This high value is calculated from the game itself, due to the high nutrition (80), and only material being “flesh”, as far as I know.
However, 833% isn’t necessarily lethal, it would be, however, toxic.
An average male needs at least 6mg/day ; 8mg/day is recommended, it would be the 100% I’d assume.
That means the 833% is 66,64 mg/day of iron. 70mg/day seems to be a lower limit where you can start seeing adverse effects of the iron poisoning, like “gastrointestinal irritation” - means, stomachaches I guess, maybe even diarrhea in worse cases(?), and systemic toxicity. It wouldn’t kill you, but you’d be hurtin.
Those numbers could be slightly wrong, of course. You know how the Internet is.