Every patient with inflammatory bowel disease (IBD) wonders what to eat to improve their symptoms. Many believe that diet affects disease progression and no one-size-fits-all diet exists for everyone. Our controlled trial in adults with IBD supported this idea when the symptoms of almost 50% of adults with IBD in either standard dietary therapy or the Mediterranean-style diet group were ameliorated, though to varying extents. This variability arises because each patient’s biology and lifestyle are unique. People’s gut microbiota, trillions of microbes living in intestine, is highly personalized and can mediate their physiological responses to diet. However, remaining concern is that chronic inflammation in IBD disrupts the gut microbiome, allowing harmful bacteria to thrive and beneficial ones to vanish. Diet alone or conventional probiotic treatments can’t fix this imbalance. I will investigate how patients’ specific characteristics and gut microbes influence their response to certain diets and how these synergize with a newly engineered probiotic designed to thrive in an inflamed gut. These findings will be used for a future clinical trial using our derived algorithm to prescribe personalized diets and a bioengineered probiotic.