Caution is needed with vitamin supplements
Do vitamin and mineral supplements have a place in the normal population?
RDAs are found on cereal packets and the like and are set by the European labelling body. It is best not to exceed the RDAs, as these have been set by scientific committees that have reviewed the evidence.
It is always better to take balanced multivitamins. Individual nutrients can cause adverse interactions, such as too much vitamin E can interfere with vitamin K, and excessive intakes of calcium can affect iron absorption as they share the same absorptive pathways. The Finnish ATBC trial showed there was an increased incidence of lung cancer in smokers who took high doses of beta-carotene supplements, other subsequent trials have also confirmed this effect, as a consequence high doses of beta-carotene should be avoided and then RNI adhered to.