Six-pack abs are the dream, right? That ripple of taut muscle on a torso that speaks of strength at a single glance, yet can withstand lengthier gazes. Despite trainers dispensing tips on the wisdom of total body workouts, the six-pack remains the holy grail of workout results.

The thing is, even in fitness—no, especially in fitness, the inside counts more than the outside. Cut abs mean nothing if your gut health is in sh*t shape, brah, and it pays to heed that old adage “Listen to your gut” literally.

Home to hundred trillions of bacteria, the gut has been getting the attention it rightfully deserves for the past couple of years, to the point that the global market for the probiotics industry ballooned to $32.6 billion in 2014, with a projected annual growth set at 20 percent minimum. Probiotics, of course, as defined by the World Health Organization, are “live micro-organisms, which, when administered in adequate amounts, confer a health benefit on the host,” such as help the microbiota in the stomach and both small and large intestines fight infection-caused diarrhea, inflammatory bowel diseases, irritable bowel syndrome, even asthma, allergies, and Type 1 diabetes. Researchers at the Institute for Immunology at the University of California, Irvine have outlined the probiotics’ role in keeping the human body functioning and alive: “the development of the gut immune system, digestion of food, production of short-chain fatty acids and essential vitamins, and resistance to colonization from pathogenic micro-organisms.” That Yakult habit you developed in childhood? Good call.

But here’s an interesting development: a growing body of research shows not only does the gut do house cleaning of the digestive system, but its state of health also affects our mental and emotional health. In her 2014 book Gut: The Inside Story of Our Body’s Most Underrated Organ, author Giulia Enders introduced the term “gut brain” to indicate the connection between the two organs and the gut’s essential role in forming a person’s identity.  She pointed out the vast network of nerves attached to the gut that transmits information to the regions of the brain, which oversee self-awareness, memory, and morality. While further studies still need to be done to draw a clear relation between what we consume and how we decide what is right from wrong, it’s hard to deny the immediate and apparent effects an afternoon of mindless junk food snacking has on our mood and energy level.

Thus, maintaining the balance of good bacteria in the gut is essential. One measure is regularly ingesting both pre- and probiotics to kickstart a gut made sluggish from an unhealthy diet and strengthen the cells that line it. Prebiotics are non-digestible carbohydrates that good bacteria feed on, found in bananas, garlic, onions, asparagus, soybeans, honey, artichokes, oats, and wheat, while probiotics like Yakult are available in health store foods as dietary supplements. Meanwhile, the likes of yogurt, kimchee, pickles, and kefir are called synbiotics, a combination of prebiotics and probiotics.

On the other hand, processed grains, excessive added sugar, excessive fat, and antibiotics wipe out the good bacteria in the gut. In fact, recent studies discovered a link between brain inflammation to gut bacteria imbalance that’s caused by the consumption of fatty foods. Inflammation is the root of almost all brain disorders, from autism and Parkinson’s to Alzheimer’s and multiple sclerosis. Thus, those under medication are advised to take doctor-prescribed dosages and to balance the antibiotics’ effects by consuming yogurt with active cultures.

Lest you think it’s a matter of balancing columns between good and bad bacteria, think again: they may almost be innumerable, but once a significant amount of microbiota is destroyed, its effect on our health isn’t easily reversible. An example: several bacterial species were found to “have failed to recover” six months after a short course of the antibiotic ciproflaxin in a 2008 study. Scary sh*t (literally). As always with health, prevention is way better than cure.

Writer: September Grace Mahino