By Katie Lowles

Fad diets come and go, with magazines and celebrities jumping on the recent fashionable way to shed some pounds while convincing others to do the same. There have been liquid diets, zero-carb diets and raw food diets but perhaps one of the strangest weight loss methods was the tapeworm diet.

Tapeworms are a type of helminth, which simply means “a worm-like parasite capable of infecting humans or animals” – appetising right? In the 1900s, when the tapeworm diet was popular, dieters were voluntarily swallowing tapeworm eggs contained inside a pill. After being swallowed, the tapeworm eggs hatch and reach maturity in the intestines where it is hoped that they absorb nutrients from the dieter’s food and ‘use up’ excess calories to help weight loss. Once the desired weight is reached, the dieter takes a tablet to kill and remove the parasite.

Unsurprisingly, ingestion of a tapeworm, which can grow up to 9 metres (!), does not come without some uncomfortable side-effects. Brain and central nervous system deterioration, organ function impairment and digestive blockage are all reported side-effects caused by tapeworm ingestion.

While it may not be advised to start swapping your spaghetti for worms to lose weight, there is evidence to suggest that worm infections may be beneficial for an altogether different reason…

Worms live rent-free in our bodies

Over millions of years, helminths have co-evolved with their hosts, resulting in a mutualistic relationship where both the helminth and their host (a human, for example) derive benefit from the relationship.

Helminths benefit from this strange co-habitation agreement by having a safe place to live and grow. Once inside their host, helminths cleverly suppress the host’s inflammatory response, meaning they can go unnoticed. They evade the immune system and inhabit the host without threat of an immune attack.

The host benefits from the immunosuppressive effect of the helminth. While inflammation is a necessary aspect of the immune response and can help fight off foreign invaders, heal injuries and remove debris, it can also lead to allergies, and inflammatory disorders. Therefore, dampening the immune response by helminth infection can be beneficial for the host as it decreases general inflammation, meaning the symptoms of many inflammatory diseases and allergic reactions are relieved. For instance, globally we see an inverse correlation between helminth infection and prevalence of Crohn’s disease – a condition where areas of the digestive tract become inflamed. Thanks, worms!

Helminths evade the immune system by deploying its immune-quietening weapons: excretory/secretory antigens (ES). The ES is a mixture of molecules released from the uterus or intestine of a helminth. It alters immune cells behaviour, skewing them towards an anti-inflammatory phenotype and away from a pro-inflammatory response.

Can deliberate helminth infection help to treat inflammatory disorders?

Inflammatory bowel disease (IBD) is an umbrella term used to describe disorders involving chronic inflammation of the digestive tract, including ulcerative colitis and Crohn’s disease. Traditional treatments for IBD aim to reduce inflammation by targeting and inhibiting pro-inflammatory mediators. However, the NHS estimates that 1 in 5 people with ulcerative colitis do not respond to medicine. Despite over 6 million people living with IBD globally, there remains an unmet clinical need for efficacious treatment.

The novel therapeutic potential of using worms to treat IBD has been discussed and investigated by parasitologists and immunologists in the scientific community for a couple of decades but so far helminthic therapies have never been introduced as a mainstream treatment option.

However, the lack of approved worm-based treatments doesn’t stop everyone from giving worms a go. In 2004, a brave but risky decision led a long-term colitis sufferer to purposely swallow parasitic worms in an attempt to cure his condition and alleviate the symptoms he was experiencing: vomiting, diarrhea, abdominal pain and weight loss. The man swallowed 1500 whipworm eggs over the course of 4 months a year later he no longer needed to take his usual colitis medication. The man got in contact with parasite immunologist, P’ng Loke, to tell him about his findings. Loke took great interest in the man’s experiment and together they conducted research to investigate exactly which components of the immune system are altered by human whipworm infection. Their work was eventually published in Science Translational Medicine journal in 2010.¹

Holding out hope for helminth treatment

At present, there is insufficient data to conclusively demonstrate a beneficial therapeutic effect of worm infection in human IBD. While some IBD sufferers may report extraordinary results after ingesting worms, the treatment is still inherently risky as the worms themselves can damage the gut and exacerbate bowel inflammation.

The future of helminthic therapy may lay in vaccines containing isolated synthetic ES components only, which could deliver the beneficial effects of worm infection without the need to have worms in our bodies at all.

Until then, anyone for spaghetti?

References

1.        Broadhurst, M. J., Leung, J. M., Kashyap, V., McCune, J. M., Mahadevan, U., McKerrow, J. H. & Loke, P. (2010). IL-22+ CD4+ T Cells Are Associated with Therapeutic Trichuris trichiura Infection in an Ulcerative Colitis Patient. Sci Transl Med, 2(60), 60-88.

Further Reading

• History’s weirdest fad diets, BBC News Magazine article by Denise Winterman (2013). Online at: www.bbc.co.uk/news/magazine-20695743
• Maruszewska-Cheruiyot, M., Donskow-Łysoniewska, K. & Doligalska, M. (2018). Helminth Therapy: Advances in the use of Parasitic Worms Against Inflammatory Bowel Diseases and its Challenges. Helminthologia, 55(1),1-11.
• World Health Organisation fact sheet on soil-transmitted helminth infections. Online at: http://www.who.int/news-room/fact-sheets/detail/soil-transmitted-helminth-infections
• Sipahi, A. M. & Baptista, D. M. (2017). Helminths as an alternative therapy for intestinal diseases. World J Gastroenterol, 23(33), 6009–6015.

About the author:

Katie Lowles is a PhD student at the university of Manchester. Her research is focused on immune cells and the circadian clock and how they affect collagen synthesis and regulation. Although Katie’s research isn’t helminth related, she’s been fascinated by their immune-altering properties ever since she learnt about them during her undergraduate biochemistry degree.

Her twitter handle is @KatieLowles and Linkedin name Katie Lowles.