Higher levels of vitamin D, serum 25(OH)D may reduce cancer incidence, mortality risk

Key takeaways:

• Higher levels of serum 25(OH)D and vitamin D were both strongly linked to reduced cancer incidence and mortality.
• However, serum 25(OH)D levels seem to be a better indicator for cancer-related mortality.

Higher vitamin D intake and serum 25(OH)D levels may provide significant benefits for cancer incidence and mortality, according to the results of a meta-meta-analysis published in Nutrients.

Low vitamin D levels negatively affect the development and progression of cancer, Mehmet Emin Arayici, AA, RD, BBA, MPH, PhD, a doctoral researcher with the Dokuz Eylul University Institute of Oncology, and colleagues wrote. Therefore, it could possibly affect a patient’s quality of life and general well-being, whether directly or indirectly.

“Increasing evidence strongly suggests that maintaining adequate vitamin D levels may play a protective and pivotal role in reducing the risk of numerous types of carcinoma,” they wrote. “However, conflicting outcomes have been reported in previous primary studies and meta-analyses regarding serum 25-hydroxyvitamin-D (25[OH]D) levels, vitamin D intake, and cancer development and progression.”

So, the researchers conducted a meta-analysis of existing meta-analyses to better understand how vitamin D intake and 25(OH)D affect cancer incidence and mortality.

They used PubMed/Medline, Scopus electronic databases and Web of Science to identify meta-analyses that focused on serum 25(OH)D levels, vitamin D intake and cancer risk, and ultimately included 35 meta-analyses.

In a pooled analysis of a total of 18 reports evaluating serum 25(OH)D level and cancer risk, the researchers found that higher 25(OH)D levels were linked to lower cancer risk (OR = 0.8; 95% CI, 0.72-0.89).

“This result also suggested that serum 25(OH)D levels are a better indicator for cancer risk,” they wrote.

Arayici and colleagues additionally found that higher serum 25(OH)D levels were associated with 26% reduced mortality risk (RR = 0.74, 95% CI, 0.69-0.8). Likewise, they found that higher vitamin D intake was linked to 11% reduced mortality risk (RR = 0.89, 95% CI, 0.85-0.93).

“These results also confirmed that serum 25(OH)D levels are a better indicator for cancer-related mortality,” they wrote.

Subgroup analyses revealed that vitamin D intake did not significantly increase or reduce total cancer risk (OR = 0.99; 95% CI, 0.97-1.01). However, vitamin D intake was connected to significant declines in lung and colorectal cancer risk: OR = 0.88 (95% CI, 0.83-0.94) and OR = 0.89 (95% CI, 0.83-0.96), respectively.

“Our results are compatible with the literature and provide a high level of evidence,” the researchers note. “The results of this study suggest that vitamin D intake and high serum 25(OH)D levels can significantly reduce the incidence and mortality of various cancers.”

However, they wrote that “careful evaluation on the basis of cancer types is recommended.”

Future research, Arayici and colleagues wrote, should emphasize exploring the potential dose-response relationship between vitamin D intake and oncology outcomes, improving study designs, including larger sample sizes and using more precise confounding controls.

“Continual evaluation of the evidence is critical in assessing the changing epidemiological landscape in studies of vitamin D and cancer, as well as in providing a solid basis for medical guidelines and clinical decision-making,” they wrote. “The findings of this study may provide a solid basis for individual decision-making regarding vitamin D in the context of cancer.”