What is Vitamin D?
Vitamin D is made up from a group of fat-soluble vitamins that helps support your immune system (both innate and adaptive), cellular function, blood sugar regulation, bone health, calcium absorption and circulation, heart and cardiovascular health, and healthy blood pressure. Vitamin D is actually a hormone, not a vitamin, and is required to absorb calcium from the gut into the bloodstream.
In addition, vitamin D directly or indirectly controls over 1000 genes (1), which is approximately 3% of our genome!
Vitamin D comes from three sources: sunlight, specific foods and supplements. It exists in several forms:
- Vitamin D2 (ergocalciferol) is made from inactive provitamin ergosterol in plants by the action of sunlight.
- Vitamin D3 (cholecalciferol) is present in small amounts in some foods.
- 1,25 dihydroxycholecalciferol (calcitrol) is the biologically active hormonal form of vitamin D, which is used by the body to form and maintain strong, healthy bones. Calcitrol is converted from cholecalciferol (vitamin D3) in the liver and kidneys.
How much sunlight should I get?
Sunlight is the preferred source of vitamin D. Vitamin D is sometimes called the “sunshine vitamin” because your body produces it in response to sunlight! Most people do not get enough vitamin D from sun exposure – even those living in sunny climates, like Australia and New Zealand. To get enough vitamin D, most people need about an average of 10-20 minutes a day of midday sun, with the face, arms, hands and legs uncovered (without sunscreen!). Dark skinned people need up to 20 minutes, fair skinned people should aim for 6-8 minutes on most days (2).
Some people may need more than the above recommendation, and at certain times of year – like winter – the sun may not even be strong enough to provide the required vitamin D.
For others, sun exposure may not be appropriate, such as burn or skin cancer survivors.
Use the above as a general guideline, not an absolute rule! And always slip, slop, slap and wrap if you plan to be in the sun longer than 10-20 minutes to protect the largest organ (the skin!) you have.
We can make up to 20,000 IU of Vitamin D in the sun. Sunshine really IS the elixir of life!
What are the best food sources of Vitamin D?
Some of the best dietary sources of vitamin D include oily fish such as salmon, tuna, herring, sardines, mackerel and trevally. Unfortunately, most people cannot get their daily vitamin D requirements from food.
These are some of the richest foods sources of Vitamin D (3):
How much Vitamin D do I need from other sources?
Data from supplementation studies and expert consensus indicate that without adequate sun exposure, a vitamin D intake of at least 800-100 IU/day is required by both children and adults.
In cases of more severe deficiency, some people may need to take more vitamin D than is reflected above. Work with your qualified health professional to figure out the right dose for you, and how long to take it for.
What kind of vitamin D supplement should I take?
The delivery method of the supplement – whether it is in capsule, liquid or spray form, isn’t so important. However, the form of the vitamin D in it is!
Look for supplements that contain vitamin D3, which is superior at optimising and maintaining vitamin D levels long term. If you prefer a plant based option, Vitamin D2 is derived from yeast or mushrooms.
For optimal absorption, take vitamin D with a meal, especially one that contains healthy fats – as a fat soluble vitamin, it is essential for absorption. Research shows that taking vitamin D with the largest meal of the day increased vitamin D blood levels by approximately 50% after just 2-3 months!
How do I know if I’m deficient?
Do you:
- Spend most of your time indoors?
- Slather on sunscreen before going outside?
- Live far away from the equator or are in the winter season?
- Have darker skin?
- Do shift work?
- Are 50+?
- Have chronic health issues?
If you answered yes to any of these questions, you have a higher likelihood of being deficient in vitamin D.
Testing for vitamin D deficiency
The only way to know for certain if you have a vitamin D deficiency is to get a blood test, which you can request through your GP or Naturopath. When you have your vitamin D level measured, the test should look at 25-hydroxyvitamin D, not 1,25-hydroxyvitamin D. 25-hydroxyvitamin D is a prohormone produced by the metabolism of vitamin D in the liver, and is subsequently converted to 1,25-hyroxyvitamin D in the kidneys (see chart, above). However, while 1,25-hydroxyvitamin D is the most active form of vitamin D in the body, it is a short-lived compound and serum levels do not accurately reflect the body’s true level of vitamin D. This is why 25-hydroxyvitamin D remains the best indicator of vitamin D status.
Work with your health professional to figure out if you need to supplement, and if so, what dose to take and for how long.
