Have you noticed that most of the information about nutrition available today comes from ads selling such products? That is a sad case because nutrition is so important. In the veterinary school curriculum nutrition is high on the list of important subjects concerned with good health of all animals we vets treat and that subject is covered extensively. It would be comforting if human physicians were to be knowledgeable about vitamins and minerals necessary for we humans. One day I predict that there will be tests to determine if a patient has the proper balance of proper vitamins and minerals.
Imagine, the human physicians permitted the national legislature to pass a regulation that anything that caused cancer would be unlawful to be permitted in any human food. Later it was pointed out that the mineral, selenium was necessary for human life but cancer causing in excess. I'm sure salt is in the same category.
An example of another problem concerning one vitamin may be old hat with you but is worth mentioning and that is the reason British sailors of years ago were called "Limies." If 100 sailors left for a year long voyage after as soon as a month some should develop sores of eyelids and lips. A month later a few more would have similar reactions . By half a year some would be dead of vitamin C deficiency. Others would die but half would return with no symptoms at all. Eventually it was found if limes were eaten the sores would disapear. Some ship Captains would carry lime trees on their voyages to prevent the problem. I use that example to suggest that not everybody requires the same amounts and frequencies of vitamins. I would wager that some proportion of humans have a much higher need of some nutrition and if lacking would have symptoms suggestive of a disease condition that would not respond to antibiotics or other medication. How important the subject of nutrition is and how lacking is sound scientific knowledge. To try to assure patients of attempting to cover nutritional deficits some human physicians advise a daily vitamin "complex." Thet's professional guess work.