A recent meta-analysis published in the journal Cancer Causes Control suggests that for each 4 ng/ml (10 nmol/L) increase in vitamin D status, the risk of lung cancer reduces by 5%.
Lung cancer is the most frequently diagnosed cancer worldwide, responsible for approximately 13% of new cancer events and 20% of all cancer deaths. The prognosis of lung cancer is very poor, with a 5-year survival rate of 16% in the United States. With the exception of avoiding tobacco, very few preventative measures have been identified. Thus, researchers have begun to investigate other potential modifiable risk factors of the disease.
Research suggests that vitamin D protects against cancer through its anti-proliferative effects and regulation of programmed cell death. A meta-analysis from the past summer concluded that high vitamin D status was associated with a lower risk of lung cancer. However, this meta-analysis included two studies that used the same sample population and the same data. In hopes of further clarifying the relationship between vitamin D status and risk of developing lung cancer, researchers recently conducted a dose-response meta-analysis.
The researchers analyzed data from ten prospective studies that were published between 2006 and 2015, totaling 2,227 lung cancer events and 120,402 participants. All but one study followed the participants for over 10 years.
They found a significant 5% reduction in the risk of lung cancer associated with each 4 ng/ml increase in vitamin D levels. This relationship did not significantly change after adjusting for confounding factors.
The researchers noted that the greatest reduction in risk was observed at levels ranging from 21 ng/ml (53 nmol/l) to 36 ng/ml (90 nmol/l). Vitamin D levels above this range did not show any significant benefit; however, there was limited data available for higher levels.
The researchers concluded,
“Findings from this dose-risk analysis of prospective studies reveal a significant 5 % (95 % CI 1–6 %) reduction in the risk of lung cancer for each 10 nmol/L increment in 25(OH)D concentrations.”
The researchers pointed out both the study’s strengths and its limitations. The meta-analysis included a very large sample population, which provided the researchers with the ability to detect even mild inverse associations. In addition, all studies were of prospective design, which reduces the possibility of biases. However, the study did not adjust the results for diet, which could be a confounding factor. The researchers stated the possibility that, “Higher circulating 25(OH)D may be simply a marker of other healthy behaviors that cause lower lung cancer.” They also lacked sufficient data of high vitamin D levels, limiting their ability to analyze the benefits of higher vitamin D levels on lung cancer.
The researchers call for clinical trials to assess whether vitamin D supplementation may reduce the development of lung cancer.
Tovey, A. & Cannell, J. Meta-analysis reports high vitamin D status may reduce the risk of lung cancer. The Vitamin D Council Blog & Newsletter, 2015.