Vitamin D

Vitamin D is a Fat-Soluble essential vitamin.
Vitamin D receptors exist in nearly every organ in the body.

The majority of individuals are not vitamin D deficient, but they are not also at the optimum levels.

Vitamin D is thought to activate over 1,000 genes in the body.

Vitamin D works with hormones secreted from the parathyroid glands, small glands just above the thyroid gland in the neck, to control calcium uptake & metabolism.

Vitamin D is required for the full expression of immune response. Without sufficient vitamin D available, a type of immune cell called Killer T-cells, which destroy incipient tumor cells in the body, cannot be activated.

Several Factors Influence The Rates Of vitamin D Synthesis From The Sun.

Vitamin D is produced by the body from cholesterol if there is enough UV Light from sun exposure. When the UV index is 3 or above, which only happens year around at the equator, there is enough UV radiation from the sun.
Latitudes That Are Further Away From The Equator Tend To Reduce vitamin D Synthesis Rate Due To Less Exposure To Solar Radiation. Weather Pattern Or Seasons That Reduce Solar Exposure, Such As Clouds Or Darkness.
To get your vitamin D from sun exposure, at least 5% of body skin needs to be exposed to the sun for 5 to 20 minutes per day, 2 to 3 times a week, which can produce 10,000 to 20,000 units of vitamin D in the skin after 15 minutes. Any excess vitamin D produced in this manner is automatically degraded in the body, so there is no danger of overdosing vitamin D through natural sun exposure.

Darker Skin Has A Slower Synthesis Rate Than Lighter Skin, And Black Persons Are At A Higher Risk For vitamin D Deficiency When Compared To Lighter Skin Tones.
The older you are, the less efficient your body becomes at converting skin cholesterol into vitamin D.

Sunscreen Can Reduce vitamin D Production Greatly, And Long-term Use Lead To Insufficiency.

The synthetic D2 form also shows less affinity for vitamin D cell receptors, meaning much less biological activity, and is also quickly deactivated in the kidneys.

 Less Than 12 ng/ml, Leading To Rickets In Children And Osteomalacia (Softening Of Adult Bones) In Adults.
For Bone Health In Elderly People, A Goal Of 75 Nmol/l (30 ng/ml) Has Been Suggested.

Vitamin D Itself Is Divided Into Two Forms, Vitamin D2 Which Is Mostly Derived From Plants and vitamin D3, Which Is The Form Produced In Mammals And Fish.
Although Vitamin D3 Is More Potent Than Vitamin D2  (Controversially). In Powder Form, Vitamin D3 Is More Stable Than Vitamin D2 .

Most People's Requirements Should Be Completely Met With 2,000iu.
Lower Oral Dosages Appear To Be More Effective In Raising Blood vitamin D Levels, Whereas Greater Doses Raise Serum Levels But Have Lower Absorption.
Vitamin D Was Found To Be Best Absorbed With A Low-fat (11g Of Fat) Meal, Compared With Both A High-fat (35g of Fat) Meal And No Meal.
The Fat Type (Polyunsaturated Versus Monounsaturated) Had No Effect On Absorption.
Daily Intake Of 20,0000iu Has Been Linked To Toxicity, however Daily Dosage Of 10,000iu Has Not.

Insufficiency:between 12-20 ng/ml.
Adequate:20-50 ng/ml
High:50 ng/ml.
1 Microgram (mcg Or mg) of Vitamin D3 Is Approx 401u.

Science organizations vary in their recommendations for vitamin D.
The Institute of Medicine suggests only 600 units of vitamin D a day for adults, which is not enough for most people to reach optimal blood levels of active 25-hydroxy-D. The Endocrine Society says that 1,500 to 2,000 units a day is best for adults. 
Some studies suggest that athletes or those engaged in intense exercise may require doses of 3,000 units a day to favorably affect muscle function.
The Institute of Medicine claims that their recommendation of 600 units of vitamin D for adults applies to 97.5% of the population, also these studies had a number of statistical errors.

Vitamin D3 supplements more stable in the blood, and is more bioavailable as you age. 

Evidence suggests that vitamin D may improve Muscle Recovery after Mechanical Damage (Vitro).

After 6 Weeks of taking, 4000iu of vitamin D Daily, Muscle Recovery after Quadriceps Eccentric Exercise was enhanced.

Vitamin D deficiency impairs cross-bridge formation in muscle.

Since vitamin D receptors are present in both the heart and vascular tissue (blood vessels), vitamin D plays a major role in promoting maximal oxygen intake.

Vitamin D suppresses the expression of myostatin.(Vitro & Rat Study)

Vitamin D may enhance muscular force and power production during exercise, which is considered to be related to an increase in calcium sensitivity in the contracting regions of muscle tissue.

Studies suggest that ingesting vitamin D can boost muscular size (Only older adults and women have been found to be affected. There have been no studies of athletes or people who engage in resistance exercise.)

