The goal of this clinical trial is to find out if vitamin D supplements help healthy adults maintain their cognitive and simple physical task performance and emotional state during highly stressful situations.
The main question it aims to answer is:
\- Does vitamin D help maintain cognitive and physical task performance and emotional state during highly stressful situations?
Researchers will compare vitamin D to placebo (a look-alike tablet that contains no active ingredients) to see if vitamin D better maintain cognitive and physical task performance and emotional state during highly stressful situations.
Participants will:
* Take vitamin D or placebo tablets daily for 8 weeks. * Perform cognitive and simple physical tasks and rate their emotional state under highly stressful situations. * Wear a stress belt that delivers mild electric shocks 1 - 5 times while participants are performing laboratory tasks. * Wear a wristwatch-shaped activity monitor for 9 weeks. * Visit the laboratory 5 times.
Male and non-pregnant, non-lactating females 18 to 40 (inclusive) years of age.
Females of child-bearing potential must be using some form of birth control, if sexually active (e.g., oral contraceptive, condom, intrauterine device, etc.)
Score of 80% or greater on a "Volunteer Comprehension Assessment" test. A maximum of two attempts is permitted.
Blood 25 hydroxy vitamin D [25(OH)D] levels at the Screening visit of 30 nmol/L (12 ng/mL) (inclusive) - < 75 nmol/L (30 ng/mL).
Contraindications due to vitamin D supplementation, including a history of hypercalcemia, malabsorption syndrome, hypervitaminosis D, or allergic/hypersensitivity reactions to vitamin D or a history of other adverse reactions to vitamin D supplementation.
Taking a vitamin D3 or D2 supplement or a supplement containing vitamin D3 or D2 (excluding vitamin D-fortified foods) during the participation. Volunteers who take vitamin D3 or D2 supplement before their participation can be eligible if they agree to stop taking the supplement(s) starting 1 month prior to the enrollment/baseline visit until the end of the post-supplementation visit. Blood 25(OH)D levels of the volunteers who stopped taking the supplements after the screening visit will be tested before the Enrollment/Baseline visit to ensure their 25(OH)D fall within the inclusionary ranges. Volunteers who are not able to stop taking vitamin D supplements or supplements containing vitamin D due to medical/health or any other reasons (especially if the volunteer is taking supplements containing vitamin D under the direction of a healthcare provider) are not eligible.
Not being able to tolerate electric shocks delivered through the stress belt.
Self-reported propensity for adverse skin reactions, such as excessive irritation, burning, itching, hives, and redness, in response to physical or heat stimuli.