Vitamin D is a fat-soluble vitamin that your body makes from cholesterol when your skin is exposed to sunlight. It is also found in some foods, such as fatty fish and fortified dairy products, or you can take it as a supplement.

Vitamin D is essential for many aspects of your health, including:

• Bone health: Vitamin D helps your body absorb calcium and phosphorus, which are the main minerals for building and maintaining strong bones. Vitamin D deficiency can lead to osteoporosis, osteomalacia, and rickets, which are conditions that cause bone loss, softening, and deformity.
• Immune health: Vitamin D supports your immune system by interacting with the cells that fight infections. Vitamin D deficiency can increase your risk of getting sick, especially with respiratory tract infections such as colds, bronchitis, and pneumonia.
• Chronic diseases: Vitamin D may also play a role in preventing or treating some chronic diseases, such as depression, type 2 diabetes, heart disease, multiple sclerosis, and even some cancers . However, more research is needed to establish a causal link between vitamin D deficiency and these conditions.

How much vitamin D do you need?

The amount of vitamin D you need depends on several factors, such as your age, skin color, sun exposure, diet, and health status. The recommended dietary allowance (RDA) for vitamin D for most adults is 600 international units (IU) per day. However, some experts suggest that this may not be enough for optimal health and recommend higher doses of up to 1,500–2,000 IU per day.

You can get vitamin D from three sources:

• Sunlight: Your skin can produce vitamin D when it is exposed to ultraviolet B (UVB) rays from the sun. However, the amount of vitamin D you make depends on the time of day, season, latitude, cloud cover, air pollution, sunscreen use, and your skin pigmentation. People with darker skin and older people may not make enough vitamin D from sunlight alone.
• Food: Few foods naturally contain vitamin D, but some are fortified with it. The best food sources of vitamin D are fatty fish (such as salmon, tuna, and mackerel), fish liver oils, egg yolks, cheese, and mushrooms. Fortified foods include milk, yogurt, orange juice, cereals, and margarine.
• Supplements: If you are not getting enough vitamin D from sunlight and food, you may need to take a supplement. There are two forms of vitamin D supplements: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is more effective at raising your blood levels of vitamin D than vitamin D2. You can find vitamin D supplements in various forms, such as capsules, tablets, drops, or sprays.

What are the consequences of low vitamin D level and how common is it in India?

Low vitamin D level can have serious consequences for your health, especially if it is left untreated for a long time. Some of the possible consequences are:

• Increased risk of fractures: Low vitamin D level can cause loss of bone density and strength, which can make your bones more prone to breaking. This can affect your quality of life and increase your healthcare costs. Fractures can also lead to complications such as infections, blood clots, and nerve damage.
• Increased risk of chronic diseases: Low vitamin D level can impair your immune system and increase inflammation, which can contribute to the development or progression of various chronic diseases, such as diabetes, heart disease, multiple sclerosis, and some cancers . Some studies have also suggested that low vitamin D level may be associated with increased severity or mortality from COVID-19 .
• Increased risk of mental disorders: Low vitamin D level can affect your mood and cognitive function, which can lead to depression, anxiety, dementia, and other mental disorders . Vitamin D may also play a role in regulating neurotransmitters such as serotonin and dopamine, which are involved in mood regulation and reward pathways.

Vitamin D deficiency is a very common problem in India, affecting people of all ages, genders, and regions. A study based on data from Tata 1mg Labs revealed that nearly 76% of the Indian population suffers from vitamin D deficiency. The study involved tests of more than 2.2 lakh people conducted across 27 cities in India. The study also found that young adults below the age of 25 were the most affected by vitamin D deficiency.

