Your Comprehensive Guide for Vitamin D

Comprehensive Guide for Vitamin D

Did you know why Vitamin D is also known as the “sunshine vitamin”? Did you know that, in addition to bone health, this essential nutrient helps with immune function?

It is well known that when the skin is exposed to sunlight, Vitamin D is naturally produced in the body. Getting enough vitamin D boosts resistance to certain diseases and aids in the growth and development of bones and teeth. It also has numerous other health benefits.

Sunshine Vitamin

This article offers a comprehensive overview of this vital nutrient. Continue reading for more information.

What is Vitamin D?

Vitamin D is a lipid-soluble prohormone that promotes calcium and phosphate metabolism, which is essential for bone and muscle health.

There are two different forms of vitamin D. 

  • Vitamin D2 (ergocalciferol), which is found in plants, is poorly absorbed and not nutritionally valuable.
  • Vitamin D3 (cholecalciferol, which is produced in the skin)

Vitamin D-rich foods include fish liver oil, egg yolks, cheese, fortified milk, and cod liver oil.

Vitamin D performs the following functions:

  • Maintain an adequate level of calcium in the plasma
  • Increased calcium absorption from the intestine
  • Vitamin D, together with parathyroid hormone, aids in bone formation.
  • Reduces the excretion of calcium and phosphate and improves reabsorption

Did you know that a Vitamin D deficiency increases your risk of developing rickets, osteoporosis, and a weakened immune system?

What are the health benefits of Vitamin D?

Vitamin D is a fat-soluble vitamin that can be absorbed through the skin or obtained through food or supplements, is stored in the body’s fat cells, and remains inactive until needed. The stored vitamin D is hydroxylated by the liver and kidneys to produce the active form, calcitriol. 

This vitamin has anti-inflammatory, antioxidant, and neuroprotective properties and thereby helps regulate various cellular functions in your body, supporting immune health, muscle function, as well as brain cell activity.

Health benefits of Vitamin D

The following are some of the health benefits of Vitamin D: 


Adequate vitamin D and calcium levels slow bone mineral loss, help prevent osteoporosis, and reduce the risk of bone fractures. 


Osteomalacia is a condition wherein the bones become soft and weak. As a result, they bend and break more easily than normal. Vitamin D supplements are used to treat adults with severe vitamin D deficiency. 


A rare condition that develops in children with a vitamin D deficiency. Supplementing with vitamin D can prevent and treat the problem. 

Cognitive Health

Low levels of vitamin D in the blood have been linked to poor cognitive function. Additionally, it is also known to increase the risk of depressive symptoms. 

Multiple Sclerosis

Long-term vitamin D supplementation is known to reduce the risk of multiple sclerosis.


Topical application of vitamin D (calcipotriene) helps treat plaque-type psoriasis.


Studies have revealed a strong correlation between calcitriol and a lower risk of developing cancer. Therefore, having sufficient vitamin D in our bodies may lower our risk of getting cancers of the breast, ovaries, colon, and prostate. 


Vitamin D deficiency has been linked to fertility problems, and studies have shown that it is a risk marker for fertility problems and undesirable pregnancy outcomes. 


According to research, people with insulin resistance and low vitamin D levels are at a higher risk of developing type 2 diabetes. 


Studies have shown that supplementation with Vitamin D has been associated with a significant improvement in asthma control and severity. 

Heart Diseases

According to research, chronic heart failure is frequently associated with vitamin D deficiency, and extremely low levels are associated with a poor prognosis.

What is the recommended daily dosage of Vitamin D?

The amount of vitamin D produced by your skin is affected by a variety of factors, including the time of day, season, and skin pigmentation. Hence, taking a multivitamin containing vitamin D may benefit bone health. 

The daily vitamin D dosages recommended are as follows:

  • Infants: 10 mcg/day or 400 IU
  • Children and Adults: 15 mcg/day or 600 IU
  • Elderly (above the age of 70 yrs): 20 mcg/day or 800 IU/day
What are the risks of excessive Vitamin D intake?

Since vitamin D is a fat-soluble vitamin, it is initially stored in fat cells before being converted to an active form. Because of this, if you have been taking higher doses, and have lower fat reserves, the excess vitamin D enters your bloodstream, and you may end up absorbing too much calcium, leading to toxicity.

Excessive Vitamin D intake

However, this is unlikely to happen through diet or sun exposure because your body regulates the amount of vitamin D produced by exposure to sunlight. A level of more than 150 nmol/L is considered toxic, and you may experience an increase in blood calcium levels as a result of vitamin D toxicity. 

This can cause a number of health problems, such as confusion, loss of appetite, dehydration, excessive urination and thirst, nausea, vomiting, muscle weakness, and kidney stones. Extremely high levels can result in kidney failure, an irregular heartbeat, and even death.

What are the signs of Vitamin D deficiency?

Vitamin D deficiency can affect anyone, including infants, children, and adults. A simple blood test can determine the levels of this vitamin in your blood, and the following are the different ranges of levels in the blood.

  • Normal range: 30-60 ng/ml or 75-150 nmol/L
  • Insufficiency: 10-30 ng/ml or 25-75 nmol/L
  • Deficient: Less than 10 ng/ml or 25 nmol/L

There are two main causes of vitamin D deficiency: not getting enough vitamin D through your diet and/or sunlight, and your body not being able to absorb vitamin D properly.

Vitamin D deficiency can be caused by a variety of factors, including medical conditions (Crohn’s disease, celiac disease, obesity, kidney, and liver disease), weight loss surgery, or certain medications. 

Children with a mild vitamin deficiency may have weak, sore, and/or painful muscles. A severe lack of vitamin D in children, on the other hand, can cause rickets, with symptoms including incorrect growth patterns due to bowed or bent bones, muscle weakness, bone pain, and joint deformities. 

While adults do not show symptoms of vitamin D deficiency, symptoms may include fatigue, bone pain, muscle weakness, muscle aches or cramps, and mood changes such as depression. 

Vitamin D is an essential vitamin that your body requires for the proper functioning of several vital cellular processes. It is difficult to obtain enough vitamin D through diet alone, and additionally, if you have risk factors for vitamin D deficiency or are experiencing symptoms, you should consult a healthcare professional and have a blood test to check your levels.

About Author –

Dr. Praveen Kumar, Consultant Orthopedic & Joint Replacement Surgeon, Yashoda Hospitals - Hyderabad
MS (Ortho), Fellow Joint Replacement

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Dr. Praveen Kumar

MS (Ortho), Fellow Joint Replacement
Consultant Orthopedic & Joint Replacement Surgeon

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