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Nutrition standardization during clinical trials: Methods of standardized food intake

Posted by Nina Carrasco Schmitz on Apr 12, 2018 5:18:00 PM

In the field of metabolic disease pathology, nutritional aspects often play a key role in clinical studies . Our metabolic ward enables us to control the impact of environmental conditions in our clinical trials. Through high standardization of food components we are able to minimize the impact of nutrients, thus reducing variability of study results and increasing the potential to further optimize the subject sample size. Our long standing experience of many years enables us to specify nutritional requirements according to objectives and rationale of the trial, varying from mixed meal tolerance test to individually adapted diets.


A standardized nutrition regimen can consist of one or more meals. The meals can be a formula diet or consist of a fixed nutrient content which will be developed with regular food ingredients by a research dietitian using software for nutritional value calculation. During screening the test subject will be informed about the sense and purpose of the dietary requirements and the composition of the meals. Any allergic reaction to any of the ingredients (even in trace form) will lead to exclusion from this particular study. In case of a meal consisting of regular food the exact amount and predefined brand will be weighed by the kitchen staff on a lab scale using the method of weighed intake.

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Dietary regimens

According to the nutritional requirements of a study the following dietary regimens (or combinations thereof) can be applied:

Regular Conventional Meals refer to the normal diet. Meals (and snacks) are served at pre-specified times during inpatient periods. The main meals (and snacks) with a known nutrient content are chosen from a choice of meals given in a menu. This setting does not include any kind of adjustment, standardization, or individualization whatsoever. Usually after a clamp investigation, subjects may freely choose a menu.

Standardized Nutrition Regimen describes a setting where all subjects of a trial receive an identical diet (i.e., all subjects receive the same breakfast/lunch/dinner/snacks independent of any individual characteristics and/or preferences). This setting includes test meals or mixed meal tolerance tests, in the form of a liquid meal test or a solid mixed meal, e.g. a breakfast.

Individualized Nutrition Regimen describes any kind of diet that is individually adapted based on subject characteristics like gender, age, height, weight (BMI), physical activity level and/or preferences. Regarding the individualized nutrition regimen (3), the highest grade of standardization, the day-by-day level of the nutrient composition either per kg body mass or per day of the respective meals is predefined. Hence, daily menus are planned based on the respective trial requirements described in the protocol and according to the American Diabetes Association and the German Society of Nutrition.  Our team of research dietitians is able to plan palatable daily menus according to individual preferences and prescribed nutrient content, while our metabolic kitchen allows for contents to be weighed down to the gram.

The individualized regimen formally also includes nutrition plans, which foresee regular conventional meals that are adjusted during the trial based on the amount consumed at an earlier time point, as well as any form of diet that is adjusted based on personal food preferences (including allergies and intolerances. A list of in the menu chosen food ingredients is created and shown to the respective test subjects during screening. Here they mark those ingredients to which they are allergic or which they dislike. Based on the selection of the subjects, and their body mass and body height individually tailored menus are created by the research dietician.

Subjects are supervised during their meals to ensure a controlled supply of nutrients

The staff of the metabolic kitchen provides the individual and standardized meals on labeled dishes and trays and prepare it according to the method of weighed intake. During the food serving a comparison between the labeled tray and the identification card of the subjects is indispensable to ensure that every subject gets the right meal. The subjects are supervised during their meals to ensure complete consumption within the prescribed time frame.

All these factors ensure a controlled supply of nutrients. Hence it becomes clear that controlled nutrient intake studies should be carried out in well setup sites that can control all these aspects. Profil has brought together this expertise and built the experience to be able to offer this type of study at the highest level. 

Topics: Clinical Trials in Diabetes, Clinical Trial Methods