Hot or Cold Beverages in Warm Weather: A Double-blinded Randomized Controlled Trial.

The research project will be conducted as a double-blinded randomized crossover trial, where the participants will drink either 10 cl of 10°C cold tea (±2°C) or 50°C hot tea (±2°C), which in a pilot study and in the literature [1,9] has been shown to be without discomfort or side effects. The order of the two interventions will be randomized.

All participants must be adults (18 years or older) and not have a fever on the day of the experiment.

Prior to participation, participants must provide written informed consent and must show up in clothing they find comfortable in the sun and be wearing sunscreen and a sun hat/cap. Participants must also complete a questionnaire on basic background information: gender, age, height, weight, clothing during the trial, and the participant's preference regarding the climate and temperature of beverages.

Walk-through of study:

1. Participants lie or sit in the sun for 10 minutes without drinking anything.
2. Then, participants drink their allocated beverage in ≤ 5 sec. while still in the sun.
3. Approximately 3 minutes (±1 min.) after ingestion of the beverage intervention, participants must answer all questionnaires and have their temperature measured.
4. Afterward, participants stay in the shade for 5 minutes (wash-out period).
5. Participants lie down (or sit) in the sun for the second time for 10 minutes without drinking anything.
6. Then, participants drink their second allocated beverage in ≤ 5 sec. while still in the sun.
7. Approximately 3 minutes (±1 min.) after ingestion of the second beverage intervention, participants must again answer all questionnaires and have their temperature measured.
8. Data collection and the research project end thereafter