Vitamin D and Colorectal Cancer

Colorectal Cancer

Colorectal cancer is a malignant tumor, which is caused by a group of cancerous cells growing in either the colon or rectum. Colon cancer starts in the cells of the colon, whereas colorectal cancer starts in either the colon or the rectum.  Since these cancers are similar, they are usually discussed together. The stage of colorectal cancer is based on the size of the tumor, and whether or not it has spread to other body parts. There are many different things that can increase your chances of developing colorectal cancer. There are some things that you can’t change, like your age or genetics, and some things you can change, like your diet or weight. It is a combination of both genetics and lifestyle factors that increase your risk of developing colorectal cancer. While it is known that there are many things that can increase your chances for developing colorectal cancer, researchers still don’t know exactly what causes colorectal cancer and causes cells to become cancerous. Researchers have found that there is a link between vitamin D and colorectal cancer. People with colorectal cancer tend to have low levels of vitamin D. People who have high levels of vitamin D in their body are less likely to develop colorectal cancer. People with higher vitamin D levels who already have colorectal cancer are more likely to have better outcomes and are less likely to die from cancer. However, research hasn’t been able to show yet that low vitamin D levels cause colorectal cancer. Doctors don’t know yet whether taking a vitamin D supplement, or getting more sun exposure, can help to prevent or treat colorectal cancer. If you have colorectal cancer or you are trying to prevent colorectal cancer and want to take vitamin D, it is unlikely to make your colorectal cancer worse or cause you any harm, as long as you take less than 10,000 IU per day. However, it’s not proven that you will have a better outcome if you have colorectal cancer. It’s also not proven if taking vitamin D will help you prevent colorectal cancer. If you have colorectal cancer, you shouldn’t take vitamin D in place of your treatment medications. Talk to your physician for more advice about taking supplements.

What is colorectal cancer?

Colorectal cancer is a malignant tumor, which is a group of cancerous cells that can grow into other areas around it. Colon cancer starts in the cells of the colon, whereas colorectal cancer starts in either the colon or the rectum.  Since these cancers are similar, they are usually discussed together and called colorectal cancer. Tumors are made when there is a buildup of unneeded, old, or damaged cells and they form a mass, which then becomes a tumor. In colorectal cancer, cancer cells can travel from the colon or rectum to other parts of the body and form new tumors, which is called metastasizing. Tumors can either be benign or malignant. Benign tumors are usually not harmful, whereas malignant tumors are cancerous and can spread to other body parts. When cancerous cells spread, they usually first spread to small organs called lymph nodes. Most of the time, colorectal cancers take several years to develop. A polyp is a non-cancerous tumor that grows in the colon or rectum. Polyps can sometimes change into cancerous tumors. The cancerous polyps can then grow into blood vessels or vessels in the lymph nodes, which makes it easy for the cancer cells to metastasize into other body parts. The stage of colorectal cancer is based on how far the cancer cells have grown into the walls of the colon or rectum, and whether or not it has spread to other body parts. A cancer that is Stage I is early-stage colon cancer. A cancer that is Stage IV is advanced cancer that has grown through all the layers of the colon and has spread to other parts of the body¹.

How common is colorectal cancer?

Colorectal cancer is the third most common cancer in the United States, excluding skin cancers.

Colorectal cancer is the third most common cancer in the United States, excluding skin cancers. Of the two types of colorectal cancer, colon cancer is more common than rectal cancer. About 1 in 20 people will develop colorectal cancer in their lifetime. There are many risk factors for colorectal cancer. A risk factor is something that can affect your chances of getting a disease. There are some risk factors for colorectal cancer that you can’t change, which include¹:

• Age. About 9 out of 10 people who have colorectal cancer are over age 50.
• Personal history of polyps. If you have had polyps in your colon or rectum before, you are more likely to develop colorectal cancer.
• Inflammatory bowel disease (IBD). If you have IBD, which includes ulcerative colitis and Crohn’s disease, you are more likely to develop colorectal cancer.
• Genetics. Some cancers are thought to be related to having unusual forms of some genes.
• Family history of colorectal cancer. If you have someone in your immediate family that has colorectal cancer, you are more likely to get it.
• Race. African Americans have the highest rates of colorectal cancer.

