Vitamin D and Everything You Need to Know About It

The Biomarker Handbook is a curated series that seeks to provide readers with insights on each biomarker we cover in our blood test packages and its relation to our body.

Vitamin D is a common topic when we speak about our health and wellness. With doctors and health experts often recommending that adults get as much as 1000 IU (International Units) per day of it.

But just what is vitamin D, and why do we need so much of it?

Let us explore this essential vitamin, its health ramifications, and find out why adequate amounts of it are key in maintaining good health.

What is Vitamin D

Vitamin D belongs in the category of fat soluble vitamins, or vitamins which require lipids (fats) for absorption. These include vitamins A, D, E and K, all of which differ from water soluble vitamins, which require only water for absorption by the body.

Due to it being fat-soluble, the body stores vitamin D and other fat-soluble vitamins more readily than it does water soluble vitamins–such as vitamins B and C–which are more easily “washed through” our systems with fluids.

Vitamin D is also responsible for a variety of bodily processes. Such as, calcium absorption, bone growth and the reduction of inflammation.

Plus, it plays a role in the activation of genes which control the release of neurotransmitters, such as serotonin and dopamine. These genes then affect our outlook and mood. Thus, making it essential in maintaining good mental health and wellbeing, along with its other physical health benefits.

Types and Variations of Vitamin D

This vitamin is unique in that it is the only vitamin which is a hormone, and it can either be synthesized by the skin, or consumed in our diet.

Vitamin D also takes on two forms:

  • Vitamin D2: Vitamin D2 is the “plant-based” form of vitamin D. It is produced by plants in response to UV radiation. This is also a common form of vitamin D in fortified foods.
  • Vitamin D3: Vitamin D3 is formed by the skin converting it from cholesterol when exposed to sunlight and is the most biologically active form of vitamin D. It is also crucial in the absorption of calcium and in maintaining strong bone structure.

Testing for Vitamin D

Vitamin D requires a blood test to verify proper levels of it in the body. The test needed is called a 25(OH) D blood test, which can be performed by your doctor, a laboratory, or in-home tests are available as well.

Most health organisations recommend at least 30 ng/ml, and as much as 100 ng/ml of Vitamin D.

However, levels of more than 150 ng/ml are widely considered to be toxic, while levels of under 12 ng/ml are considered insufficient by most organizations.

Frequency of tracking for Vitamin D

Frequency of testing for this vitamin varies from person-to-person, and hinges on a variety of factors. For example, diet, skin pigmentation and weight—all may affect our levels of vitamin D.

For instance, people who avoid Vitamin D rich foods and live in less sunlit areas should go for more frequent testing. This is in comparison to those who consume Vitamin D rich foods such as fish and eggs, and live in areas with abundant sunlight.

Likewise, those of darker skin pigmentation need more frequent testing. This is because our skin’s pigment may impede the skin’s ability to convert cholesterol to vitamin D.

Additionally, as we age, our kidneys become less able to convert vitamin D to its active form. This makes sun exposure, diet and supplementation even more critical as we grow older. It is recommended that levels be tested at more frequent intervals for older people.

How to balance levels of Vitamin D

Typically, the best way to get adequate amounts of vitamin D is through exposure to sunlight, diet, or supplementation.

However, so far as raising vitamin D levels with sunlight, a few factors should be noted:

  • Time of day: The skin produces vitamin D most efficiently from the midday sun.
  • Time of year: Winter and fall are the seasons when the angle of the sun prevents maximum UVB (Ultraviolet) rays. These rays are necessary in the production of vitamin D.
  • Location: The further away from the equator we live, the less UVB rays are available. Those living in tropical climates near the equator, for example, can benefit from sun exposure nearly year-round. However, people in northern climates spend more time with the sun blocked or at a low angle. Thus, they require more supplementation or dietary sources of vitamin D.
  • Pigmentation: The paler the skin tone, the more readily vitamin D is produced. Darker people need more sunlight exposure for vitamin D production. This is as they produce more of the sun-blocking pigment melanin than those fairer skinned. However, lighter skin is more prone to sunburn. Thus, remember to guard against over-exposure to sunlight by using sunscreen, hats or scarves.
  • Sunscreen: Overloading on sunscreen blocks UVB rays, and thus, vitamin D production. This is as limiting your body’s sun exposure actively prevents your body from producing vitamin D.


It is recommended that fair-skinned people get around 10-minutes per day of direct sunlight. This refers to your skin free of sunscreen, extra clothing, or any other means of blocking out the sun’s UVB rays.

Darker skinned and elderly people should also get adequate sun exposure. Additionally, they may choose to add supplements and food sources such as salmon, mushrooms and eggs to their diet.

Doing so can help prevent many diseases, including osteoporosis, cancer, and heart disease. Additionally, it may also prevent depression, over activity of the immune system, and insomnia.

If you’re interested in finding out whether you have a deficiency in vitamin D, take a look at our lifestyle article here!

Interested in other biomarkers, check out the rest of The Biomarker Handbook.

For more information, drop us a message and we will get back to you.

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