poor

Haven't found an studies on it though.

Just searched page 1 of google "is rust in diet harmful U.S. Environmental Protection Agency" "is rust in diet harmful"

Most reliable link was https://www.foxnews.com/health/is-using-rusty-cookware-really-that-big-of-a-deal not sure if fox is reliable (iirc fox's opinion pieces are unreliable)

Rust might increase bodily iron: "Limitations of all pot types, except stainless steel, included heavier weight and rust formation. In addition, even though cast iron and blue steel pots were less expensive and leached greater quantities of iron, stainless steel pots were lighter, less likely to rust and presumably less likely to cause iron overload"