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Study under review: The effect of vitamin D supplementation on survival in patients with colorectal cancer: systematic review and meta-analysis of randomised controlled trials
Introduction
Colorectal cancer affects up to 1.8 million[1] people each year and it is responsible for roughly 850,000 deaths[1] worldwide. There appears to be at least some environmental components[2] to colorectal cancers, as there are major differences in incidence rates based on geographical locations and socioeconomic strata. One hypothesis for the substantial differences in incidence rates is that vitamin D may play a role in the development and progress of several cancers, including colorectal cancers.
There is data linking vitamin D to colorectal cancer. For example, an observational study found that there is an inverse correlation[3] between colorectal cancer incidence rates and sunlight exposure by geographical location. Mechanistically, cultured colon cancer cells[4] divide at a slower rate when treated with vitamin D, compared to when they’re untreated. However, not all research has produced supporting evidence. For example, a Mendelian randomization study did[5] not show a clear causal impact of blood 25-hydroxyvitamin D level on CRC risk. Furthermore, several studies have reported that supplementation with vitamin D does not reduce the risk of developing cancer[6], including colorectal cancer[7]. In addition to prevention, there have been several randomized trials examining the effect of vitamin D supplementation on the progression of already established colorectal cancer. The present study was systematic review and meta-analysis of randomized controlled trials examining the effect of vitamin D supplementation not on incidence of colorectal cancer, but on the survival and progression of disease in participants who had already developed it.
Vitamin D has been linked to colorectal cancer through observational and mechanistic research. Recently, several randomized trials have investigated the role of vitamin D supplementation on slowing disease progression and improving survival among people with colorectal cancer. The present study was a systematic review and meta-analysis of randomized controlled trials examining the effect of vitamin D supplementation on disease progression and survival among people with colorectal cancer.
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Other Articles in Issue #73 (November 2020)
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NERD News: The gut microbiome probably plays a significant role in type 1 diabetes
Recent research provides substantial evidence that gut microbiota can play a big part in new-onset type 1 diabetes.
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Can switching from meat to plant-based meat alternatives reduce cardiovascular disease risk?
This study found that replacing meat with Beyond Meat lowers both TMAO and LDL-C.
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Deep Dive: Does beta-alanine improve training performance?
If there are any effects present, they're mostly small. But small effects can still be worthwhile for some competitive athletes.
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Probiotics for celiac disease
The current evidence is promising but should be seen as preliminary and weak. A lot more research needs to be done to see which probiotics, if any, work well for celiac disease.
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Nerd Nulls: September-October 2020
Know new nulls now!
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Is honey an effective remedy for symptoms of upper respiratory tract infections?
This meta-analysis hints at a small-to-moderate effect, but the overall quality of the evidence ain't great.
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Deep Dive: Reducing common vertigo with vitamin D and calcium
This large, long trial found a pretty strong effect of supplementation on benign paroxysmal positional vertigo recurrence. But there are some problems beneath the surface of these promising findings.
