What is Colorectal Cancer?
Colorectal cancers are any cancers that start in the rectum or colon. These cancers usually start as polyps, or growths, on the innermost lining of the rectum or colon. Like many cancers, this type can spread very quickly and grow to all the other layers of the colon and rectum; other times it is indolent.
The American Cancer Society predicted that 1 in 21 men and 1 in 23 women in the United States will develop some type of colorectal cancer throughout their lifespan and over 50,000 people die from this cancer every year. This is an alarming number. Once this cancer spreads it needs to be treated aggressively via chemotherapy, radiation or other invasive therapies.
Some risk factors for colorectal cancer include, genetic predisposition, lifestyle (diet, smoking, inactivity), type II diabetes, obesity and a history of polyps. Thankfully, there is something you can do to help protect yourself against developing colorectal cancer, even if you are at an increased risk from other factors.
Research on vitamin D and colorectal cancer
Studies show a connection between vitamin D status and colorectal cancer. One meta analysis showed an inverse relationship between vitamin D levels and risk of colorectal cancer. They also found that patients who had colorectal cancer experienced improved survival rates if they had a higher vitamin D status.
A recent article pooled 17 cohort studies and evaluated the research on circulating vitamin D status and risk of colorectal cancer. The 17 cohort studies consisted of 5,706 participants with colorectal cancer case and 7,107 controls who all had varying levels of circulating 25(OH)D. They considered vitamin D deficiency as levels below 12 ng/mL (30 nmol/L), sufficiency as levels between 20-25 ng/mL (50-62.5 nmol/L), and optimal levels ranged between 30-40 ng/mL (75-100 nmol/L).
Here is what the researchers found:
- Vitamin D levels below 12 ng/mL was associated with a 31% increased colorectal cancer risk (RR: 1.31; CI: 1.05-1.62).
- Those with vitamin D levels between 30 – 34.9 ng/mL experienced a 19% decreased risk of developing colorectal cancer (RR: 0.81; CI: 0.67 to 0.99).
- Vitamin D levels between 35-40 ng/mL was associated with a 27% reduced risk of colorectal cancer (RR: 0.73; CI: 0.59-0.91).
- They also found in women, for each 10 ng/mL (25 nmol/L) increase in circulating vitamin D, there was a 19% decreased risk of colorectal cancer.
The researchers concluded,
“Optimal 25(OH)D concentrations for colorectal cancer risk reduction, 75-100 nmol/L (30-40 ng/ml), appear higher than current IOM recommendations.”
The findings showed that the inverse relationship of 25(OH)D and risk of colorectal cancer was statistically significant in women (p < 0.001) but not statistically significant in men (p = 0.20). This analysis suggests that colorectal cancer risk decreases as circulating 25(OH)D increases up to 40 ng/mL (100 nmol/L).
Vitamin D Council recommendations
Supplementing with 5,000-10,000 IU vitamin D3 per day to help reduce one’s risk of colorectal cancer. If levels > 40 ng/ml are more protective, like in breast cancer, no studies have addressed it. If you have or know anyone with this cancer, we encourage you to reach out to us at email@example.com and tell us your story.
Namery, R. & Cannell, JJ., MD. Vitamin D protects against colorectal cancer. The Vitamin D Council Blog & Newsletter, 6/2018.