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Importance of Vitamin D during Adolescence

As we know, Adolescence is the transitional stage of development between childhood and adulthood. It is associated with marked physical growth, reproductive maturation, and cognitive transformations. Hence, vitamin D is an important micronutrient for Adolescents.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that is important for maintaining normal calcium metabolism and is therefore necessary for bone health. Moreover, it has been considered a bone builder along with other biological factors.

The emerging research suggests that vitamin D may be far more versatile, offering many health benefits it absorbs calcium and phosphorus, which is important for bone and teeth health, prevents heart disease and type 2 diabetes & reduces the risk for depression. 

The status of Vitamin D is best assessed by measuring blood levels. Test of Vitamin D measures the level of vitamin D in your blood to make sure you have enough vitamin D to work well. Before utilization of vitamin D in Your body, the liver must change it into another form called 25 hydroxyvitamin D, or 25(OH)D. Vitamin D blood tests measure the level of 25(OH)D in the blood. 

Different Forms of Vitamin D

Vitamin D exists in two forms that are vitamin D2 (ergocalciferol)and vitamin D3 (cholecalciferol) which differ in the structure of their side chains.

  1. Ergocalciferol (vitamin D2): It is synthesized by plants & formed by breaking of a photochemical bond specifically by the action of ultraviolet light (UV-B or UV-C) on ergosterol, a form of provitamin D2. Ergocalciferol is an inactive from of Vitamin D. In our body, vitamin D needs to go through two processes to become active. Firstly, in the liver, it transforms into 25-hydroxy ergocalciferol. Afterward, in the kidney, it further changes into its active form known as 1,25-dihydroxy ergocalciferol. This active version of vitamin D is vital because it activates the vitamin D receptor in our body, playing a crucial role in many bodily functions.
  1. Cholecalciferol (vitamin D3): It is synthesized by the mammalian skin following UVB light exposure. It is converted to calcidiol (25-hydroxyvitamin D) in the liver which is then converted to calcitriol (1,25-dihydroxyvitamin D) in the kidney. One of its actions is to increase calcium uptake by the intestines. It can be found in eggs, some fish, beef liver, and cheese. Plants, fruit juice, cow milk, margarine and yogurt also. 

Functions of Vitamin D

Although vitamin D is classified as a vitamin, it actually functions like a hormone. It is made in one part of the body, but its action is in other parts of the body because it absorbs calcium and phosphate from the gut into the bloodstream. Functions of Vitamin D include:-

1. Bone Growth & Maintenance

It is needed for bone growth and maintenance. It has an important role to play in the absorption of dietary calcium from the intestine and its deposition in bone. Vitamin D stimulates osteoclast (bone cell) differentiation and calcium reabsorption of bone. Vitamin D promotes the mineralization of the collagen matrix in bone. 

2. Regulation of Blood Calcium

Calcitriol, also known as the active form of vitamin D, is a hormone made in the kidney. It plays a major role in our body by helping control the amount of calcium in our blood. Calcitriol works by activating special parts of our cells called vitamin D receptors, which then tell our body to absorb more calcium and phosphorus from the food we eat. This helps make our bones stronger. Additionally, calcitriol reduces the amount of calcium our kidneys get rid of, which indirectly helps in building strong bones by depositing calcium in them.”

3. Decrease Risk of Cancer

Recent studies show that vitamin D is capable of influencing differentiation in some cancer cells. So a good vitamin D status may be linked to a decreased risk of some cancers, like breast, colon, and prostate (Lappe et al. 2007). This is because Calcitriol may play a role in decreasing the risk of Cancer because calcitriol regulates the cell cycle, induces apoptosis (cell death), promotes cell differentiation, and acts as an anti-inflammatory factor within the tumor microenvironment.

4. Helps in Functioning of Parathyroid gland

Recent studies have also shown that active vitamin D controls the growth and functioning of the parathyroid gland. When vitamin D level in the body is low, the absorption of calcium in the intestines becomes less, which then causes the level of calcium in the blood to go down. When calcium levels become low, parathyroid glands become more active and produce more parathyroid hormone that causes calcium to come out of the bones, therefore weakening the bones.

5. Promote immunity 

Vitamin D helps our immune system work properly and would keep our body safe from infections. It does this by affecting different cells in our immune system. Vitamin D stops the immune system from making too much immunoglobulin, a substance our body produces during infections. It also prevents certain immune cells, called B cells, from growing too much and changing into different types of cells.

6. Protect from Diabetes

Researchers found that the chance of developing insulin resistance went down when an additional amount of vitamin D supplement was taken because Vitamin D also contributes to insulin secretion and may offer protection against diabetes. Researchers say this might indicate that vitamin D3 is a protective factor in the occurrence of insulin resistance because it helps lower inflammation and inflammation raises the risk for insulin resistance.

