Netflix's 'Hack Your Health': Is the Gut Always to Blame?

A new Netflix documentary, "Hack Your Health: The Secrets of Your Gut," explores how bacteria in the gut may affect overall health. We ask experts about the science behind the movie.

Previous Netflix health documentaries, such as "You Are What You Eat," have been criticized for exaggerated claims and promoting the views of activists rather than unbiased scientists.

Unsurprisingly, all eyes are now on "Hack Your Health: The Secrets of Your Gut," a documentary released in April that dives deep into the world of bacteria.

The documentary follows the journey of four individuals: a Michelin-starred pastry chef, Maya, who is recovering from an eating disorder and is trying to rebuild a healthy relationship with food. There is also Daniell, who follows a highly restrictive diet as she suffers from several gut issues, including irritable bowel syndrome.

Kimmie, an entrepreneur and a single mother, constantly tries to lose weight without success. A competitive eater, Kobi no longer feels hungry, making him wonder whether his profession is to blame.

The participants take home tests examining their gut bacteria and start their journey to recovery, guided by Giulia Enders, a German doctor and the author of the bestselling book "Gut: The Inside Story of Our Body’s Most Underrated Organ," accompanied by her American colleagues.

How the gut affects our health

The movie claims that many conditions previously thought to be determined by genetics may be attributable to microbiome. John Cryan, a professor of neuroscience at the University College Cork who was featured in the documentary, says the gut affects the whole body and calls it "the second brain."

The gut microbiome is the ecosystem of about 100 trillion microbes — bacteria, viruses, and fungi — that live in the intestines. These microbes help break down certain food components and support the immune and nervous systems.

The disbalance of the gut microbiome, called dysbiosis, is linked to conditions like inflammatory bowel disease, irritable bowel syndrome, obesity, and cancer.

Colon bowel disease concept.
Image by 9dream studio via Shutterstock

Evidence suggests that gut bacteria play a role in a wide range of chronic conditions, says Dr. Marco Jost, an assistant professor of microbiology at Harvard University.

"Sometimes it can protect from chronic disease or alleviate the symptoms of disease, and sometimes it can predispose to disease or exacerbate the symptoms," Jost tells Healthnews.

The field of gut microbiome research has been booming in recent years, as has the global digestive health product market, which was valued at $51.62 billion last year.

Emerging evidence links gut bacteria to neurological and mental health conditions. For example, a 2023 study suggests that nearly 30% of gut bacteria in Parkinson's disease patients differ from those without the condition. Changes in gut microbiome were also observed in people with symptomatic Alzheimer's disease.

Studies have associated dysbiosis with the onset and progression of depression via regulating the gut-brain axis, which is bidirectional communication between the gut and brain. This prompted researchers to explore the possible benefits of probiotics or prebiotics for the treatment of conditions like depression and anxiety.

Jost says many human studies examining the link between gut bacteria and brain disorders show associations but rarely prove that a specific bacterium causes certain diseases.

The best evidence, which is difficult to extrapolate from, is animal models, where you can manipulate the microbiome and monitor effects on diseases. In these models, bacteria's clear causal role in autoimmunity and many other diseases has been established. The challenge then is to extrapolate that from laboratory animals to humans, which is not always clear-cut.

Jost

The scientists in the movie acknowledge that research is still in the early stages. Tim Spector, a genetic epidemiologist at King's College in London, called it the tip of the iceberg.

"There's another 97% more to discover," he said.

Do gut bacteria cause obesity?

Kimmie's gut analysis showed that her microbiome lacked diversity and had low bacteria count which is linked to improved ability to lose weight and feeling full. She was advised to make life-long changes in her diet, introducing more plant foods.

The bacterial composition of gut microbiomes differs between obese and lean individuals, although the significance of these differences is not fully understood. Animal studies show the potential of gut microbiome interventions for treating obesity, but the findings may not necessarily apply to humans.

The "Hack Your Health" documentary cites well-known experiments that involved germ-free mice receiving fecal transplants from obese donors. Following the transfer, the mice became obese and saw changes in their microbiome composition.

Diet is one of the major disruptors of the gut microbiome, as foods high in calories, heavily processed convenience foods, emulsifiers, and artificial sweeteners appear to compromise the protective lining in the gut.

Man farmer with homemade vegetables in his hands.
Image by Tatevosian Yana via Shutterstock

Dr. Annie Gupta, an assistant professor at the University of California, Los Angeles, and one of the scientists featured in the movie, suggests diversifying the gut microbiome by eating 20 to 30 different plant foods a week.

Kaitlin Colucci, a consultant dietitian and founder of The Mission Dietitian, tells Healthnews that eating a wide variety of plants introduces diverse types of fibers, polyphenols, and other bioactive compounds, which serve as substrates for different microbial species in the gut, promoting microbial diversity.

Moreover, a diverse intake of plants boosts the production of short-chain fatty acids, such as butyrate, which play a crucial role in maintaining gut barrier integrity, reducing inflammation, and supporting immune function.

A diverse diet helps build a resilient microbiome that can better withstand disruptions caused by antibiotics, infections, or poor dietary choices.

Colucci

When it comes to weight loss, Jost warns against reducing a complex community of gut microbes to a single number — diversity. He cites the study suggesting the microbiome's composition can predict how long mice are going to exercise.

Jost tells Healthnews, "We can envision that, for example, gut microbes affect the production of hormones in the intestine regulating satiety and food intake. However, it comes down to which microbes are present and what they're doing, and less so a single number like diversity."

Colucci says people with less diverse microbiomes may face challenges losing weight due to dysbiosis, which can lead to increased gut permeability, systemic inflammation, and metabolic dysfunction.

Don’t try fecal transplantation at home

In the documentary we see Daniell, a student with multiple gut issues that profoundly affect her quality of life, has been experimenting with fecal microbiota transplantation (FMT). The procedure involves transferring the bacteria from the healthy donor’s feces to the recipient’s colon during colonoscopy or endoscopy.

Last year, the U.S. Food and Drug Administration (FDA) approved the first fecal microbiota product taken orally to prevent recurrence of C. difficile infection in adults.

When Daniell received gut bacteria from her brother, who is suffering from acne, she claimed she started having skin issues. She tried using the fecal matter of her boyfriend, who has a mental condition, which exacerbated her depression, Daniell claimed.

In the movie, Daniell is trying her luck again with DIY transplants — viewers can see the couple making enemas from the boyfriend’s stool. Experts criticized the experiment, emphasizing the dangers of transplanting gut bacteria at home.

Abby Langer, a registered dietitian, called the notion that FMT may cause or alleviate mental health issues an anecdote.

"When you get the good bacteria from someone in an FMT, you also get the bad. There are also huge risks to randomly inserting someone else's poop into your body, so please: don't try this at home," Langer wrote on her website.

The transfer of live organisms to patients with illnesses may be risky: there are documented cases of E. coli infections due to investigational FMT treatments.

Moreover, there is a theoretical possibility of increasing the risk of non-infectious conditions, ranging from insulin resistance to cancer. That’s why prospective FTM donors must undergo rigorous screening: in some programs, as many as 97% of them are rejected.

Criticism over autism misinformation

Despite relatively positive reviews from nutrition experts, the documentary did not avoid criticism. The National Autistic Society urged Netflix to take down the movie that "casually promotes dodgy and untested science about autism."

The leading U.K. charity wrote on X, "The show refers to autism as a 'disease' and 'brain problem.' Autism is a lifelong disability, not a disease linked to gut health, and cannot be treated or cured. To suggest otherwise is wrong, deeply irresponsible, and offensive to autistic people and their families."


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