Vitamin D: Benefits, Deficiency, Sources, And Dosage

The human body needs a constant supply of certain vitamins to remain healthy. Each vitamin poses its own roles in the body, interacting with cells to ensure specific functions can be performed.

Vitamin D has many benefits and is a critical hormone that the body is unable to produce on its own. This means the vitamin needs to be consumed through external sources. What makes vitamin D so unique is that the body can synthesize the nutrient when exposed to the sun. 

Even though classified as a vitamin, it is vital to note that vitamin D is technically a pro-hormone. This is a fat-soluble nutrient that is absorbed into the bloodstream with the help of fat contents found in food.

The vitamin plays a critical role in the absorption of calcium and has several other roles to play as well. 

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What Is Vitamin D?

Vitamin D is one of the many nutrients the body needs. It is classified as a fat-soluble vitamin. This means the body needs fat content to absorb vitamin D.

The vitamin is only present in a small number of food sources. It can also be obtained through the consumption of fortified foods. Additionally, some supplements contain Vitamin D2 or vitamin D3. 

Vitamin D is sometimes referred to as the “sunshine vitamin.” This is because sun exposure helps with vitamin D synthesis. An endogenous production process happens when a person is exposed to the sun. The ultraviolet rays of the sun cause a synthesis process to trigger. 

When vitamin D enters the body, there are two processes that it needs to undergo. These processes are referred to as hydroxylations. 

The liver converts vitamin D into a chemical called 25-hydroxyvitamin D. This particular form of vitamin D is also called calcidiol. The kidneys then create an active type of vitamin D. This form is known as 1,25-dihydroxy vitamin D. The 1,25-dihydroxy vitamin D chemical is often referred to as toa s calcitriol. 

Vitamin D is involved in many processes in the body. It helps with the growth of cells. It also plays a role in elements like inflammation and immunity. Getting enough vitamin D is critical in both children and adults. Failure to do so may lead to a deficiency in this vitamin. The result may be unpleasant complications that can become serious in some cases. 

When there is uncertainly about the vitamin D level in a patient, 25(OH)D serum concentration is generally tested. This provides an excellent marker to determine if the patient is getting enough of the vitamin. 

10 Benefits Of Vitamin D

Many benefits come with an adequate intake of vitamin D. We take a look at essential benefits that come with enough vitamin D in the blood below:

  • In men, prostatic epithelial cell growth is inhibited. These are primary cultures in cases of prostate cancer. With this in mind, vitamin D may provide a protective function against prostate cancer. 
  • Low vitamin D  levels link with an increased risk of cognitive decline. A recent double-blind, randomized, placebo-controlled trial found that Vitamin D supplementation for 12 months appears to improve cognitive function through reducing oxidative stress.
  • Calcium and phosphate both regulate more effectively. This provides an improvement in bone mineral density. It also results in healthier and stronger bones. 
  • Teeth remain healthy with adequate consumption of vitamin D. 
  • The vitamin contributes to the maintenance of healthy muscle tissue. It also helps to optimize muscle function, which is especially useful for athletes. 
  • Vitamin D helps to regulate a person’s blood pressure levels more effectively. Hypertension is a serious concern around the world. It causes damage to blood vessels. The condition also contributes to heart disease. By lowering blood pressure, vitamin D also helps to reduce the risk of these complications. 
  • The immune system becomes stronger. This leads to a more effective defense system against pathogens. The result is generally a reduction in the frequency of infections. It may also be an effective protective mechanism against the growth of cancerous cells. 
  • Vitamin D is critical for healthy skin. It helps to prevent skin from looking dry and dull. 
  • Some evidence has shown that vitamin D may stimulate the pancreas. In turn, the pancreas may release more insulin. This could be an effective way of regulating blood glucose levels too. It may be useful for people with a low level of insulin sensitivity
  • Individuals at risk for vitamin D deficiency are also at increased risk for atrial fibrillation. This is a prevalent type of arrhythmia event in older adults. One study found that supplementation with vitamin D in high concentrations may decrease the risk of this type of arrhythmia by 30%. Further studies are required to confirm these findings, mainly due to previous research with conflicting results. The dose required for the maximal reduction in atrial fibrillation risk was 3,200 IU/d, significantly reducing the number of cardiovascular events in a 2-year follow-up.

