Nutrition Basics

Vitamin D-everything you need to know

8 Mins read

What is vitamin D?

Vitamin D is a fat soluble vitamin that is required for regulating calcium in the human body – essential for bone health. It is also known as ‘Sunshine Vitamin’ because our body can make it from sunlight exposure. However, in order to make vitamin D from sun exposure our body requires cholesterol. Without enough cholesterol the biochemical reaction of making vitamin D from sunlight does not take place. Besides bone health and calcium regulation, Vitamin D performs a lot of other critical functions in the body such as regulating circadian rhythm, regulating gene expression, cognitive function etc. Vitamin D can be obtained from sunlight as well as food. However, it’s not very widely found in foods. It is necessary to prioritize sun light exposure in order to maintain proper vitamin D levels in the body.

Difference between vitamin D2 and D3

In foods and supplements vitamin D is found in two forms namely – Vitamin D2 and Vitamin D3. Vitamin D2 is found in plant based foods such as mushrooms whereas vitamin D3 is found in animal based foods such as dairy, egg yolks, fish etc. The main difference between the two is that vitamin D3 is more potent than vitamin D2. Vitamin D3 digest and absorbs better and it is much more effective in raising vitamin D levels in the body than vitamin D2. Both of these forms however do not have any direct function in the human body. They are converted to an active form in order to be utilized for various physiological processes. The first step is the conversion of D2 and D3 to 25-hydroxyvitamin D3 – also known as calcidiol in the liver. Calcidiol is the storage form of this nutrient. Further, the Calcidiol is converted to 1.25-dihydroxy vitamin D3 which is known as Calcitriol. It is THE actual metabolically active form of vitamin D which circulates throughout the body and is used for various functions.

Why vitamin D is essential?

Vitamin D affects almost every organ of the body and has extensive health implications.

  • Regulation of calcium and phosphorus in the body: The most well known function of vitamin D is its role in regulating calcium and phosphorus levels in the body. Without vitamin D your body cannot absorb and maintain calcium and phosphorus properly.
  • Maintaining strength of bones and teeth: Vit D is essential for proper calcium levels and calcium provides strength to bones and teeth. Vit D however also works with vitamin K2 to provide structural strength to bones and teeth.
  • Muscle recovery after exercise: Vit D is also crucial for skeletal muscle function and regeneration especially after exercise. If you are deficient in it you may not recover as fast after exercise and may also experience muscle spasms, cramps and soreness for longer time.
  • Helps you Sleep properly: Circadian rhythm which is the natural sleep wake cycle of our body is regulated by Vit D. If you’re deficient in Vit D you may have trouble sleeping at night. Problems such as insomnia or waking up in the middle of the night arises.
  • Essential for brain function: Cognitive function of the brain such as learning and remembering things, perception, memory, concentration are all affected by Vit D. For instance, there’s always a deficiency of Vit D in diseases related to brain such as Alzheimer’s, Parkinson’s, dementia.
  • The immune system: Your body’s defense mechanism is very much dependent on Vit D especially with fighting infections and allergies. A deficiency in this nutrient means your chances of getting infected goes high.
  • Proper lung function: Vit D promotes healthy lung function and improves lung related problems such as asthma, bronchitis, pneumonia significantly. It is even used in the effective treatment of respiratory tract infections such as tuberculosis and influenza.
  • Reduces the chances of getting cancer: Vit D has antiproliferative effects which means that it reduces the growth of cancer cells and also reduces your chances of getting cancer.
  • Hair and Skin health: The growth of your hair and health of your skin cells are dependent on Vit D. If you’re deficient your hair will be dry and brittle and you may also experience hair loss. In skin a Vit D deficiency can cause psoriasis, eczema and even acne.
  • Helps you deal with stress: Vit D plays role in regulating cortisol, a stress hormone released by your adrenal glands which is necessary to deal with stress. Without enough vit D you will feel stressed and depressed.
  • Regulation of blood glucose: Vit D is necessary for proper insulin secretion, Insulin is a hormone which maintains blood sugar levels. The beta cells in pancreas release insulin, these cells require Vit D for proper function.
  • Heart health: A strong relation between heart health and Vit D exist. Vit D deficiency has been associated with chronic heart failure and other heart related problems such as arterial calcification, stroke, atherosclerosis etc. Also, if you have a high blood pressure there are high chances that you are low in Vit D.
  • Reproduction: Vit D is crucial for reproduction. In females low vitamin D will result in problem with ovaries such as PCOS, infertility, low sex drive and other complications during pregnancy. In males low Vit D results in enlarged prostate, infertility, erectile dysfunction and low libido.
  • This vitamin is also important for expression of the genes during reproduction.

Vitamin D deficiency 

In children Its deficiency results in rickets which is characterized by demineralization of bones during growth years which causes them to become soft and ultimately results in bowing of the legs and deformation of the curvature of the spine.

In adults, its deficiency results into poor calcium and phosphorus absorption. As a result of this the bone matrix is preserved but the bone loses its mineralization eventually resulting into poor bone density.

Several other organs are affected by vitamin D and its deficiency can cause diseases of brain like Alzheimer, Dementia etc, Infectious lung diseases like Asthma, pneumonia etc, Poor immune function, Poor recovery after exercise, Heart disease, Arthritis, Poor sleep cycle and many more.

