Vitamin D supplements may reduce the risk of developing advanced cancer

For many years, researchers have sought to pinpoint the tantalizing link between vitamin D and cancer. Epidemiological studies have shown that people living near the equator, where sun exposure produces more vitamin D, have lower incidence and death rates from certain cancers. In cancer cells in the laboratory and in mouse models, vitamin D has also been shown to slow the progression of cancer. But the results of randomized clinical trials in humans have not given a clear answer. The Vitamin D and Omega-3 (VITAL) trial, which concluded in 2018, found that vitamin D did not reduce the overall incidence of cancer, but suggested a decreased risk of death from Cancer. Now, in a secondary analysis from VITAL, a team led by investigators from Brigham and Women’s Hospital focused on the link between taking vitamin D supplements and the risk of metastatic or fatal cancer.

In an article published in the JAMA Network Open, the team reports that vitamin D was associated with an overall 17% reduction in the risk of advanced cancer. When the team looked only at participants with normal body mass index (BMI), they found a 38% reduction in risk, suggesting that body mass may influence the relationship between vitamin D and decreased blood sugar. advanced cancer risk.

“These results suggest that vitamin D may reduce the risk of developing advanced cancers,” said corresponding author Paulette Chandler, MD, MPH, a primary care physician and epidemiologist in Brigham’s Division of Preventive Medicine. “Vitamin D is a readily available, inexpensive supplement that has been used and studied for decades. Our results, in particular the strong reduction in risk observed in people of normal weight, provide new information on the relationship between vitamin D and advanced cancer. “

The VITAL study was a rigorous, placebo-controlled study that took place over a period of more than five years. The VITAL study population included men 50 years of age or older and women 55 years or older who did not have cancer at the start of the trial. The study population was racially and ethnically diverse. VITAL was designed to test the independent effects of vitamin D and omega-3 supplements as well as to test the synergy between the two. Participants were divided into four groups: vitamin D (2000 IU / day) plus omega-3; vitamin D plus placebo; omega-3 plus placebo; and placebos for both. The primary endpoints were major adverse cardiovascular events and cancer incidence. VITAL did not find a statistical difference in overall cancer rates, but researchers did see a reduction in cancer-related deaths.

In their secondary analysis, Chandler and colleagues followed the possible reduction in cancer deaths with an assessment of advanced cancer (metastatic or fatal) in participants who took or did not take vitamin D supplements during the trial. They also examined the possible effect of modifying BMI.

Of the more than 25,000 participants in the VITAL study, 1,617 were diagnosed with invasive cancer over the next five years. This included a wide range of cancers (breast, prostate, colorectal, lung and more). Of the nearly 13,000 participants who received vitamin D, 226 were diagnosed with advanced cancer compared to 274 who received the placebo. Of the 7,843 participants with normal body mass index (BMI less than 25) taking vitamin D, only 58 were diagnosed with advanced cancer, compared to 96 on placebo.

While the team’s findings on BMI may be due to chance, there is previous evidence that body mass may affect the action of vitamin D. Obesity and associated inflammation may decrease effectiveness. vitamin D, possibly by reducing the sensitivity of vitamin D receptors or altering vitamin D signaling. In addition, randomized trials in vitamin D and type 2 diabetes have found greater benefits vitamin D in people of normal weight and no benefit in obese people.

Vitamin D deficiency is common in cancer patients, with one study reporting vitamin D deficiency rates as high as 72% in cancer patients. There is also evidence that higher amounts of body fat are associated with an increased risk of several cancers.

“Our findings, along with the results of previous studies, support the continued evaluation of vitamin D supplementation for preventing metastatic cancer – a link that is biologically plausible,” Chandler said. “Further studies focusing on cancer patients and examining the role of BMI are warranted.”