What is vitamin D?

Vitamin D is an essential vitamin responsible for numerous body functions, ranging from supporting bone health to regulating the immune system. Unlike other vitamins, vitamin D functions as a hormone, meaning that it serves as a messenger, controlling and coordinating activities throughout the body.

Vitamin D can be obtained from some foods, but the body can also create its own. Often called the “sunshine vitamin”, vitamin D is synthesised by the body when invisible UVB rays from the sun are absorbed by the skin. Vitamin D may also be obtained through supplementation if food intake and sun exposure do not provide enough.

Health benefits of vitamin D

Vitamin D has many important health benefits in the body but the main ones include:

1. Promotes health bones

Vitamin D is essential for maintaining strong, healthy bones. Bone mass is determined by a number of factors, including genetics, physical activity, and nutrition. By age 40, bone mass begins to decline, increasing our risk of fractures and osteoporosis, a condition characterised by low bone mass.

Calcium, a mineral that helps build and maintain strong bones, requires vitamin D for proper absorption. Vitamin D helps the body absorb calcium and maintain adequate calcium in the blood, which promotes bone mineralization. If vitamin D levels are not sufficient, calcium is released from the bones to help maintain blood calcium levels, contributing to soft, brittle bones.

2. Boosts immune health

The  immune system is influenced heavily by vitamin D status. Low levels of vitamin D are associated with increased susceptibility to infection.

Research has also identified a link between poor vitamin D status and multiple autoimmune diseases, including lupus, multiple sclerosis (MS), and rheumatoid arthritis (RA). Deficiency is common in individuals with autoimmune disease, however, improving vitamin D status, though supplementation, diet, and sun exposure, may have protective effects against autoimmune disease.

Vitamin D supports the immune system by stimulating immune cells, such as macrophages and T-cells, that defend the body against harmful pathogens.

3. May delay age-related cognitive decline

Age-related cognitive decline may be associated with vitamin D deficiency. Vitamin D receptors are found throughout the brain and research has shown that vitamin D may have neuroprotective effects.

4. Reduces depression

Research has shown that vitamin D might play an important role in regulating mood and reducing risk of depression.

Signs & symptoms of vitamin D deficiency:

Vitamin D deficiency is very common, affecting almost half of the population. Low levels of vitamin D can have serious consequences and are associated with several health concerns, including diabetes, cancer, osteoporosis, and high blood pressure.

Certain populations are at increased risk of developing a vitamin D deficiency, including older adults, those who live in northern regions of the world, breastfed infants (often a result of low vitamin D status in the mother), individuals with darker skin, people with a BMI ≥30, and individuals with certain chronic conditions affecting fat absorption (e.g., coeliac disease and ulcerative colitis).

Vitamin D deficiency may manifest itself in any of the following ways:

  • Bone pain
  • Chronic fatigue
  • Muscle pain

Sources of vitamin D

There are three key sources of vitamin D – sunlight, dietary sources, and supplements.

1.  Sunlight

Sunlight is a reliable source of vitamin D. When the UVB rays from the sun (the same rays that cause sunburn) come into contact with our skin, cholesterol in skin cells reacts by converting these rays into vitamin D. The success of this reaction depends on the amount of skin exposed to sunlight, as well as the amount of melanin in the skin. Melanin is the pigment that determines the colour of our skin, hair, and eyes. The more melanin your skin contains, the darker your skin, resulting in fewer amounts of UVB rays absorbed by the skin.

How much sun exposure is enough?

Spending approximately five to 30 minutes outdoors, twice per week, between the hours of 10 a.m. and 3 p.m. typically provides enough UVB to meet vitamin D needs. The face, arms, legs, or back, without sunscreen, should be exposed to the sun during this time. It’s important to note that sun exposure can increase the risk of skin cancer, so only spend short periods of time in the sun without protection

2.  Dietary sources

Vitamin D is naturally found in a limited number of foods, as well as in some vitamin D-fortified products. The list below outlines the most common food sources.

Natural food sources of vitamin D include:

  • Beef liver
  • Cheese
  • Egg yolk
  • Fatty fish (e.g., mackerel, salmon, and tuna, sardines)
  • Shell fish
  • Some mushrooms (e.g., chanterelle, maitake, and UV-treated portabella)

Foods fortified with vitamin D often include:

  • Breakfast cereals
  • Dairy products (e.g., milk and yogurt)
  • Non-dairy milk (e.g., soy and almond milk)
  • Orange juice

Since vitamin D is a fat-soluble vitamin, pairing vitamin D-rich foods or supplements with high-fat foods, such as avocados or nuts, can significantly increase absorption.

3.  Supplements

People who spend limited time in the sun, have genetic mutations on their vitamin D receptors, don’t consume enough vitamin D-containing foods, or have low blood levels of vitamin D may benefit from a vitamin D supplement. Vitamin D supplements are typically available in various forms, including capsules, chewable tablets, liposomal, drops and even injections. If supplementing with oral vitamin D, it’s best to consume it with healthy dietary fat such as avocado, nuts and seeds, extra virgin olive oil etc.


Vitamin D is a fat-soluble vitamin and is extremely important for your overall health. Even if you follow a healthy diet, you may require supplements to achieve optimal blood levels. It’s important to talk to your practitioner before taking any vitamin D supplement.

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