There are also some things related to your lifestyle choices that can increase your chances of developing colorectal cancer. These include¹:

• A diet that is high in red meats and processed meats. When meats are cooked at a high temperature, chemicals are created that may increase cancer risk.
• Type 2 diabetes. If you have type 2 diabetes, you are more likely to get colorectal cancer. Type 2 diabetes can be prevented with a healthy lifestyle.
• Obesity.
• Not getting enough exercise.
• Long-term smoking.
• Drinking more than 2 drinks per day.

What causes colorectal cancer?

While it is known that there are many things that can increase your chances for developing colorectal cancer, researchers still don’t know exactly what causes colorectal cancer and causes cells to become cancerous. Researchers do know that cancers come from strange changes in cells and genes. Some genes have instructions that can control when a cell will grow, divide or die.  For example, genes called tumor suppressor genes can slow cells from growing into cancerous cells. When people don’t have enough tumor suppressor genes, they don’t slow the cancer cell growth, so colorectal cancer is more likely to develop. Another example is that some people might have changes in their DNA which causes them to have more genes called oncogenes, which cause cells to divide faster and make tumors. People can be born with these DNA changes that increase your chances of getting cancer. However, sometimes you can develop these DNA changes over time, rather than be born with them. Since there are risk factors that you can’t change, like age and race, and risk factors you can change, like your diet or smoking, it’s clear that a combination of both genetics and environmental (lifestyle) factors causes colorectal cancer¹.

What is the link between vitamin D and colorectal cancer?

Many studies have shown that there is a link between vitamin D and colorectal cancer. People who have low levels of vitamin D are more likely to develop colorectal cancer. Researchers are still trying to figure out why this is. Vitamin D receptors are found on the surface of a cell where they receive chemical signals. By attaching themselves to a receptor, these chemical signals direct a cell to do something, for example, to act in a certain way, or to divide or die. There are vitamin D receptors in colon and rectal cells, and vitamin D can bind to these receptors. This can cause cells like oncogenes to die or stop growing, and can stop the cancer cells from spreading to other parts of the body.  Therefore, it is thought that vitamin D may help in protecting against colorectal cancer, by making cancer cells less likely to grow and spread. Although there is a link between high levels of vitamin D and protection against colorectal cancer, the relationship is still being studied and needs more experiments².

What does the research say in general about vitamin D and colorectal cancer?

Preventing colorectal cancer

Places where people are exposed to the lowest amount of sunlight have higher rates of colon cancer than people in sunny places.

Places where people are exposed to the lowest amount of sunlight have higher rates of colon cancer than people in sunny places³. Since sun exposure helps you make vitamin D, researchers think that the higher rates of colon cancer may be due to low vitamin D levels. A recent review of many studies found that high vitamin D levels in your body are linked to a lower risk of developing colon cancer⁴. Another review found that people with the highest levels of vitamin D were half as likely to develop colorectal cancer compared to people with the lowest levels of vitamin D. Other studies have found what is called a dose-response relationship, where for each increase in vitamin D levels in the body, there is a decreased chance of getting colorectal cancer⁵. However, most prevention studies on vitamin D and colorectal cancer have been observational, which means that researchers can’t for sure say whether vitamin D can prevent colorectal cancer or not.

Treating colorectal cancer

There have not been any studies done on treating colorectal cancer solely with vitamin D. However, some studies have shown that there is a link between vitamin D levels and colorectal cancer outcomes, such as death from colorectal cancer. A review of many studies involving people with colorectal cancer found that those who had normal vitamin D levels were more likely to survive than those who were low in vitamin D⁶. Research has found that people with advanced stages of colorectal cancer have lower levels of vitamin D than people with early stages of colorectal cancer. Other studies have concluded that exposure to high amounts of vitamin D through sunlight is linked to better survival among colorectal cancer patients⁷. However, these studies were observational, which means that the researchers can’t say for sure whether or not low vitamin D levels can cause worse cancer outcomes.

