These values are used in assessing the diets of groups of people. There are four categories of dietary reference value:
The estimated average requirement for food energy or a nutrient. Many people will need more than this value and many will need less.
The amount of a nutrient that is enough for almost every individual - even someone with high needs for that nutrient.
The amount of a nutrient which is enough for only a small number of people with low needs. People regularly eating less than the LRNI are likely to be deficient.
Where there is not enough information to estimate requirements of a nutrient, a safe intake is the amount of the nutrient which is judged adequate for almost everyone's needs, but small enough not to cause undesirable effects.
Energy requirements are determined mainly by the Basal Metabolic Rate (BMR - the rate at which the body uses energy when it is at complete rest) and Physical Activity Levels (PAL - the ratio of overall daily energy use to the BMR - hence, multiplying BMR by PAL gives the daily energy requirement).
PALs range from 1.4 for a person with a job requiring little energy expenditure, and non-active leisure pursuits, to 1.9 for a man in energy demanding work with very active leisure pursuits.
There are no deficiency symptoms associated with low intakes of any of these nutrients, and so strictly speaking, there can be no LRNI, EAR or RNI values. However, consumption of high levels of these nutrients is known to have adverse effects on health. Hence, the published figures refer to a desirable upper level of intake.
Table salt is, in fact, Sodium Chloride. It is the Sodium part which seems to cause health problems such as high blood pressure. It is difficult to measure intake if you use salt in cooking and at the table because you cannot weigh such small amounts. The RNI (i.e. the upper level of intake) for sodium is 1600mg per day. This equates to 4g of salt - ie. 1 teaspoon full.
The case studies in the food resources section use the RNI value for salt.
All other nutrients in the case studies in the food resources section of D&T Online use EAR values. Hence the data in the case studies is made up as follows: