Certain vitamins are very safe at levels tens or even hundreds of times the NRV, whereas for others the safety level is much closer to the NRV. For this reason every vitamin and mineral needs to considered on an individual basis in terms of its upper safe level. The Nutrient Reference Value (NRV) is the amount of a vitamin or mineral which has been calculated to help prevent basic deficiency states in the general population. However, certain vitamins and minerals at optimal levels, above the NRV, have consistently been shown to have positive benefits in specific areas of health. This is why some Vitabiotics formulas have certain nutrient levels greater than 100% NRV. All Vitabiotics products has been developed using the latest research and contain effective levels of vitamins and minerals, while avoiding any excessive amounts, in accordance with official upper safe limits for vitamins and minerals. Vitabiotics avoids "mega dose" levels of isolated nutrients and instead we have always stressed the importance of safe, moderate and sensible levels of vitamins and minerals, carefully balanced to maximise their combined effect; an approach which has been supported by many experts and researchers over the years.