I'm dubious of the "vegetables are obviously wonderful" meme. We almost never see hunter-gatherer groups pursue leafy or cruciferous veggies as a source of significant calories. Instead we see a lot more calories coming from starchy sources, tubers etc. In my investigation of micronutrient content, I haven't seen much evidence that there are any substances you get from leafy/cruciferous veggies you can't get elsewhere pretty easily. I think the reason they show a link to longevity is that the person who eats lots of vegetables is either consciously or inadvertently optimizing their diet for high micronutrient content*, and I think there are other ways to get there. I wouldn't mind being wrong about this if anyone has some contrary evidence.
*A study on seasonal fluctuations in the micronutrient contents of foods correlated very well to mortality and sickness in New Zealand, this area of research deserves a lot more study than it is currently getting.
We know a lot less about hunter-gatherers than most people think, and hunter-gatherer tribes fluctuate a lot in terms of their diets/lifestyles, as one would expect with the diversity of the world.
Vegetables tend to be low calorie, so you wouldn't expect tribes to expend a lot of effort getting them. That doesn't really apply to a modern environment where getting enough calories isn't a concern and vegetables can be bought at your local supermarket.
Dying or becoming severely physically/mentally ill is very likely going to significantly lower the output of your utility function, so it would probably be a very bad idea to ignore the low-hanging resources which can significantly extend the time for which you are alive and well. I have attempted to search LessWrong for a list of such resources, and haven't been able to find one.
Are there any books, websites, or posts that contain significantly low-hanging fruit in this area? If so, please list them in the comments below.