Vitamin D Deficiency

Due to the many roles that vitamin D plays in the human body, people must understand what can happen when they do not obtain enough of this nutrient. 

The main complication often linked to a vitamin D deficiency would be weaker bones. This is because vitamin D plays a critical role in the absorption of calcium in the human body. When there is not enough vitamin D, the body will not be able to take full advantage of calcium. 

There are other issues related to the complications that may occur in people who suffer a vitamin D deficiency. These include:

  • Osteomalacia, a condition where the bones become soft, leading to an increased risk for fractures and other potential problems. 

  • Rickets occurs when a newborn’s bones do not become strong and somewhat soften during early development. 

  • Hypophosphatemia, referring to a low level of blood phosphate. 

Symptoms Of Vitamin D Deficiency

When vitamin D levels decline too much, serious complications can develop. There are a few earlier signs that can show a patient their vitamin D levels may be low.

By learning about these symptoms, a patient can detect a deficiency in vitamin D early on. This ensures appropriate treatment is initiated to prevent serious complications. 

We will consider some of the most prominent symptoms that should be recognized in this section. The symptoms do not necessarily mean a patient has a vitamin D deficiency. They can be related to other conditions too. Still, it is crucial that the patient take action and at least see a doctor when these symptoms occur. 

Immune Function

Vitamin D plays a role in immune function. When levels of the vitamin decline a lot, it can cause the immune system to become weak. This may lead to recurrent infections. The immune system is responsible for warding off invading pathogens. With a low vitamin D level, its ability to do so becomes limited. Pneumonia, bronchitis, and colds are all relatively common. 

Wound Healing

The immune system is also involved in the wound healing process. When the immune system is compromised due to low vitamin D consumption, it can affect the rate at which wounds heal. This leads to impaired wound healing. A patient will find that it takes longer for injuries to heal completely. 

Bone Issues

Vitamin D affects calcium absorption. It is also involved in the process of keeping bones healthy and strong. When vitamin D levels are low, bone pain is possible. This has been noted in many patients with a deficiency in the vitamin. Many people also complain about back pain if they have low levels of vitamin D. 

Bone loss is also possible among individuals with a vitamin D deficiency. Studies have linked vitamin D deficiency to a poor bone mineral density. This may increase the risk of certain bone-related diseases


Some studies have also linked vitamin D deficiency to depression. This symptom does seem to be more common among older individuals with a low vitamin D level in their bloodstream. 

Tiredness or fatigue

Tiredness and fatigue are two particularly common symptoms among people with a deficiency in this vitamin. Research has shown that this particular symptom may harm a patient’s quality of life. Many individuals with vitamin D deficiency complain about chronic fatigue during the day, even if they get enough sleep. 

Muscle Problems

Due to the effects of vitamin D on muscle tissue, a significant decline in vitamin D levels can cause problems with muscles too. Chronic muscle pain has been noted among people with a Vitamin D deficiency. This is because there are vitamin D receptors at nociceptors, which are specific types of nerve cells. 

Hair Loss

Another symptom that may sometimes develop is hair loss. There are many causes of hair loss. People often overlook Vitamin D deficiency as a potential reason. A patient can develop alopecia areata when their vitamin D levels are too low. 

Causes Of Vitamin D Deficiency

When symptoms of vitamin D deficiency exist, testing for serum concentrations is important. This helps a person identify a deficiency and take appropriate actions. There are several reasons why vitamin D deficiency can occur.

Initial treatment may include supplementation with vitamin D. It is, however, also important to identify why the deficiency developed. This helps to provide a longer-term targeted approach.

When addressing the causes, it also helps to prevent a future occurrence of a vitamin D deficiency. 

There are many reasons why vitamin D deficiency may occur. We list some of the reasons below. 

  • Breastfeeding babies over a long period of time without providing them with vitamin D supplementation.

  • Failure of government entities to emphasize the fortification of foods with vitamin D and other nutrients.

Obesity is one particular factor that needs to be mentioned. Those obese or overweight individuals seem to be at a higher risk of suffering vitamin D deficiency. In fact, there is a 35% increase in risk of this deficiency among obese people than healthy-weight individuals. 

Another important reason for vitamin D deficiency is limited sun exposure. The sun plays an important role in providing a person’s body the elements required to synthesize this vitamin. When a person is unable to gain adequate sun exposure, they may be at a higher risk of suffering from a vitamin D deficiency – especially if the foods they consume do not offer them this particular nutrient. 

