Explain the Safe Requirement of nutritional needs?

Given the individual variations in nutritional requirements that have been discussed earlier, the lowest continuing intake level of a nutrient to satisfy good health varies from one individual to another. In practice, we want to set up requirements that would meet the needs of most people and will be safe at the same time for all. For defining the safe requirement, we use the statistical probability concept. 'The lower and upper limit of the range of intake in which the risk of inadequacy, as well as, the risk of excess is zero is taken as the range of safe requirement'.