Health & Nutrition
February 23, 2021
• Updated on
25 Jul

11 Lesser Known Facts about VITAMIN D

Amidst the pandemic, an unlikely superhero rose to the occasion and offered hope of life and survival. An inexplicable link between people with Vitamin D deficiency getting infected with COVID-19 and mortality rates gained substantial scientific traction. 

While health experts recommended 'washing hands' as the best defence against novel coronavirus, Vitamin D was postulated as the best way to stave off or combat COVID 19. Evidence is slowly mounting in favour of vitamin D benefits that go beyond mitigating the threat of COVID-19.  

Vitamin D is a fat-soluble vitamin, which also comes in two forms, Vitamin D2 and D3, which are either naturally available in various food items, or through dietary supplements or endogenously produced when our skin absorbs UV rays from the sun. 

The most common and ideal of the three sources is direct sunlight. However, there are countries which get little to no direct sunlight for months and are predominantly cold. In which case, consuming supplements are the next best option to get maximum vitamin D benefits. 

Researchers had also suggested that having ideal vitamin D levels played a central role in metabolic and immune function and reduced the risk of certain community-acquired respiratory illnesses.

Redefining the role of Vitamin D, the scientists and researchers increased the ambit of its role vis-à-vis health. The correlation between severe Vitamin D deficiency and high COVID-19 mortality rates is not entirely a matter of chance. 

Vitamin D is traditionally known for its role in bone health, but it has a crucial role in the immune system. It is commonly known that low vitamin D levels often leave people susceptible to various infectious diseases, including upper respiratory tract infections. 


Vitamin D benefits also include fortifying the immune system. Preventing the immune system from becoming overactive is one vitaminD benefits that are not commonly known. Vitamin D assists in shooting down the immune system's misdirected inflammatory response, which may ultimately kill many people with COVID-19.  


Vitamin D
Vitamin D plays an important role in regulating mood and reducing the symptoms of depression.

1. The connection of vitamin D deficiency to depression

Though the cause of depression cannot be isolated to vitamin deficiency alone, supplementation to increase the levels of vitamin D in such patients is likely to reduce the symptoms of depression. Though there are still ongoing studies for this, its collectively said that there is a correlation between the two but no causation.

2. Infectious disease

Although vitamin D benefit is associated mostly with bone-related conditions, studies suggest that vitamin D plays a significant role in preventing infectious disease targeting the Respiratory Tract Infections (RTI), influenza and the like.

3. Autoimmune diseases

Vitamin D is a modulator of the immune system, and it is involved in regulating cell proliferation and differentiation. The multiple sclerosis is an autoimmune disease which damages the nerve cells in the brain and research suggests that since it's geographically more prevalent in people who reside away from the equator, it has led to the understanding that lower vitamin D levels could be a reason.

4. Cancer

According to some studies, vitamin D might inhibit carcinogenesis and slow tumour progression and thereby lowering mortality risks for breast cancer, colorectal cancer, lung cancer, pancreatic cancer, prostate cancer. Further research is needed to determine whether inadequacy of vitamin D increases the risk of cancer, and if more significant exposure to it can prevent cancer.

5. Cardiovascular disease

Vitamin D helps to steady blood pressure, vascular cell growth and inflammation. For these reasons, heart health and cardiovascular diseases are linked to vitamin D.

6. Type 2 diabetes mellitus

Certain studies suggest a correlation between vitamin D in stimulating insulin secretion, hence playing a role in glucose metabolism. Observational studies have linked lower levels of serum 25(OH)D, which is the primary circulating form of vitamin D, to an increased risk of type 2 diabetes.

Research has found that people with higher levels of belly fat and larger waistlines are more likely to have lower vitamin D levels.

7. Obesity

Individuals with obesity have higher chances of vitamin D deficiency and illnesses along with it. The probable reasons for it could be because of its dilution to greater volumes of muscles.

8. Vitamin D acts more like a hormone

Vitamin D behaves much less like a vitamin and much more like a hormone. That means vitamin D aids in the process rather than a participant in metabolism, potentially affecting everything from weight to how organs function.

9. Liver & Kidneys synthesise Vitamin D

As discussed earlier, the primary vitamin D source is direct sunlight. When theUVB radiation from sunlight strikes our skin, a chemical reaction turns it to vitamin D3, carried to our liver to form 25(OH)D which then travels to the kidney where it further transforms to the biologically active form of vitamin D-calcitriol.

10. Dark Skinned people need more Vitamin D

The pigment called melanin in our skin's epidermal layer results in darker skin.This pigment reduces the skin's ability to synthesise vitamin D from sunlight, making it imperative for dark-skinned people to have more sunlight exposure.

11. It helps regulate calcium & phosphorus

Vitamin D stimulates calcium and phosphorus absorption resulting in normal bone growth and mineralisation.


