March 1, 2018

Is vitamin D a vitamin or a hormone? And why its role is so important?

Contrary to its name, vitamin D is actually not a vitamin but a hormone that is synthesized by sunlight.

Vitamin D promotes the body’s absorption of calcium, which is essential for the normal development and maintenance of bones and teeth. The body must maintain an adequate level of calcium in order to form and sustain strong bones, especially in children and the elderly. It protects against infections by keeping your immune system healthy. It also improves the function of muscles, which can improve your balance and decrease the likelihood of falling and suffering a fracture.

There are two sources of vitamin D: food (mainly eggs, butter, liver and fatty fish) and synthesis by the body in the skin on exposure to ultraviolet rays from the sun. Sunlight stimulates the body to produce vitamin D. Vitamin D is unusual in that, unlike other vitamins, it is produced by the body as well as being available in food.

Calcium surplus and vitamin D deficiency

There is growing evidence that vitamin D deficiency may play a role in prostate cancer development. Data suggesting a link between vitamin D deficiency and increased risk of prostate cancer can be outlined as follows:

  • The Japanese have one of the lowest rates of prostate cancer, and their diet is rich in vitamin D (fish).
  • Elevated consumption of dairy products that are rich in calcium have been associated with an increased risk of prostate cancer; calcium depresses blood levels of vitamin D.
  • As we age, our bodies are less able to manufacture vitamin D. This may partially explain why prostate cancer develops in older men.
  • African Americans have the highest rates of prostate cancer in the world. The melatonin in black skin may interfere with the synthesis of vitamin D.
  • Men who live in colder countries, where there are fewer hours of sunlight, are more likely to develop prostate cancer.


Despite the consumption of foods rich in vitamin D, its intake contribution is insufficient. Because of the northern latitude of Canada and the weak sunlight in autumn and winter, it is recommended that all Quebecers, men with prostate cancer or those at risk of developing one to take vitamin D supplements. Who is particularly at risk?

You’re probably not getting enough vitamin D if:

  • You are over 50
  • You have dark skin
  • You don’t go outside very much
  • You wear clothing covering most of your skin

If you fall into one of these categories, talk to your doctor about whether you should take a vitamin D supplement of 1000 to 2000 IU every day, all year round.

Prostate Cancer – Understand the Disease and Its Treatment
NIH-National Cancer Institute-October 31, 2017
Osteoporosis Canada


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