Modern medicine focuses on symptoms rather than the causes of diseases. Physicians study pathology and learn the drugs and techniques to respond to pathologies. Little effort is directed towards understanding the ideal of human health and how to support it.
Without understanding ideal health, which should be everyone's goal, we are unlikely to achieve it.
Some common sense warnings are very sensible, smoking and excessive alcohol consumption are obviously destructive. Exercise is beneficial, yet there is great confusion as to what type and how much, with many myths competing for dominance. We are warned against salt and cholesterol, yet science doesn't support the paranoia. Fat is demonized while sugar, which is much more harmful gets a pass.
We have been warned away from large doses of Vitamin D because it is oil soluble, yet recent science has shown that amounts of 20 to 25 times the RDA of 400 IU are necessary for good health. I have taken 6000 IU daily for some years and have now increased my intake to 8000 IU.
The RDA for Vitamin C has been around 100 mg, yet other mammals synthesize their own Vitamin C at levels which would equate to about 17,000 mg daily for an adult male. Linus Pauling, the Nobel Prize winning scientist who long advocated increasing Vitamin C intake, had a patent with a German medical doctor for reversing heart disease by increasing daily intake to 5000 mg and adding the amino acids proline and lysine.
Many have also found relief from lower back pain by increasing Vitamin C intake to levels of 5000 mg daily. Personally, I try to maintain an intake of at least 4000 mg daily.