This question is controversial because it doesn’t really have an answer. Theoretically you can supply all the nutrients you require from a healthy diet. However, the practicalities of modern global living often mean this is not possible. The nutrients least likely to be present in high enough quantities in foods is probably vitamin D. Research suggests that for adults, intakes of vitamin D should be around 2000 IU per day in the absence of strong sunlight in order to maintain good health. However, this intake is far higher than could be supplied by foods. Those living at high latitudes with weak sunlight for six months of the year therefore must supplement with vitamin D or run the risk of ill health.