What is vitamin D?
Despite its name, vitamin D is more than a vitamin - it’s closer to a hormone that the body can synthesise under the right conditions. Regardless, we need to consume it regularly in order to maintain overall health and wellbeing.
How is it produced?
The trigger for vitamin D synthesis is the sun, which emits UVB light that hits our skin. The UVB light reacts with a type of cholesterol found in the deeper layers of the skin, which produces a vitamin D precursor called pre-vitamin D. This is then converted to active vitamin D (calcitriol) by the liver and kidneys, and it’s this form that travels around the body to interact with cells.
In the UK, even in the summer, you cannot get adequate vitamin D levels from sun exposure because of the inconsistencies in weather and therefore the sun’s UV index isn’t as effective. We can also get small amounts from our diet. Meals that include eggs, oily fish, foods fortified with vitamin D, and mushrooms are all popular dietary sources of the vitamin.
What it does in the body
Vitamin D has many functions within the body, including:
Balancing calcium levels in the body (including in the bones)
- Supporting healthy levels of white blood cells
Aiding in immune function during infection
This list isn’t at all exhaustive and, in fact, scientists are only just scratching the surface of what vitamin D may help with. More recently, research has found that it may even help to reduce inflammation — suggesting it could aid in the recovery of a disease or condition that has inflammation as a characteristic.1
Can we get enough vitamin D from the sun?
As we’ve already said, the sun is the trigger for vitamin D synthesis, but does this mean we get enough from sun exposure? Well, it depends. Everyone produces vitamin D at different rates, and many are at risk of vitamin D deficiency.
Dr Sarah Brewer says: 'Public Health England recommends that everyone over the age of one year should take a daily supplement providing 10mcg vitamin D during autumn and winter. This is very much a minimum to prevent deficiency diseases – I believe that most adults would benefit from taking 25mcg (1.000 IU) per day, increasing to 50 mcg (2,000 IU) per day from the age of 50 onwards, when your ability to synthesis vitamin D in the skin starts to decline. Choose a vitamin D3 (cholecalciferol) supplement which is the same form made in the skin by the body on exposure to sunlight, and which is more effective in producing active vitamin D3 (calcitriol) than the plant-based vitamin D2 (ergocalciferol) form.’
Who is most at risk of vitamin D deficiency?
Those who are most vulnerable to vitamin D deficiency include:
- People who live in cold climates (such as the UK)
- People who get little direct sun exposure e.g. someone who works in an office job
- Those with a long-term illness that tends to confine them indoors
- People who keep the majority of their skin covered e.g. for religious reasons
- Dark-skinned people
- The elderly
- People who wear sunscreen or use products that contain SPF regularly
However, everyone is at high risk of becoming vitamin D deficient, especially during winter. In fact, low vitamin D levels might explain why we’re more prone to becoming sick during flu season — another reason why you should get your levels checked at the start of each winter2. Even living in a city over the countryside may induce the risk of becoming deficient. You can find out more about this here.
Vitamin D: the benefits
There’s also a lot of emerging research to suggest vitamin D may help in specific health conditions.
Vitamin D and mental health
Recent studies suggest that vitamin D deficiency might have some role to play in depression.
One such study investigated a large group of people with current or previously diagnosed depression. It found that one-third of the participants had vitamin D deficiency.
According to the study, those with lower vitamin D levels were more likely to not only have current depression but also suffer from the most severe symptoms. In fact, those with current depression, but had sufficient vitamin D levels, experienced less severe symptoms3.
Another study looked at the link between overweight and obese people who experienced depression and vitamin D. It found that those with lower vitamin D levels had more depressive traits, but that after one year of supplementing vitamin D, they experienced a significant improvement in their symptoms4.
With more and more research being conducted into the role vitamin D may play in mental health, the clearer it’s becoming just how essential this vitamin can be for many people. Find out more about the links between vitamin D and mental health here .
Vitamin D and exercise
If you’re an athlete, or just fitness-conscious, knowing your vitamin D status should be on your priority list. Recent research suggests that there could be a link between your sports performance and how optimal your vitamin D levels are.