The optimal plasma level of D reduces the production of various inflammatory cytokines, which are proteins produced by immune cells. 
These cytokines extend the level of inflammation produced after exercise in muscle, to the extent that they delay complete muscle recovery following training.
In addition, D promotes the production of other cytokines that are largely anti-inflammatory, which speeds exercise recovery.

Vitamin D Supplementation to rectify a deficit may help Athletes Perform better.

The use of 4,000iu of vitamin D/day in combination with Weight Training was linked to an increase in Power output, but the Placebo was not. 

In studies, Even athletes (elite basketball players) have been found to be vitamin D deficient.

Vitamin D Deficiency is linked to an Increase in Fat levels in Skeletal Muscle Tissue.

Numerous Studies have discovered a Link between Low vitamin D Levels And Obesity.

Most ingested vitamin D in obese people with high body fat is deposited in fat tissue & does not interact with cellular vitamin D receptors or be converted into the active form, 25-hydroxy-D.

The suggested vitamin D intake to 1,885 and 2,802 units of vitamin D a day for normal and overweight people, with the 6,235 units still suggested for those carrying a lot of body fat.PMID: 26690210

It's Possible that A vitamin D Deficit might affect sleep quality, And That restoring vitamin D Levels might improve sleep function to some extent (Limited Evidence).

Low vitamin D Levels Have Been Linked To The Risk Of Cardiovascular Disease In Certain Studies (Some, But Not All).

According to a Study, vitamin D appears to be Linked to Sleep Quality.

Vitamin D appears To Be A Tissue-specific Aromatase Modulator, Increasing or Decreasing Aromatase Activity Depending on the Tissue.
Appears To Be Able To Influence Cell Death In Neurons Via Modulating A Subset Of Calcium Channels (Animal Data).
Low Blood vitamin D Level Are Linked To an Increased Risk Of Parkinson's Condition, Severity Of The Disease.

Though the drop in related Blood Pressure with vitamin D intake appears to be small in size in humans, It does appear to Lower Blood Pressure modestly in some Hypertensive Patients.

By decreasing Oxidation in Macrophages, Vitamin D appears to inhibit Atherosclerosis.

In Non-diabetic people, vitamin D levels are inversely associated with Insulin Resistance.
Reduced vitamin D Level in the blood raises the chance of developing Diabetic.
Vitamin D deficiency has been linked to Type 1 Diabetic complications. Supplementing with vitamin D improves Type 2 Diabetic results.

Supplementation of vitamin D appears to reduce the Risk of Falls in the Elderly.

Vitamin D Insufficiency may contribute to age related Loss of Muscular function in old people because the expression of the vitamin D receptor in Muscle Cells declines with age.

In One Study, vitamin D Supplementation was linked to the maintenance of Type 2 Muscular Fiber in Old People.

Vitamin D Levels in the Blood appear to be linked to total Androgen Status, with adequate vitamin D levels balancing Testosterone Levels.

Vitamin D appears to play a Role in Estrogen regulation Via the Aromatase Enzyme (Converting Androgens Into Estrogens).

Studies have shown that men with low testosterone levels often show low levels of vitamin D. 

Other studies show that men who have higher levels of vitamin D show higher levels of testosterone in their blood.

Two theories exist to explain the mechanisms
1) vitamin D inhibits the enzyme, Aromatase.
2) vitamin D can enhance the binding of androgen cell receptors

NOTE: If the receptors shut down, testosterone and anabolic steroids will do nothing.

Vitamin D Appears to Increase Sperm Motility and Cell Survival by acting on the Sperm itself.

Pregnant Women's Serum vitamin D levels appear to be Lower than Non-pregnant Women's, and these Lower Levels have been Negative Consequences for both Mother and Child.

Vitamin D And vitamin K Supplementation may be Synergetic, Since they share numerous Mechanisms of action in the Cardiovascular and Bone Metabolism Systems.

Calcium Absorption was 65%  better in those with 86.5 Nmol/l mean Serum Levels than in persons with 50 mmol/l mean Serum Levels.

Some people may be more susceptible to possible side effects linked to excess vitamin D intake. 

One Meta-analysis found a Greater Risk of Kidney Stones when vitamin D and Calcium Supplements were combined. 

The most serious consequences of this is calcium accumulation in the arteries, which leads to cardiovascular disorder.

This problem can be avoided simply through ingesting vitamin K with D supplements.

Especially the K2 form, is required for the production of osteocalcin, with sufficient osteocalcin calcium is not deposited in arteries.

Only the K2 form of K will help to prevent the development of calcium deposits in arterial linings.

Vitamin K1,in this form, is used mostly in the blood clotting process, rather than in preventing the calcium deposition in soft tissue.The suggested dose of vitamin K ranges from 50 to 1,000 units.

Studies show that very large doses of K (45 mg of MK-4) when combined with vitamin D can completely prevent the onset of osteoporosis, a common bone-thinning disease in older women.