Vitamin D Deficiency Treatment

When a serious deficiency in vitamin D occurs, simply entering the sun may no longer provide an adequate restoration of this vitamin to the individual. This is why several treatments have been developed to assist in restoring optimal levels of the nutrient in a patient’s body. 

The specific treatment used depends on certain factors. The significance of vitamin D deficiency will be one of the first factors a healthcare provider will consider. A more serious deficiency may require a higher dose drug to restore levels of vitamin D. 

The most common treatment would include the use of ergocalciferol over an eight-week period. This is an oral drug that is taken by mouth and is also known as vitamin D2. A 50,000 IU weekly dose will be provided during the treatment period. 

Following this treatment phase, the patient may be provided cholecalciferol, or vitamin D3, with a dose of up to 1,000 IU on a daily basis. This will usually be an ongoing supplement that the person will continue taking to assist with maintaining a better balance of their vitamin D levels. 

The cholecalciferol will usually be provided to the patient in supplement form, instead of a pharmaceutical drug. The patient should take note that they follow the guidance provided by the physician to ensure their vitamin D levels do not fall too low again, as this may lead to the need for another treatment phase with the use of ergocalciferol. 

Sources Of Vitamin D

Vitamin D is not as readily available as some of the other vitamins and minerals the body depends on. This is why careful consideration needs to be made to prepare meals and snacks for the day.

Some people also have a higher risk of vitamin D deficiency. In these scenarios, the individual needs to consider additional ways to increase their intake of vitamin D

Foods high in vitamin D

  • Salmon 

  • Mackarel

  • Tuna

  • Beef liver

  • Egg yolks

  • Cheese

  • Mushrooms

Fatty fish like Salmon and Tuna remains the best sources of vitamin D. Eating enough of these foods may help to ensure a person gets an adequate amount of vitamin D. 

Moderate sun exposure is also important. The skin uses the sun’s ultraviolet rays to synthesize vitamin D. Too much sun exposure can be bad. This may lead to an increased risk of skin cancer. Excessive sun exposure also causes sunburn and skin damage. 

Apart from these, fortified foods with added vitamin D is available. This is a good option for vegetarians and vegans. Cereals, milk products, and many other foods are enriched with vitamin D, vitamin B12, and other important nutrients. 

Taking a vitamin D supplement is another option to help increase the intake of the nutrient. Various supplements exist. Some will only provide the person with vitamin D. Other supplements will contain vitamin D and other vitamins and minerals. 


An optimal intake of vitamin D helps to prevent a deficiency from developing. This is an effective strategy to help reduce the risk of complications associated with vitamin D deficiency too.

It is, however, important that a person understand what an optimal dose of vitamin D is. Taking too little may lead to a deficiency. On the other hand, getting too much of the vitamin can sometimes be dangerous. 

The majority of individuals can follow the general guidelines that have been set out for vitamin D consumption. It is advised that healthy individuals get between 400 IU and 800 IU of vitamin D. This is enough to support the functions that vitamin D contributes to in the human body. 

Some people do need more or less vitamin D, however. Individuals with a deficiency may be advised to consume up to 4,000 IU of vitamin D per day. This is generally provided over a short period of time. The higher dose helps the person balance their vitamin D levels faster and may help prevent some of the severe complications that come with a deficiency. 


There are risks associated with a high intake of vitamin D. When a person overdoses or takes too much of the vitamin, a condition known as vitamin D toxicity may develop. This is a serious risk as it can cause harm to the patient’s body. 

An excessive buildup of calcium in the patient’s blood is one of the initial risks. This is a condition known as hypercalcemia. It can cause frequent urination, weakness, and vomiting.

Vitamin D toxicity has also been linked to problems with the kidneys. There is a higher risk for the development of calcium stones in the kidneys. Bone pain may also occur in people who take too much vitamin D. 


Vitamin D has many benefits and plays an important role in the body. There are various sources of this nutrient. Many supplements contain Vitamin D3 to reduce the risk of deficiency. Getting enough vitamin D helps to promote healthier bones and contributes to a hormonal balance.

An appropriate vitamin D level may also be good for the prostate. Vitamin D deficiency can be harmful and lead to serious complications. This is why it is important to look out for symptoms of a deficiency. 

Next Up


Find out 10 Immune Boosting Vitamins.


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