We’ve known for a while that vitamin D is needed for healthy bones- but, in recent years, interest in this vitamin has exploded, and with good reason. It’s been found to play an incredibly important role in our body, with its effects ranging from improving our sleep to even protecting us from infections.
Vitamin D is a collective term for several forms of the vitamin, including two major ones: vitamin D2 (called ‘ergocalciferol’) and vitamin D3 (called ‘cholecalciferol’). The former is derived from certain foods, while the latter is produced in our skin, in response to the sun’s UVB rays – that’s what’s led to vitamin D being termed as the “sunshine vitamin”. 
These forms of vitamin D are inactive, which means they can’t perform any functions. Before they can, our liver converts them to ‘calcidiol’, a form that circulates in our bloodstream and eventually reaches the kidneys (along with other tissue). There, calcidiol is converted to ‘calcitriol’, a hormone that can finally exert the wide-ranging effects of vitamin D on the body.
Why vitamin D is important for our health
Interest in vitamin D sparked when researchers realised that at least 800 genes in the human body are regulated by vitamin D. They also found that an enzyme that converts vitamin D to calcitriol was ubiquitous in the body, being present across tissue in the skin, blood vessels, pancreas, the kidneys, heart, immune system and intestines. Since then, further research has found that does indeed affect these aspects of our health.
Bones and muscles
Without vitamin D, only 10-15% of the calcium and about 60% of the phosphorus from our diet are absorbed by the body.
It also plays a major role in maintaining the balance between our levels of calcium and phosphorous, which need to be tightly controlled within a narrow range, to help numerous physiologic functions related to our nerves and muscles, the way our cells communicate, the structure of cells and much more.
Both elements are also essential for the formation of strong bones, which is why consuming vitamin D has been shown to greatly reduce the risk of fractures.
Vitamin D also strengthens our muscles. It does so by aiding the formation of proteins in our muscles, and enhances our nervous system’s ability to contract them. Since our muscles work by contraction and relaxation, their strength is directly linked to their contraction.
Because our immune cells have vitamin D receptors, vitamin D can regulate the genes and proteins that help them grow, mature and function.
A deficiency increases our susceptibility to infections. In fact, research has clearly shown that a vitamin D deficiency is associated with cold and flu occurrences, given that these generally take place when days are duller, without much sunlight.
Even autoimmune diseases like rheumatoid arthritis can be managed by vitamin D. A deficiency can increase the risk of autoimmunity (an overactive immune system that can attack healthy tissue).
Research has demonstrated an inverse relationship between vitamin D levels in the blood and high blood pressure (HBP or hypertension). In other words, the lower the vitamin D, the higher the blood pressure. High blood pressure increases the strain on and damage to our coronary arteries, greatly increasing the risk of a heart attack.
When it comes to being happy, the evidence is clear: the lower your vitamin D levels, the more likely you are to feel blue rather than happy.
Low levels of vitamin D have long been associated with a higher incidence of depression. Interestingly, when vitamin D3 supplements were compared to anti-depressants in a 2014 study, their effects on the subjects’ state of mind were similar to the latter’s.
People with vitamin D deficiencies also tend to be fatigued, which has been found to improve when the levels of vitamin D were brought back to normal. Similarly, sleep disorders like shorter sleep duration are also related to vitamin D deficiencies.
Skin and hair
Vitamin D helps maintain the health of our skin cells, by fighting free radical damage, and even contributes to their growth. Additionally, our skin has its own immune system, which vitamin D helps optimise through the vitamin D receptors present in the immune cells.
Topical vitamin D creams are also used to manage skin conditions like rashes and more aggressive forms of dermatitis.
When it comes to hair health, research suggests that vitamin D could help create new hair follicles (pores/cavities present in our skin which regulate our hair’s growth). Lower levels of vitamin D have been found to be related to hair fall.3-6
Lowers the risk of diseases
Although the reasons haven’t been made clear yet, low vitamin D levels have also been associated with other diseases such as diabetes, symptoms of PCOS, kidney disease and cancer.
Getting enough Vitamin D
A rough estimate indicates that, globally, about 1 billion people are either vitamin D ‘deficient’ (defined as a concentration of calcidiol – the form of vitamin D that circulates in our blood – being less than 50 nmol/L), or vitamin D ‘insufficient’ (defined as the concentration of calcidiol being less than 75 nmol/L).
A high prevalence of vitamin D deficiency has been reported throughout India, for all age groups including infants, school-going children, adolescents, adults, pregnancy, lactating women, and senior citizens.
Here are some factors that can lead to its deficiency:
Age: As we age, the conversion of vitamin D’s inactive forms to calciferol slows down.58
Obesity or any underlying disorders: For instance, children who struggle with obesity tend to have a vitamin D deficiency.54 This is possible because, being fat-soluble, vitamin D gets stored in fat tissue, which reduces the amount circulating in the blood. Even certain diseases, such as of the digestive tract, can lead to a vitamin D deficiency.
