It has been estimated that the daily minimum requirement of man is approximately 15mg. Modern man has depleted what was once essentially fertile soil, and modern fertilizing generally provides minerals inadequately. Dr. Pfeiffer states that soil depletion is more severe than generally recognized.
Many factors decrease the effective zinc in food and water in modern society.
If the plant, grain, fruit or nut has enough zinc from the soil, then we will have a normal zinc level. Modern food processing also removes zinc. Milling reduces the zinc level of wheat flour by 80 percent, cornstarch contains considerably less zinc than corn meal and frozen vegetables such as frozen peas, broccoli or spinach have been treated with the chelating agent EDTA, which not only makes the vegetables look bright green, but also removes zinc as well as calcium and manganese. This explains why people generally have a high copper level and a zinc deficiency at the same time. It has also been found that meals served in cafeterias, hospitals and other institutions have extremely low zinc contents and eating such diets, over a period of time, most likely results in a more severe zinc deficiency.