4. USERS’ GUIDE

Sources of data

Users of the food tables must be aware that very few foods have a constant nutrient composition and that the data presented here do not represent absolute values. The purpose of this publication is to present, as far as possible, a reflection of the usual composition of foods as available and/or consumed, based on representative samples. However, the data have been collected from many different sources and represent samples from many different countries and laboratories.

Some nutrient values in these tables are presumed, “borrowed” from similar foods, or calculated using estimated yields and retention factors, rather than being obtained from food analyses. This process has been necessary to obtain complete tables of core nutrients with a minimum number of missing values.

Source codes

The different sources are listed below with a code, and full citations for published sources appear in the Reference section.

TABLE 1. Source codes

Each food record is made up combinations of data sources. Pacific Island-generated analytical data are presented when available. Data from other relevant sources were used to supplement analytical data to avoid missing values. Hence, each record is made up of more than one source, and no single record represents a fully “borrowed” data set. These concise tables provide only the major source of the nutrient data for each food record in the source column in Appendix VI - Food index. Knowing the source, the user can then make an informed choice about which data to use when there is a choice of more than one entry in the table for the same food or similar foods. Source codes can also assist the user in deciding on the validity and acceptability of the data for a particular purpose.

Layout of the tables

There are 20 food groups in the tables, each identified by a letter of the alphabet. Some letters have been deliberately omitted to avoid confusion (e.g. the letters I and O look very much like the numbers 1 and 0, so I and O are not used).

There are 22 nutrients presented in the tables. These are: water, energy in kilojoules and kilocalories, protein, total fat, available carbohydrate, dietary fibre, cholesterol, sodium, potassium, calcium, magnesium, iron, zinc, total vitamin A equivalents, retinol, B-carotene equivalents, thiamin, riboflavin, niacin, vitamin B12, vitamin C and vitamin E. For each food, 11 nutrients are presented on one page and the other 11 on the facing page.

Mean values presented in all food records are rounded to a fixed number of decimal places or a fixed number of significant figures for each nutrient.

Food key

Beside each food name is a code, or key, that uniquely identifies each food in the larger database from which the tables have been developed. For example, A010 is the key for cassava flour. The key will be maintained for this food in the continuing development of the database and in each edition of printed tables. If the food is deleted from the database, the key will also be deleted.

Edible portion and measures

Each food in the tables represents the edible portion of the food. In most records, the edible part is described, for example, “flesh and edible seeds”. In some records this information is not given because it was not provided in the original source. No calculations are necessary for refuse or waste.

If the food is normally cooked before eating, then every attempt was made to include nutrient data for the cooked food. Note, though, that for some foods, such as root crops and green leaves, data are presented on the raw food, even when it is not eaten raw. This was done for the purpose of showing differences in nutrient composition between foods without the confounding influence of different cooking methods.

Serving sizes are determined on the basis of amounts commonly purchased or eaten. These are just a guide as to what might be a usual amount eaten or a measure used for serving food. In most cases this common serving measure was provided by Pacific Island dietitians/nutritionists. Measures presented in these tables are not meant to be used as a recommended serving size or portion. All measures are on an edible portion basis, so no adjustments are required for refuse. The volume amounts used are metric standards, as listed in Table 2. Volume measures are converted to weight in grams, based on the foods’ density, and nutrient values are presented on the weight basis.

TABLE 2. Metric standards

Finding a food in the tables

In the tables, foods are listed within food groups. If you cannot find the food in the group you expect it to be in, turn to the food name index (Appendix VI), which contains all foods listed alphabetically regardless of chapter. This listing shows the English name and a number of local language names. For example, Solomon Islanders looking for the nutrient composition of ngali nut would not find that food name listed in the tables. Appendix VI, however, shows ngali nut listed, with a note saying “see Pili nut”. Pili nut could then be found in the nut group. Because there are so many local names, it was not possible to list them all in this publication. Similarly, there are some commonly eaten foods not included in these tables, including mixed cooked dishes, because they have never been analysed.

Full name of foods and scientific name

Appendix V lists the full names of all foods in the tables within chapters, and includes the scientific name if it is identifiable beyond doubt. The food preparation or cooking method is also included as appropriate.

Description of foods and terms used

Foods are described as completely as possible and, for some foods, this includes brand names. Identification by brand name is not an endorsement for the product.

The same foods, with different processing or preparation, are not always derived from the same sample. Data are obtained from many sources and represent different growing years, growing areas, cultivars, laboratories and different methods of analysis. Therefore, differences in values for various forms of the same food do not necessarily represent the effect of the processing or preparation. For other foods, only the raw sample was analysed and the cooked values were obtained by calculation.

The term “raw” when used with meat refers to meat that has been freshly killed and not processed before being prepared for analysis. The term “uncooked” refers to meat that has been processed in some way, yet has not undergone or does not require post-purchase cooking. For example, the word “uncooked” is used for ham and cured bacon.

The term “separable lean” refers to meat muscle, but includes fat striations within the muscle.

The term “separable fat” refers to the visible fat layer and removable intramuscular fat.

“Baked” means cooked in an earth oven, an electric oven, or a gas oven, without fat and with dry heat. Food described as baked can be used where “grilled on hot coals” or “dry roasted” values are required.

Cooked mixed dishes

Recipes were used to calculate the nutrient composition of most of the cooked mixed dishes. Calculations were made using the composition of ingredients, together with yields and individual nutrient retention factors specific to the method of preparation. Recipe ingredients and amounts used are provided in Appendix IV.