7. Protection from other diseases

Vitamin D is important for our health. Some research suggests it might protect against diseases like dementia, multiple sclerosis (a type of immune disorder), and infections such as tuberculosis. In fact, sunlight, which helps our body produce vitamin D, can directly help fight tuberculosis. Foods like cod liver oil are rich in vitamin D and have been used to treat tuberculosis and prevent infections.

Problems of Deficiency

Deficiency of Vitamin D in infants and children results in the failure of bone to mineralize, leading to a condition known as rickets, but cases of rickets have also been reported during stages of puberty and adolescence. There are various bone conditions associated with vitamin D deficiency including rickets in children &  osteomalacia in adult life.


Rickets is a disease of growing children that affects bone development in children. It causes softening of bone & bone pain, poor growth, and weak bones that can lead to bone deformities. Rickets could be inherited or acquired. The acquired rickets are due to poor nutrition. 


A lack of vitamin D from diet & lack of exposure to sunlight can cause rickets in children. Deficiency of Vitamin D can result from a lack of the vitamin in the diet, inefficient dietary absorption, insufficient conversion in the skin by ultraviolet light, or the abnormal conversion of vitamin D to its metabolites.

Some people who live in places with not much sunlight, like colder areas, and those with dark skin might lack vitamin D. Also, if someone has certain health problems like kidney, liver, or stomach issues, their body might struggle to absorb vitamin D. This is because their body can’t convert one form of vitamin D to another, which is needed to absorb calcium.


Initial stages of this deficiency include:

  • restlessness, 
  • lack of muscle tone in the limbs and abdomen, 
  • softening of the bones of the skull, 
  • delay in the eruption of the teeth and delay in learning to sit, crawl, and walk. In some cases, the child is unable to walk. 

Rickets may produce conditions such as:

  • swelling at the ends of the ribs which gives the appearance of a rosary (a set of prayer beads ), 
  • bowlegs ( legs bent like a bow ), 
  • knock-knees ( both knees touching each other ), 
  • a bulging forehead, and short stature. 
  • Deformities of the chest with the breast bone becoming prominent are common. 


Rickets is a condition often caused by not having enough vitamin D and calcium in the body. To treat rickets, it’s essential to do the following: 

  • focus on increasing vitamin D and calcium levels. This can be done by including more foods in the diet that are rich in these nutrients. For vitamin D, you can rely on foods like fatty fish (such as salmon and tuna), egg yolks, and fortified products like milk and orange juice. When it comes to calcium, include dairy products such as milk, cheese, and yogurt in your diet. Leafy green vegetables like broccoli and kale, as well as nuts and seeds, are also good sources of calcium
  • taking daily vitamin D supplements, especially with healthy fats, has proved to be  beneficial. 
  • Spending time outdoors in the sunlight is also crucial because sunlight helps the body produce vitamin D naturally, turning it into the active form necessary for overall health. 

By following these steps, individuals can effectively address the deficiencies causing rickets and promote better bone health.


There are several steps to prevent Ricket in children. These include adequate exposure to sunlight, taking a healthy balanced diet that contains vitamin D & calcium & include vitamin D supplements.


Osteomalacia is like grown-up rickets. It happens when adults have really soft bones because they don’t get enough vitamin D for a long time. This makes their bones not as strong as they should be. Osteomalacia often affects women between 15 and 45 years old.


The common causes of osteomalacia are incomplete mineralization & low levels of vitamin D in the diet. It can also be caused by some Digestive Disorder & Other possible causes include lack of phosphorus, kidney problems, celiac disease, liver disorders & genetic factors. These are some of the factors that interfere with the absorption of vitamin D.

Clinical Manifestations

Bones become soft (legs, spine, thorax, pelvis) and bend in deformities, General weakness, Pain of rheumatic type in the bones of legs and lower back, Difficulty in walking, especially in climbing stairs, spontaneous multiple fractures as bones become brittle.


To treat osteomalacia, make sure that a person gets the levels of vitamin D & nutrients they need to support the process of bone mineralization. Take therapeutic dosages of supplements of vitamin D, calcium, or phosphate by doctor’s prescription for strong & healthy bones. Get regular exposure to sunlight, while taking precautions to avoid damage from the sun.


The exposure to sunlight is the best way to prevent osteomalacia. Once the deformities occur then you can not correct them. Take a diet rich in vitamin D and calcium, exercise regularly, and eat a healthy diet containing vitamin D and calcium. Take supplements if needed. 

Recent research is revealing the important roles of vitamin D which plays other functions in the body too. Some observational studies show that a low level of vitamin D in the blood increases the risk of the follwing:-

Increased risk of cardiovascular disease

Low vitamin D is associated with a variety of cardiovascular-related outcomes. Long-term Research on 3577 adolescents aged 12 to 19 years by NHANES (National Health and Nutrition Examination Survey) shows that low serum vitamin D is associated with an increased risk of high blood pressure, high blood sugar, and metabolic syndrome which increase the risk of cardiovascular disease because of improper absorption of vitamin D in the body.

