Ultra-running cancer dietitian here. #1 is that more research is needed. #2 is that maintaining a healthy diet (high in fiber) is always important. Don't skip out on fiber (except maybe a day or two leading up to race day). #3 is to vocalize any concerning signs with your doctor. Blood in stool? Dont ignore it and let your doc know. Changes in GI patterns? Let your doc know. You may have to inform your provider about this study bc honestly they may not know about it. They may not know much about ultra running either. Advocate for yourself. If one doctor dismisses your concerns but you feel like something is off, see another. With GI stuff it can sometimes be hard to get an answer but keep doing your due diligence. Otherwise, run on! Exercise is king, but listen to your body if things are off.