The very name "dietary supplement" indicates the function that these food products perform, because it is supplementation, and thus supplementing the daily diet. Supplements are needed because many nutrients are not present in sufficient amounts in the normal diet, but also because the body may need larger amounts of the appropriate nutrients in certain situations. There are data from which 21 concrete conclusions can be drawn about the deficiencies of certain nutrients.

It is also worth paying attention to groups of people who have higher than average demand, i.e. children and adolescents, pregnant women, the elderly. The use of concentrated mixtures can be beneficial to meet their nutritional needs.

It is important to buy products from proven companies, although the black market is popular, which may be due to lower prices of products that can be purchased on it. Products that come from unreliable sources can have adverse effects, because it is often not even known what exactly a given product contains (European Nutraceutical Association, 2014). You can buy literally everything online, there are also false assurances about various products, e.g. miraculous supplements, thanks to which you will lose unnecessary kilograms in just a few days. Simple criticism of offers and paying attention to the composition and labeling of dietary supplements can help in their proper and safe intake, and since these products are often needed to provide the right amount of nutrients for a given person, it is worth using them when there are indications.