Composite foods

“Composite” in these tables means the average of several similar foods. For example, composites of several varieties of sweet potato and several types of reef fish are provided. These data are useful in consumption studies when the specific variety or type is not known or recorded.

Symbols

Anumber of symbols have been used throughout the tables and in the appendixes. The source codes and keys have been explained above. All units in the tables are metric.

Recommended daily intakes

Specific recommended nutrient intakes (RNIs) based largely on the recommendations of FAO/WHO (2002) are provided in Appendix III.

Notes on nutrients

There are 22 nutrients in the main body of the tables, which are presented in a fixed format for each record. The order of presentation is based on major nutrient categories and convention.

Users of these food composition tables will have a basic understanding of the food components within each nutrient category. Therefore, this section relates only to specific information that is not obvious or self-explanatory.

For some of the older food records, the methods of nutrient analysis were not available from the original source. In some cases, values were recalculated to provide information on the form of the nutrient required for the format of this publication. Where the method was ambiguous, not supplied or was incomplete, a best estimate was used.

The sum of the proximates usually falls within the range of 97 - 103 g per 100 g edible portion. A margin of plus or minus 3 percent is considered acceptable (Greenfield and Southgate, 2003), particularly as many of the components were determined independently on different samples in different laboratories. For some food records, the sum is outside this range. Explanations for this situation include the presence of high levels of unusual constituents not measured in the proximate analyses, and analytical error.

Energy is expressed in units of both kilocalories (kcal) and kilojoules (kJ). All values were calculated from the energy-producing food components using conversion factors listed in Table 3 as recommended by FAO (2004) and the Codex Alimentarius Commission (2001), with one exception: available carbohydrate was calculated using 16.5 kJ/g. For most foods, the difference is insignificant. For the few foods presented with a large measure and a high carbohydrate content, the difference may be as high as 40 kJ. (Note: the energy factor for dietary fibre was not included in the previous edition of these tables.)

TABLE 3. Energy conversion factors (FAO, 2003)

Table 4 provides the list of nutrients, the units of expression, the INFOODS tagnames for the majority of that nutrient presented in the tables, and summary notes including formulas and factors for calculations.

TABLE 4. Components, units, INFOODS tagnames,¹ and relevant notes

¹ Klensin et al., 1989

For all entries, the protein value is based on the total nitrogen multiplied by a specific factor (Jones, Munsey and Walker, 1942). Conversion factors for mixed foods containing more than one protein source were derived using the proportion of each source with its appropriate conversion factor. Total nitrogen values and factors are captured in the full database.

Available carbohydrate values are expressed as the weight of the carbohydrate. Food records from the United States Department of Agriculture (USDA) and FAO sources have had the total carbohydrate by difference value recalculated to represent available carbohydrate in these tables. New Zealand and British data for available carbohydrate in monosaccharide equivalents were recalculated to represent the weight of the saccharide in the food.

There is considerable controversy over the most appropriate definition of dietary fibre, which creates difficulties for analysts and users of food composition tables. Different methods of analysis measure variable amounts of the different fractions of the dietary fibre complex, with each value being specific to the method used. The majority of fibre values in these tables have been determined by the dietary fibre method of Englyst and Cummings (1988), Southgate (1976) and the AOAC total dietary fibre method reported by Prosky et al. (1984). For many records, however, no documentation of method was available.

Total vitamin A, or retinol equivalents, are calculated as the sum of retinol and 1/12 the b-carotene equivalents value.

The previous edition of these tables used the factor of 1/6 b-carotene equivalents value in calculating vitamin A.

The b-carotene equivalents value is calculated as the sum of b-carotene and one-half the sum of the other measured pro-vitamin Acarotenoids.

Iodine - not all nutrients could be included in the tables, given the constraints of working time, availability of data, etc. Values for iodine in foods have not been included in the tables because data are lacking.

Iodine deficiency disease (IDD) is a public health problem in parts of Papua New Guinea and also parts of Fiji. Iodine is widely distributed in foods, with the best sources being seafood. A low intake of iodine may be due to the consumption of plant foods that are deficient in iodine because the soil in which they are growing is deficient in iodine. It can also be due to the consumption of goitrogens, naturally occurring compounds present in some foods. Goitrogens interfere with the absorption of iodine.

To remedy the problem of IDD, at this time, the most commonly recommended measure is to produce and distribute a table salt that has potassium iodate added to it.

FAO/WHO (2002) recommends an intake of 100 - 135 µg of iodine per day for adults and 200 µg/day for women who are pregnant or lactating. Iodine content of seafoods is generally in the range of 70-100 µg/100 g edible portion.

Uses of the food composition tables

There are many uses to which food composition data can be put. These include:

• calculating the nutrient intake of individuals or groups,

• planning nutrition improvement programmes,

• developing nutrition education materials, such as bar charts showing diagrammatically the content of important nutrients of various local and imported foods,

• planning special diets for people with diseases such as diabetes, high blood pressure and kidney disease,

• selecting and promoting the consumption of foods high in particular nutrients for children and/or adults with deficiency diseases, for example in communities with vitamin Adeficiency,

• selecting or promoting a decrease in the consumption of foods/diets known to contribute to an increased risk of chronic disease,

• planning balanced menus for institutions such as boarding schools, hospitals and prisons,

• selecting highly nutritious plants to grow in the family food garden and for commercial production,

• developing new, manufactured food products with specific nutrient contents, and teaching and research.