Three sets of figures used to assess the adequacy of diets for populations. The first set of figures is the Reference Nutrient Intake (RNI) which represents the amount of a nutrient that is deemed by a country's government to be sufficient to meet the needs of practically all healthy people - even those with higher than normal needs. In the UK it is roughly equivalent to the old Recommended Daily Amount (RDA) which was formerly the only set of figures used.

The Estimated Average Requirement (EAR) represents the amount of a nutrient that is deemed sufficient to meet the needs of the average individual. Dietitians are taught that if a group of people are consuming these levels of nutrients, they are unlikely to develop nutritional deficiencies. According to a spokesperson for the British Dietetic Association, meals in institutions will, generally speaking, be considered adequate if they achieve vitamin and mineral levels between the RNI and the EAR.

Finally the Lower Reference Nutrient Intake (LRNI) represents an amount of a nutrient that is virtually certain to be inadequate. (The average intake of the trace element selenium in the UK falls well below this figure).

Dietary supplements

Preparations of vitamins, minerals, amino acids, essential fatty acids, enzymes, fibre and other factors which fulfil a useful or necessary physiological function and are found in food or synthesized within the body from food. These preparations may be chemically synthesized or natural extracts. Dietary supplements can also be concentrated plant- or animal-source preparations such as fish oils, yeast, probiotics, algae and plant or herb extracts, used to supplement the diet with the nutrients they contain, or for their health-giving properties.