Vitamin D (Calciferol) is a fat-soluble vitamin in a family of compounds. In humans, the most important compounds in this group are vitamins D-1, D-2 (Ergocalciferol), and D-3 (Cholecalciferol). Despite its name, vitamin D is not a vitamin, but a prohormone, or precursor of a hormone.
It is naturally present in very few foods ( such as fish-liver oils, fatty fish, mushrooms, egg yolks, and liver.), added to others ie: fortified foods (such as milk and cereal), and available as a dietary supplement. Your body also naturally produces it endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Hence why Vitamin D is sometimes called the “sunshine vitamin” because it’s produced in your skin in response to sunlight.
Vitamin D2 is manufactured by plants or fungus, and it can be acquired through fortified foods such as juices, milk, and cereals. Vitamin D3 is formed when the body is exposed to sunlight. This occurs mainly through the exposure of the skin to the sun's ultraviolet A (UVA) and ultraviolet B (UVB) rays. Vitamin D3 can also be obtained by consuming animal products.
Vitamin D is essential to the body and has multiple benefits & roles. Some of which include [1, 2] :
- major role of vitamin D (calciferol) is to help the body absorb calcium and maintain bone density to prevent osteoporosis
- promoting healthy bones and teeth
- Help with muscle strength
- supporting immune, brain, and nervous system health
- regulating insulin levels and supporting diabetes management (protecting against type 2 diabetes)
- supporting lung function and cardiovascular health
- influencing the expression of genes involved in cancer development (protecting against cancer)
- Vitamin D fights disease
- reduces depression
- boosts weight loss
The body is able to synthesize pre-vitamin D3 in the skin when exposed to sunlight. The pre-vitamin D3 is rapidly converted into vitamin D3 (cholecalciferol). Vitamin D3 is then transported through the blood to the liver (where cholecalciferol [ie: undergoes first hydroxylation via vitamin D 25-hydroxylase enzyme leading to the formation of] is converted to 25-hydroxyvitamin D3 [25(OH)D3], also known as calcidiol). Plasma 25-hydroxyvitamin D3 is the major circulating metabolite of vitamin D and is a very sensitive measure of vitamin D stores in the body. After passing through the liver vitamin D it is transported through the blood to the kidney where it is ultimately converted (calcidiol is catalyzed by enzyme 25(OH)D 1-α hydroxylase into calcitriol) into the hormone calcitriol, the active form of vitamin D [ie: 1,25-hydroxyvitamin D3 (1,25(OH)2D3)]. 
Many factors can affect your ability to get sufficient amounts of vitamin D through the sun alone. These factors include  :
- Being in an area with high pollution
- Using sunscreen
- Spending more time indoors
- Living in big cities where buildings block sunlight
- Having darker skin. (The higher the levels of melanin, the less vitamin D the skin can absorb)
***These factors contribute to vitamin D deficiency in an increasing number of people. That’s why it’s important to get some of your vitamin D from sources besides sunlight.
The signs & symptoms of a vitamin D deficiency in adults include [1, 2]:
- Depression, low mood,
- impaired wound healing
- hair loss
- aches and pains,
- muscle weakness,
- general sense of not feeling well
- severe bone or muscle pain or weakness that may cause difficulty climbing stairs or getting up from the floor or a low chair, or cause you to walk with a waddling gait
- stress fractures, especially in your legs, pelvis, and hips
- associated with the diseases rickets (bone deformities) in children and osteomalacia (poor bone mineralization leading to weak, painful bones) in adults
If Vitamin D deficiency continues for long periods, it may result in complications, such as [1, 2]:
- cardiovascular conditions
- autoimmune problems
- neurological diseases
- pregnancy complications
- certain cancers, especially breast, prostate, and colon
Doctors can diagnose a vitamin D deficiency by performing a simple blood test.
It is estimated that 40% of the U.S. population is vitamin D deficient, therefore supplementing the diet with extra vitamin D is essential for optimal health. Numerous factors influence the skin’s synthesis of pre-vitamin D3 including: location, climate, sun exposure, skin color, age and use of sunscreen. When you combine all of the factors that influence vitamin D synthesis with the existing widespread deficiency, vitamin D supplementation is the most efficient and convenient way to ensure optimal vitamin D intake.
As with all of Dr. Kenawy's professional line products, we use the best manufactures in making our formulas. Dr. Kenawy’s formula is a highly bioavailable form of Vitamin D, Cholecalciferol has a longer shelf life and higher potency compared to Ergocalciferol products. Our cholecalciferol (D3) is a natural, highly bioavailable form of Vitamin D derived from lanolin (vegetarian). Even though the human body can manufacture Vitamin D under ideal circumstances, there is strong evidence that much of the American population suffers from a deficiency of the nutrient. This means that supplementation may be important. The role of Vitamin D in helping maintain bone density and strength is clear. It is required for the process of moving calcium through the intestinal wall into the bloodstream. †
- Contains vitamin D-3 (cholecalciferol), a highly bioavailable form of Vitamin D.
- Sourced from lanolin (a vegetarian source of Vitamin D).
- Delivered as an easy to swallow soft gel capsule.
- Gluten free.
- We have it available in 1000IU (click here), 2000IU (click here)
- Vitamin D is essential for calcium and phosphorus absorption and utilization.†
- Stimulates osteoblast (bone producing cell) activity, which helps maintain bone density and strength.†
- Stimulates the synthesis of osteocalcin, an important protein involved in bone formation.†
- Helps maintain adequate blood calcium levels which help support cellular metabolic processes, cardiovascular and neuromuscular/neurological functions.†
- Vitamin D is important for normal, healthy cell growth and function.†
- Helps support normal, healthy insulin secretion.†
- Vitamin D helps support healthy immune function.†
†These statements have not been evaluated by The Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease. Information and statements made are for education purposes and are not intended to replace the advice of your General Practitioner. If you have a severe medical condition or health concern, see your physician.
 Ware, M. R. (2019b, November 7). What are the health benefits of vitamin D? Medical News Today. https://www.medicalnewstoday.com/articles/161618#benefits
 the Healthline Editorial Team. (n.d.). The Benefits of Vitamin D. Healthline. https://www.healthline.com/health/food-nutrition/benefits-vitamin-d#vitamin-d-deficiency
 Previtamin D3 - an overview | ScienceDirect Topics. (n.d.). ScienceDirect. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/previtamin-d3#:%7E:text=Vitamin%20D%20metabolism.,other%20vitamin%20D%20target%20tissues.