Taking vitamin D daily may reduce cancer mortality by 12%

Vitamin D is a vitamin essential to a person’s overall health. It helps with:

A person normally obtains vitamin D either from eating foods high in vitamin D, a supplement, or from exposure to the sun’s ultraviolet rays.

Foods naturally high in vitamin D include:

There are two main types of vitamin D:

• Vitamin D2 is mostly found in plant-based foods and supplements
• Vitamin D3 is mainly obtained through sun exposure and eating certain meat-related foods

Currently, the average recommended daily intake of vitamin D for most people is between 400 to 800 IU (10 to 20 micrograms). The range relates mainly to age, with 400IU recommended for young babies and 800IU for adults ages 71 or older.

Signs of a vitamin D deficiency include:

This is not the first study to look for a correlation between vitamin D and cancer. Researchers have examined vitamin D’s use to lower cancer risk and as a treatment.

Scientists have also studied vitamin D as a preventive measure for specific cancers, such as breast cancer and liver cancer. However, the results have been mixed. For example, a recent review reported that vitamin D supplementation in adults with healthy vitamin D levels did not prevent cancer or provide other demonstrable health benefits.

According to Dr. Ben Schöttker, an epidemiologist and research group leader in the Division of Clinical Epidemiology and Aging Research at the German Cancer Research Center and senior author of this study, he and his team decided to study the impact of vitamin D on cancer mortality as previous trials have provided evidence that cancer mortality is one of the health outcomes that is likely to show a response to vitamin D supplementation.

Additionally, for this study Dr. Schöttker and his team focused specifically on vitamin D3.

“A previous systematic review and meta-analysis showed no effect for vitamin D2 on cancer mortality but an effect of vitamin D3 on cancer mortality,” he told Medical News Today. “One can only speculate on the reasons.”

For this study, researchers analyzed data and findings from 14 studies for a total of almost 105,000 participants. Scientists only included studies where participants had been randomly assigned to receive either vitamin D3 or a placebo.

After reviewing all the data, the research team found no statistically significant results emerged until they considered the dosage each study participant received.

When study participants were intermittently given very large vitamin D3 doses, researchers found no effect on cancer mortality. However, when participants took vitamin D3 daily, the research team found they reduced their cancer mortality rate by 12%.

Additionally, Dr. Schöttker and his team found people ages 70 and older who took vitamin D3 daily benefited the most from the therapy.

“The older you get, the higher your cancer risk,” Dr. Schöttker explained.

“Thus, preventive actions against cancer mortality get more effective the older the patients are. As the cancer risk already starts to increase from the age of 50 on, I personally would already check patients for potential vitamin D supplementation from the age of 50 years on and not only from the age of 70 years on,” he told MNT.

Additionally, the beneficial effect was most evident when vitamin D3 was taken preventatively before a study participant ever received a cancer diagnosis.

“This does imply that basically everyone aged 50 and older, including people who have never had cancer, might profit from vitamin D supplementation if they are vitamin D insufficient.”
— Dr. Ben Schöttker

“This does imply that basically everyone aged 50 and older, including people who have never had cancer, might profit from vitamin D supplementation if they are vitamin D insufficient.”

“Doctors cannot know who might develop cancer at a later time. However, in Germany, the risk [of developing] cancer once in life is very high — 43% for women and 51% for men — and thus, the chance to treat someone who might profit from that in the future is quite high. I guess the lifetime risk to develop cancer is comparable in most other industrialized countries,” Dr. Schöttker added.

There were limitations in the included studies that made it difficult to assess the true impact of vitamin D supplementation on cancer mortality.

For instance, most of the included trials did not test vitamin D levels at the start of the trials, so it is unclear how many of the participants were vitamin D deficient. In addition, while all participants were allocated to either vitamin D3 or a placebo, most of the trials allowed participants in the placebo group to self-medicate with vitamin D supplements.

Medical News Today also spoke with Dr. Wael Harb, a hematologist and medical oncologist at MemorialCare Cancer Institute at Orange Coast Medical Center in Fountain Valley, California about this research.

He explained that while there have been many studies over the years investigating the role of vitamin D and reducing cancer, the data has been conflicting with some studies showing positive results and others showing no benefit.

“We’re always trying to find a lifestyle intervention or supplement that reduces cancer because once a cancer is diagnosed, especially if it’s diagnosed late, the outcome is not always favorable. So, the best way to address cancer is to prevent it in the first place,” he explained.

Dr. Harb said primary care physicians should not only talk with people about their vitamin D levels but also other lifestyle modifications they can make to help lower their cancer chances.

“We know there’s a lot of things that can be done to decrease cancer — avoiding tobacco, being physically active, being at a healthy weight, eating a healthy diet, limiting alcohol intake, avoiding sun exposure, and following the guidelines for appropriate cancer screening.”
— Dr. Wael Harb