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The two key health benefits of growing up on a farm, according to a new study

It’s all to do with hygiene hypothesis.
It’s all to do with hygiene hypothesis. It’s all to do with hygiene hypothesis.

Children who grow up on farms surrounded by animals and germs have better immune systems, a small study suggests.

The research also indicates those who are brought up in rural environments might be at lower risk of mental illness compared with pet-free city dwellers.

The team, from the University of Ulm in Germany and CU Boulder in Colorado, US, says their work adds evidence to the “hygiene hypothesis” – which suggests that overly sterile environments can create health problems.

Study author Christopher Lowry, professor of integrative physiology at CU Boulder, said: “It has already been very well documented that exposure to pets and rural environments during development is beneficial in terms of reducing risk of asthma and allergies later in life.

“This study moves the conversation forward by showing for the first time in humans that these same exposures are likely to be important for mental health.”

City life
City life Those brought up in rural environments might be at lower risk of mental illness compared with city dwellers (Stefan Rousseau/PA)

The scientists recruited 40 healthy German men between 20 and 40 years old, half of whom were raised on a farm with animals, while the others grew up in cities without pets.

The volunteers were asked to complete a series of tasks aimed at causing stress: first, they gave a speech in front of people about why they deserved their dream job, which was followed by an attempt to solve a mathematical problem.

The men raised in cities were found to have higher levels of peripheral blood mononuclear cells (PBMCs) and interleukin 6 – compounds in the immune system that indicate a strong inflammatory response to stress.

While inflammation – a process which involves chemicals being released from the white blood cells into the blood – plays a key role in maintaining a healthy immune system, previous research has suggested that people who have chronic inflammation are at higher risk of developing mental health disorders like depression and post-traumatic stress disorder (PTSD).

Mr Lowry said: “People who grew up in an urban environment had a much-exaggerated induction of the inflammatory immune response to the stressor, and it persisted throughout the two-hour period.

Muddy hands
Muddy hands Exposure to pets and rural environments can help reduce the risk of asthma and allergies later in life (Natalie_board/Getty Images) (natalie_board/Getty Images/iStockphoto)

“This exaggerated inflammatory response is like a sleeping giant that they are completely unaware of.”

According to the researchers, more than 50% of the world’s population live in urban areas, meaning humans are exposed to far fewer microorganisms than they evolved with.

Mr Lowry added: “If you are not exposed to these types of organisms, then your immune system doesn’t develop a balance between inflammatory and anti-inflammatory forces, and you can develop a chronic, low-grade inflammation and exaggerated immune reactivity that makes you vulnerable to allergy, autoimmune disease and, we propose, psychiatric disorders.”

The team says the next step of their research is to study larger samples, which will include women as well as new locations.

The research is published in the journal Proceedings of the National Academy of Sciences (PNAS).