changing equations

The very microbes that helped humans evolve now make us sick

Our bodies have not changes as much as the standard for what constitutes a good microbe versus a bad one.

Between the mid-1990s and the mid-2000s alone, the likelihood of having a classmate with a food allergy increased by 20 per cent in the United States. In fact, over the past five decades, the incidence of all allergies and autoimmune diseases – caused by your body attacking itself – has skyrocketed. What could explain our sudden hypersensitivity to our surroundings and ourselves? Since evolution operates on the timescale of millennia, the culprits lie not in our genes but somewhere within our environment.

One thing that has changed in public health is our awareness of germs and how they spread. In response to that insight, over the past half-century our implementation of hygiene practices has spared us from debilitating infections and enormous human misery. But the new vigilance might have altered the development of our immune system, the collection of organs that fight infections and internal threats to our health.

The idea that too clean an environment might be harmful has been dubbed “the hygiene hypothesis”. The concept has been perverted by some to suggest that the less clean the environment, the better. But its meaning is different: it is not dirt that we are missing but exposure to certain microbes that normally contribute to the development of our immune system. “It’s not that we aren’t exposed enough to microbes but that we’re not exposed to the right types of microbes,” says the immunobiologist Ruslan Medzhitov at the Yale School of Medicine, also head of the Food Allergy Science Initiative at the Broad Institute.

So what has changed? In short, it’s the standard for what constitutes a good microbe versus a bad one. “Take bacterial species that increase nutrient absorption from food,” Medzhitov says. These were immensely beneficial at a time where you had to go days without eating. Today in the parts of the world with an overabundance of food, having such bacteria in your intestine contributes to obesity. “Microbes that cause intestinal inflammation are another example of what we call bad microbes because they induce [detrimental immune] responses. But in the past, these microbes could have protected you from intestinal pathogens,” he adds.

The most common such foes are helminths, commonly known as intestinal worms. While they have been eradicated in most of the economic West, their absence from our environment might be contributing to the increase in allergic and autoimmune diseases by diverting our immune system’s attention towards our food and ourselves. This is what Ken Cadwell, a microbiologist at New York University, contends. He is interested in better understanding Crohn’s, an autoimmune disease caused by our immune system attacking our gastrointestinal tract.

Worm treatment

Cadwell’s team discovered that the bacterium Bacteroides vulgatus causes reduced mucus secretion in mice, something that results in the condition. In collaboration with the parasitologist P’ng Loke, also at NYU, Cadwell then decided to treat mice that had Crohn’s disease with helminths, known to trigger mucus secretions in the intestine. And it worked! The two researchers identified that the ensuing establishment of Clostridiales bacteria in the gut cured the mice.

But would it work in humans? Loke collected stool samples from populations living in helminth-endemic areas in Malaysia before and after deworming treatment, and he noticed something intriguing. People from these regions had abundant Clostridiales in their gut before treatment and a lower incidence of autoimmune bowel diseases. After successful deworming, the protective bacteria disappeared, setting the stage for autoimmune illness to rear its head.

Yet treating humans with worms will not work as a public-health measure. Worm treatment is beneficial only for those Crohn’s patients with a genetic make-up causing reduced mucus-secretion and lacking Clostridiales bacteria. For everybody else, it is just a harmful infection. Now scientists are trying to better understand how to reap the benefits of worm therapy while avoiding its downsides. “I am more in favour of an alternative that gives the same [health] effect without having to give somebody a live parasite,” says Cadwell. “That would be ideal.”

Besides the change in our exposure to microbes, our modern lives include diets much higher in sugar, salt and carbs. Now a team from Harvard and Yale has discovered that even moderate increases in salt consumption trigger activation of immune actors, known as Th17 cells, especially prevalent in such autoimmune diseases as arthritis and multiple sclerosis, to name just two. “Recent studies found that if you have the right [genes], your likelihood of developing rheumatoid arthritis goes up 10-fold from the average risk in the population. But if you combine that with smoking, it leads to an increased risk of 100-fold. Now a recent study also showed that if you have the right [genes], you smoke, but you also consume a high-salt diet, the risk goes up 500-fold,” says the immunologist Vijay Kuchroo at Harvard, who did the work with his colleague, the neurologist David Hafler of Yale.

We are forced to conclude that the explosion of allergies and autoimmune diseases results from a mismatch between genes selected by pressures of our evolutionary past and the reality of modern life. While we have adapted in the past, we might not be able to adapt again by relying on biology alone. There is no going back – the old world is gone. To curtail the increase in allergies and autoimmunity, we have to evolve our social, political and scientific regimes, providing healthier food options at lower cost and improving our understanding of the underlying immunological mechanisms at play.

