Food sources of vitamin have to come from animal sources. The best is cod liver oil but only those that have not been stripped of it's vitamins through processing(most are). Fish, dairy products(milk, cheese, cream, yogurt, high vitamin butter), eggs and organ meats are other sources. It would still be tough to get 4-5000IU from food. The Inuits and Eskimos would have had to get theirs almost exclusively from food.

I've never tried MSM. My guess is I wouldn't react well since it's concentrated sulfur. I do OK on sulfer containing foods that are not goitrogenic but concentrated stuff like that or NAC/Cysteine is too much given my current toxicity load.