Vitamin D is an essential nutrient that maintains bone, musculoskeletal and immune system health and regulates phosphorus and calcium levels, essential for strong teeth and bones.
Vitamin D, popularly called the sunshine vitamin, is produced in the skin after exposure to sunlight. It can also be taken through dietary sources. Foods high in vitamin D are fish, red meat, egg yolks, and fortified food.
Vitamin D deficiency means shortage of vitamin D in the body, which can lead to loss of bone density, fractures, osteoporosis, heart disease, and depression. An individual may not know that they have low vitamin D, but there are common symptoms that indicate Vitamin D deficiency.
Vitamin D Benefits
Vitamin D strengthens bones and teeth, improves resistance to several diseases, supports immune health, and reduces chances of severe flu and severe COVID-19 symptoms. It regulates mood, reducing chances of depression, and may help in weight loss.
What is Vitamin D?
Vitamin D is a fat-soluble vitamin whose source is dermal synthesis (synthesis occurring when skin comes in contact with sunlight). Vitamin D from dermal synthesis, animal sources, or fortified foods is biologically inactive and requires enzymatic conversion to active metabolites. It is converted enzymatically in the liver to 25-hydroxyvitamin D- the precursor to calcitriol, the circulating form of vitamin D, and then in the kidney to 1,25-dihydroxy vitamin D- the active form of vitamin D.
It is found in two forms- vitamin D2 (ergocalciferol) & vitamin D3 (cholecalciferol).
Difference between vitamin D2 and D3?
There are two forms of vitamin D in the human body: vitamin D2 and vitamin D3. Both are called vitamin D.
1. Vitamin D3 is the main form of vitamin D, synthesised by the body on exposure to sunlight.
2. Vitamin D3 is found in animal sources of foods, including fatty fish (sardines, salmon, tuna), red meats, and egg yolk, whereas Vitamin D2 can be obtained from plant sources (like sun-dried wild mushrooms)
3. Vitamin D3 is directly absorbed in the body, whereas Vitamin D2 is converted into D3 for absorption.
Causes of Vitamin D Deficiency
There can be several reasons for vitamin D deficiency.
One of the main causes is minimal exposure to sunlight- due to lifestyle differences, sitting in sunlight for even 10-15 minutes has become a daunting task, leading to the deficiency of the sunshine vitamin.
Other reasons for vitamin D deficiency are:
1. The liver or kidneys cannot convert it to its active form.
2. One is taking medication that interferes with the ability to breakdown or absorb vitamin D
3. Dark skin- having more melanin (pigment which gives skin its colour) reduces vitamin D synthesis
4. People above 65
Vitamin D Deficiency Symptoms
Low vitamin D symptoms, if untreated, can lead to problems like rickets, osteoporosis, fractures, and more. However, many people with Vitamin D deficiency are asymptomatic.
1. Bone and joint Pain:
Vitamin D increases bone mass, preventing bone loss. Bone, lower back, and joint pain may be because of vitamin D deficiency. A study published by the National Center of Biotechnology Information states vitamin D deficiency is common in patients with rheumatoid arthritis. Supplementation with vitamin D may prevent osteoporosis and work as a pain reliever for patients with rheumatoid arthritis.
2. Bone Loss:
Vitamin D deficiency may cause bone loss, leading to osteoporosis and fractures, mineralisation defects, which may lead to osteomalacia in the long term and muscle weakness, causing falls and fractures.
3. Muscle pain:
Research indicates that vitamin D deficiency may cause muscle pain. In one study, 71% of people with chronic pain were found to be vitamin D deficient. A few studies suggest vitamin D supplements may reduce pain in people with a vitamin D deficiency.