What does recent research say?

Preventing colorectal cancer

There is a lot of research that links vitamin D to colorectal cancer, which means that getting enough vitamin D may have a protective effect in helping to prevent colorectal cancer. An experiment done in 2006 in the United States^8,9 called the Women’s Health Initiative studied a large group of post-menopausal women. The researchers gave the women either a supplement of 1,000 mg calcium plus 400 IU vitamin D, or a dummy pill for 7 years. There was no difference in your chances of getting colorectal cancer whether you took the calcium and vitamin D pill or the dummy pill. In 2011, different researchers re-analyzed the results from this study because they thought there were some flaws. A lot of the women in the study were taking personal vitamin D or calcium supplements, so the researchers separated these women in their study. They found that:

• Women in the calcium plus vitamin D supplement group had a 17% decreased risk of colorectal cancer.
• Women in the calcium plus vitamin D group who were also taking personal calcium or vitamin D supplements did not have extra protection against colorectal cancer.

Since the experiment didn’t only look at vitamin D supplements, it’s hard to tell for sure if vitamin D is what lowers cancer risk, or if it’s calcium and vitamin D combined. Vitamin D and calcium might work together to lower the chances of getting cancer. The researchers concluded that calcium plus vitamin D supplements can lower the chances of developing colorectal cancer in women. A paper published in 2011¹⁰ looked at 9 different studies involving vitamin D levels and the risk of developing colon or rectal cancer later in life. They found that:

• People with the highest levels of vitamin D in their body had a 50% lower chance of developing rectal cancer, and a 23% lower chance of developing colon cancer than people with the lowest levels of vitamin D.
• There was a stronger link between vitamin D and rectal cancer than vitamin D and colon cancer.

The researchers concluded that low vitamin D levels are linked to higher colorectal cancer risk. However, since the study was observational, researchers can’t say for sure if not getting enough vitamin D can cause colorectal cancer.

Treating colorectal cancer

A study done in 2011 in the United States^11,12 looked at people with polyps in their colon or rectum. Polyps are sometimes benign, but can become cancerous. People with multiple polyps have a high chance of one of them becoming cancerous. The people in the study were divided into 4 groups, one group getting 2,000 mg of calcium per day, one group getting 800 IU vitamin D per day, another group getting 800 IU vitamin D plus 2,000 mg of calcium per day, and another group getting a dummy pill. The researchers then tested their blood to learn about levels of inflammation in their bodies. They found that:

• The people who got vitamin D had 77% lower rates of inflammation than the dummy pill group.
• Supplementation with vitamin D may decrease the inflammation that promotes tumor growth.
• Men in the vitamin D group had a greater decrease in inflammation than the women in the vitamin D group.

This means that people with polyps who have high levels of vitamin D may be less likely to have their polyps turn into colorectal cancer. People with colorectal cancer tend to have more inflammation in their bodies. People with high levels of these inflammatory markers in their body are more likely to have worse outcomes and tumors that spread faster. A study from 2007¹³looked at people with colon cancer who live in one of three regions in Norway that get different levels of sun exposure. The researchers also looked at the season in which the people got diagnosed with colon cancer, and then followed them over 28 years. They found that:

• People with colon cancer living in the area with the highest amount of sun exposure had a lower risk of death from cancer.
• Colon cancer survival outcomes were better for people who were diagnosed in summer or autumn.
• High levels of vitamin D in the body may improve the chances of survival from colorectal cancer.

The researchers concluded that death from colon cancer may depend on the season of diagnosis. People with more exposure to sunlight, and therefore more vitamin D, had better colon cancer outcomes. This study was observational, which means that we can’t say for sure whether getting enough vitamin D can cause better outcomes in colon cancer or not.

Key points from the research

• People who have low levels of vitamin D in their body are more likely to develop colorectal cancer.
• Regions where people are exposed to the lowest amount of sunlight have higher rates of colorectal cancer than people in sunny places.
• Studies have found what is called a dose-response relationship, where for each increase in vitamin D levels in the body, there is a decrease in colorectal cancer risk.
• High levels of vitamin D in the body may improve survival from colorectal cancer.
• Most studies on vitamin D and colorectal cancer have been observational, which means that researchers can’t say for sure whether vitamin D can prevent colorectal cancer or not.
• Overall, more experiments are needed to give clearer answers about whether taking a vitamin D supplement can prevent or treat colorectal cancer.