Osteomalacia, which refers to softening of bones, is most often caused by a vitamin D deficiency.

The primary vitamin D benefit is that it aids in calcium absorption and maintains adequate levels of phosphorus levels in the blood, which enables bone mineralisation and help prevent hypocalcemic tetany, which is a condition which promotes involuntary muscle contraction- cramps and spasms. 

Since vitamin D is crucial for cardiac and neuromuscular function, the body does not allow the levels to fall when vitamin D deficient. Instead, it mobilises calcium from our bones to make up for this deficiency and continue cardiac function. As a result, bone density drops thereby becoming brittle and fracture prone. 

Highlighting the major illnesses that occur with vitamin D deficiency:


Both vitamin D2 and D3 are absorbed into the small intestine.Rickets is a disease widely seen in infants and kids due to vitamin D deficiency. The bone tissues fail to mineralise correctly, leading to soft bones and skeletal deformities.


Adults and adolescents get a condition called osteomalacia, which has symptoms similar to rickets. Patients with this illness would have their bones defectively or incompletely mineralised and result in weak bones.This is different from osteoporosis, in which the bones are porous and brittle, and in osteomalacia bones are soft.


Osteoporosis is often associated with calcium deficiency, though the actuality is that its caused by insufficient vitamin D intake causes it, which hinders calcium absorption. Osteoporosis increases bone fragility and increases the risk of fractures.


The causes of deficiency can be from lifestyle choice to dietary choice. Other than from sunlight, it also depends on consuming what foods are high in vitamin D. It's quite common for a vegetarian or vegan with a sedentary lifestyle to get an inadequate amount of vitamin D from the diet as most vitamin D rich foods are animal-based like fish oils, egg yolk and liver. 

∙ With the pandemic especially, and work from home being a norm, daytime usually goes in work, without stepping out to even commute to work, for most middle-class population thereby preventing adequate exposure to sunlight.


∙The country of residence matters. Most European countries get very less direct sunlight geographically as opposed to Asian countries.Additionally, pollution can also hinder the synthesis of Vitamin D by the skin, thereby inhibiting from attaining the complete vitamin D benefits.


∙ Being dark-skinned and using excessive sunscreen restrains UVB ray absorption even more. 


∙Phytic acid and oxalic acid present in sweet potatoes, spinach, beans and rhubarbs can deplete Vitamin D and increase calcium requirements.


∙ Covering the skin entirely with burqa or purdah as part of cultural practice obstruct imbibing the full vitamin D benefit.


∙ Exclusively breastfed infants have chances of vitamin D deficiency, as vitamin D content in breastmilk is related to mother's vitamin D status, and if the mother is not having enough supplements or sunlight exposure, it could affect the infant.


∙ The skin's ability to synthesise vitamin D reduces with age, and that coupled with high indoor time compared to younger adults, it increases the chance for vitamin D deficiency.


∙ Medical problems like celiac disease, cystic fibrosis, and Crohn's disease, can affect the ability of your intestines to absorb vitamin D from food.


Sun bath in the morning for a few minutes is good way to get some Vitamin D benefits.

Adequate exposure to sunshine

You can get sufficient vitamin D benefits from being out in the sun for just short intervals while uncovering your hands, forearms or legs. However, UVB radiation is what aids in vitamin D absorption; it's essential to avoid overexposure to protect from possibilities of damage to skin and skin cancer. People with darker skin tone might need more prolonged exposure (a couple of hours) to sunlight than light-skinned people (up to 15 minutes being sufficient).

Exercise daily

Regular outdoor exercise primarily assists with the production of vitamin D. Exercising is a good way to get vitamin D from the sun. The time of the day also matters. Research suggests that the skin produces more vitamin D during the middle of the day. Schedule your daily chores which involves going out like buying provisions, during midday. This way, you get vitamin D benefits while not sacrificing time off your busy schedule.



Amaranth, Ragi and Sesame seeds are some foods rich in vitamin D

Milk: Vitamin D is naturally available in some foods we eat, though some have a high content per serving versus the others, and the most common and readily available dietary source ofVitamin D is milk, which has 120 IU of vitamin D per cup.

There are alternatives for people who have lactose intolerance and want to choose natural sources to get vitamin D benefits over supplements. For instance, 1 tbsp of cod liver oil has 34 mcg or 1,360 IU of Vitamin D. Three ounces of trout and salmon have 645 IU and 570 IU ofVitamin D, respectively. 

Animal Based: Egg yolks and cheddar cheese are other vitamin D sources, with up to 44 IU and 12 IU, that you can easily add to your breakfast routine. Beef liver and Tuna fish are other options with a high count of 42 IU and 40 IU, respectively.


Plant-Based – Mushrooms, Amaranth, Ragi, Soybean, Curry leaves, Sesame seeds are some other foods rich in Vitamin D, though the amount of vitamin D per serving is considered low to get necessary vitamin D benefits.