Lack of awareness: It is not just the general population, but also healthcare professionals who are vitamin D deficient. Among 2,119 healthy, middle-aged Indian healthcare professionals, it was found that only 6% have sufficient vitamin D levels. The study, conducted across 18 different cities in India, showed that 15 % were insufficient and 79% had a deficiency. 
Given all of its effects on our health and functioning, it’s important to check your levels of vitamin D and take steps towards bringing up your levels if you are deficient.
How to make sure you’re getting enough vitamin D
Many people are cautious about being out in the sun, but staying indoors doesn’t help your vitamin D levels. The sun’s UVB rays, which are responsible for producing vitamin D, can’t penetrate glass or even certain types of clothing.
Exposing your arms and legs to the sun for just 15 to 30 minutes (twice a week) can be enough to prevent a vitamin D deficiency.
However, this depends on 3 factors:
A] Skin complexion
If a person with fair skin goes out in the sun for about 20 minutes wearing a bathing suit, their skin can produce about 20,000IU (International Units) of vitamin D. However, darker skin tends to absorb more of the sun’s UVB rays in their skin’s melanin (colour pigment). This helps protect the skin from UV radiation, but also makes it harder for the skin to get enough vitamin D. If your skin is darker, it’s best to stay in the sun for the entire recommended duration of 30 minutes.
B] The strength of the sun’s UV rays
Our geographic location can also influence the amount of vitamin D produced in the body through sunlight.
India lies at a latitude of 15-30 degrees North. Based on the strength of the sun’s rays reaching us, a pan India study has revealed that the best time to absorb maximum vitamin D from the sun is between 11 am to 2 pm.
Even the weather affects the brightness of the sun and its rays, along with the pollution in the atmosphere. On overcast, rainy days, it’s best to be out in the sun for at least 30 minutes – regardless of skin complexion – and always make the most of clear, sunny days!
C] Sun protection
Wearing a sunscreen with a sun protection factor (SPF) of 30 reduces the amount of vitamin D produced in the skin by more than 95%. It’s best to apply sunscreen after your required amount of sun exposure. 
Remember, vitamin D is stored in the body (which is why we don’t necessarily need to spend every day in the sun), but its level needs to be maintained by regular sun exposure.
Diet and supplementation:
The amount of vitamin D present in foods is simply not enough to meet our requirements. Mushrooms are one of the few natural plant-based sources of vitamin D, but only when they have been exposed to the sun’s UVB rays. Even then, the amount they contain will be low.
For non-vegetarians, some fish sources like salmon, mackerel, herring do provide appreciable amounts (a large piece would deliver about 1,000IU. ). However, they’ll need to be consumed every day, to give us enough vitamin D, which may not be practical.
Given that foods fortified with vitamin D aren’t really available in India, supplementing may be the only effective way to treat a deficiency. People who are deficient are generally recommended supplements containing 60,000 IU on a weekly basis for 6-8 weeks.
If your exposure to sunlight is minimal, supplementing with 400 IU a day is recommended by the Nutrition Foundation of India. (However, there may be a need to update these guidelines, given that the magnitude of vitamin D’s role in almost every aspect of our health has only recently been acknowledged).
Vitamin D supplements may be available as single-ingredient products or in combination with calcium and other micronutrients. Evidence suggests that vitamin D3 is approximately three times more potent as vitamin D2, making it a good idea to opt for that form.
Since fats increase our absorption of vitamin D, taking your supplement with or after a meal can help improve its absorption.
- Holick MF. N Engl J Med 2007; 357: 266–81.
- Nair R, et al. J Pharmacol Pharmacother. 2012 Apr-Jun; 3(2): 118–126.
- Kulie T, et al. J Am Board Fam Med November-December 2009 22 no. 6 698-706
- Tiwari P, et al. J Pharma Care Health Sys 2017, 4:3 Role of Vitamin D in Various Illnesses
- Cannell JJ, et al. Epidemiol Infect. 2006 Dec;134(6):1129-40. Epub 2006 Sep 7
- Bischoff F, et al. 2004 Apr 28;291(16):1999-2006.
- Burgaz A, et al. J Hypertens. 2011 Apr;29(4):636-45
- Sandra W, et al. Ethn Dis. Author manuscript; available in PMC 2010 May 31.
- Spedding S. 2014 Apr 11;6(4):1501-18
- Kerley C. How Important is Vitamin D? Facts You Need to Know. Center for Nutrition Studies: 6 March 2018. Available from
- Lhamo Y, et al. Indian J Pharm Sci. 2016 Jan-Feb; 78(1): 41–47
- Harinarayan CV, et al. Dermatoendocrinol. 2013 Jan 1; 5(1): 130-141.
- Aranow C. J Investig Med. 2011 Aug; 59(6): 881–886.
- Beloyartseva M, et al. Arch Osteoporos 2012; 7: 187-192.