Some of the factors that contribute to the high prevalence of vitamin D deficiency in India are:

• Low sun exposure: Despite being a tropical country with abundant sunlight, many Indians do not get enough sun exposure due to various reasons, such as air pollution, indoor lifestyle, cultural practices, clothing habits, and use of sunscreen .
• Low dietary intake: Few foods naturally contain vitamin D, and many Indians do not consume enough foods that are fortified with vitamin D, such as milk and cereals . Moreover, many Indians follow a vegetarian or vegan diet, which limits their intake of animal sources of vitamin D, such as fish and eggs.
• Genetic factors: Some genetic variants may affect the synthesis or metabolism of vitamin D in the body, leading to lower blood levels or higher requirements . For example, some studies have found that Indians have lower levels of vitamin D binding protein (VDBP), which is involved in transporting vitamin D in the blood .

How do you know if you have vitamin D deficiency?

The only way to know for sure if you have vitamin D deficiency is to get a blood test that measures your level of 25-hydroxyvitamin D (25[OH]D), which is the main form of vitamin D in your blood. The optimal range of 25(OH)D for most people is between 30 and 60 nanograms per milliliter (ng/mL).

However, some signs and symptoms of vitamin D deficiency may include:

• Bone pain
• Muscle weakness
• Fatigue
• Mood changes
• Frequent infections
• Slow wound healing

If you have any of these symptoms or risk factors for vitamin D deficiency, such as being older than 65 years old, having darker skin color or wearing clothing with extensive skin coverage, living in a northern latitude or having limited sun exposure, following a vegan diet or having a malabsorption disorder, you should talk to your doctor about getting tested and treated for vitamin D deficiency.

Some vitamin D rich foods for vegetarians , non vegetarians and vegans : 

Some vitamin D rich foods for different dietary preferences are:

• For vegetarians: Vegetarians can get vitamin D from dairy products, such as milk, yogurt, and cheese, that are fortified with vitamin D. They can also get vitamin D from mushrooms, especially those that are exposed to UV light. Egg yolks are another option for vegetarians who eat eggs.
• For non-vegetarians: Non-vegetarians can get vitamin D from oily fish, such as salmon, trout, tuna, sardines, and herring. They can also get vitamin D from fish liver oils, such as cod liver oil. Egg yolks are another source of vitamin D for non-vegetarians.
• For vegans: Vegans can get vitamin D from plant-based foods that are fortified with vitamin D, such as soy milk, almond milk, oat milk, orange juice, cereals, and margarine. They can also get vitamin D from mushrooms, especially those that are exposed to UV light. Some vegan supplements may also contain vitamin D.

How can you prevent or treat vitamin D deficiency?

The best way to prevent or treat vitamin D deficiency is to get enough vitamin D from sunlight exposure (if possible), food sources (especially fatty fish and fortified foods), and supplements (if needed). You should also avoid smoking and excessive alcohol consumption, as these habits can impair your body’s ability to make or use vitamin D.

Depending on your blood level of 25(OH)D and your health condition, your doctor may prescribe different doses of vitamin D supplements to correct your deficiency. For example:

• If your level is between 20 and 30 ng/mL (mild deficiency), you may need to take 1,000–2,000 IU of vitamin D3 per day.
• If your level is below 20 ng/mL (moderate to severe deficiency), you may need to take 5,000–10,000 IU of vitamin D3 per day for 6–12 weeks, followed by a maintenance dose of 1,000–2,000 IU per day.
• If your level is below 10 ng/mL (very severe deficiency), you may need to take 50,000 IU of vitamin D2 or D3 once a week for 8 weeks, followed by a maintenance dose of 1,500–2,000 IU per day.

You should always consult your doctor before taking any vitamin D supplements, as they can interact with some medications or cause side effects if taken in excess. The upper limit of vitamin D intake for adults is 4,000 IU per day. Taking more than this amount can cause toxicity, which can lead to high blood calcium levels, nausea, vomiting, kidney damage, and other serious complications.

Conclusion 

Vitamin D is a vital nutrient for your health, especially for your bones and immune system. It may also help prevent or treat some chronic diseases. However, vitamin D deficiency is very common and can cause various symptoms and complications. To avoid vitamin D deficiency, you should get enough vitamin D from sunlight exposure (if possible), food sources (especially fatty fish and fortified foods), and supplements (if needed). You should also get tested regularly and follow your doctor’s advice on how to correct your deficiency.