They are flawed in principle though, the principle is wrong.
I think the "added insult" point is pretty key. See: the West. High intake of sugars, sometimes stemming from physiological impulses related to chronic stress, which are in turn paired with sleep problems. Sugars are highly available for cheap, and few people know enough to tell you that they're total garbage.
Overabundance of (stupidity re:) anything can kill you, even water-soluble Vitamin Bs. Vitamin deficiencies are indeed, often the result of extreme deprivation as well - and it is in these instances where select, high dosages of vitamins and minerals have practical, therapeutic applications. Out of curiosity, what do those here think of medicine in general? Certainly it is a complex topic.
I periodically review my posts and pick apart my writing, minor though it may be. My reply quoted is not particularly relevant to the issue you brought up.
Regarding the "principle" -- certain aspects of most readily available foods are less nutrient-rich (supposedly in part due to generations of industrial farming practices), and lifestyle doesn't necessarily allow for moderately consistent, good nutrition. An occasional, reasonably-dosed multivitamin can be a helpful supplement in this case. Please describe to me your understanding of how multivitamins are flawed "in principle", since I'm certain we have different ideas about this.
The researchers followed them up to see which ones developed prostate cancer.
The results, published in the International Journal Of Cancer, show that total antioxidant intake – from foods or pills – neither increased nor decreased the risk of a tumour. Antioxidants fight the process, called oxidation, that destroys cells.
There was some suggestion antioxidants from coffee had a slightly protective effect.
But the most alarming finding was that men with the highest intake of antioxidants from vitamin pills were 28 per cent more likely to get lethal prostate cancer than those who took the lowest amount of pills or none.
Supplements are used in healthcare settings sometimes and do have uses in certain situations under medical supervision, but the majority of people buying multivitamins and other supplements are buying them because they "read something" that sounds plausible, but doesn't have any strong evidence showing the function that people are looking for. You may hear how much better someone feels after taking a multivitamin, but it's likely placebo, unless they are horrifically deficient; in which case they have bigger problems anyways.
"Supplements" covers a broad range of substances from herbs, to "nutraceuticals", to bodybuilding supplements. There is a vast world of uneducated, misleading, or downright false advertising that surrounds 99% of products because, as far as this discussion is concerned, they are a business. While I do find this type of behavior reprehensible, I also have sort of a hard time finding sympathy for those that take the bait - hook, line, and sinker.
Generally speaking, if the product in question is a derivative (amino acid, vitamin, mineral, antioxidant, etc), it may not be advisable for long-term use, under extreme circumstances, or in high doses without consulting a trusted medical professional. Many herbal products have a long history of use, and can be much safer to use, but still they should not be used in high-doses without taking the appropriate precautions.
I personally find a lot of things in herbal medicine very appealing. A lot of the stuff is free (grow plants, forage for mushrooms, etc.), and natural in the most literal sense, with hundreds, if not thousands of years oh historical use.