In one study, researchers created a trial that looked at the effects of supplementation on a group of UK athletes and non-athletes. Initially, they found that 62% of athletes and 73% of non-athletes had vitamin D deficiency.
But when the same groups were given 5000IU of vitamin D a day for 8 weeks, it not only significantly increased their vitamin D levels, but it also had an impact on their physical performance. For instance, those who were given the supplement found a significant improvement in their 10m sprint time and vertical jump height. Find out more about vitamin D and exercise here.5
Vitamin D and cardiovascular health
Cardiovascular disease is a massive health issue, causing more than a quarter of all deaths in the UK.6 However, recent studies are suggesting that there’s a hidden superstar when it comes to heart health: vitamin D.
One study found that men who were vitamin D deficient had a significantly higher risk of a heart attack, even after controlling for known risk factors. It suggested that even those who had only a slight deficiency still had a higher risk than those with sufficient vitamin D.7
Another study suggested that there was a strong link between vitamin D deficiency and increased risk of heart failure, but specifically in elderly people. This is particularly concerning, as 65% of the participants were vitamin D deficient, indicating that such deficiency is common among older adults.8
A well-known factor in heart disease risk is blood pressure, and recent research has shown that in a hypertension model, vitamin D can increase the production of nitric oxide — a compound that lowers blood pressure. Although further research is needed to support this, it does suggest, at least initially, that optimal vitamin D levels can support healthy blood pressure.9
Vitamin D and bone health
Although vitamin D is essential for every age, it may be especially important for babies and children to get a sufficient amount. This is because vitamin D can helps maintain optimal calcium levels to support the growth and development of healthy teeth and bones in young children.
Children who don’t get enough vitamin D may be at risk of developing osteomalacia — the softening of the bones. Osteomalacia can lead to bowing of the bones, particularly of the larger bones (such as leg bones).10
Making sure you get enough vitamin D for bone health isn’t limited to just children, it is also important for the elderly. One study looked at the effects of vitamin D supplementation in combination with low-level exercise amongst the elderly, and found that this combination was effective at reducing falls in the elderly participants.11
Vitamin D and IBS
One review of current research on this link found that not only is low vitamin D common for people with IBS but that there was a link between symptoms and vitamin D levels. The higher a person’s vitamin D levels, it suggested, the less likely they were to experience severe IBS symptoms — and that supplementing with vitamin D is advised.12
Vitamin D and fertility
Infertility is on the rise, and more couples are struggling to start a family. But for those undergoing assisted reproduction treatment, it’s been suggested that you may want to consider vitamin D as a supportive nutrient.
A review and analysis of 11 trials supported this claim, finding that women with sufficient vitamin D levels were more likely to have a live birth than those with lower levels. Women who had sufficient vitamin D were also more likely to achieve a positive pregnancy test and clinical pregnancy.
Previous research found that low vitamin D levels are associated with increased risks of complications in implantation and pregnancy, so maintaining a healthy level may prevent these issues.
Research has shown that Vitamin D deficiency is also an important condition to treat in women who wish to undergo procedures such as IVF and insemination.13
Vitamin D and pregnancy
When a woman becomes pregnant, vitamin D is essential in helping the baby remain healthy.
One systematic review looked at the impacts of vitamin D supplements used during pregnancy. It found that vitamin D not only increased maternal vitamin D levels, but was also linked to a higher average birth rate and a reduced risk of the baby being small for its gestational age at birth.
The review also found that taking vitamin D supplements during pregnancy reduced the risk of the child experiencing wheeze by the age of three.14
With these benefits in mind, you may be concerned about what the safe dose of vitamin D is during pregnancy. Well, one study found that 100 mcg (4000 IU) per day was a safe and successful level — but it’s important to consult your healthcare provider for advice as different doctors have different opinions. 15
Vitamin D and type 2 diabetes
Around 1 in 16 people in the UK have diabetes, with the majority having type 2 diabetes. What we eat and how we live life plays a big role in its development.16
Research from Australia has seemingly uncovered a link between type 2 diabetes and vitamin D. It found that people with a higher vitamin D status had lower fasting glucose levels and HbA1C, which shows long-term blood sugar control. So, having a healthy level of vitamin D could potentially help to reduce a risk of type 2 diabetes. 17
We can clearly see from the research and studies evidenced here that vitamin D can play a huge in overall health and wellbeing, as well potentially aiding in specific health conditions and ailments. Remember, though, if you’re not sure if vitamin D is right for you, ask your friendly healthcare practitioner.
