Wood to use for raised veg beds

I want to build some raised beds in my garden for veg growing and have been looking to source wood e.g. seeing sites selling scaffolding boards made from <span style="font-size: x-small;">European Whitewood. But, I'm also seing suppliers selling Tanalith E treated wood to add protection. I'd rather not use wood that's been chemically treated however, won't untreated wood just start to slowly rot once it comes in to contact with damp conditions? I see maybe untreated oak sleepers as an alternative but they are very expensive even if they are supposed to last 20 years.
Any help welcome, thanks.

Untreated wood will certainly slowly rot but i believe you will get a good few years out of scaffold boards before they will have to be replaced. How about if you have the time and inclination to cover the inside face of the boards with any plastic or butyl just to help prolong the life of the boards?

Sleepers sound lovely but I went away from them because of the price as well.  it depends what look you want.  Mine will be in sight of my kitchen window so I wanted them to look good so I've just bought some 2"x9" timber and had it cut to the size I want (for three beds) before delivery (from Jewsons).  It is new wood but I plan 2 coats of stain/treatment in a nice oak colour once put together.  I deliberately chose new timber rather than rough sawn & treated because I wanted the finished article to look more expensive than they were, I wanted to chose what colour they were and the timber I chose had the edges already slightly rounded for a more expensive/professional look.  With the corner pegs (50p each) and screws I will get each bed for under £20 - a lot cheaper than buying them already made.  When I dig the trenches for them to sit in I plan to line them with pea shingle to ensure drainage, hopefully this will prolong their life even more.  Hope you get what you want.

is it possible to use treated timber gravel boards for a raised bed for vegtables

I would have thought so. using stakes you couldbuild them up to a decent height, and still paint them to suit

I used old scaffold boards, they were only going to be chopped up and burnt. So far so good. Its great being able to dig without standing on and impacting the soil.

I used some decking boards that were in a clearance sale, then bought 4 fence posts which I cut down. Looks much better than I (or more importantly my good wife) thought.