Can what you eat really make you change your mind? Spend any time in the mental health and wellness corners of social media, and the answer seems to be a resounding Yes: Influencers all over the internet preach the gospel of using probiotics and diet to treat everything from depression and anxiety to PTSD.
For once, many scientists are echoing this hype on social media: In the last decade, researchers have begun to discover exactly how the microbes in our gut affect our brain chemistry. In the last episode of Gastropod, “gut feeling”, co-hosts Cynthia Graber and Nicola Twilley address the science and history behind this exciting new field of medicine.
One of its leaders is John Cryan of the University of Cork, and in 2011 he and his colleagues coined a new word to describe this new science: psychobiotics. “A psychobiotic is an intervention that targets the microbiome for the benefit of mental health,” he told Gastropod; which encompasses probiotics, or the kind of beneficial bacteria you can find in your yogurt, as well as prebiotics, which are foods like green leafy vegetables and whole grains that the beneficial bacteria already living in your gut like to eat .
Interestingly, although this type of food-based mental health therapy seems brand new, in the early 2000s the idea that gut bacteria could play a role in psychological problems was a rather radical and speculative suggestion – the idea behind this is not at all. In fact, in the late 1700s and 1800s, the medical historian ian miller says that most physicians thought of the stomach as “the great nerve center of the body, or the great sensorium”; in other words, that the stomach was more important than any other organ, including the brain, in determining how you felt. But it wasn’t until the 1840s, when scientists realized that bacteria (then a relatively new discovery) could be found in the human intestine, that they too began to investigate why things that affect digestion can also affect the mind.
As soon as they were discovered, this microscopic gut microbiota began to take the blame for a variety of mental and physical illnesses. In the late 1800s, a handful of physicians developed the theory that the consumption of certain foods and their subsequent breakdown by microbes in the gut could create toxic substances that, if absorbed, could induce melancholy, stress, and general mental decline, among other things disastrous consequences. They called this condition “autointoxication” and, for a while, it was all the rage.
In 1914, the fabulously named Dr. Bond Stow, a New York pathologist, framed the era’s focus on autointoxication as a “battle royale,” writing that physicians must “attack the root of the problem by dispelling malevolent intestinal flora with a benefic.” A few years earlier, in 1909, the British physician Hubert Norman reported that sour milk had been shown to be an effective cure for “melancholia” in one of his patients. Around the same time, at Bethlem Royal Hospital ( better known by the term it inspired, Bedlam), Dr. George Porter Phillips claimed that he could treat mental illness with a kind of prescription kefir, made up of a microbe commonly found in yogurt. lactobacillus bulgaricus, combined with whey. Phillips’ drink has been called the world’s first psychobiotic.
Until now, these treatments have ranged from harmless to scientifically promising by modern standards. But things took a turn in the 1920s. A handful of doctors, including an American, Henry Cotton, began promoting the idea of ”surgical bacteriology.” Cotton began removing all or part of the colon from patients at the New Jersey State Lunatic Asylum, the most direct way, he claimed, to get rid of all those bad gut bacteria. (He also recommended removing all of the patients’ teeth, to ensure any oral bacteria were also removed.) Cotton claimed that 80 percent of patients so treated were cured of their mental illness, yet the procedure had a staggering 30 percent mortality rate. surgery alone and of course those who were “cured” then faced the significant challenge of driving without a major part of their digestive system.
However, just as Cotton and his cohorts wielded their scalpels in an attempt to cure mental illness through gut modification, new theories were emerging that signaled the end of this early psychobiotic enthusiasm. In the 1930s, Sigmund Freud’s psychoanalytic theories and his emphasis on talk therapy, much less complicated than colon surgery! — had become the new mental health orthodoxy. Around the same time, scientists were investigating the chemicals that brain cells, neurons, use to signal to each other inside the brain. In 1951, the first neurochemical antidepressant, iproniazide, was discovered by accident among happy tuberculosis patients. Drugs like Prozac, Paxil, and Zoloft, which seem to work by adjusting the levels of different neurotransmitters in the brain, soon followed.
In the late 20th century, the standard for treatment of mental health disorders consisted of various flavors of talk therapy, often administered in combination with medications that targeted brain chemistry. Guts were no longer part of the conversation. That is, until today.
So were those early pioneers up to something? Can you really improve your mental health by modifying the bacteria that inhabit your gut? What do scientists know works and what are they still discovering? Follow and subscribe to Gastropod to learn about the science behind the hype – it’s news we can all use, combined with the story of some sad mice, stressed out students, and a new US military experiment.
