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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As India turns 70, London School of Economics asks some provocative questions

Is India ready to become a global superpower?

Meaningful changes have always been driven by the right, but inconvenient questions. As India completes 70 years of its sovereign journey, we could do two things – celebrate, pay our token tributes and move on, or take the time to reflect and assess if our course needs correction. The ‘India @ 70: LSE India Summit’, the annual flagship summit of the LSE (London School of Economics) South Asia Centre, is posing some fundamental but complex questions that define our future direction as a nation. Through an honest debate – built on new research, applied knowledge and ground realities – with an eclectic mix of thought leaders and industry stalwarts, this summit hopes to create a thought-provoking discourse.

From how relevant (or irrelevant) is our constitutional framework, to how we can beat the global one-upmanship games, from how sincere are business houses in their social responsibility endeavours to why water is so crucial to our very existence as a strong nation, these are some crucial questions that the event will throw up and face head-on, even as it commemorates the 70th anniversary of India’s independence.

Is it time to re-look at constitution and citizenship in India?

The Constitution of India is fundamental to the country’s identity as a democratic power. But notwithstanding its historical authority, is it perhaps time to examine its relevance? The Constitution was drafted at a time when independent India was still a young entity. So granting overwhelming powers to the government may have helped during the early years. But in the current times, they may prove to be more discriminatory than egalitarian. Our constitution borrowed laws from other countries and continues to retain them, while the origin countries have updated them since then. So, do we need a complete overhaul of the constitution? An expert panel led by Dr Mukulika Banerjee of LSE, including political and economic commentator S Gurumurthy, Madhav Khosla of Columbia University, Niraja Gopal Jayal of JNU, Chintan Chandrachud the author of the book Balanced Constitutionalism and sociologist, legal researcher and Director of Council for Social Development Kalpana Kannabiran will seek answers to this.

Is CSR simply forced philanthropy?

While India pioneered the mandatory minimum CSR spend, has it succeeded in driving impact? Corporate social responsibility has many dynamics at play. Are CSR initiatives mere tokenism for compliance? Despite government guidelines and directives, are CSR activities well-thought out initiatives, which are monitored and measured for impact? The CSR stipulations have also spawned the proliferation of ambiguous NGOs. The session, ‘Does forced philanthropy work – CSR in India?” will raise these questions of intent, ethics and integrity. It will be moderated by Professor Harry Barkema and have industry veterans such as Mukund Rajan (Chairman, Tata Council for Community Initiatives), Onkar S Kanwar (Chairman and CEO, Apollo Tyres), Anu Aga (former Chairman, Thermax) and Rahul Bajaj (Chairman, Bajaj Group) on the panel.

Can India punch above its weight to be considered on par with other super-powers?

At 70, can India mobilize its strengths and galvanize into the role of a serious power player on the global stage? The question is related to the whole new perception of India as a dominant power in South Asia rather than as a Third World country, enabled by our foreign policies, defense strategies and a buoyant economy. The country’s status abroad is key in its emergence as a heavyweight but the foreign service officers’ cadre no longer draws top talent. Is India equipped right for its aspirations? The ‘India Abroad: From Third World to Regional Power’ panel will explore India’s foreign policy with Ashley Tellis, Meera Shankar (Former Foreign Secretary), Kanwal Sibal (Former Foreign Secretary), Jayant Prasad and Rakesh Sood.

Are we under-estimating how critical water is in India’s race ahead?

At no other time has water as a natural resource assumed such a big significance. Studies estimate that by 2025 the country will become ‘water–stressed’. While water has been the bone of contention between states and controlling access to water, a source for political power, has water security received the due attention in economic policies and development plans? Relevant to the central issue of water security is also the issue of ‘virtual water’. Virtual water corresponds to the water content (used) in goods and services, bulk of which is in food grains. Through food grain exports, India is a large virtual net exporter of water. In 2014-15, just through export of rice, India exported 10 trillion litres of virtual water. With India’s water security looking grim, are we making the right economic choices? Acclaimed author and academic from the Institute of Economic Growth, Delhi, Amita Bavisar will moderate the session ‘Does India need virtual water?’

Delve into this rich confluence of ideas and more at the ‘India @ 70: LSE India Summit’, presented by Apollo Tyres in association with the British Council and organized by Teamworks Arts during March 29-31, 2017 at the India Habitat Centre, New Delhi. To catch ‘India @ 70’ live online, register here.

At the venue, you could also visit the Partition Museum. Dedicated to the memory of one of the most conflict-ridden chapters in our country’s history, the museum will exhibit a unique archive of rare photographs, letters, press reports and audio recordings from The Partition Museum, Amritsar.

This article was produced by the Scroll marketing team on behalf of Teamwork Arts and not by the Scroll editorial team.