There is now considerable evidence demonstrating that having sufficient Vitamin D  in your body might prevent cancers from forming. Although all the actions of Vitamin D are not yet completely understood, there are enough biochemical, genetic and observational studies  to today recommend aiming for Vitamin D blood levels of 100 – 150 nmol/l. In fact a 2016 summary shows a 65% reduction in new cancers when blood levels are above 100 nmol/l (40 ng/ml). Modern research has lead to the understanding that Vitamin D is involved in a complex regulatory process influencing genes, inflammation and behaviour of cancer cells.

Cancer survival appears strongly linked to a good vitamin D supply. In 2019 a large summary of randomised trials showed a 13% survival benefit when taking vitamin D.
Also in 2019 the large US trial of VITAL published a similarly large survival benefit for cancer patients who took vitamin D.

Much research has been performed in the last few years and a summary of all randomised controlled trials in cancer was published in 2023 by a large group of worldwide experts showing that taking vitamin D (more than 400 IU) gave a 12% survival chance in comparison to placebo.

Quality of life and chances of survival may be influenced, and the side effects of chemotherapy  have been shown to be reduced by increasing Vitamin D levels. More and more research is published showing that survival after cancer diagnosis is influenced by higher vitamin D levels.

Vitamin D supports the immune processes that defend the body against infection and the growth of malignant cells. Having sufficient Vitamin D allows your immune system to be in its best working order. People with cancer often have low levels of Vitamin D, so it makes sense to check and improve them where necessary, giving you the best chance of keeping well and fighting the disease.

We advise supplementation with Vitamin D straight away after diagnosis, unless a person’s calcium levels are abnormally high, aiming for a cancer patient target blood level of 130-150 nmol/l. Suggested starting doses are 4-6,000 IU daily (100 -150 mcg). Once Vitamin D levels are re-checked after a few months, the dose of the Vitamin D supplement may need adjustment. Please also note the warnings in our Where To Get Vitamin D section.