A nutritional or dietary supplement is usually a compound containing substances in much, much higher concentrations that can be found in natural products. For instance a person may get the equivalent of iron in a small tablet that would require the person to eat 2 kg of spinach, however that tablet is not supplying other nutritional and roughage that the spinach is, so a definition of a supplement could be - something taken in the form of a concentrate, metabolite, constituent, extract, or combination of any of the above to rectify the level of a deficiency (normally vitamins or minerals) in the diet.
Furthermore, it must also conform to the following criteria:
• intended for ingestion in pill, capsule, tablet, powder or liquid form
• is not represented for use as a conventional food or as the sole item of a meal or diet
A dietary supplement cannot claim to cure, mitigate, or treat a disease, as it would be considered to be a form of drug or medicine and thus have to satisfy the relevant regulations.
Today the only reason for malnutrition is the shortage of food because we can get all the nutrition we need from consuming appropriate amounts of the right foods. There may be a few exceptions like Vitamin D which is the principal vitamin produced from sunlight though fish oil is supposed to supply it, and a regular diet of fish may not be accessible for some communities especially inland away from rivers and the ocean.