What does this mean for me?

Research has shown that there is a link between vitamin D and colorectal cancer. People with low levels of vitamin D are more likely to develop colorectal cancer.

Studies have shown that people who get the most amount of sunlight throughout life are less likely to have colorectal cancer.

Studies have shown that people who get the most amount of sunlight throughout life are less likely to have colorectal cancer. People who live in areas with low amounts of sunlight tend to have worse colorectal cancer outcomes, like tumors that spread faster, and increased risk of death from cancer. However, research hasn’t been able to show for sure yet that low vitamin D levels cause colorectal cancer. Doctors don’t know yet whether taking a vitamin D supplement, or getting more sun exposure, can help to prevent or treat colorectal cancer. If you have colorectal cancer or you are trying to prevent colorectal cancer and want to take vitamin D, it is unlikely to make your colorectal cancer worse or cause you any harm, as long as you take less than 10,000 IU per day. However, it’s not proven that you will have a better outcome if you have colorectal cancer. It’s also not proven if taking vitamin D will help you prevent colorectal cancer. If you have colorectal cancer, you shouldn’t take vitamin D in place of your treatment medications. Talk to your physician for more advice about taking supplements.

References

1. American Cancer Society. Colorectal Cancer. 2013. Web. Accessed 16 December 2013. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/colorectal-cancer-facts-and-figures/colorectal-cancer-facts-and-figures-2011-2013.pdf
2. Welsh J. Cellular and molecular effects of vitamin D on carcinogenesis. Arch Biochem Biophys 2012;523(1):107-114.
3. Garland CF & Garland FC. Do sunlight and vitamin D reduce the likelihood of colon cancer? Int J Epidemiol 1980;9:227-231.
4. Stubbins RE, Hakeem A, & Nunez NP. Using components of the vitamin D pathway to prevent/treat colon cancer. Nutr Rev 2012;70(12):721-729.
5. Gorham ED, Garland CF, Garland FC, et al. Optimal vitamin D status for colorectal cancer prevention. Am J Prev Med 2007;32(3):210-216.
6. Buttigliero C, Monagheddu C, Petroni P, et al. Prognostic role of vitamin D status and efficacy of vitamin D supplementation in cancer patients: a systematic review. The  Oncologist 2011;16:1215-1227.
7. Giovannucci E. Epidemiology of vitamin D and colorectal cancer. Anti-Cancer Agents in Medicinal Chemistry 2013;13:11-19.
8. Wactawski-Wende J, Kotchen JM, Anderson GL, et al. Calcium plus vitamin D supplementation and the risk of colorectal cancer. N Engl J Med 2006;354:684-96.
9. Bolland MJ, Grey A, Gamble GD, et al. Calcium and vitamin D supplements and health outcomes: a reanalysis of the Women’s Health Initiative (WHI) limited-access data set. Am J Clin Nutr 2011;94:1144-9.
10. Lee JE, Li H, Chan AT, et al. Circulating levels of vitamin D and colon and rectal cancer: the Physician’s Health Study and a meta-analysis of prospective studies. Cancer Prev Res (Phila) 2011;4(5):735-743.
11. Hopkins MH, Owen J, Ahearn T, et al. Effects of supplemental vitamin D and calcium on biomarkers of inflammation in colorectal adenoma patients: a randomized, controlled clinical trial. Cancer Prev Res (Phila) 2011;4(10):1645-1654.
12. College of American Pathologists. Colon Polyps: Colon Adenomatous Polyps. 2011. Web. Accessed 13 January 2014. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920990/
13. Moan J, Porojnicu A, Lagunova Z, et al. Colon cancer: prognosis for different latitudes, age groups and seasons in Norway. Journal of Photochemistry and Photobiology B: Biology 2007;89:148-155.