What is vitamin D?
Vitamin D is a fat-soluble vitamin that has many roles in the body including:
- Helping regulate the amount of calcium in the body
- Healthy bones and teeth
- Muscle health
- Reducing inflammation
- Cell growth
- Immune function
- Helping to support mental health and moods[1]
Types of Vitamin D
There are three different types of vitamin D, and they differ based on their source:
Vitamin D2 (ergocalciferol) is produced in plants and can be found in:
- Fortified foods such as milks and cereals
- Mushrooms that are grown under UV light or placed on a windowsill in sunlight
- Supplements
Vitamin D3 (cholecalciferol) is produced in animals, including humans, and can be found in:
- Oily fish such as salmon, mackerel, and sardines
- Liver
- Egg yolks
- Butter
- Supplements including fish oil
Vitamin D3 (Calcifediol) is produced from algae. Cholecalciferol and Ergocalciferol convert to Calcifediol in the liver before being pushed into the kidneys to come Calcitriol which is the active form of vitamin D. It can be found in:
- Supplements (VitamoreD™)
The best way to get vitamin D is actually from sunlight. The skin naturally makes vitamin D3 when it is exposed to the sun, without sunscreen. Where you live and the colour of your skin, both affect how easily you can make vitamin D. For example, winter sun in the northern hemisphere is not strong enough for the skin to make vitamin D, or the darker your skin colour the harder it is for you to make vitamin D as the natural skin pigment, melanin, blocks vitamin D production.
Signs and symptoms of low vitamin D
Some of the signs of low vitamin D in adults includes:
- Muscle pains, aches or cramps
- Fatigue
- Bone pain
- Stress fractures
- Low mood
Why Vitamin D testing is important
It is important to test your vitamin D levels to ensure that you are not low or deficient. By testing your vitamin D levels you can then ascertain what level you are at, and therefore if you need a higher or more concentrated dose to restore optimal levels.
Some people are typically more at risk of having a vitamin D deficiency including:
- People over the age of 65
- Those who have darker skin and/or spend most of their time indoors or live in a country with little sunlight
- Certain medication such as steroids or diuretics
- Those who have obesity
- Those with irritable bowel disease (e.g., Ulcerative colitis, Coeliac or Crohn’s) as it is harder to absorb vitamin D from food
- Those who have liver or kidney disease
Optimal vitamin D levels
What your vitamin D level means when using a rapid vitamin D test:
| ng/ml | nmol/l | ||
| Level 1 | < 20 ng/ml | < 50 nmol/l | Critical low Vit D |
| Level 2 | 21 - 30 ng/ml | 52.5 - 75 nmol/l | Long term Vit D deficiency |
| Level 3 | 31 - 40 ng/ml | 77.5 - 100 nmol/l | Sufficient Vit D |
| Level 4 | 41 - 60 ng/ml | 102.5 - 150 nmol/l | Good Vit D |
| Level 5 | 61 - 90 ng/ml | 152.5 - 225 nmol/l | Very good Vit D |
| Level 6 | 90 ng/ml | >225 nmol/l | High Vit D |
Cautions and vitamin D toxicity
As with all supplements, you need to be mindful that you’re not taking too much, which is where testing your vitamin D levels regularly helps. Taking too much vitamin D can affect calcium levels in your body and lead to hypercalcaemia, [2] which can weaken bones and damage the kidneys and heart.
Vitamin D excess can cause toxicity, leading to bone pain, kidney stones or even kidney damage. There has even been a case of hypervitaminosis whereby an individual took 50,000IU a day for several months, which is abnormally high. [3]
Those who have kidney disease have an impaired ability to produce vitamin D, and certain medications, such as anticonvulsants and blood pressure medications, can affect your body’s ability to make or increase the amount of vitamin D. Hence; it is essential to always speak to your GP first before taking a vitamin D supplement.
You cannot overdose on vitamin D from the sun.
Cautions and suboptimal vitamin D
As much as we hear about the risks of too much vitamin D, the reality is that over 80% of the population suffers from drastically low levels, which can be detrimental to your health over time. Vitamin D is fat-soluble and has a half-life of 45 days, and the body only begins to store vitamin D for the winter months when our levels are above 40ng/ml or 100 nmol/l. It’s not something that should be supplemented freely, yet we also need to ensure that individuals are getting enough to bring their bodies to a place of optimal. The best way to do this is on-the-spot vitamin D testing, which gives the person a snapshot of their vitamin D levels at any given point. Testing and waiting for results can lead to some inaccuracies, as vitamin D fluctuates by 10 to 20% throughout the day.
It is also helpful to know that a person needs 10,000 i.u. of vitamin D per 70kg of body weight to push their vitamin D levels up by 1ng/ml or 2.5nmol/l, depending on which metric you use. So once you have the vitamin D results, you can calculate how much vitamin D a person needs per day and for how long before they look to re-test.
If you’re suboptimal and only taking 1,000-4,000IU/day, you may never reach a state of optimal as your body is using up its daily amount without enough to restore the deficit you started with. This is why you must test and understand your level using the chart and then supplement accordingly.
Scientific references
- [1] https://pubmed.ncbi.nlm.nih.gov/32987320/
- https://pubmed.ncbi.nlm.nih.gov/32491799/#:~:text=Toxicity%20of%20vitamin%20D%20leads,manifestations%20and%20symptoms%20of%20toxicity.
- https://pubmed.ncbi.nlm.nih.gov/32354763/