Alshammari and colleagues (2022) prospectively measured changes in carcinoembryonic antigen (CEA) and lactate dehydrogenase (LDH) in 37 patients with colorectal cancer who observed Ramadan, comparing results between those who fasted for 20 or more days against the results for those who fasted less than 20 days. This evidence concerns the gene CEACAM5 and colorectal cancer.