What restaurants are the most Coumadin-friendly?

My husband takes the anti-coagulant Coumadin (warfarin). It is important not to eat too many foods that are rich in vitamin K while on Coumadin because they interfere with each other. So, we try to keep his K intake constant from day to day, avoiding large swings.

The hard part is when we dine out. If something is cooked in soy or canola oil, it contains much more vitamin K than the same thing cooked in, say, peanut or corn oil. Because of this, we have to ask questions about what oil restaurants use, and it’s hard when we get answers like “we cook with non-hydrogenated oil” or “we use Sysco brand” when we’re really looking for an answer like “We use 100% soybean oil” or “our fries are made using peanut oil.”

Do you know which oil any various restaurants use? (Have you perhaps worked there and are in the know, or have done Coumadin-related research that you want to share?) We’re especially looking for ones that use oils other than soy (“vegetable”), canola, or olive, but even knowing for sure that a particular chain uses one of those will help us rule it out as well.

(I know that results may vary based on franchises, and that if we want to be 100% sure we should just stay home. Sometimes, though, like when travelling, that is just not possible – and we are also unwilling to stop living and never venture forth from the house.)

Thank you for reading. It gets old, eating at home all the time because we don’t know what restaurants are cooking with.