No, because they find out really quickly what they're deficient in when symptoms show up (or they revert back to their previous diet). I admit I worded that paragraph poorly though, that wasn't my intention.
> Fwiw, I've been vegetarian for like twenty years, don't really track much of anything in terms of vitamin intake, and am doing just fine according to the last time I had blood work done. I eat eggs and beans and rice for protein, and cook on a cast iron for iron... And that's the sum of my thought on vitamin intake. My partner takes b12 supplements, though.
So you get blood work done regularly, ensure you have certain things in your diet, and you intentionally try to make up for a common nutrient deficiency?
You may not see that as a lot of effort, but for people that don't really care about their health, every one of those things can make a significant difference in terms of lifespan.