Vitamin D, better known as the sunshine vitamin is a group of fat-soluble vitamins, which are involved in the regulation of essential minerals like calcium and phosphorus responsible for maintaining strong and healthy bones.

The two major types of vitamins in the group are Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). Vitamin D2 is made by plants and is not found in humans, but D3 can be synthesized in skin with the help of sunlight.

On exposure to UV radiation provitamin D3 (7-dehydrocholestrol) in skin is converted to previtamin D3. Previtamin D3 is then isomerized into a more stable form by a thermal reaction. This is precisely why the vitamin is called sunshine vitamin and those who barely get this exposure, suffer from vitamin D deficiency.


Both the forms of vitamin D are equal considering their ability to cure rickets, however Vitamin D3 is three times more effective than vitamin D2, since the binding proteins have a greater binding affinity for D3, which allows them to stay in system longer than D2. Vitamin D2 is less potent and comparatively has a shorter duration of action. [M1]


Whether the vitamin enters through the oral route or is synthesized in skin, the next step is being bound to proteins like albumin and vitamin D binding proteins that carry it to the liver.

In the liver it is converted into calcidol, also known as 25-hydroxycholecalciferol or 25-hydroxyvitamin D3. Likewise, Vitamin D2 is converted into 25-hydroxyergocalciferol or 25-hydroxyvitamin D2.

The calcidol undergoes another reaction in the kidney and is converted into 1,25-Dihydroxyvitamin D or calcitriol- the biologically active form of Vitamin D. This form circulates as a steroid hormone in the body and is responsible for regulation of minerals.

Calcidiol and 25-hydroxyvitamin D2 are the two metabolites that determine the status of vitamin D in serum. Calcidiol is the primary circulating form and the most commonly measured form in the serum.


Vitamin D stands out from the rest of the vitamins because our body can synthesize it. It plays a vital role in maintaining healthy, strong bones and in a number of processes. The following are the uses and benefits of vitamin D

· The most important role of Vitamin D is to increase the calcium levels of blood. It does this by facilitating absorption of calcium in small intestine and also its out flux from the bones. Vitamin D production itself is increased and decreased under the effect of parathyroid hormone.

· Regulates immune system

· It plays an important role in maintaining cognitive functions of the brain. This is supported by studies, later in the article.

· It reduces the severity of asthma symptoms and the following frequency of hospitalization as well

· It helps in maintaining a healthy body weight. According to a study published in the American Journal Of Clinical Nutrition, healthy levels of vitamin D are associated with weight loss in post menopausal women who are over weight [M2] [12]

· Vitamin d receptors are there in more than 30 different types of cells and its role in preventing diseases like diabetes, cardiovascular diseases and cancer has gained immense popularity and has become the objective of numerous studies.


Vitamin D is obtained through sunlight exposure, food high in vitamin D and vitamin D supplements. Let us shed light on all the three sources one by one;

Safe Sun Exposure- Large amounts of vitamin D are made when we get the correct amount of sunlight exposure. This is the most natural and effortless way of getting vitamin D. The amount of vitamin D produced however depends on the time of the day you choose for the task, color of your skin and part of the world you live in.

Vitamin D Foods– Tuna fish, certain kinds of mushrooms, cod liver oil, eggs and dairy products like cheese and milk are vitamin D rich foods. All these foods if made a part of regular meals, will keep you miles away from vitamin D deficiency.

Supplements- This alternative, saves you from the hassle of getting sun burns and developing skin cancer, which unfortunately is the case with UV light exposure.

What is the best kind of Vitamin D Supplement to take?

According to the Vitamin D council, the best kind of supplement to take is Vitamin D3.

Vitamin D Dosage

These supplements are available in the form of vitamin D capsulesVitamin D tablets and liquid vitamin D, basically makes use of administering vitamin D drops through a dropper to an infant or child.

Vitamin D is also available in the form of Vitamin D creams and lotions, that are often prescribed by doctors as a part of treatment of psoriasis (a skin diseases). Studies have also shown a positive role of topical Vitamin D application in skin fibrosis[13].

Vitamin D spray is another form of the supplement, which is taken under the tongue once a day or as prescribed by the doctor. This spray combats vitamin Ds deficiency.


6 days of casual sunlight exposure can make up for 49 days of no sunlight exposure. This is how quickly and efficiently sunlight can make vitamin D levels go up to an adequate level in body. Surprisingly, vitamin D deficiency is one of the most common deficiencies that one comes across.

