Zinc deficiency is common, but not normal for the body physiology, in parts of Africa and Asia and other countries where people consume large quantities of cow milk, which is high in calcium and low in zinc, and of starches and fibers, which interfere with zinc absorption. Administering iron to a zinc-deficient person is EXTREMELY RISKY.
Not only does iron stimulate bacterial growth, but, by aggravating zinc deficiency, it weakens the body immune system of the person being supplemented.
Many metabolic related diseases have been said to be caused by 'virus', which is business motivated to boost the drugs/supplements sales to the unsuspecting consumers.
Remember, never take iron supplements unless you have diagnosed iron deficient. Pregnancy is the possible exception to this rule, check with your obstetrician.
The best test for iron deficiency is a blood test called the serum ferritin level. Ferritin is a protein that carries iron, and low ferritin levels are a common sign of body's iron deficiency. Because the human body has a limited capacity for iron absorption, it does not make any sense to take in more than 20 milligrams of elemental iron at a time if you have a documented iron deficiency.