Living with friends may slowly change the bacteria inside your body. A new study from the University of East Anglia suggests this idea. The research shows that a small colony of tiny birds share most of their gut microbiome with birds they spend most of their time with. According to the study researchers, the same principle almost applies to humans too.
Earlier human studies suggested this idea. People who live together, like couples or friends, often have similar gut bacteria. This happens even if they are on different diets. The new bird study shows something clearer. It proves that being close to others matters.
Not just the environment, but social bonding helps share gut bacteria.
How did the research happen?
Scientists studied a small bird called the Seychelles warbler. These birds live on a tiny island called Cousin Island in the Seychelles. The island is isolated, and the birds do not leave it. This made it easier for researchers to track them closely.
The team collected faecal samples from the birds over several years. These samples helped them study the gut microbiome. This is the community of bacteria living inside the digestive system. Some of these bacteria are very important for health, as they play crucial roles in digestion, immune function, and overall well-being.
The researchers looked at birds with different social roles. Some birds were breeding pairs. Others helped raise young birds. Some birds lived in the same group but were less involved in raising young birds, which meant they did not participate in the nurturing activities that characterised the breeding pairs. This approach allowed the team to compare birds that spent a lot of time together with those that did not.
The main focus was on anaerobic bacteria. These are bacteria that live without oxygen. They cannot survive outside the body for long. Because of this, they usually spread through close contact. The results were clear. Birds that spent more time together shared more of these gut bacteria. Breeding pairs and helpers at the nest had very similar microbiomes. Birds that had less contact shared fewer bacteria.
It shows that close social behaviour plays a key role. It is not only the environment that matters. Direct interaction also helps bacteria move between individuals. The study provides strong evidence of how this process works. Earlier human studies had suggested similar patterns. For example, couples who live together often have similar gut bacteria. The same is true for long-term housemates. Such changes can happen even if their diets are different.
The bird study helps explain why. Since anaerobic bacteria cannot survive in open air, they must pass through close contact. In birds, this process happens at the nest. In humans, it may happen in everyday life. Simple daily actions could play a role. Hugging, kissing, and sharing food spaces may all help transfer bacteria. Even sitting close together may have an effect over time.
The researchers believe this has important health effects. Many gut bacteria support digestion. They also help the immune system. Some bacteria can protect against disease. When people share these beneficial microbes, it may improve health across a household. Over time, people living together may develop more similar internal ecosystems, which can lead to enhanced immune responses and overall health benefits for the household members.
The study also highlights the value of the island setting. Cousin Island acts like a natural laboratory. Every bird is marked with coloured rings. This allows scientists to follow each bird throughout its life. Researchers can track behaviour, health, and relationships in detail. At the same time, the birds live in a natural environment. They eat natural food and behave normally. This approach gives more reliable results than a lab setting alone.
The scientists say the experiment is a rare opportunity. It allows them to study long-term biological processes in the wild. Few places offer such controlled yet natural conditions. The findings may change how we think about human health. People often focus on diet and lifestyle. But social relationships may also play a hidden role.
The gut microbiome is not only shaped by what you eat. It may also be shaped by who you spend time with. The people around you could influence your health in small but meaningful ways. This does not mean all bacteria sharing is beneficial Some microbes can cause illness. But many are beneficial and help the body function well.
The study suggests a simple idea. Living closely with others connects us in more ways than we realise. Even at a microscopic level, our lives are linked.