While you take your share of the natural sunlight during the day, body stores it in fatty acids and releases it during the sunlight-deprived time. People who are likely to suffer from vitamin D deficiency are;

· Elderly

· Those who don’t get enough exposure to sunlight (Canadians and north Americans)

· Sometimes seen in people living in sunny areas

· Vegetarians

· Pregnant and breastfeeding women, especially teenagers

· Infants and children under 5 years

· People with darker skin

According to a study, exposure to natural sunlight increases 25-hydroxyvitamin D levels, depending on the season. Therefore, sunlight exposure should definitely be encouraged in this group [1]


Boston University vitamin D expert Michael Holick, recommends a dose of 1000 IU of vitamin D for infants and adults, except if they have adequate sun exposure. However, Institute Of Medicine has set a dietary reference intake for vitamin D according to the age group in which the person is. [3]

0-6 months 400 IU/ day 1000 IU/day
6-12 months 400 IU/day 1500 IU/day
1-3 years 600 IU/day 2500 IU/day
4-8 years 600 IU/day 3000 IU/day
9-70 years 600 IU/day 4000 IU/day
71+ 800 IU/day 4000 IU/day

Vitamin D plays an important role in maintaining a healthy body and lack of vitamin D can play havoc with the structural and functional balance of human body.


Whether the vitamin enters through the oral route or through the cutaneous pathway, only a fraction of it is converted into the active metabolite. Most of it remains in the serum as calcidiol or 25(OH)D. Hence, the best way to assess the body’s vitamin D status is by measuring total calcidiol.

The interpretation of the results is based on the following chart [5];

<10ng/ml Severe deficiency
10-25ng/ml Mild to moderate deficiency
25-80ng/ml Optimum
80ng/ml Toxicity possible

A level of less than 10ng/ml corresponds to severe deficiency and places one at the risk of rickets and osteomalacia.

A level of 10-25ng/ml characterizes mild to moderate deficiency and increases the chances of osteoporosis and hyperparathyroidism

25-80ng/ml is widely considered as the normal vitamin D levels. More than 80ng/ml is the lower limit with which toxicity incidents have been reported.


Before we discuss the vitamin D deficiency symptoms, let us shed some light on the root cause of the problem. What causes vitamin D deficiency?

Vitamin D deficiency can be attributed to a number of reasons. Most of the reasons that are going to be listed, appeared in a review paper of a medical journal, Acta-Dermato-Venerologica in 2011[2]. Here are a few of them;

· Inadequate intake- Most of the Vitamin D sources are animal based, so for those who strictly consume fruits and vegetables and avoid animal derived food, vitamin D deficiency should not be a surprise.

· Limited or no sunlight exposure- Limited exposure to sunlight can place you at the risk of vitamin D deficiency. This limited exposure can in turn be due to a variety of factors. These factors include covering yourself from head to toe, living in northern areas, occupational factors or simply because you sleep throughout the day and stay up at night.

· Inadequate absorption- Conditions that affect the health of gut indirectly have an effect on the absorption of Vitamin D. The absorption of this vitamin in part takes place in the small intestine and is facilitated by pancreatic enzymes, stomach juice and bile. Any disease that affects the integrity of gut or disturbs the functional balance will eventually hinder Vitamin D’s absorption.

· Melanin- Dark skinned people have a greater amount of melanin in their skin, which competes for UVB, with the substance in skin that is responsible for starting the production of Vitamin D. Therefore, dark-skinned people need more sunlight exposure as compared to light-skinned people.

· Age- Older people are not able to produce vitamin D as efficiently as younger people, because of low amount of the substance that is converted into Vitamin D by UVB. Therefore, in old age, one might have to rely on oral supplements.

· Liver diseases- Certain kinds of liver diseases hinder the absorption of vitamin D by affecting the activity of enzyme 25-hydroxylase. Also, there are anti-epileptic medications that disturb the process of absorption [4]

The bottom line is, that you need to keep a tab on certain signs, which act as a heads-up for you to increase your Vitamin D consumption, either orally or through sunlight. These signs of Vitamin D deficiency are;

ü You are 50 or older

ü You’re overweight

ü You have darker skin

ü You have a gut disease (Inflammatory Bowel Disease- Crohn’s disease pr ulcerative colitis)

ü Bone pains

ü You’re down in the dumps

Now that you are familiar with the causes of Vitamin D deficiency, let us have a look at symptoms of low vitamin D as well as its deficiency that should set off the alarm bells.

