What is Vitamin D3?
Vitamin D3 is a fat-soluble nutrient that individuals can obtain from sunlight exposure or by consuming milk, eggs, and fish. However, the effectiveness of sun exposure at increasing Vitamin D3 depends on a variety of factors. Distance from the equator, weather patterns (clouds and darkness), and seasons can all reduce the amount of Vitamin D your body synthesizes from the sun. [1,2,3]
While most people are not deficient in Vitamin D3, they do not have the ideal amount in their system either. Taking supplements can boost Vitamin D3 levels to improve cognition, boost the immune system, and promote healthy bones.
Why Vitamin D3
Not all Vitamin D supplements provide the same benefits. The main active ingredient in Vitamin D3 is cholecalciferol. The body is able to raise serum levels of Vitamin D more effectively with cholecalciferol than with other Vitamin D supplements such as Vitamin D2 (ergocalciferol). 
Vitamin D3 5000 iu Benefits
While Vitamin D3 will not enhance cognitive function in healthy adults, it is vital to maintaining your current cognitive state. Low levels of Vitamin D3 actively contribute to cognitive decline.  Many individuals suffering from age-related cognitive decline are Vitamin D deficient. Boosting Vitamin D3 in these individuals can improve cognition and mood.  There is also an inverse correlation between Vitamin D3 and poor mood in healthy individuals as well.  This means Vitamin D3 is necessary to maintain your sense of wellbeing.
Vitamin D3 and Longevity
Studies associate low levels of Vitamin D3 with reduced longevity in the general population. [8,9] Vitamin D3 supplementation is able to improve longevity, with increased efficacy in the elderly. This is likely because Vitamin D reduces frailty.  Vitamin D3 is vital to achieving this benefit as other types of Vitamin D and its analogues provide no significant benefits.  Vitamin D3 is able to improve your immune health during winter months as well. [12,13]
Vitamin D3 and Athleticism
While Vitamin D3 may not improve your performance in the gym in a dramatic way, it can help keep you healthy and able to power through tough workouts. Vitamin D3 can improve muscle recovery after difficult workouts.  Healthy individuals experience some performance benefits as well, with overweight individuals seeing a much larger boost in power output. [15,16] Vitamin D3 can also protect athletes from injury and illness. [17,18]
Perhaps the most well-known benefit of Vitamin D3 is its ability to promote strong and healthy bones. With the downward trend of milk consumption, Vitamin D3 supplementation is vital to maintain bone mass and strength.[19,20] Supplementing with Vitamin D3 can reduce the risk of bone fractures. It can reduce the risk of falling in elderly individuals who are already deficient in Vitamin D as well. 
Vitamin D3 can improve sperm motility which is the ability for sperm to swim.  However, this does not mean men should start consuming high amounts of Vitamin D3. Both low and excessive levels of Vitamin D3 reduces sperm motility.  To achieve maximum motility and thus improve fertility, Vitamin D3 levels need to remain within normal ranges. Stick with the recommended dosage to achieve the best results.
Vitamin D3 5000 iu Dosage
Individuals should take one 5000IU Vitamin D3 soft gel capsule per day. As Vitamin D3 is fat-soluble, individuals should take it with a meal or fat source such as fish oil for maximum absorption. 
Commonly Referred to as: Vitamin D