I am what some people call a skeptic. Others call me much worse. One thing I have always been skeptical of is the dietary supplement market. I have yet to read a single scientific report that has convinced me that food supplements are anything more than placebos. One of the greatest scientists of the past 100 years was convinced that vitamin C had uncanny beneficial effects on the human condition. He never proved his theories. He did take a lot of vitamin C and excrete it as urine.
It is with this preamble that I present two related links.
A science blog article about how dietary supplements get away with deceitful marketing and poorly regulated preparations.
A Scientific American piece describing conflict over US Preventative Services finding that calcium and vitamin D supplements do not provide any benefit to properly nourished people.