Cognitive Decline- According to a study there has been evidence of link between low vitamin D levels and cognitive decline. In older people with intact cognitive functions, a 25(OH)D level of less than 75nmol/L predicted the possibility of decline in cognitive functions over the next 4 years. [6]

Vitamin D Deficiency Fatigue- along with muscle weakness and bone pains is one of the earliest symptoms of vitamin D deficiency. This should definitely make you have safe sun exposure a regular part of the routine.

These vague symptoms of tiredness and aches can be associated with a number of other conditions, but testing serum 25(OH)D levels and watching your diet can give you an idea if they are because of vitamin D deficiency or not.

Joint pain- According to a research conducted, to study the effect of vitamin D deficiency on the progression on osteoarthritis, it was found that it had a positive effect on the progression of knee osteoarthritis. [7]

Other than these symptoms, vitamin D deficiency symptoms include muscle cramps, high blood pressure, weight gain, restlessness, constipation or diarrhea, headaches and bladder pain.


Vitamin D deficiency has been linked to a number of medical conditions and diseases. Let us briefly discuss all of them one by one.

Rickets- Vitamin D is essential for strong and healthy bones and a deficiency of this vitamin would naturally have the strongest impact on the skeletal system. Prolonged vitamin D deficiency causes softening and weakening of bones in children, since phosphorus and calcium are not regulated in its absence [8]. The disease is characterized by

– Delayed growth

– Muscle weakness

– Pain in spine, legs and pelvis

– Bowed legs

– Breastbone projection

– Thickening of wrists and ankles

Osteoporosis and Osteopenia- is a disease which involves weakening of bones, that places you at risk of unexpected fractures. Regardless of age, both these conditions can affect women. The first sign of these silent conditions is usually a fractured bone.

Dementia– According to a study [9], vitamin D deficiency has an association with the development of dementia and other degenerative diseases like Alzheimer’s disease. The study further stated that, there is a 53 percent greater chance of developing dementia in people with low vitamin D levels.

Prostate cancer– symptoms like burning micturation, pain during micturation , frequent urges to urinate and loss of bladder control could be included in the category of Vitamin d deficiency symptoms in men, that indicate the possibility of prostate cancer.

According to a study done on African-American and European American men, there was an association between severe vitamin deficiency and high gleason grade and tumor stage [10]

Erectile dysfunction- could either be due to high blood pressure, diabetes and prostate cancer or could be a result of vitamin D deficiency. It was proved in a research that severe erectile dysfunction was seen in people with severe vitamin D deficiency while milder forms of the dysfunction were seen in those with mild to moderate deficiency. [11]

Other diseases associated with vitamin D deficiency are parkinsons disease, autoimmune diseases, multiple sclerosis, psoriasis, fibromyalgia, infertility and PMS, gout and chronic fatigue syndrome.


Vitamin D overdose can lead to a serious condition that is not very common. Usually vitamin D toxicity occurs due to intake of supplements in excess. For you to experience vitamin D toxicity, 50,000 IU of the vitamin have to be consumed for several months. Symptoms of vitamin D overdose are attributed to the increased levels of calcium in blood (hypercalcemia) and these symptoms are;

· Nausea and vomiting

· Poor appetite

· Weakness

· Frequent urination and other kidney problems

Although the toxicity occurs at extremely high levels, patients suffering from kidney diseases should specifically consult their doctors before starting such supplements.

The bottom line is that Vitamin D is safe whether taken orally or injected. There are no side effects of vitamin D unless it is taken in very large quantities for several months


1) http://www.ncbi.nlm.nih.gov/pubmed/25311734

2) http://www.health.harvard.edu/healthbeat/9-things-that-can-undermine-your-vitamin-d-level

3) http://www.webmd.com/osteoporosis/features/the-truth-about-vitamin-d-how-much-vitamin-d-do-you-need

4) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2912737/table/T2/

5) http://www.mayomedicallaboratories.com/articles/hottopics/transcripts/2009/2009-1b-vitamind/1b-14.html

6) http://www.medscape.com/viewarticle/835226?nlid=70743_2982&src=wnl_edit_dail&uac=226237SV

7) http://www.ncbi.nlm.nih.gov/pubmed/25411034

8) http://www.mayoclinic.org/diseases-conditions/rickets/basics/symptoms/con-20027091

9) http://www.neurology.org/content/early/2014/08/06/WNL.0000000000000755.full.pdf+html

10) http://clincancerres.aacrjournals.org/content/20/9/2289.abstract

11) http://onlinelibrary.wiley.com/doi/10.1111/jsm.12661/abstract

12) http://www.fredhutch.org/en/news/releases/2014/04/vitamin-d-effect-on-weight-loss.html

13) http://www.ncbi.nlm.nih.gov/pubmed/24788893