The process of nutrient analysis for controlled feeding trials: a comparative study of two South African nutrient databases with chemical analysis.

BACKGROUND

There is an increased tendency in the field of nutrition research to conduct more outpatient controlled feeding trials. The formulation of accurate diets is essential in order to assemble valid scientific data, which will substantiate hypothesised relationships between a nutrient variable and an outcome. Research dieticians rely on the accuracy of computerised nutrient databases when designing the menu.

OBJECTIVE

The reliability of the two computerised nutrient databases available in South Africa containing foods from different food sources were investigated, comparing them with each other and with the reference standard of chemical analysis.

METHODS

A seven day Westernized menu providing an energy level of 7500 kJ/day was entered into FoodFinder3 (2002) and Dietary Manager (modified 2006 version) Software programmes. Food prepared according to this menu was chemically analysed for the macronutrient profiles (carbohydrate, fat and protein), fatty acid distribution (saturated fatty acids, mono-unsaturated fatty acids and poly-unsaturated fatty acids) and total fibre, insoluble and soluble fibre in order to compare data.

RESULTS

The two nutrient databases' values did not differ significantly from each other despite using different food sources, however, there were differences between the chemically analysed values and the databases' calculated values for selected nutrients. There were no significant differences between the amount of total energy, protein, carbohydrate, poly-unsaturated fatty acids and total fibre. The total fat, saturated fatty acid and mono-unsaturated fatty acid content using both FoodFinder3 and Dietary Manager were statistically and practically significantly higher than the chemical analysis (p<0.05). FoodFinder3 produced significantly lower levels of insoluble and soluble fibre compared to the chemical analysis.

CONCLUSION

The use of computerised nutrient databases in menu design for controlled feeding trials is functional and assists the research dietician with this challenging task. However, computer nutrient databases are not reliable enough to exclude the step of menu validation by chemical analysis before the start of the intervention.