Portion size

In order to determine the potential intake, information about portion size and consnmption patterns is needed. " Typical information that can be useful for this analysis inclndes ... 

If the validated test method requires 1 g of material but only 100 mg is available, you must find out if the method is sufficiently robust to stand this amount of scaling down. This has to be checked before the analysis starts, i.e. the method must be validated for analysis of 100 mg of material. Even if the method of analysis is found to be robust, scaling down is only a viable option if the smaller test portion size remains representative, within acceptable limits. This will depend on the homogeneity of the material. 

An indication of the minimum size of a subsample can be obtained by using the concept of a sampling constant. For example, in the laboratory, the sampling constant can be used to estimate the minimum size of the test portion. However, the suitability of the chosen test portion size must be confirmed as part of method validation. The sampling constant Ks has units of mass. This is the mass of the test portion necessary to ensure a relative subsampling error of 1% (at the 68% confidence level) in a single determination. The value of /Ks is numerically equal to the coefficient of variation, CV (see Chapter 6, Section 6.1.3) for results obtained on 1 g subsamples in a procedure with insignificant analytical error. 

Canada Canadian Food Inspection Agency No ban. Recommended to choose smaller portion sizes and prepare the fish in a way to reduce oil content CFIA (2007)... 

Food Isoflavones (total) (pg/g) pg per average portion size (g)... 

How to Avoid Portion Size Pitfalls to Help Manage Your Weight." Centers for Disease Control and Prevention (CDC), May 22, 2007. Available online. URL www.cdc. gov/nccdphp/dnpa/nutrition/nutrition for everyone/ healthy weight/portion size.htm. Accessed November 13,... 

Case 1 The available composite residue data reflect the residue levels in the food commodity as consumed. This is the case where either the commodity is well mixed during processing e.g. cereals, or where the normal portion size reflects the consumption of many units of the commodity e.g. cherries. Essentially, Case 1 is used when a serving of a food commodity is comprised of numerous units. 

Food frequency questioimaires determine the frequency with which certain foodstuffs are consumed over a given period. Thus it is necessary to predefine the foodstuffs of interest and these may be targeted to a nutrient(s) or food(s) of specific interest. They are rarely conducted for specific contaminants arising from the packaging of the foodstuffs consumed. It is possible (Parmar et al. 1997) to combine the food frequency quesfioimaire with portion sizes (MAFF for example) in order to obtain an estimate of food intake, particularly where consumption data are limited. 

MAFF, Food portion sizes, second edition/HMSO publication ISBN 0-11-242961-0. 

Rolls, B. J., E. L. Morris and L. S. Roe (2002). Portion size of food affects energy intake in normal-weight and overweight men and women. Am J Clin Nutr 76(6) 1207-13. 

Accurate assessment of supply and intake is a complex procedure. In practice, a crude estimate of intake can be obtained from a careful clinical history taken by an experienced practitioner or from a food frequency questionnaire that summarizes the content of the individuars diet over several days, depending on how frequently particular typical foods are consumed. A more accurate quantitative assessment usually requires a minimum of three days recording of a complete dietary diary, which is subsequently analyzed using a computer program with reference tables of the nutritional contents of most foods. Unfortunately, estimates of the portion size, amounts consumed, and actual nutritional composition of the food consumed may be inaccurate. In addition, the disease process also affects the amount actually consumed and absorbed, further reducing the accuracy of the estimate of nutritional intake. 

Retrospective dietary-assessment methods are simpler and less expensive than prospective and duplicate-diet methods, and therefore are used more often as the basis of dietary expostrre assessments. Food-fiequency studies take the form of participants identifying their typical fish consrrmption (e.g., How many times per week/month do you usually eat fish AT). Diet histories involve recollection of specific meals over a specific time (e.g. 24-hr or 1-week periods). In the studies mentioned above, Sherlock et al. (1982) and Haxton et al. (1979) used retrospective assessment of typical consumption to preselect subjects. In a recent study of MeHg exposure among pregnant women in New Jersey (Stem et al. 2000), participants were asked to identify their typical consumption frequency and typical portion size of 17 species of fish and... 

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