You may register your study in a clinical trial database (more 2.7.6). Registration is not mandatory for clinical studies such as those on nutritional supplements. However, it is recommended as a good research practice in order to avoid publication bias and selective reporting. It also increases transparency in research and is considered a sign of a study of good quality.

It is highly advisable to carry out a pilot study that will include the same steps as the main study (the next 10 steps described below), except that it will have fewer subjects and may last less (in the case of a prolonged study). The purpose of the pilot study is to check that everything works as planned, to locate and solve unanticipated problems and improve the design of the main study (more 2.7.7).

Recruit your volunteers according to the guidelines given above and according to your predefined inclusion and exclusion criteria. Arrange your first meeting with each one of them in your research facilities. Also, give them the opportunity to meet the researchers who will participate in the study. Help the volunteers complete the questionnaire. As they do, make sure they meet all inclusion criteria and do not meet any exclusion criterion; otherwise, you will need to exclude them (more 2.7.8). Thoroughly inform them about the study and answer any questions they may have. At the end, have them sign a copy of the consent form and keep it in a safe place. Sign another copy of the consent form and give it to the volunteer as guarantee.

Provide the volunteers with detailed written and oral instructions about what to do during the study. Pay special attention to that in order to ensure maximal compliance and correct execution of each step (more 2.7.9).

Choose which volunteers will receive what or when as described. In case you implement a single-blind study, the individuals (researchers or volunteers) who are to be blinded must not know the results of randomization. In case you implement a double-blind study, both (researchers and volunteers) must not know the results of randomization. If the researchers are to be blinded (single-blind or double-blind study), ask a third person (one who will not be involved in the study) to do the randomization and keep a record of it in two copies in different safe places.

Create electronic forms to record the data from each volunteer's measurements (more 2.7.10). You may input the data either directly into a computer or on printouts of the forms.

These measurements (more 2.7.11) may or may not be made during the first meeting with the volunteers, depending on what is more convenient. More than one visit may be necessary to complete all measurements. Also, the volunteers may need to visit another laboratory for some measurements because your research facilities may not have the necessary equipment.

Before you administer the supplements, you will need to obtain baseline values of all the outcome measures of the study. These may be part of the screening measurements (such as body mass index) or may be measurements not needed for screening (such as body composition and resting energy expenditure) (more 2.7.12).

If the volunteers are to be blinded (single-blind or double-blind study), package the supplements in identical containers. If the researchers are to be blinded (single-blind or double-blind study), have the person who did the randomization do the packaging as well. Then distribute the supplements to the volunteers after the baseline measurements (more 2.7.13).

To ensure that the volunteers' habitual diet will not affect the outcome measures, you need to apply some sort of dietary control. The kind of dietary control depends on the kind and aims of the study. Generally, it can be in the form of a dietary plan, instructions to consume or avoid certain foods, or instructions to keep dietary records (more 2.7.14).

Ask the volunteers to faithfully follow the instructions they received, including consumption of the supplements. In prolonged studies, you need to regularly check with them to ensure that everything proceeds according to schedule. The volunteers must, on specific days based on the protocol, visit the research facilities for the experimental measurements, such as anthropometric parameters, physical examination, performance tests, and sampling of biological fluids (more 2.7.15). This includes possible intermediate measurements and, of course, the final measurements. Data need to be carefully collected and stored. It is important to point out that volunteers must follow the same preparatory steps at the experimental measurements as they did for the baseline measurements.

Throughout the study, encourage the volunteers to contact you if they experience adverse events. When they do so, discuss their experiences with them thoroughly and openly, trying to find solutions.