Vitamin D: Needs, Sources, Benefits & Deficiency
Article by Rhiannon Lambert, BSc MSc RNutr
What is vitamin D?
Vitamin D, which is one of the four fat-soluble vitamins alongside vitamins A, C, and E, is needed by the body for a variety of functions. We get the majority of vitamin D from the exposure to the sun’s UVB rays, hence why it’s often referred to as the sunshine vitamin.
There are some dietary sources, including oily fish, mushrooms, egg yolks, and fortified foods, however they contain fairly low amounts of vitamin D, so even if you have a balanced and varied diet, it’s unlikely that you will get enough vitamin D from the diet alone.
What are the benefits of vitamin D?
One of its most important functions is to help regulate the amount of phosphorus and calcium within the body. This regulation is needed to help keep our teeth, bones, and muscles healthy.
In addition, vitamin D helps maintain and support a healthy immune system. Research conducted as a result of the coronavirus pandemic suggested there may also be a link between vitamin D intakes and risk of COVID-19. However, this remains inconclusive and we cannot say with certainty that vitamin D should be taken to help prevent getting the infection and be protective against the disease.
Vitamin D foods to eat
Although most of our vitamin D comes from exposure to the sun, there are also some foods we can eat which can improve our vitamin D status. Most sources of vitamin D, particularly vitamin D3, come from animal-based ingredients including:
Oily fish including salmon, sardines, mackerel, trout, pilchard and kippers
Red meat
Liver
Egg yolks
There are also a small number of foods that are suitable if you follow a predominantly plant-based diet such as:
Some types of mushrooms that are naturally grown in the sun’s UV light
Fortified foods including plant-based milks, orange juice, breakfast cereals
Algae
Dietary supplements
It’s always good to check the front and back packaging labels to better understand which type of vitamin D, as well as any other ingredients are in a product, especially when it comes to fortified foods and supplements containing vitamin D.
What is vitamin D3?
Vitamin D3, alongside vitamin D2, is one of the main forms of vitamin D. The majority of dietary sources of vitamin D3 come from animal sources oily fish, liver and egg yolks. However, there are some exceptions where you can also find vitamin D3 in plants.
For example, it can be found in algae which means that even if you follow a vegan or primarily plant-based diet you can still increase your vitamin D intake.
This is especially important as most vitamin D supplements, that contain vitamin D3, use fish oils which are not suitable for vegans or plant-based eaters.
So the fact that algae is a good source of vitamin D3 means there is a better variety of vitamin D supplements for those who follow this diet.
What is vitamin D deficiency?
A vitamin D deficiency simply means we don’t get enough vitamin D from the sunlight or our diets. It’s important to avoid being deficient in this vitamin because an inadequate intake can lead to various health complications, such as osteoporosis in adults and rickets in children.
Some people may have a higher risk of deficiency in vitamin D as a result of reduced sunlight exposure from wearing clothing that covers their skin and elderly people who don’t go outside often. People with darker skin, such as those of African, African-Caribbean or south Asian origin, may also not produce enough vitamin D during summer months in the UK or in other northern climates. In cases like this, people should consider supplementing with a high quality vitamin D supplement all year round, to ensure they get the required amounts to help support healthy teeth, bones, and muscles.
What are vitamin D deficiency symptoms?
The signs and symptoms of a vitamin D deficiency include:
Tiredness
Weakness
Getting frequent infections
Poor wound healing
Muscle and joint pain
Hair loss
Bone deformities and rickets in children
Osteomalacia in adults
If you think you may be deficient then it’s a good idea to speak to your GP as they will be able to do the relevant blood tests to establish a deficiency and then prescribe the correct amounts depending on your individual needs.
Vitamin D supplement to use
As discussed, vitamin D is produced in the body as a result of being exposed to sunlight. In the UK, the sun’s rays are only strong enough for vitamin D production in the summer months (April to September), therefore throughout the autumn and winter months to avoid deficiency the NHS recommends that everyone needs to take a daily supplement which contains 10mcg of vitamin D, such as Rhitrition+ Vitamin D.
By supplementing with Vitamin D during the autumn and winter months alongside naturally in April-September this will help your body regulate the amount of calcium and phosphorus in the body which are needed for healthy bones, muscles and teeth. This will aid muscle strength, protect against rickets and osteomalacia as well as supporting the immune system.
How much vitamin D should you consume?
The Department of Health and Social care recommends that children and adults over the age of 4 years, in the UK, should be consuming 10mcg of vitamin D each day. In the summer months we can get what we need from the sunlight, however in the colder months (October to March) we need to take a high quality vitamin D supplement to help maintain the body’s reserves of it, as we cannot get enough from the diet alone
For babies and infants under the age of 4 years old, the guidance from the NHS is as follows:
| Age | Amount | When | ||
|---|---|---|---|---|
| Breast-fed babies | Birth - 1 years | 8.5 - 10 mcg | All year round | |
| Formula-fed babies who have less than 500ml of formula a day | Birth - 1 years |
|
All year round | |
| Children | 1-4 years | 10 mcg | All year round |
You can get specially formulated children’s vitamin D supplements or drops from most supermarkets and pharmacies, but remember to always check the label to make sure there are no unnecessary ingredients contained within the supplement. If you’re unsure then it’s a good idea to speak with your doctor or another healthcare professional such as a registered nutritionist or dietitian to offer bespoke advice.
Which vitamin D should I take?
As mentioned there are two main types of vitamin D: vitamin D2 and vitamin D3. But are they both the same or is one better for us than the other?
Whilst they may be similar in their chemical structure and functions within the body, there are some key differences between these two types of vitamin D which should be considered when looking at food sources and dietary supplements. Both vitamin D2 and D3 are absorbed into the bloodstream, however the way in which they are metabolised by the liver is different.
In the liver, they are both converted into calcifediol (also known as calcidiol) which is the main form of circulating vitamin D found in the blood, but evidence suggests that vitamin D3 is more effective at raising circulating vitamin D levels within the blood compared to vitamin D2. Both forms may be used in dietary supplements but based on the current finds within the scientific literature, those which contain vitamin D3, both vegan and non-vegan varieties, may be superior.
Does vitamin D cause side effects?
It is not possible to get too much vitamin D from exposure to sunlight, however, if you take a vitamin D supplement then it’s important to not take too much. In the long term, a consequence of taking too many vitamin D supplements is that it can cause a build up of calcium in the body, known as hypercalcaemia, which may weaken the bones and cause damage to the kidneys and the heart.
The NHS recommends that we should take more than 100mcg (4,000 IU) of vitamin D a day as it could lead to adverse health outcomes. They suggest that 10mcg (40 IU) of vitamin D a day will be enough for most people.
For children aged 1 to 10 years no more than 50 micrograms (2,000 IU) a day of vitamin D should be taken and for infants under 12 months this should be no more more than 25 micrograms (1,000 IU) a day.
In some cases, people may have medical conditions which mean that they need to take more or less than the daily recommendations. Always speak with your doctor before taking on any new supplements and only ever take the amount you are prescribed.
Evidence
https://www.bda.uk.com/resource/vitamin-d.html
https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
https://assets.publishing.service.gov.uk/government
https://www.healthline.com/nutrition/vitamin-d-deficiency-symptoms#12
