If you are going to paint a garden bed you'll need to seal it with plastic inside to stop water penetrating the timber and blowing the paint off the surface. Builder's film would be suitable for lining the beds. The best paint to use would be an exterior water-based product similar to Dulux Weathershield as it would be the least toxic in our range.
In regards to your question, no chemical harm will be done to your vegetables however this paint does not meet criteria for non-toxic labelling.
Please let me know if you need further information or had questions.