact your microbiome (aka, gut bacteria). 

Stress, the Microbiome and Your Health

As you may know, the microbiome affects far more than your digestive health. In fact, imbalances in gut bacteria have been linked to everything from inflammatory bowel disease to obesity to changes in immune function, and other health issues. An unbalanced microbiome has also been associated with greater symptom severity in depression, anxiety, autism, and schizophrenia, and has been linked to dementia, problems with memory, and other psychological symptoms. 

Many factors can impact the composition of your gut bacteria. Positive social interactions have been linked to increased numbers of beneficial gut bacteria and greater diversity in the microbiome, both of which are linked to better health. Factors that can negatively impact the microbiome include medical conditions, poor diet, alcohol consumption, and stress, including stress related to social situations.

Certainly, holidays in general usually mean changes to everything from one’s diet to the amount of alcohol consumed to changes in sleep quantity and quality to falling out of an established exercise routine. In addition, there are both the stresses of holiday travel and feeling financially overextended due to gift giving. These factors can potentially contribute to temporary disturbances in gut bacteria and increased overall stress regardless of whether a holiday is spent with one’s own versus a partner’s family. 

But is there a difference between the overall impact on your stress levels and gut health depending on whom you celebrate with? 

The Study

In this novel research, investigators asked the question: Is there a difference between effects on the microbiome when spending the Christmas holiday with in-laws versus one’s own family? To answer, the team obtained fecal (stool) samples and other data from 28 healthy volunteers who were either visiting their own family or their in-laws; 24 participants provided sufficient data for statistical analysis.

The fecal samples and other data were collected on December 23, 2016, and again on December 27, 2016 from participants who spent Christmas with either their own families or their in-laws. The team performed ribosomal DNA sequencing of these samples and discovered there were two significantly different microbial biomarker signatures between those participants who had spent Christmas with their own families versus with their in-laws. 

In all, there were seven types of gut bacteria that were significantly different between the two groups after Christmas as compared to before. In those who spent Christmas with their own families, there was an overall increase in Ruminococcus bacteria but a decrease in two Ruminococcaceae genes. In those visiting their in-laws, there was a significant decrease in all species of Ruminococcaceae.

Decreased amounts of Ruminococcus genes have been linked to increased symptoms of stress and depression. This difference between the groups was present despite similar reported dietary macronutrient intake and alcohol consumption.

It’s worth noting that the decrease in levels of two of the Ruminococcaceae genes in the own-family-visit participants could also be due to increased psychological stress. It is generally accepted that holiday visits with one’s own family have the potential to increase stress. 

The Scoop on In-laws and Changes in Poop

Why might visits with in-laws be more stressful than those with one’s own family? It probably would not take a study to recognize that holidays with in-laws can pose their own unique stressors. For one, family dynamics vary between households and families of origin. And even if both partners were raised celebrating the same holiday, each family may have different ways of observing it, as well as specific family traditions that may or may not feel comfortable to a partner. Additionally, in-law visits may feel obligatory rather than voluntary, increasing the potential for stress. And any interpersonal tension between a partner and in-laws is bound to feel intensified when spending several days together or in the context of a holiday spent without one’s own family. Finally, most people can't help but regress somewhat when returning home; this can be stressful for both partners.


This was a small study that was observational in nature; participants were not randomly assigned to a condition. In addition, researchers did not collect data regarding psychological stress; rather, the team relied on changes in the microbiome to infer differences in stress levels depending on whose family participants visited. These and other study design issues limit the conclusions that can be drawn; however, they are thought-provoking and may generate further study about how holiday visits impact the gut.


de Clercq, N. C., Frissen, M. N., Levin, E., Davids, M., Hartman, J., Prodan, A., ... & Nieuwdorp, M. (2019). The effect of having Christmas dinner with in-laws on gut microbiota composition. Human Microbiome Journal, 13, 100058.

Nemani, K., Ghomi, R. H., McCormick, B., & Fan, X. (2015). Schizophrenia and the gut-brain axis. Progress in Neuro-Psychopharmacology & Biological Psychiatry, 56, 155-160.