Chromium, widespread through the food supply, may stimulate insulin, a hormone important for converting blood sugar into energy. Consequently, chromium supplements have become popular among people worried about diabetes. But the IOM called chromium supplement studies inconclusive and couldn't set an RDA or a safe upper limit because so little is known about the nutrient. Americans today eat 25 to 35 micrograms daily. Found in green leafy vegetables and certain oils, it's essential for blood clotting.
Copper is found in organ meats, seafood and nuts.
Eat 150 micrograms a day of iodine but never more than 1.1 milligrams a day. Found mostly in iodized salt but also some seafood and grains, it's important for proper thyroid gland function.