Fortified foods: In India, Vanaspati (dalda) is fortified with 200 IU of Vitamin D per 100 g. Milk products & breakfast cereals of certain brands are also fortified with Vitamin D up to 80 IU per serving and can be considered in the category of foods rich in vitamin D.



Vitamin D supplements may help some people, but you should speak with your doctor first and take them strictly as directed. Taking vitamin D with food can enhance its effectiveness, as it's fat-soluble.

Vitamin D exists in two primary forms — vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol), both absorbed in the small intestine. Typically, D2 comes from plants and is cheaper to produce than D3, which comes from animal-sourced foods.

Your liver metabolises vitamin D2 and D3 differently, and research suggests that D3 may be significantly more effective at improving vitamin D in the bloodstream. A single dose of vitamin D3 is twice effective as vitamin D2 to raise calcifediol levels, so look for a supplement with D3.

Magnesium is a macronutrient and most essential minerals, and macronutrients do not work in isolation. Magnesium helps to regulate vitamin D levels and directly contributes to bone crystal formation and bone density. Since magnesium and vitamin D work together, it's important to consume both in the right ratio to get maximum vitamin D benefits.  

According to the American Osteopathic Association Journal, people with magnesium deficiency when supplemented with vitamin D alone showed higher phosphorous and calcium levels in the bloodstream. Magnesium deficiency prevents vitamin D from absorbing, and vitamin D deficiency prevents calcium absorption to bones. Excessive calcium in the bloodstream without getting absorbed into bones leads to calcification of arteries resulting in poor cardiovascular health.  



Recommended amounts of vitamin D per day for an average human to get vitamin D benefits

The Institute of Medicine guidelines indicate theRecommended Dietary Allowance (RDA) for vitamin D, which is how much vitamin D per day is needed to maintain healthy bones and ideal calcium metabolism.

RDA: The Recommended Dietary Allowance(RDA) for children, teenagers and adults up to 70 are 600 IU or 15 mcg. Adults aged 71 years and above need 800 IU or 20mcg.

UL: The Tolerable Upper Intake Level for vitamin D for adults and children aged nine and above is 4,000 IU, though doctors may prescribe more than 4,000 IU to improve a vitamin D deficiency. 


Vitamin D is best taken after a meal and in the daytime, as opposed to night when it can affect sleep pattern.

Certain vitamins and minerals are more effective when had at a particular time of the day. Some vitamins need to be taken on an empty stomach while some after a meal. Vitamin D is best taken after a meal and in the daytime, as opposed to night. Studies suggest that consuming vitamin D at night can affect sleep pattern. Melatonin is the hormone generated by our body which controls the sleep pattern, and vitamin D might hinder the production of this melatonin. 

The logical reasoning for this could be that our body naturally is used to synthesise vitamin D from sun exposure which we experience in the daytime only.

Consuming vitamin D supplements should only be with a doctor's prescription, and recommendation as the dosage will be based on your present blood report, which is subjective.

Vitamin D being fat-soluble, the general theory is to have it after a meal that contains fat, which would make it effectively absorbed to the bloodstream. A study conducted by the Journal of the Academy of Nutrition and Dietetics has mentioned that individuals who had vitamin D with fat included in a meal had up to 32% more vitamin D absorption than those who had a fat-free meal. 

If you are using vitamin D medication's liquid form, measure the right amount with a measuring cup than a household spoon which is less accurate. If its the chewable tablet or wafer form, chew the medication thoroughly before swallowing.

If consuming the rapidly-dissolving tablet variant, dry your palms before opening the package. Allow it to dissolve completely and then drink water if needed. You do not need to take this medication with water. 

As with every other medication, follow prescription and take this medication regularly to get the most benefit from it. If you take this medication weekly once, remember to take it on the same day each week.


Too much of any element is as dangerous as deficiency of it. Getting the right quantity of vitamin D per day is crucial to yield ideal vitamin D benefits. Excessive amounts of vitamin D increases calcium absorption in the gastrointestinal tract resulting in hypercalcemia, hypercalciuria and highserum 25(OH)D levels. Hypercalcemia can cause nausea, loss of appetite, neuropsychiatric disturbances, muscle weakness and kidney stones. 

 An extreme case of vitamin D toxicity can also cause cardiac arrhythmias, renal failure and even death. Vitamin D toxicity can be caused by frequent use of tanning beds or overdose of supplements that were consumed in excessive amounts or were incorrectly prescribed by physicians or because of manufacturing errors. It's unlikely to get vitamin D toxicity through diet and sun exposure. If you are planning to take vitamin D supplement, it is advisable to check with your physician or nutritionist for dosage.

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Lovneet Batra
Lovneet Batra is a clinical nutritionist with over a decade of experience treating patients and educating people on the benefits of a healthy diet. One of Delhi’s most sought-after nutritionists...
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