Vegetable safe sealer for raised bed

[yippee]

Hello. This year, I am looking to start making the transition from container gardening to raised bed gardening. I'll probably switch half this year, and half next year. Due to lumber prices this year, I decided that I couldn't justify the extra cost for cedar right now. I'm trying to build these and give them the best chance to last me several seasons, and maybe by then I can reevaluate the building materials. If you were to seal the wood to help keep moisture out, while picking a food safe product, what would you recommend?

Thank you.

 

[TXChookstead]

I'm using boiled linseed oil, but I know there are other possibilities. Maybe just lining them with plastic sheeting would work to some degree. Interested in reading what others say.