Eat your beans

A link between the gut and diet may mean a cure for an incurable disease

“The hypothesis has always been that bacterial composition is tightly linked to diet.”

Plate of Baked Beans
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Your gut is a thriving universe unto itself. This tiny cosmos is inhabited by thousands on thousands of microorganisms, which together make up your gut microbiome.

Among other things, this internal ecosystem contains bacteria that we rely on to help us break down and process the foods that we’re not readily equipped to digest. But a slew of recent scientific studies shows that our gut also connects more broadly to our holistic health, even to things that are seemingly unrelated, like our brains.

The science is preliminary, but there is compelling evidence that what you eat — and in turn, that changes the gut microbiome — has an outsized influence on your health. But not in the way you’d think.

What’s new — A new study published on Friday in the journal Science Advances looks at how diet could alter multiple sclerosis (MS) symptoms via the gut microbiome. By feeding mice with an MS-like condition a specific diet, scientists were able to reprogram their gut bacteria — and reduce their symptoms.

The study started with the observation that the gut microbiomes of people with MS lack a kind of bacteria that, in most folks’ gut, breakdowns a nutrient called isoflavones. This nutrient is commonly found in everyday staple foods, like soy and beans.

So, the team hypothesized that MS might be related to the absence of these bacteria — and in turn, eating more foods with isoflavones in them could alleviate the symptoms.

From there, they were able to demonstrate the critical difference that the bacteria’s presence or absence can make in this disease.

Why it matters — This study is so intriguing because it identifies a clear relationship between the gut, the food we eat, and our brain and body health.

In the new study, the researchers go further than past work by not only establishing a clear link between gut bacteria and diet, but also the mechanisms driving the relationship — and how to potentially game it to our advantage.

“The hypothesis has always been that bacterial composition is tightly linked to diet,” says Sergio Baranzini, a neurology professor at the University of California, San Francisco who was not involved in the research. While other studies have investigated this relationship, “what those studies fell short of is showing what could be the potential mechanism.”

MS is rare, but it also occupies a place in the public consciousness, in part because of its insidious effects on the body. TV personality Jack Osbourne and actress Selma Blair have both been diagnosed with the disease.

Selma Blair has become a vocal advocate for MS awareness and treatments.

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MS essentially wreaks its havoc by putting the central nervous system out of business. Over time, people with MS will slowly lose their sensory, motor, and cognitive abilities. There is no cure — but this study hints at the promise of dietary interventions to quell some of its effects.

Baranzini was impressed with the revelation. “I was surprised to see that everything was working,” he says. “It felt like, ‘Can this be too good to be true?’ ”

Digging into the details — First, it’s key to learn about isoflavones, a nutrient present in many common foods, and what it does in the body.

Foods rich in isoflavones include:

  • Soybeans
  • Lentils
  • Pistachios
  • Chickpeas
  • Peanuts
  • Other beans and legumes.

Our guts can’t naturally break down isoflavones, so we host a strain of bacteria that do the hard work of metabolizing them.

While beans and legumes offer myriad benefits, it’s not the isoflavone itself that is the secret ingredient to health. Rather, it’s the type of bacteria in our gut microbiome that metabolize the isoflavone. If you introduce isoflavone by eating lots of beans and peanuts, then the bacteria will flourish.

Eating foods like pistachios may influence the gut microbiome in positive ways.

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How they did it — In this study, the researchers fed a group of mice infected with an experimental version of MS an isoflavone-rich diet and also fed another group of infected mice an isoflavone-free diet.

The mice that ate the isoflavone-free diet deteriorated far more rapidly over the course of three weeks, while the mice that ate the isoflavones deteriorated at a much slower rate.

The reason for this effect has to do with how the different elements of the microbiome work together to safeguard our body’s health, according to Ashutosh Mangalam, the study’s corresponding author and a pathology professor at the University of Iowa’s Carver College of Medicine. He likens the gut microbiome to a town. The town doctor is one of the most crucial elements, and if you remove the doctor, then the town as a whole suffers. But, if the doctor comes back, then the town can recover.

But if you are worried about MS, there is no reason to start eating a bean-rich diet just yet (although beans are great).

“In science we have learned that everything is a Goldilocks system,” says Mangalam. Everything is good in moderation.

What’s next — This study is a first step on the road to treatments that are cheap, effective, and simple. There’s currently no cure for MS, but more broadly, the effect seen here of a bean-rich diet hints at the influence of both isoflavones and the gut on other conditions to do with aging and neurodegeneration, like ALS, or Lou Gherig’s Disease, something Mangalam is confident will bear out.

Testing this idea in humans is on the horizon, though any human participants will follow a slightly different diet regimen — more beans.

Baranzini also cautions that making the jump from mice to humans carries new challenges. While it may be possible to treat experimentally induced MS with a nutrient found in beans, MS in humans is another beast entirely.

Mangalam plans to seek out how the microbiome influences MS in other ways, too.

“I am well aware that MS is not a singular disease,” he says. “We might have to divide MS patients into certain categories based on microbiome function.”

“That’s what my dream research is for the next five to 10 years, to try to identify what [other bacteria are] lacking.”

Abstract: The gut microbiota is a potential environmental factor that influences the development of multiple sclerosis (MS). We and others have demonstrated that patients with MS and healthy individuals have distinct gut microbiomes. However, the pathogenic relevance of these differences remains unclear. Previously, we showed that bacteria that metabolize isoflavones are less abundant in patients with MS, suggesting that isoflavone-metabolizing bacteria might provide protection against MS. Here, using a mouse model of MS, we report that an isoflavone diet provides protection against disease, which is dependent on the presence of isoflavone-metabolizing bacteria and their metabolite equol. Notably, the composition of the gut microbiome in mice fed an isoflavone diet exhibited parallels to healthy human donors, whereas the composition in those fed an isoflavone-free diet exhibited parallels to patients with MS. Collectively, our study provides evidence that dietary-induced gut microbial changes alleviate disease severity and may contribute to MS pathogenesis.
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