Vitamin D regulates calcium and phosphorus and is essential for bone, muscle and immune health. Adults need 10 micrograms a day. Most people make it from sunlight on skin, but indoor lifestyles, sunscreen, latitude and pigmentation all reduce that — which is why UK guidance recommends a 10μg supplement from October to March, and year-round for some groups. Food sources include oily fish, egg yolks, UV-exposed mushrooms and fortified cereals.
We know that vitamin D is a very important vitamin, but why do we need it and how can we make sure we aren't deficient?
What is vitamin D?
- Vitamin D is a fat-soluble vitamin that is an essential part of a balanced diet.
- It is required for regulation of calcium and phosphorus metabolism and is therefore important for musculoskeletal health.
- It is synthesised in the skin upon exposure to sunlight containing sufficient ultraviolet B (UVB) radiation and this is the main source for most people.
- It can also be obtained from foods or dietary supplements.
- Calcium and vitamin K are needed to absorb vitamin D. Taking vitamin D supplements with a meal also improves absorption.
How much vitamin D do you need?
- Vitamin D is essential for bone mineralisation and neuromuscular function.
- It has been suggested that vitamin D may also have a role in other health outcomes, which include reducing the risk of cancers, cardiovascular disease (CVD), infectious diseases and autoimmune diseases.
The recommendations are:
0-1years 8.5-10μg /day
Everyone else 10μg/day
- Vitamin D toxicity can lead to the deposition of calcium in soft tissues, demineralisation of bones and irreversible renal and cardiovascular toxicity. Don't take more than 100 μg/day of vitamin D as it could be harmful. This applies to adults, including pregnant and breastfeeding women and the elderly, and children aged 11 to 17 years. Children aged 1 to 10 years shouldn't have more than 50 μg /day. Infants under 12 months shouldn't have more than 25 μg /day.
- It is not possible to overdose on vitamin D through exposure to sunlight. However, if spending a long time in the sun remember to cover up or put sun cream on to reduce the risk of skin damage and skin cancer.
What is the prevalence of vitamin D deficiency?
- Vitamin D deficiency is prevalent worldwide, and around 1 billion people worldwide are thought to be deficient. It is frequently spoken about as the most underdiagnosed and undertreated nutritional deficiency in the world
- In India it’s estimated that 90% of people are deficient in vitamin D.
Why are people facing deficiencies?
- Increased indoor lifestyle, thereby preventing adequate exposure to sunlight. This is mainly in the urban population.
- Pollution can prevent the synthesis of Vitamin D in the skin by UV rays.
- Changing food habits contribute to low dietary calcium and Vitamin D intake.
- Phytates and phosphates which are present in fibre rich diet, can deplete Vitamin D stores and increase calcium requirement.
- Increased skin pigmentation, application of sunscreens and covering of skin due to cultural or religious beliefs.
What are the effects of being deficient in vitamin D?
- Rickets in children and osteomalacia and osteoporosis in adults. Many studies have shown an association between low Vitamin D concentrations and an increased risk of fractures and falls in older adults.
- Vitamin D deficient patients take significantly longer duration for recovery from depression than nondeficient persons.
- Vitamin D insufficiency was seen in patients with Parkinson's therefore Vitamin D could act as a potential preventive/therapeutic strategy for this disorder. However, there is a need for further studies.
- Evidence reveals that Vitamin D reduces the risk of progression and development of type 2 diabetes mellitus.
- Research shows some other potential consequences of Vitamin D deficiency are autoimmune diseases, cardiovascular diseases, cancer, and tuberculosis.
How can you ensure you get adequate vitamin D in your diet?
- As mentioned earlier there are two main ways to get vitamin D in your diet. The first is sunlight and the second is from food and supplements.
- Food sources of vitamin D are limited. Wild mushrooms are a rich natural source. It has even been shown in some research that if you leave your shop brought mushrooms on a windowsill in sunlight or outside in the sun for half an hour, they become a good source of vitamin D.
- Calcium and vitamin K are needed to absorb vitamin D. It has also been shown that consuming vitamin D with a meal will also improve absorption due to the high fat content.
- Eating foods fortified with vitamin D is also a good way to incorporate it into your diet. In some countries such as the UK, lots of the breakfast cereals eaten are fortified with vitamin D.
- Taking good quality vitamin D supplements can provide you with your required dose of vitamin D if you do not have access to the suggested foods or are unable to incorporate enough sunlight into your lifestyle.
Conclusion- if you do not get enough vitamin D from the sunlight then you should be taking a supplement daily.
Always consult your doctor if you have a health condition or are taking medication that may interact with the supplements.
Last reviewed: June 2026
Studies discussed in the article
Vitamin D Deficiency
Omeed Sizar; Swapnil Khare; Amandeep Goyal; Pankaj Bansal; Amy Givler.
link- https://www.ncbi.nlm.nih.gov/books/NBK532266/
Vitamin D deficiency in India
Aparna, P., Muthathal, S., Nongkynrih, B., & Gupta, S. K.
Link- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6060930/
Photobiology of vitamin D in mushrooms and its bioavailability in humans
Keegan, R. J., Lu, Z., Bogusz, J. M., Williams, J. E., & Holick, M. F.
Link- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897585/