Cognitive impairment  

Vitamin D influences Neurological function and brain development. This vitamin plays an immunomodulatory role in the central nervous system. Tetany caused by hypocalcemia (low calcium) may be associated with vitamin D deficiency in children and adults. Symptoms of Tetany include loss of feeling in the lip or tongue regions and in the fingers, facial spasms, and sometimes seizures. It has been postulated that the increase in the prevalence of autism over the last decades could be due to less or even no sunlight exposure and low vitamin D levels. Although children with autism have several markers that may be controlled with high vitamin D doses, autism is a heterogeneous condition in which children with autism are selective with food intake and have behavioral difficulties.


According to the research, 25(OH)D levels are positively correlated with insulin sensitivity, but negatively correlated to hemoglobin A(1c), which suggests that obese children and adolescents with low vitamin D levels are at increased risk of developing metabolic disorders like diabetes. The most common second chronic disease in childhood is Type 1 diabetes. According to a research based on the experimental study, it finds that mice raised with a vitamin D deficiency status develop diabetes at a much earlier age than animals without vitamin D deficiency. Case-control studies showed that receiving vitamin D supplements may reduce the risk of type 1 diabetes because, in Diabetes, absorption of the active form of vitamin D gets hindered.

Risk factors for Vitamin D insufficiency in adolescents

Diets with inadequate Vitamin D.

Nowadays, adolescents love to eat junk food that doesn’t have good amounts of Vitamin D & even deficient in other micronutrients which cause vitamin D deficiency. If they avoid vitamin D-rich food during puberty, their bone growth & body maintenance will retard, causing many health issues so a vitamin D-rich diet is very important at this stage.


People with higher amounts of body fat have lower amounts of Vitamin D circulation in the blood because Vitamin D is a fat-soluble vitamin and fat cells keep vitamin D isolated so it’s not released. Due to this reason, obese people need higher amounts of vitamin D and require larger doses of vitamin D supplements to maintain normal levels.

Darker skin 

People with darker skin make less vitamin D from sunlight compared to those with lighter skin. This happens because the melanin in darker skin absorbs the sunlight that helps make vitamin D, but it doesn’t do it as well as in lighter skin. So, darker-skinned people produce less vitamin D than those with lighter skin because the process is not as efficient.

Certain medical conditions

Certain health problems like cystic fibrosis, diabetes, and certain stomach issues can make it hard for our body to absorb vitamin D. This is because these conditions reduce the enzymes our body needs to change vitamin D into a form it can use. If we don’t have enough of these enzymes, our body can’t use vitamin D properly. This can be a problem, especially if the health conditions aren’t treated, as our intestines might not be able to absorb enough vitamin D even if we take supplements.

How can Adolescents get enough Vitamin D? 

(1) Include Vitamin D rich diet

Adolescents should eat a diet rich in Vitamin D to avoid deficiency of Vitamin D. Some of the food sources of vitamin D are:-

For vegetarian:- cheese, mushrooms, fortified milk, fortified cereals & juices

For Non Vegetarian:- fatty fish, such as salmon, mackerel, and tuna, egg yolks, beef liver

So, if you have to take a Vitamin D supplement, you can pair it with a food containing healthy fat. Try eating whole eggs, nuts, avocado, fatty fish, extra virgin olive oil, or full-fat dairy with your supplement because it improves the absorption of Vitamin D.

(2) Spend some time in Sunlight

 Teenagers should spend 15 to 30 minutes outdoors, soaking up sunlight two or three times a week. This helps make enough vitamin D in the body. Sunlight has two types of energy: ultraviolet A (UVA) and ultraviolet B (UVB). UVB helps the skin make vitamin D, but it can also harm the skin and cause cancer. UVA damages the skin and makes it age faster. To stay safe, avoid strong sun between 10 a.m. and 2 p.m., especially in summer. If you have light skin, 15 minutes of sun is good. Darker skin needs a couple of hours, according to the Vitamin D Council.

(3) Drink plenty of fluids

Keep hydrated when playing outdoor games because According to new research presented at the 24th European Congress of Endocrinology in Milan, Study shows that milk and water were shown to be effective and most efficient options for enhancing the absorption of Vitamin D.

(4) Take prescribed Supplements

Sometimes the primary care provider (PCP) will recommend supplements of Vitamin D. Supplements including Vitamin D pills, multivitamins, chewables, sprays & liquids.  

By reading this blog, you have understood now that Vitamin D not only supports bone growth & body Maintenance but also has multiple functions, it may support a healthy immune system, normal blood pressure, cardiological health, lessened total mortality, cognitive performance, and healthy aging so, include a diet rich in vitamin D, spend few minutes on sunlight & if needed then you can take supplements to avoid vitamin D deficiency.

And for personalized guidance on crafting a diet that caters to your specific needs, reaching out to FitandCure, the best dietician in Noida, is highly recommended. Specializing in diets tailored for children as well, FitandCure is the go-to dietician for kids in Noida. Take charge of your health journey with expert advice from FitandCure—your partner in achieving optimal well-being.







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