Vitamin D: Sources, Function & Deficiency

Table of Contents

What is Vitamin D?

Vitamin D is a nutrient that is required in our body in order to develop and maintain strong bones.
Vitamin D is a type of vitamin that helps the body to absorb and retain calcium and phosphorus.
Vitamin D is a fat-soluble vitamin that is added to certain foods, found naturally in a few, and available as a dietary supplement.
Vitamin D is both a nutrient that we eat and a hormone that our body produces
This is due to the fact that vitamin D is required for our body to properly absorb calcium, which is the main component of bone.
The human body produces vitamin D endogenously as a response to sun exposure where ultraviolet (UV) rays from sunlight strike the skin and trigger its synthesis.
A person can boost their intake by eating specific foods or taking supplements.

Few foods naturally contain vitamin D, while some are fortified with it.
Supplements is another good sources of Vitamin D. There are two types of vitamin D supplements: vitamin D2 (also known as ergocalciferol or pre-vitamin D) and vitamin D3 (also known as cholecalciferol).
The term “the sunshine vitamin” refers to both of these naturally occurring forms, which are generated when exposed to ultraviolet-B (UVB) rays from the sun.
However, D2 is produced by plants and fungi, whereas D3 is produced by mammals, including humans.
The flesh of fatty fish and fish liver oils are also the finest sources of vitamin D.
Cheese, cow liver, and egg yolks all contain smaller quantities.
Some mushrooms contain vitamin D2, and some mushrooms that are marketed commercially have higher levels of vitamin D2 because they have been purposefully exposed to a lot of UV radiation.
Vitamin D is added to a variety of foods and supplements, such as in cereals and dairy products.

Food sources of Vitamin D include:

The amount of vitamin D you need each day depends on age. The recommended dietary allowance in international units (IU), are:

Calcium, the building block of bones, is absorbed by the body as a result of the presence of Vitamin D, which is particularly important in the natural growth and remodeling of bones.
It lowers the danger of fracture, strengthens the bones, keeps the body’s balance, and gives the body a strong, ideal skeletal framework.
A by-product of vitamin D aids in the relaxation and contraction of muscles.
It strengthens gums, lowers the incidence of oral infections, and prevents tooth damage and loss.
Being a fat-soluble vitamin, it is essential for controlling renal functioning and safeguarding the kidney against infections.
It is crucial for cellular development, maintenance, and metabolism. The healing and restoration of wounds can be greatly aided by a decent amount of sunlight exposure.
Additionally, it is essential for preventing obesity and maintaining a healthy weight.
The abundance of vitamin D in the body restores the function of leptin, which makes us feel full and lessens the tendency to constantly nibble, helping to lose weight.

Children who have mild vitamin deficiencies may only experience weakness, discomfort, or pain in their muscles.
On the other hand, children who severely lack Vitamin D will develop Rickets.
Symptoms of rickets include:
- Bowed or bent bones that cause improper development patterns
- Muscle weakness
- Bone pain
- Deformities in joints
Most adults who are vitamin D deficient don’t exhibit any symptoms.
However, a continuous deficiency can lead to hypocalcemia, a disease in which there is insufficient calcium, and hyperparathyroidism, a condition in which the parathyroid glands generate an imbalanced hormone that raises the blood calcium levels.
These conditions can lead to secondary symptoms of Vitamin D deficiency. It may may include:
- Tiredness, aches, and pains
- Osteoporosis
- Stress fractures, particularly in the legs, pelvis, and hips
- Extreme numbness or pain in the muscles or bones.
- Mood changes, like depression

Children with vitamin D deficiency have growth retardation as well as the typical rickets signs and symptoms.
Adults with Vit. D deficiency will experience osteopenia, osteoporosis, and an increase in fracture risk.
Vitamin D deficiency has long been linked to muscle weakness.
Skeletal muscle has a vitamin D receptor, and deficiencies have been linked to proximal muscle weakening, an increase in body sway, and a higher risk of falling.
Adults with Vit. D deficiency may also have abnormal skeletal mineralization.
The periosteal coating receives minimal structural support from the unmineralized osteoid.
As a result, individuals with osteomalacia may express isolated or generalized bone soreness in addition to joint and muscle pain.

If Vit. D deficiency continues for a long period, it may result in following consequences:

Breastfed infants, because human milk is a poor source of vitamin D
Older adults, because skin doesn’t make vitamin D when exposed to sunlight as efficiently as when young
People with dark skin, can synthesize less vitamin from sunlight.
Those who cannot adequately manage fat due to conditions like Crohn’s disease or celiac disease, as Vit. D needs fat to be absorbed.
Obese people, as some vitamin D is bound by body fat in these individuals and cannot enter the bloodstream.
Individuals who had gastric bypass surgery
Those who have osteoporosis
Those who suffer from liver or renal problems.
Those who have hyperparathyroidism
Patients with sarcoidosis, tuberculosis, histoplasmosis, and other granulomatous disorders
People who have certain types of lymphomas
People who use medications that interfere with vitamin D metabolism, such as cholestyramine (a cholesterol medication), anti-seizure medications, glucocorticoids, antifungal medications, and HIV/AIDS medications.