4. Tiredness and muscle weakness:
Vitamin D plays a vital role in maintaining bone health- its deficiency can cause fatigue and muscle weakness. A study by the National Center of Biotechnology, Information states 77.2% of people who complained of fatigue were deficient in vitamin D. After regularising vitamin D levels, improvement in the symptoms was observed in all fatigue assessment parameters. Source:
Lower levels of Vitamin D may increase the risk of depression. A study by the National Center of Biotechnology Information revealed serum Vitamin D levels inversely correlate with clinical depression. Another study from Netherlands stated depression patients showed 14% lesser circulating concentrations of Vitamin D (25-hydroxyvitamin D) than those not diagnosed with depression.
6. Weak Immune system:
Vitamin D plays a vital role in regulating innate and adaptive immune responses. It directly interacts with immune cells that fight infections. Various studies have shown a link between vitamin D deficiency and various autoimmune diseases, including Inflammatory bowel disease, systemic lupus, rheumatoid arthritis and more. Evidence establishes a clear link between sufficient vitamin D levels, immune health, and avoidance of autoimmune diseases.
7. Weight Gain:
Overweight and obese people are more likely to have low Vitamin D levels than individuals with a normal BMI. A study on women above 65 found individuals with a lower vitamin D level experienced more weight gain. Various other studies have established similar links between Vitamin D deficiency and weight gain. It was found Vitamin D deficiency was 35% higher in individuals with obesity and 24% higher in participants who were overweight.
8. Muscle spasms:
Muscle spasms (tetany) may be the first sign of rickets in infants, caused by low calcium levels in the blood in pregnant women with severe vitamin D deficiency.
9. Hair Loss:
Vitamin D is closely linked with several signalling pathways of growth and differentiation of hair follicles. A study conducted by the Indian Dermatology Online Journal found vitamin D deficiencies could worsen hair loss over time, causing alopecia, one of the common cause of hair loss or hair thinning in men or women.
10. Impaired Wound Healing:
Vitamin D regulates inflammation and addresses infections for desired healing. In a 12-week study, 60 people with diabetes-related foot ulcers were involved- those on Vitamin D supplementation experienced positive results in wound healing compared with the non-studied group.
How is Vitamin D deficiency treated?
Vitamin D deficiency is treated with supplements. Consult a doctor for dosage recommendations. The Recommended dietary intake of Vitamin D for adult men and women is 600 IU/day as per the ICMR (NIN-2020).
Sources of Vitamin D
1) Vitamin D from Sunlight
The sun is the ideal source of vitamin D- regular sun basking is the best way to get the required vitamin D levels. To maintain healthy blood parameters, take at least 10–30 minutes of sunlight during afternoon (11am-3pm), several times a week. Factors like time of the day, skin colour, geographical areas, sunscreen, and amount of skin exposed might create a difference.
2). Vitamin D from animal sources
If you living in an area where sunlight is scarce, you can get vitamin D from animal sources like egg yolks, red meat, and fatty fish like Tuna, Sardines, and Salmon. Sun-dried mushrooms are the best natural plant sources of this essential vitamin.
3). Vitamin D from fortified foods
Vitamin D in animal food sources might not be sufficient for your body- you can add fortified foods to meet daily micronutrient requirements. Consume vitamin D-enriched foods like fortified breakfast cereals, rice milk, soy milk, and orange juice, which also contain calcium that helps maintain vitamin D levels in the body.
4). Vitamin D from Supplements
As there are very few food sources of Vitamin D, a majority of the population suffers from its deficiency. Vitamin D supplements are readily available- dosage depends on scarcity level. Adding a Vitamin D supplement to your diet will help absorb calcium, preventing bone demineralisation, maintain the immune system, and reduce the risk of cardiovascular disease.
Who is More at Risk for Vitamin D Deficiency?
Vitamin D deficiency has become a global issue. Around 50% of the world’s population has insufficient vitamin D. The amount of Vitamin D adults get from their daily diet is usually less than the recommended parameters. Obese people, individuals with dark skin, people above 65, and those who do not get adequate sun exposure are at high risk for Vitamin D deficiency.