Love is in the air…and in your gut

Have you ever considered that your social circle, the people you live with and the close relationships in your life mean you’re not only sharing space, food or experiences, but microbes as well? As Valentine’s Day approaches, when connection and sharing the love is at the heart of its celebrations, here’s a reminder that shared intimacy runs deeper than we often realise… 

How close relationships shape our inner ecosystem

Each of us carries a vast and complex community of microorganisms in our gut, known as the microbiome. These microbes live in and on our bodies and play important roles in digestion, immune function, mood and overall health. While we often think of the microbiome as something deeply individual and personal, research increasingly shows that it is also social. The people we spend the most time with help shape our internal ecosystems in subtle but impactful ways.

Studies have found that individuals who share a household tend to have more similar gut microbiomes than those who don’t (Song et al 2013). This similarity goes beyond genetics and diet alone. Shared meals, furniture, pets and daily routines all contribute to overlapping microbial exposure. Over time, these shared environments encourage the exchange of bacterial strains, leading to microbiomes that begin to resemble one another.

Close relationships strengthen this effect even further. Family members, close friends and romantic partners who regularly spend time together (especially those who share food), tend to show increased microbial similarity (Dill-McFarland et al (2019). Eating the same meals supports the growth of similar bacterial populations, while physical closeness and shared surfaces allow microbes to move naturally between people.

Intimate relationships amplify this exchange to yet another level. Couples, in particular, tend to share even more bacterial strains due to frequent and direct contact. Kissing alone can transfer millions of bacteria in just seconds, contributing to more similar oral and gut microbiomes between partners through the oral-gut axis. Over time, these everyday acts of affection such as hugs, sharing pillows or finishing each other’s plates, leave measurable microbial traces. 

This process isn’t something to be concerned about; it’s a reflection of how interconnected human life really is. Our microbiomes respond to our social worlds just as much as they respond to what’s on our plates. In this way, our relationships leave a biological imprint, one that mirrors the rhythms of our shared lives.

What does this mean for us?

Understanding that our microbiomes are shaped by the community around us, reminds us that health isn’t only an individual pursuit. It’s influenced by connection, proximity and the environments we build together. Whether sat together around a dinner table or embracing your bestie, the bonds we form extend further than we might expect, right down to the microscopic level. 

With that said, this Valentine’s Day, whether you’re sharing a candlelit dinner, a long hug, a kiss goodbye or quality time with friends, remember: love isn’t just in the air…it’s in your microbiome too! 

References

Song, S. J., Lauber, C., Costello, E. K., Lozupone, C. A., Humphrey, G., Berg-Lyons, D., & Knight, R. (2013). Cohabiting family members share microbiota with one another and with their dogs. elife, 2, e00458.

Dill-McFarland, K. A., Tang, Z. Z., Kemis, J. H., Kerby, R. L., Chen, G., Palloni, A., ... & Herd, P. (2019). Close social relationships correlate with human gut microbiota composition. Scientific reports, 9(1), 703.

Kort, R. (2026). A sweet kiss with a bacterial touch: a potential positive feedback loop involved in shaping the oral microbiota. Evolution and Human Behavior, 47(1), 106777.

Kort, R., Caspers, M., van de Graaf, A., van Egmond, W., Keijser, B., & Roeselers, G. (2014). Shaping the oral microbiota through intimate kissing. Microbiome, 2(1), 41.