N08016: Critical appraisal of methods to estimate non-milk extrinsic sugars in foods - identification of a recommended approach

Study Duration: July 2000 to July 2001

Contractor: University of Newcastle

The Food Standards Agency carries out surveys - such as the National Diet and Nutrition Survey programme (NDNS) - to collect information on the types, amounts and nutritional value of the food eaten by people in the UK. The information from these dietary surveys is vital to:

• collect the evidence needed to promote a healthier diet;
• work out the levels of contaminants in our diets.

Dietary surveys are also used in research to examine the relationships between diet and health.

As part of these surveys, information is collected on the amounts and sources of sugars in the diet, which includes calculating the amounts of non-milk extrinsic sugars (NMES) that are consumed. These sugars are more likely to damage teeth than other types of sugar, as the amount of NMES in the diet - and the frequency with which they are consumed - has been positively related to the incidence of dental caries.

NMES were first classified in the Committee on Medical Aspects of Food Policy (COMA) report on Dietary Sugars in Human Disease, published in 1989. The report indicated that NMES "includes fruit juices and honey and 'added sugars', which comprise recipe and table sugars". Hence NMES are found in a wide range of foods, the main sources in the diet being table sugar, confectionery, soft drinks and fruit juices and biscuits and cakes.

NMES are chemically indistinguishable from other sugars in foods, so cannot be measured by direct analysis. Instead, they are estimated using data on the amounts of different sugars (that can be measured by analysis) that are present in foods. Different dietary survey researchers have devised a number of different methods for NMES estimation. Each method applies slightly different "rules of thumb" or assumptions about the amounts of different sugars that should be included when estimating the NMES content of different foods. These assumptions often cause difficulties when others attempt to use one of the methods to estimate the NMES content of the diet. In addition, the variability in the NMES content of foods obtained by the different methods has not been investigated.

The main aim of this project was to review the existing methods identified for estimating NMES, in order to recommend one method for future use.

¹ Department of Health (1989) Dietary Sugars and Human Disease - Report on Health and Social Subjects no. 37 HMSO, London

A literature review was conducted to identify the different methods of NMES estimation used since 1987 (the 1989 COMA report included a summary of the methods identified before this time). The researchers found 32 publications in which NMES were reported, and identified 5 different methods of calculation that had been used. The methods identified underwent an initial evaluation in terms of rationale and practicality of application, and three methods were chosen to take forward and use in the remainder of the project.

The methods selected were:

A: The method currently used by the Food Standards Agency (and MAFF before it) to determine NMES intake for the NDNS since 1995 and other surveys it undertakes.

B: A method developed by MAFF, used to estimate NMES intakes for earlier NDNS surveys (pre-1995).

C: A method developed at the University of Newcastle that has been used to investigate trends in sugar consumption.

The report of the research project gives detailed descriptions of each of these methods.

These three methods were used to estimate the NMES content of a range of foods, in order to assess how easy and logical they were to apply. The results of this first stage of work were then applied to a set of dietary survey data held by the researchers in order to estimate NMES intakes, and the contribution of different food groups to the intake of NMES, by the three different methods.

When calculating the NMES content of a range of foods, method B generally gave higher figures than the other two methods. The researchers considered that method B over-estimated the amounts of NMES present. Methods A and C gave very similar results for most food groups, the only exception being confectionery for which method C gave lower values. The researchers noted that different methods of NMES estimation would give different figures for dietary NMES intake in dietary surveys.

The values obtained for individual foods were then applied to the dietary survey data. Mean intakes of NMES were substantially higher (by about 15-20%) when estimated using method B than when using methods A and C. Methods A and C gave broadly similar results, the slight difference between them being attributed to the differences in the NMES values for confectionery given by the two methods.

In conclusion, whilst method B was simple to apply, and would be easy to adopt for future use, it was felt to over-estimate the NMES content of foods, and hence the diet. The researchers felt that to get meaningful results for the NMES content of foods, a more detailed approach was required. Methods A and C were both sufficiently detailed and gave similar results, but Method A was felt to be more accurate and logical, and was also relatively easy to apply. The researchers therefore recommended that Method A - that currently used by the Agency for its NDNS and other surveys - should be used in future dietary surveys.

The Agency will continue to use the recommended method in its dietary surveys. In addition, details of the method will be made more widely available for use by other researchers.

Final report is available from the FSA Library and Information centre. To obtain a copy, please contact the Enquiry Desk, Dr. Elsie Widdowson Library and Information Services, Food Standards Agency (020 7276 8181/8182 or at library&info@foodstandards.gsi.gov.uk).

Nelson M, Dick K, Holmes B (2002) Food Budget Standards and dietary adequacy in low income families. Proceedings of the Nutrition Society, 61, 1-9. In press.

Contact: Victoria Targett
Tel: 020 7276 8913
Email: Victoria.targett@foodstandards.gsi.gov.uk