The Link Between Vitamin D and Cancer

The Link Between Vitamin D and Cancer
The Link Between Vitamin D and Cancer

Scientists think that they may have found the next piece to the cancer puzzle: vitamin D.

In the past, the talk around vitamin D was linked to keeping teeth, bones, and skeletons healthy.

But we now know that a deficiency in vitamin D could possibly increase the risk many cancers, too.

What is Vitamin D?

Vitamin D is a fat soluble vitamin, best known for playing a role in maintaining calcium balance in the body.

Vitamin D also acts like a hormone, with vitamin D receptors found in the bone, gut, brain, breast, nerve, and other tissues.1

The two major forms of vitamin D are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol):

  • Vitamin D3 is the pre-vitamin form found naturally in foods like salmon, pilchards, and egg yolks. Vitamin D3 is also made in the skin when the UVB rays from sunlight are exposed to our skin.
  • Vitamin D2 is the naturally occurring form found in plant foods, like mushrooms.

In the UK, one in five2 people have low vitamin D levels.

In our country, our multi-ethnic population combined with vast differences in climates and the number of hours of sunshine across the large country makes it difficult to know the vitamin D status of South Africans.3

What is the Link with Cancer and Low Vitamin D Levels?

Researchers seem to think that the active vitamin D metabolite, vitamin D3, may stop the spread of cancer cells.4

Vitamin D3 is involved in regulating many of the genes that are responsible for the multiplication and spread of cancer cells.

Vitamin D may also help in immune function and in reducing levels of inflammation, both in cancer patients and non-cancer patients alike.

Vitamin D deficiencies are common in patients with breast cancer5, and evidence suggests that low vitamin D levels may increase the risk for breast cancer development and progression.

Vitamin D deficiency increases the risk of developing ovarian cancer6 and also colon cancer.4

In fact, randomized trials have even shown that vitamin D supplementation may reduce cancer mortality.7

How do we Increase Our Vitamin D Levels?

When we expose our skin to UVB rays from sunlight, the body makes vitamin D.

The more sun you get, the more vitamin D your skin will make.

UVB light cannot pass through glass or sunscreen, making these measures deterrents to increasing your vitamin D levels.1

The amount of sunlight exposure needed depends on factors like skin type, season of the year, and time of day.

While there is no consensus as to how much sun to get, it is safe and sensible to get about 15 minutes of sunlight three times per week on exposed legs and arms with no sunscreen.1

Can I get Vitamin D from Food?

Vitamin D is measured in international units (IU).

The recommended dietary allowance of vitamin D is 600 IU per day.1

Dietary sources usually make up 5-10% of the vitamin D that the body requires.

Vitamin D in the skin lasts twice as long in the blood as vitamin D eaten from the diet.1

Unfortunately, vitamin D is naturally present in few foods.

  • With almost one third of our daily needs in one large egg, eggs are a source of vitamin D. Most of the vitamin D is found in the egg yolk.
  • Tinned fish like pilchards (where you eat the bones) contain some vitamin D. There is also vitamin D in fish like salmon, tuna, and mackerel.
  • Mushrooms are the only plant food that have vitamin D. The amount of vitamin D in mushrooms can be increased simply by leaving your mushrooms in the sun for a few minutes before cooking and/or eating.

Should I Take Vitamin D Supplements?

When exposure to sunlight is limited, vitamin D supplements may be needed.

Vitamin D supplements are available in both forms (D3 and D2). However, high doses of vitamin D2 seem to not be as potent as vitamin D3.

Studies have also shown that taking smaller but more frequent daily doses is more effective in increasing blood vitamin D levels compared to taking much larger weekly or monthly doses.1

A deficiency of vitamin D is diagnosed with less than 12 ng/mL, while 12 – 20 ng/ml is considered insufficient, and above 20 ng/mL is defined as sufficient.

Evidence from new trials show that vitamin D levels above 75 ngl/mL may prevent cancer and improve survival after diagnosis.

To achieve this, 1000–2000 IU per day may be needed.8

There are however currently no recommendations for vitamin D supplementation for preventing and/or treating cancer.8

Since vitamin D is fat soluble, taking excessively high doses for prolonged periods of time may be toxic.

Excess vitamin D causes increased calcium levels in the blood, which deposit in soft tissues like the lungs, kidneys, and heart.

Speak to your dietitian or doctor about taking vitamin D supplementation.

While we wait for more conclusive evidence about vitamin D and cancer, it does not take away the need to continue to follow all the other established cancer prevention guidelines, such as managing your weight through heathy dietary patterns rich in plant foods (e.g. fruit, vegetables, legumes, wholegrains, pulses), with modest meat, fish and dairy, low in alcohol and processed meats, and being active.


  1. Mahan L, & Raymond J. (2017) Krause’s Food and the Nutrition Care Process. Appendix 49; pg. 107, 201,337,1071-1072. .
  2. Buttriss JL. Vitamin D- Sunshine vs. diet vs. pills. Nutrition Bulletin. 2015; DOI: 10.1111/nbu.12172.
  3. Norval M. Vitamin D Status and Its Consequences for Health in South Africa. International Journal of Environmental Research and Public Health. 2016;13:1019. .
  4. Ferrer-Mayorga1 G et al. Mechanisms of action of vitamin D in colon cancer. .
  5. Welsh KJ. Vitamin D and Breast Cancer: Past and Present. J Steroid Biochem Mol Biol. 2018; 177: 15–20. .
  6. Guo H et al. The role of vitamin D in ovarian cancer: epidemiology, molecular mechanism, and prevention. J Ovarian Res 11, 71 (2018).
  7. Sluyter JD et al. Vitamin D and Clinical Cancer Outcomes: A Review of Meta-Analyses. JBMR Plus, 2021;5(1). DOI: 10.1002/jbm4.10420. .
  8. Muscogiuri G et al. Vitamin D and chronic diseases: the current state of the art. Arch Toxicol. 2016. DOI 10.1007/s00204-016-1804-x. .
  9. Wiseman MJ. Nutrition and cancer: prevention and survival. British Journal of Nutrition. 2019;122:481-487.
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