1.Zhang, Y., Leung, D.Y., Richers, B.N., Liu, Y., Remigio, L.K., Riches, D.W., and Goleva, E. (2012). Vitamin D inhibits monocyte/macrophage proinflammatory cytokine production by targeting MAPK phosphatase-1. The Journal of Immunology, 188(5), pp.2127-2135.
2.Alvarez‐Rodriguez, L., Lopez‐Hoyos, M., Garcia‐Unzueta, M., Amado, J.A., Cacho, P.M., and Martinez‐Taboada, V.M. (2012). Age and low levels of circulating vitamin D are associated with impaired innate immune function. Journal of leukocyte biology, 91(5), pp.829-838.
3.Husemoen, L.L.N., Ebstrup, J.F., Mortensen, E.L., Schwarz, P., Skaaby, T., Thuesen, B.H., Jørgensen, T., and Linneberg, A. (2016). Serum 25-hydroxyvitamin D and self-reported mental health status in adult Danes. European journal of clinical nutrition, 70(1), p.78.
4.Jorde, R., Sneve, M., Figenschau, Y., Svartberg, J., and Waterloo, K. (2008). Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial. Journal of internal medicine, 264(6), pp.599-609.
5.Close, G.L., Russell, J., Cobley, J.N., Owens, D.J., Wilson, G., Gregson, W., Fraser, W.D., and Morton, J.P. (2013). Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: implications for skeletal muscle function. Journal of sports sciences, 31(4), pp.344-353.
7.Giovannucci, E., Liu, Y., Hollis, B.W., and Rimm, E.B. (2008). 25-hydroxyvitamin D and risk of myocardial infarction in men: a prospective study. Archives of internal medicine, 168(11), pp.1174-1180.
8.Porto, C.M., Silva, V.D.L., Luz, J.S.B., and Silveira, V.M. (2018). Association between vitamin D deficiency and heart failure risk in the elderly. ESC heart failure, 5(1), pp.63-74.
9.Khan, A., Dawoud, H., and Malinski, T. (2018). Nanomedical studies of the restoration of nitric oxide/peroxynitrite balance in dysfunctional endothelium by 1, 25-dihydroxy vitamin D3–clinical implications for cardiovascular diseases. International Journal of Nanomedicine, 13, p.455.
11.Imaoka, M., Higuchi, Y., Todo, E., Kitagwa, T., and Ueda, T. (2016). Low-frequency Exercise and Vitamin D Supplementation Reduce Falls Among Institutionalized Frail Elderly. International Journal of Gerontology, 10(4), pp.202-206.
12.Williams, C.E., Williams, E.A., and Corfe, B.M. (2018). Vitamin D status in irritable bowel syndrome and the impact of supplementation on symptoms: what do we know and what do we need to know?. European journal of clinical nutrition, p.1.
13.Chu, J., Gallos, I., Tobias, A., Tan, B., Eapen, A., and Coomarasamy, A. (2017). Vitamin D and assisted reproductive treatment outcome: a systematic review and meta-analysis. Human Reproduction, 33(1), pp.65-80.
14.Roth, D.E., Leung, M., Mesfin, E., Qamar, H., Watterworth, J., and Papp, E. (2017). Vitamin D supplementation during pregnancy: state of the evidence from a systematic review of randomised trials. Bmj, 359, p.j5237.
15.Hollis, B.W., Johnson, D., Hulsey, T.C., Ebeling, M., and Wagner, C.L. (2011). Vitamin D supplementation during pregnancy: Double‐blind, randomized clinical trial of safety and effectiveness. Journal of bone and mineral research, 26(10), pp.2341-2357.
17.Pannu, P.K., Piers, L.S., Soares, M.J., Zhao, Y., and Ansari, Z. (2017). Vitamin D status is inversely associated with markers of risk for type 2 diabetes: A population based study in Victoria, Australia. PloS one, 12(6), p.e0178825.