New Study Reveals How Much You Share Your Microbiome With Your Romantic Partner
A study published in Cell Press Blue has found that cohabitating romantic partners share approximately 44% of their oral microbiome and 19% of their gut microbiome.
The Research
The study analyzed microbiome DNA data from 430 people across 207 households in Italy and Fiji. Lead author Vitor Heidrich of the University of Trento explained that the lab was investigating sources of microbes, since humans are born without a microbiome.
While previous evidence suggested cohabitation leads to microbiome sharing, this is the first study to quantify transmission by relationship type and to include the oral microbiome.
How Microbes Move Between Partners
Heidrich suggested transmission could occur through shared dishes or toothbrushes touching.
Romantic partners share significantly more oral microbiome than other cohabitants (44% vs. 26%), likely due to direct saliva exchange—including kissing.
Gut microbiome sharing (19%) is similar regardless of relationship type, implying ingestion of fecal matter from housemates.
Heidrich noted that even a single microbial cell can enable transmission.
Health Implications: What This Could Mean
"We found that a lot of the very transmissible species are also linked with higher risk of Type 2 diabetes." — Vitor Heidrich
Most bacteria are harmless or beneficial; only about one in a billion bacterial species are human pathogens. However, the researchers observed that some transmissible microbes were associated with poor health.
Dr. Jessica Queen of Johns Hopkins University raised questions about whether a partner's microbiome health impacts disease risk.
Heidrich cautioned that the field is far from making such claims, adding, "We are only starting to investigate this as a possibility."
Queen noted that proving causation versus correlation in microbiome research remains difficult.
Expert Perspectives
"It's exciting that signals were detected in the oral microbiome, which is harder to study." — Ilana Brito, Cornell University
Queen emphasized the need for more long-term longitudinal data and animal model studies to establish causal relationships.
Brito stated that exchanging microbes may be protective or have no substantial effect, and there is no reason to stop embracing or exchanging microbes.
Study Limitations and Context
Heidrich acknowledged that his own household (with wife and cats) likely contributes to his microbiome, but pet-to-human transmission has larger ecological barriers due to different gastrointestinal environments.
He views microbe exchange as intrinsic to the human experience, given that humans have lived together for millions of years.