Similar values for Vitamin D are IU and for vitamin C it is 75 mg to 90 mg.|Worries about the coronavirus, the stock market and the general disruption of life have added to our stress levels, but we know that stress also can make you more susceptible to respiratory illness. The National Academy of Sciences establishes national nutrition recommendations. These are the same standards you find listed on the labels of foods sold in US grocery stores. While researchers broadly agree that you need enough of these essential nutrients, some claim you can get additional benefit from consuming more than that in some cases.