Detailed dietary analysis

This paper has treated the food consumption data from the UK almost as representative of EU food consumption data in general. Doing so, however, is mainly out of convenience at this time. The UK food consumption database is well documented, among the most readily available in electronic format, and suitable for detailed distributional analysis. The 97.5 percentile consumption estimates from the UK database have formed the basis of the NESTI acute dietary exposure estimates discussed previously [8]. In addition to the UK data, a Dutch dietary exposure model using Dutch data is under development, but is not readily available at this time [19]. The German data have also been used to estimate chronic dietary exposure [20]. 

Another important dietary source of trans fat is conjugated linoleic acid, a class of compounds collectively known as CLA. Many CLA isomers contain conjugated cis/trans and trans/trans double bonds. Interest in CLA research has increased significantly in the past few years because several cis/trans CLA isomers have been reported to exhibit different beneficial physiological effects in animal studies (Yurawecz et al., 1999). The reader is referred to a collection of analytical papers published in a dossier (Mossoba, 2001, and references therein) that details several chromatographic and spectroscopic techniques and procedures that have been successfully applied to CLA analysis. 

The problems associated with the isolation and analysis of cell walls are (1) those arising from the preparation of cell wall material, (2) those associated with the isolation of wall components, (3) those associated with the fractionation of the carbohydrate polymers. There are also problems associated with the determination of the constituent sugars, their mode of occurrence, and fine structural details these are discussed later. The problems encountered in dietary fiber analysis and lignin determination, and measures for overcoming them, have been discussed at some length in a recent review (Selvendran and Du Pont, 1984) and will not be described in this chapter. 

Finally, a note of caution is needed to secure proper handling of biological specimens for GC analysis. Many of the recommendations as well as the rules for GC analysis are similar to the requirements for other clinical determinations (collection rules, sample storage, transportation, etc.), but special needs for GC may sometimes arise. For example, while certain foreign compounds (preservatives, dietary artifacts, therapeutic drugs, etc.) may not matter in conventional determination, they may be a problem in GC analysis. A publication by Jellum [15] discusses this matter in some detail. 

A detailed analysis of the positional distribution of the dietary and heart TG revealed that position 2 of TG undergoes the greatest change (Myher et a/., 1979). As seen in Table VIII, the concentration of molecular species of heart TG with 18 2 and 18 3 in position 2 is significantly lower than that found in the dietary oil. The opposite is found for molecular species with saturated and monounsaturated fatty acids in position 2. Of particular interest is the relatively high concentration of erucic acid in position 2 of cardiac TG, which in rapeseed oil (Brockerhoff an Yurkowski, 1966) and mustard oil (Myher et al., 1979), is in positions 1 and 3. 

Using the data of the latter study, a new procedure was developed for the untargeted analysis of data from crossover design nutritional intervention studies with a kinetic component. In this approach the kinetic measures of all relevant metabolites are estimated by fitting the appropriate kinetic models to the evolution curves over time. This allows detailed investigations of the inter-individual variation in response to dietary intervention. An example is given in Figure 2 where the total urinary output after consumption of a black tea extract is shown, and a clear distinction can be made between hi and low metabolizer phenotypes. 

The estimated daily intake of a substance in the context of the entire diet is of paramount importance in assessing the safety of any food ingredient. In the case of infant formulas, this determination should be straightforward as long as formulas are the sole source of nutrition. When solid food is introduced, a more detailed analysis must be conducted based on dietary records and panel data if the substance naturally occurs in the diet. For example, a careful record (diary) of all food consumed for a period of a few weeks should be kept and then analyzed for the substance in question. Another approach is to analyze available consumption data for foods containing the substance and calculating an estimated level of intake. These values are then combined with the estimated intake from the formula, appropriate safety factors are applied, and a safety determination is conducted. 

Epidemiological data on human populations show a strong positive correlation between age-adjusted mortality from breast cancer and dietary fat intake in different countries of the world (Carroll Khor, 1975 Carroll, 1975) but, as in the experiments with animals, there does not seem to be a correlation with intake of essential fatty acids. More detailed analysis of the data showed a positive correlation with intake of animal fat, but little or no correlation with intake of vegetal fat (Carroll, 1975). Moreover, although breast cancer mortality is about 5 times as hi in Americans as in Japanese, the per capita intake of linoleic acid is reported to be about the same in both countries (Insull et al, 1969). In addition, an analysis of the fatty acid composition of adipose tissue showed a level of 16.5% linoleic acid in Japanese compared to 10.2% in Americans (Insull et al, 1969). 

TAS, 1996. EX-4 (Acute) Detailed Distributional Dietary Exposure Analysis, Version 3.35. and EX-1 Chronic Dietary Exposure Analysis, Version 3.2. Technical Assessment Systems, Inc., Washington, D.C. 

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