Common Symptoms of vitamin D deficiency

  • Fatigue
  • Joint pain
  • Muscle pain and aches
  • Depression or bad mood
  • Hair loss
  • Constantly getting sick

What causes vitamin D deficiency?

1.Inadequate sun exposure

Sunlight is very critical to life. Insufficient sunlight exposure has become a major public health problem in modern times as people spend most of their time working indoors. Since, Vitamin D is not found in foods very widely it is necessary to get it from sun exposure. People who live in countries near the equator can make vitamin D from sunlight much more efficiently as compared to those living far from equator simply because the intensity of sunlight is greater near the equator than it is near the poles. For example: India is a very sunny country and lies near the equator so, people spending time outdoors can obtain enough vitamin D. However, even on the sunniest days people living in countries like Canada, Norway, Sweden, Belgium and likes may not be able to synthesize enough vitamin D from the sun. these people do have access to vitamin D rich foods like fatty fish, seal blubber, liver from animals such as seal, polar bear etc. all of which are rich in vitamin D.

2.Use of sunscreen despite adequate sun exposure

Sunscreen were designed to absorb UVB rays from the sun. Sunscreens contains something called sun protection factor(SPF) which measures the protection from the sun for example: A sunscreen with a Sun protection factor of 30 will absorb 95-98% of solar UVB radiation, this allows you to stay in the sun for longer without any sunburns and skin damage. However, this application of sunscreen on the skin also reduces the ability of your body to produce vitamin D from the sun. This was demonstrated in study in which application of a sunscreen of SPF of only 8 reduces the blood levels of vitamin D after sun exposure. Another data says that farmers in the mid west who wore sunscreen for more than a year while spending time outdoors demonstrated that at the end of the summer their blood levels of vitamin D were significantly lower and most were even deficient in vitamin D.

3.Low fat diets

Making vitamin D from sun requires cholesterol, the nutrient which is being demonized for causing heart attacks. However, that is not the case. As a matter of fact, Cholesterol is very vital for good health. It is required to maintain the integrity of cell membranes, production of sex hormones like testosterone, estrogen and progesterone, production of vitamin D from sun etc.. It also helps you deal with stress as it is a precursor to stress hormones like cortisol.

Do not avoid foods such as butter, ghee, full fat milk or its products and other animal fats such as lard, tallow, fatty meat because a low fat diet can affect the process of making vitamin D from sun negatively.

4.Low levels of magnesium in the body  

Magnesium is very critical for the regulation of vitamin D and its conversion to active form. Magnesium deficiency can eventually result in low levels of vitamin D in the body regardless of how much you take it from food, supplements or sunlight.

5.Darker skin complexion 

Dark skinned individuals have to spend more time in sun to get the same amount of vitamin D as a light skinned people. Darker individuals have more concentrations of a substance called melanin in their skin which can effectively absorb most of the UVB radiation from sun preventing the synthesis of vitamin D in the skin. this is why it takes them longer time to make vitamin D from the sun in comparison to lighter skinned individuals. This was demonstrated in a study in which adult whites and adult blacks were exposed to UVB radiation on a tanning bed, the white adults raised their vitamin D levels but black adults showed no significant increase in the vitamin D concentration. However, when black adults were exposed to 5 times more UVB radiation the vitamin D concentration in their blood was increases by 15 fold.

So if you have darker complexion you may still be deficient in vitamin D despite staying in the sun.

Food sources of vitamin D

1.Animal based food sources

It is primarily found to be rich in foods of animal origin such as egg yolks, liver especially cod liver, fatty fish, good quality butter are some of the good sources.

2.Plant based food sources 

In foods of plant origin mushrooms are rich in vitamin D but they contain D2 instead of D3 and as discussed previously D2 is far less potent than D3 because D3 is more bioavailable to the body. However, most of the vitamin D fortified products in the market are fortified with vitamin D2.

How much vitamin D do you need?

The RDA for vitamin D is 15μg (600IU) for adult males and females, older people should get more(20μg/800IU) because of their reduced capacity to make vitamin D from sun and convert vitamin D to its active form in the body.

Note: Practically, It is hard to get enough vitamin D from food because the richest sources are only available in certain regions. Sun exposure of 15-30 mins a day should be taken without wearing sunscreen. This will prevent vitamin D deficiency in most individuals. Certainly, this varies with the type of skin color and region.

Tip: If you need to convert IU to μg, 40IU equals 1μg of vitamin D.


Almost every organ is affected by vitamin D therefore, it is important to maintain adequate levels for overall good health. Vitamin D3 is much more beneficial than D2 both in supplements as well as food. Also, It is hard to get enough vitamin D from food so, everyone must prioritize Sun exposure of 30mins at least without wearing sunscreen. It is also important to eat enough cholesterol and magnesium because without them vitamin D cannot be regulated in the body. Darker skinned individuals need to spend more time in the sun than lighter skinned individuals because it takes them longer to produce enough vitamin D from sun exposure.





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About author
Hey, I am Chetan and i am the author of “The Primitive diets” I hold a degree in Nutrition sciences and create content around health and nutrition. My principles are centered around primitive and holistic values which have been used since hundreds and thousands of years to treat diseases and improve health.
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