BLOG BY Abi Woodliffe-Thomas - @Happetite_

What Is Vitamin D And Why Is It So Important?

Vitamin D acts as a catalyst for many of our bodily systems, from bone development to strong immune systems, and even our circadian rhythm. Researchers have also expressed the potential links between adequate Vitamin D protecting us against coronavirus. (1) So, when the sunshine fades and the nights draw in, just how important is this fat-soluble vitamin for our health? And just how do we get it?

Before we get into the scientific facts about Vitamin D, it is important to understand what the sunshine vitamin is, what it does and how we can get it.

What is Vitamin D?

Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate.
Its most common function is aiding the growth and formation of bones and teeth via calcium absorption. These nutrients are needed to keep bones, teeth, and muscles healthy at all stages of life and development. However, A lack of vitamin D can lead to bone deformities such as rickets in children, and bone pain caused by a condition called osteomalacia in adults. (2)

The sunshine vitamin:

There are two main types of vitamin D and termed the sunshine vitamin, Vitamin D is the only vitamin our bodies can manufacture in the presence of sunlight. But during winter, it can be very difficult to maintain good levels of Vitamin D through natural means alone. A prime reason is that there are few sources of this vital nutrient besides sunlight. On the topic of sunlight, particularly Vitamin D3 UV exposure, it has been shown that In Indian people, an estimated half an hour of midday sun twice a week provides an adequate amount. (3) Counties further away from the equator, however, require longer durations of UV sunlight exposure to ensure the recommendation are met.

Vitamin D2 Vs. D3:

At this point, it is important to point out that there are two main forms of Vitamin D: Vitamin D2 and D3. Both are essentially converted in the same way by our bodies into an active form. Vitamin D3 is the type we make in sunlight and is also found in a limited number of animal foods, such as oily fish and cod liver oil. Vitamin D2 comes from plants and fungi, including mushrooms grown under UV light. Since Vitamin D2 is cheaper to produce, it is the most common source within fortified foods, such as cereals and milk. Even so, be sure to check the label on milk and cereals to ensure the product is fortified with vitamins and minerals for the best results.
Vitamin D3 appears to be better than D2 at improving vitamin D status, although both sources are absorbed through the bloodstream, the liver metabolizes them differently into separate compounds, collectively known as calcifediol (main circulating form of vitamin D, and its blood levels reflect your body’s stores of this nutrient). (4)

Sources of vitamin D:

Oily fish, such as salmon, mackerel, and sardines, as well as lean red meat, eggs (specifically the yolk) and fortified cereals and milk are all great sources of vitamin D. It is important here to ensure they are fortified, as, without the vitamin and mineral fortification, the nutrient profile will not as supportive when focusing on Vitamin D.

But if it is available, then why are so many people deficient?:

According to comprehensive NDNS figures, the proportion of adults aged 19-64 failing to reach the governments recommended minimum value of Vitamin D (10 μg per day, NHS)
has grown from 20% to 23%. Furthermore, 22% of children aged 11-15 have depressed levels, therefore taking the proportion of both groups to a shocking 40% in the winter months. This means 4 in 10 people have a deficiency in vitamin D. (5)

Daily supplementation is something that should be mandatory between the months of October and April when daily exposure to sunlight decreases, however, there are many ways in which our nutrition can contribute to higher Vitamin D intake, and therefore increase the function of calcium absorption without the expense of a sunny holiday! (6) Vitamin D works in tangent with calcium to promote good bone health. The two are a team because vitamin D increases our absorption of calcium, which we know is integral for strong, healthy bones. Adequate levels of this fat-soluble vitamin ensure the function of muscles are optimum, Immunity is supported, and our sleep schedule is stable, ultimately leading to a balanced, homeostatic life. Conversely, overconsuming vitamin D supplements over a long period can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart.

Common signs of a Vitamin D deficiency:

Much like many side effects, signs, and symptoms, they are all individual. However, here are the tops signs and symptoms to be aware of which could potentially be a sign of lower Vitamin D levels:


Joint pain

Muscle weakness, aches, and pains

Mood changes

High blood pressure

Wheezing and respiratory issues – hence the potential links to Covid-19

Increased risk of infection

Pale skin with dark eye circles

With that being said, there are numerous health benefits of adequate Vitamin D levels in the body, highlighting the importance of this fat-soluble vitamin. As already mentioned above, Vitamin D and calcium work hand in hand in promoting strong bones through the absorption of both calcium and phosphorus. Vitamin D has been associated with lower cancer rates due to the connection between vitamin D and cell-to-cell communication and growth. (7) Vitamin D assists the body with the growth and formation of new tissues, as well as destroying bacteria and viruses helping to strengthen our immunity. There has been links between vitamin D and type 2 diabetes, researchers explain that adequate levels of Vit D can reduce the risk of insulin resistance and stabilise glucose metabolism, with one study explaining that vitamin D is associated more closely with glucose metabolism than obesity. (8)

The bottom line:

Vitamin D is clearly essential for an abundance of bodily processes, so ensuring we reach the recommendations will help us remain both physically, and mentally healthy. It cannot go unnoticed that although this is the sunshine vitamin, ensuring we supplement throughout October, through to April, will ensure that our levels remain at a stable rate and therefore reduce the risk of signs and symptoms linked to a deficiency.

Meltzer, D.O., Best, T.J., Zhang, H., Vokes, T., Arora, V. and Solway, J., 2020. Association of vitamin D status and other clinical characteristics with COVID-19 test results. JAMA network open, 3(9), pp.e2019722-e2019722. (1)

nhs.uk. Vitamins and minerals - Vitamin D. Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d (2)

Harinarayan, C.V., Holick, M.F., Prasad, U.V., Vani, P.S. and Himabindu, G., 2013. Vitamin D status and sun exposure in India. Dermato-endocrinology, 5(1), pp.130-141. (3)

Holick, M.F., 2009. Vitamin D status: measurement, interpretation, and clinical application. Annals of epidemiology, 19(2), pp.73-78. (4)

Bates Bea. National Diet and Nutrition Survey Results From Years 5 and 6 (Combined) of the Rolling Programme (2012/2013 −2013/2014). London: TSO (2016). (5)

nhs.uk. 2021. How to get vitamin D from sunlight. [online] Available at: https://www.nhs.uk/live-well/healthy-body/how-to-get-vitamin-d-from-sunlight/ (6)

Medically reviewed by Debra Sullivan, Ph.D., MSN, R.N., CNE, COI — Written by Megan Ware, RDN, L.D. on November 7, 2019 (7)

Ozfirat, Z. and Chowdhury, T.A., 2010. Vitamin D deficiency and type 2 diabetes. Postgraduate medical journal, 86(1011), pp.18-25. (8)

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