The writer is a graduate student in immunology at the Iwasaki Lab at the Yale School of Medicine.

This article was first published on Aeon.

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“My body instantly craves chai and samosa”

German expats talk about adapting to India, and the surprising similarities between the two cultures.

The cultural similarities between Germany and India are well known, especially with regards to the language. Linguists believe that Sanskrit and German share the same Indo-Germanic heritage of languages. A quick comparison indeed holds up theory - ratha in Sanskrit (chariot) is rad in German, aksha (axle) in Sanskrit is achse in German and so on. Germans have long held a fascination for Indology and Sanskrit. While Max Müller is still admired for his translation of ancient Indian scriptures, other German intellectuals such as Goethe, Herder and Schlegel were deeply influenced by Kalidasa. His poetry is said to have informed Goethe’s plays, and inspired Schlegel to eventually introduce formal Indology in Germany. Beyond the arts and academia, Indian influences even found their way into German fast food! Indians would recognise the famous German curry powder as a modification of the Indian masala mix. It’s most popular application is the currywurst - fried sausage covered in curried ketchup.

It is no wonder then that German travellers in India find a quite a lot in common between the two cultures, even today. Some, especially those who’ve settled here, even confess to Indian culture growing on them with time. Isabelle, like most travellers, first came to India to explore the country’s rich heritage. She returned the following year as an exchange student, and a couple of years later found herself working for an Indian consultancy firm. When asked what prompted her to stay on, Isabelle said, “I love the market dynamics here, working here is so much fun. Anywhere else would seem boring compared to India.” Having cofounded a company, she eventually realised her entrepreneurial dream here and now resides in Goa with her husband.

Isabelle says there are several aspects of life in India that remind her of home. “How we interact with our everyday life is similar in both Germany and India. Separate house slippers to wear at home, the celebration of food and festivals, the importance of friendship…” She feels Germany and India share the same spirit especially in terms of festivities. “We love food and we love celebrating food. There is an entire countdown to Christmas. Every day there is some dinner or get-together,” much like how Indians excitedly countdown to Navratri or Diwali. Franziska, who was born in India to German parents, adds that both the countries exhibit the same kind of passion for their favourite sport. “In India, they support cricket like anything while in Germany it would be football.”

Having lived in India for almost a decade, Isabelle has also noticed some broad similarities in the way children are brought up in the two countries. “We have a saying in South Germany ‘Schaffe Schaffe Hausle baue’ that loosely translates to ‘work, work, work and build a house’. I found that parents here have a similar outlook…to teach their children to work hard. They feel that they’ve fulfilled their duty only once the children have moved out or gotten married. Also, my mother never let me leave the house without a big breakfast. It’s the same here.” The importance given to the care of the family is one similarity that came up again and again in conversations with all German expats.

While most people wouldn’t draw parallels between German and Indian discipline (or lack thereof), Germans married to Indians have found a way to bridge the gap. Take for example, Ilka, who thinks that the famed differences of discipline between the two cultures actually works to her marital advantage. She sees the difference as Germans being highly planning-oriented; while Indians are more flexible in their approach. Ilka and her husband balance each other out in several ways. She says, like most Germans, she too tends to get stressed when her plans don’t work out, but her husband calms her down.

Consequently, Ilka feels India is “so full of life. The social life here is more happening; people smile at you, bond over food and are much more relaxed.” Isabelle, too, can attest to Indians’ friendliness. When asked about an Indian characteristic that makes her feel most at home, she quickly answers “humour.” “Whether it’s a taxi driver or someone I’m meeting professionally, I’ve learnt that it’s easy to lighten the mood here by just cracking a few jokes. Indians love to laugh,” she adds.

Indeed, these Germans-who-never-left as just diehard Indophiles are more Indian than you’d guess at first, having even developed some classic Indian skills with time. Ilka assures us that her husband can’t bargain as well as she does, and that she can even drape a saree on her own.

Isabelle, meanwhile, feels some amount of Indianness has seeped into her because “whenever its raining, my body instantly craves chai and samosa”.

Like the long-settled German expats in India, the German airline, Lufthansa, too has incorporated some quintessential aspects of Indian culture in its service. Recognising the centuries-old cultural affinity between the two countries, Lufthansa now provides a rich experience of Indian hospitality to all flyers on board its flights to and from India. You can expect a greeting of Namaste by an all-Indian crew, Indian food, and popular Indian in-flight entertainment options. And as the video shows, India’s culture and hospitality have been internalized by Lufthansa to the extent that they are More Indian Than You Think. To experience Lufthansa’s hospitality on your next trip abroad, click here.

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This article was produced by the Scroll marketing team on behalf of Lufthansa as part of their More Indian Than You Think initiative and not by the Scroll editorial team.