Old friends from the dirt make you happy and healthy

„Dirt is good“. This is the heading to one of our most-read and most-discussed articles on hygiene and health. The many likes and shares in the social media prove the importance of the topic to many of our readers. End of May, the University of Colorado at Boulder published an >>> article on why dirt is so good for us.

The Hygiene Hypothesis

In 1989, the British scientist David Strachan introduced the hygiene hypothesis, saying that many of our civilization diseases such as allergies or asthma are caused by growing up in a too sterile environment that leaves our immune systems unchallenged in regards to germ resistance. According to the theory, childhood is the key time for getting in contact with dirt. The book „Dirt is Good“ by Prof. Rob Knight and Dr. Jack Gilbert, which we discussed in the above mentioned article, confirms the hygiene hypothesis and advises young families (and all people in general) to refrain from excessive hygiene measures and let children play in the dirt (given that it is not chemically contaminated).

But why is dirt so good?

The now published research was able to further refine the hygiene hypothesis. The mere observation that people who get in contact regularly are healthier and happier was now added a possible explanation. Until now, the thesis was that the homeopathic doses of germs and viruses in the dirt stimulate our immune system. The latest findings, however, assume that there are rather „old friends“ dwelling in the dirt that make us strong.

Prof. Christopher Lowry, senior author of the study, identifies Mycobacterium vaccae as such an old friend. The bacterium is found in soil and Lowry could prove an anti-inflammatory effect in our system. Tested on rodents, Mycobacterium vaccae furthermore triggered an antidepressant effect. The reason for the sudden change of mood for the better presumably also lies in the anti-inflammatory substances.

The key essence defined in his study is a lipid called called 10(Z)-hexadecenoic acid that Lowry was able to prove by modern sequencing techniques. The study further examined the interaction of the acid with macrophages, or immune cells, and found that they matched like lock and key. After successful binding, a receptor is activated, (it is the so-called peroxisome proliferator-activated receptor, short: PPAR), releasing anti-inflammatory substances.

Who benefits from these findings?

The study underlines once more the importance of dirt in our lives and the harm that excessive hygiene can do. But the study also takes it one step further. The now known reasons for stress-relieving effect of dirt can be used for a kind of „anti-stress vaccination“ that is now in the focus of further research. People in high-stress situations like soldiers could benefit from the results. The therapeutic value of the now identified acid gives way to a great number of application areas.

And Lowry is sure: „This is only the tip of the iceberg“. He is sure that there are millions of these health-boosting „old-friends“, perfectly matching our organisms. In the civilized society we live in, we simply lack the occasions of a „dirt-near“ living that our ancestors lived and therefore need these findings to stay physically and mentally healthy.