Several minerals have been heavily researched and optimum supplementation levels have been determined. These include calcium, magnesium and zinc. The dosage of others are more controversial, such as vanadium and molybdenum. Selenium, which is quite deficient in modern diets, appears to be a potent antioxidant. As a word of caution, no one should take iron supplements without a physician's prescription.
Solid evidence links excess iron intake with the development of cancer.
In addition to herbs, there is a whole range of supplements available, which are neither vitamins, nor minerals. These include items such as glucosamine sulfate, shark's cartilage, amino acids, DHEA and melatonin, to name a few. While such items are legal for sale without a prescription, they are not really nutrients. Some are actually more similar to drugs. The proper use of these items is highly specific.