As the link in the OP actually denotes, no, that's not always the case.
Bodybuilders and performance trainers - as well as Soviet Union sports scientists - have known for decades that Vitamin D supplementation is vital. This has been rejected by a significant number of general practitioners and other medical experts who are and were anti-supplement simply out of rote thinking.
Yes, people should be tested for their levels. But this simply isn't feasible for poor people, and telling them to get serum tests for Vitamin D before taking a lower-bound amount of the cheap supplement from the grocery store is ridiculous.
http://www.rollingstone.com/sports/news/russia-banned-from-2...
It is always possible to arrive at a correct conclusion through entirely incorrect reasoning.
Or, as the saying goes, a broken clock is right twice a day.
Homeopathy is crap. But bodybuilding/powerlifting/athletic training often finds the answers well ahead of peer-reviewed science.
Truth be told, doctors still don't know much about IBS and/or Crohn's. Or even conditions like rosacea and/or dermatitis. Mark my words, better gut flora/microbiome will be the cure for these conditions in the near future and doctors will contest this up until the evidence is too loud to ignore.
A fruit or vegetable that have traveled thousand of miles before being delivered to you has almost no vitamins left in it and probably didn't have much to start with considering soil depletion.
I believe (emphasis on believe) that supplementation is necessary even if you "eat right".
I know it sounds downright crazy, but it's possible that someone who's studied medicine and practiced it for years, actually knows better than random anonymous forum users.