Red meat

Fiber isn't needed for regular bowel movements, diabetes is caused by sugar AND fat not just fat, the study correlating cancer with red meat technically only found less than one percent risk increase (not to mention it was for omnivores on the Standard American Diet), and scurvy doesn't happen because glucose competes with Vitamin C so now it has no competition also lower inflammation so absorption is higher. There's very little evidence to suggest that they would suffer any significant health problems, but then again, we still don't really know the details. Now that there are a couple thousand participants of said diet we might see some studies in the near to distant future!