Everyone—even children—seem to be deficient in zinc–when tested using new highly sensitive testing. Again, this is probably due to depletion in our soils. Supplementation with zinc has been shown to be effective in shortening cold duration, and in improved skin healing after plastic surgery. If we were getting enough zinc in our diet to optimize our metabolic functions, no such wound healing effect would be seen. Zinc is critical in cell to cell signaling. You can get a small dose of zinc in most multivitamins. But recent studies show that deficiency of zinc causes the body to substitute copper, and this elevated copper/zinc ratio is associated with cancer. In human case studies of terminal cancer with metastases, infusions of zinc into the cancers killed both the primary and the metastases without patient harm. So a bigger zinc supplement has large potential benefit. I try to take at least 16 mg if not more of zinc a day.