Written by Ben Bunting BA(Hons) PGCert.

With the long nights and overcast weather blotting much of the sunlight out, you may wonder whether this can harm your vitamin D status. This is a question we shall address in this article; we shall cover the following points:

  • What’s vitamin D?
  • The benefits
  • Is it essential?
  • Deficiency side effects
  • Causes of a deficiency
  • Who’s at risk?
  • Regions at risk
  • Guidelines
  • Conclusion

What is vitamin D?

Vitamin D is nicknamed the “sunshine vitamin” because it is produced by the human body during exposure to sunlight.

Exposure to sunlight allows your skin to synthesize vitamin D3 from cholesterol. Vitamin D3 then travels through the bloodstream into your liver, where it is converted into a hormone called calcitriol.

Calcitriol travels to the kidney and then, along with phosphorus and calcium, becomes part of a compound that helps your body build strong bones and teeth.


Vitamin D is a fat-soluble vitamin that the body produces when skin is exposed to sunlight and absorbs energy from the sun. It is important for health and well-being because it helps maintain bone health and boosts the immune system.

It is essential for health, but it needs to be converted into a hormone to function properly.

There are many benefits of Vitamin D.

Some of these are:

– Improves mood

– Helps with absorption of calcium

– Strengthens teeth and bones

– Prevents chronic disease such as cancer, diabetes, cardiovascular disease (CVD), dementia, depression

– Maintains healthy levels of testosterone

– Possible prevention of COVID-19 symptoms

Is it essential?

Vitamin D is an essential nutrient. It is a nutrient that the body needs to grow, develop, and maintain health.

Essential nutrients are often categorized into two types: macronutrients and micronutrients.

Macronutrients are needed in larger quantities. They provide energy and include carbohydrates, protein, and fats.

Micronutrients are needed in smaller quantities for normal body growth, maintenance, and some metabolic activity.

These don’t provide energy but are necessary for the maintenance of good health. Essential nutrients include vitamins A, C, D, E; minerals such as iodine or selenium.

Deficiency side effects

A vitamin D deficiency can cause many signs. One of the most common is bone pain. It is also common to experience muscle weakness and general fatigue.

Other signs are mood swings, poor appetite, and trouble with memory. If you think that you might have a vitamin D deficiency, then you should talk to your doctor about it. Treatment for this ailment can be done in many ways.

The side effects of low vitamin D include the tell-tale signs of muscle aches and pains but can lead to further issues such as an increased risk of chronic diseases like heart disease and diabetes, depression, and other mental disorders such as schizophrenia. It can also cause bone fractures when the concentration of calcium in the body falls too low.

If you are vitamin D deficient, you can have a higher risk of developing certain cancers, autoimmune diseases, and anxiety.

Causes of a deficiency

There are many people in Europe and indeed the world who suffer from a vitamin D deficiency because they do not get enough exposure to the sun. This can cause serious health problems like osteoporosis, muscle weakness, and poor immune system responses.

The main reason for this is that people who live in northern latitudes or mountainous regions usually have a higher risk of having vitamin D deficiencies because these areas are less exposed to sunlight.

On top of this, people who wear sunscreen when they go outside also experience a reduction in vitamin D levels because sunscreen blocks out the UVB rays that could lead to the production of vitamin D. Other factors that contribute to this problem include skin colour, age, clothing, and occupation.

The body can manufacture all the vitamin D that it needs through exposure to direct sunlight but if there’s isn’t enough sunlight, you are at risk of becoming deficient.

Who is at risk?

The main cause of people’s lack of vitamin D is because many people live in cities and don’t get enough sun exposure, they cover their skin either to stay warm, protect from the sun’s heat, or for religious reasons. Many people also stay inside all day for work or leisure activities.

Those who are particularly at risk include:

  • Those with darker skin
  • Infants and children of less than 5 years
  • Pregnant and breastfeeding women
  • The elderly
  • Obese people

Other people who are also dealing with various diseases or health conditions are also at risk as outlined by the National Library of Medicine.

However, a vitamin D deficiency is not something that just affects older people or people living in cold climates. Around 1 billion of the world’s population suffer from a vitamin D deficiency.

Do children need more vitamin D?

Some studies have shown that vitamin D has a few positive effects on children including reducing the risk of type 2 diabetes, asthma, multiple sclerosis, and bone deformities such as rickets.

Therefore, it is important for children to have enough vitamin D in their diet for healthy growth and development.

Do athletes need more vitamin D?

Athletes should supplement with vitamin D because they have been identified through various studies which place them at high risk for vitamin D deficiency. This is because their high physical activity levels place an increased demand for the vitamin.

Additionally, some research suggests that vitamin D can reduce chronic pain and improve general performance with a study demonstrating those with higher circulating vitamin D levels had an increased VO2max compared with those of a lower vitamin D status.

Regions at risk?

A review released by the University of Birmingham identifies the UK’s location as not receiving the required UVB rays from the sunlight for most of the year.

The findings show that there are high levels of vitamin D deficiency in all regions of the UK with around 11 million adults receiving inadequate vitamin D during the winter months when sunlight exposure is at its lowest.


A new guideline for vitamin D intake has been released by the Scottish Government. The guidelines recommend that most people should take supplements containing 10 micrograms (mg) of vitamin D which equates to 400 international units (IU).

The guidelines are based on scientific evidence and are based on what is deemed to be safe and sufficient to meet our needs for bone health.

They also reflect current UK-wide and international standards which are being used elsewhere around the world – meaning there is consistency between countries and organisations.

Athletes can have up to 5000 international units daily and there have been no signs of toxicity from 30,000 international units daily.


As we now know, vitamin D is classified as a fat-soluble vitamin that aids in the absorption of calcium and phosphorus. It can be consumed through oral supplements or through food sources.

However, the food sources that are high in vitamin D are quite low, therefore taking a vitamin D supplement is necessary.

The foods that you should consider including in your diet as outlined by The Association of UK Dietitians are as follows:

  • Oily fish (tuna, salmon, mackerel, sardines)
  • Eggs (yolk)
  • Fortified cereals or milk
  • Cheese
  • Beef liver
  • Red meats


It has been identified by various research institutes and studies that the population of the UK does not receive adequate UVB rays from the sun throughout the year to prevent a vitamin D deficiency.

Therefore, the government recommends taking a supplement of 10mg daily to avoid any potential health complications associated with a deficiency. This is especially true for those who spend the majority of the daylight hours indoors, covered up, have darker skin tones, and athletes.