Dietary Sources of Essential Nutrients

The content of essential nutrients in foods and beverages is a vital piece of information for us all to know.

Without this information we cannot make the informed and appropriate food choices that are needed to provide a balanced and nutritious diet for ourselves and those in our care.

Information Provided

Three types of information are provided for each essential nutrient:

• information provided by the National Diet and Nutrition Survey, NDNS, of British adults aged 19 years to 64 years on the sources of nutrients as well as the provision by nutritional supplements from all four NDNS
• the content per 100 g of the top ten to fifteen foods for each individual nutrient with identification of the foods that are most likely to be fortified with the nutrient
• factors that influence the provision of that nutrient from food including losses from storage and cooking or factors reducing its absorption

Armed with this information the reader can then determine how he/she can change their dietary habits to increase or decrease their intake and the body’s assimilation of the nutrient.

References

Data on the food sources of essential nutrients are derived from:
- Food Standards Agency (2008) Manual of Nutrition, Eleventh edition. London: TSO
- Food Standards Agency (2002) McCance and Widdowson’s The Composition of Foods, Sixth summary edition. Cambridge: Royal Society of Chemistry
- Holland B, Welch A A, Unwin I D, Buss D H, Paul A A, Southgate D A T (1991) McCance and Widdowson’s The Composition of Foods, 5th edition. The Royal Society of Chemistry, Cambridge.
- US Department of Agriculture Standard Reference 20 available at www.ars.usda.gov/Aboutus/docs.htm?docid=6300  This useful site also provides access to food tables from Australia, New Zealand and Denmark as well as The Food and Agriculture Organisation, FAO.

Nutrient Requirements and Dietary Reference Values

The current standards for nutrient intake were set by the Department of Health in 1991 with the publication of Dietary Reference Values for Food Energy and Nutrients for the United Kingdom.  Several measures by which the adequacy of diets of sampled groups or individuals could be assessed were given.  In this section reference is made to the Estimated Average Requirement, EAR, for adults (mostly 19 to 50 years) so that the reader can gauge the degree of provision by individual foods. 

EAR is defined as the “Estimated Average Requirement of a group of people for energy or protein or a vitamin or mineral.  About half will usually need more than the EAR, and half less.”

The EAR and other Dietary Reference Values replace the RDAs, Recommended Daily Amounts, which are retained for labelling purposes.
The EAR for a nutrient will lie approximately halfway between the Reference Nutrient Intake and the Lower Reference Nutrient Intake, which are defined as:

“Reference Nutrient Intake for a protein or a vitamin or mineral.  An amount of the nutrient that is enough, or more than enough, for about 97% of people in a group.  If average intake of a group is at the RNI, then the risk of deficiency in the group is small.”
“Lower Reference Nutrient Intake for protein or a vitamin or mineral.  An amount of the nutrient that is enough for only the few people in the group who have low needs.”

- Department of Health (1991) Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. London: The Stationery Office

National Diet and Nutrition Surveys

The National Diet and Nutrition Surveys are a series of four surveys of the British population that provides data on the intake of nutrients as well as laboratory measures of their status in representative samples of the population.

These surveys involved an enormous amount of work and produce valuable data which is representative of the situation at the time at which they were performed.  However dietary habits as well as use of supplements may have changed with time and this should be borne in mind.  Furthermore the population sampled will under-represent the most unwell and undernourished members of our society.

The four NDNS surveys and the year(s) in which they were conducted are:

• NDNS Children aged one and a half years to four and a half years (1992/3)
• NDNS Young People aged 4 years to 18 years (1997)
• NDNS Adults 19 years to 64 years (2000/1)
• NDNS People aged 65 years and over (1994/5)

This section is broken down into more detail with:

• Energy and Protein
• Vitamins
• Minerals
• Essential Fatty Acids