Vitamin D may decrease odds of cancer death, but it's not a silver bullet, study finds

20 Aug 2019 --- Vitamin D supplementation reduces the risk of cancer death by 16 percent, according to a recent study published in the British Medical Journal (BMJ). However, vitamin D supplementation alone was not associated with preventing all causes of death, only cancer. The findings reveal another win for vitamin D’s function in human health. However, the leading professor on the study, Dr. Fang Fang, warns that the supplement is no silver bullet for longevity.

“All-cause mortality is the most important outcome for the human. Our results showed that vitamin D supplementation did not significantly reduce all-cause mortality. These findings imply that the widespread use of vitamin D supplementation for adults may be unjustified,” Dr. Fang tells NutritionInsight.

In a response statement to the study, the Council for Responsible Nutrition (CRN) says it “considers the newest findings to be promising” and encourages more studies to be done. CRN also points out that the prevalent deficiency of vitamin D makes it a nutrient of public health concern.

“Everyone, at any life stage, has a nutritional need for vitamin D. It is an essential nutrient, critical to overall health, and yet most people do not get enough. Additionally, the prevalence of vitamin D shortfalls – and the adverse health outcomes affiliated with under-consumption of this nutrient – is why so many healthcare practitioners recommend their patients take a vitamin D supplement,” says Andrea Wong, Ph.D., Vice President, Scientific and Regulatory Affairs at CRN.

Vitamin D in the spotlight
Vitamin D, the nutrient which the skin naturally produces in response to sunlight, has gained traction for its beneficial effects on a range of diseases. Supplementation with the vitamin exhibited the potential to slow the progression of Type 2 diabetes in newly diagnosed patients and those with prediabetes, according to a study published in the European Journal of Endocrinology.

One study showed that patients with Parkinson's tend to have significantly lower levels of vitamin D. All patients who had low levels of vitamin D tended to suffer from falls, insomnia, depression and anxiety more than the other cohort.

In addition, vitamin D screening and supplementation during pregnancy may prevent high blood pressure later in life.

Lastly, another study concluded that vitamin D plays a role in preventing cancer from forming, especially liver cancer. In contrast, Fang’s study only finds that it reduces the likelihood of death by cancer. 

“Vitamin D may operate at multiple stages of carcinogenesis. It may also decrease tumor invasiveness and propensity to metastasize and influence immunomodulatory properties,” Fang notes.

Vitamin D is an essential nutrient, critical to overall health, yet most people do not get enough.No silver bullet
Fang is not quick to draw miracle-promising conclusions from the study. “In my own opinion, researchers have paid much attention to the effect of supplementation of nutrition, especially vitamin D, on preventing diseases. Unfortunately, although observational studies have revealed an inverse association of vitamin D status and life-threatening conditions such as cancer and cardiovascular disease, recently published large randomized controlled trials did not confirm an effect of vitamin D supplementation on preventing these diseases. For example, in the Vitamin D and Omega 3 Trial (VITAL), vitamin D supplementation did not reduce the incidence of cancer,” says Fang.

The incongruent evidence was one of the reasons Fang and researchers took on this topic. “Because of the conflicting evidence, limitations of previous reviews, and availability of new data, we aimed to conduct a systematic review and meta-analysis of randomized controlled trials to evaluate the effect of vitamin D supplementation on all-cause mortality,” reads the study’s introduction.

Type of vitamin D and dosing  
One of the key findings is that the type of vitamin D is influential on health outcomes. “The study found that vitamin D3 supplementation is superior to vitamin D2 supplementation in reduced risk of all-cause mortality and cancer mortality,” says Fang.

“In terms of dosing, there was no significant difference between a high and low daily dose (≥2000 vs. <2000 IU),” Fang adds. Another study from Japan confirms this finding on dosage. The authors concluded that there was a ceiling effect to vitamin D, where taking more did not yield more benefits.

Prevention as medicine
Nutrition continues to be an essential piece of the puzzle in unraveling the causes of cancer and other illnesses. However, experts have noted that engaging with the potential role nutrition may play in cancer prevention has not attracted funding due to the medical over-focus on cure.

One Australian study found that consuming flavonoids reduces the risk of cancer mortality, particularly in people smoke and drink heavily. Meanwhile, the consumption of poultry has been linked with a decreased risk of breast cancer according to another study. 

CRN reports, “taking vitamin D supplements is a safe and appropriate way to achieve healthy levels, especially because vitamin D is not easily obtained through food alone.” The organization also encourages consumers to have their serum vitamin D levels checked.

By Missy Green