Vitamin D and Cancer Risk

Review of Am J Public Health. 2006;96(2):252-61.

This article addresses thoughtful questions that were submitted by one of our website users. The website user asked, "Is vitamin D related to cancer risk? Is vitamin D helpful for people who already have cancer?" In this article, Cancer Nutrition Info, LLC addresses these questions. We discuss the results of a recent, very important research review on vitamin D and cancer. We describe how the newest information on the connection between vitamin D and cancer risk can be incorporated into your own cancer-fighting nutrition plan.

Note: Numbers appearing at the end of sentences indicate research references. References are listed at the end of each article.

WEBSITE USER QUESTION

"I have read a lot of information lately about the connection between vitamin D and cancer. Is vitamin D related to cancer risk? Is vitamin D helpful for people who already have cancer?"

CNI ANSWERS

Thank you for your thoughtful question. You may have heard a lot about vitamin D lately because this nutrient has been in the news. A quick search on the internet will give you links to over 1,000 news stories on vitamin D from the last month alone (1)! More and more researchers are studying the connection between vitamin D and cancer too (2-22). And some of this research is looking at how vitamin D may be helpful for people even after they have had cancer (5,7,19). Clearly, vitamin D is a "hot health topic" at the moment.

Other Vitamin D Concerns

Another reason for the recent interest in vitamin D is that more people may have vitamin D deficiency than previously thought. In other words, health experts believe that a very large number of people in the United States and around the world do not get enough vitamin D in their diet for good health (23,24). Research shows that in the United States, up to 32% of young adults are at risk of being deficient in vitamin D (25). These people are felt to have vitamin D insufficiency. In other words, they do not have full-blown vitamin D deficiency. However, they do have very low levels of vitamin D in the body. These low vitamin D levels appear to increase risk of cancer, heart disease, osteoporosis (excessive bone loss) and many other serious diseases.

Even more of a concern is vitamin D for older people and for people with darker skin color. This is because our bodies form vitamin D when sunlight hits our skin. However, our ability to form vitamin D from sunlight decreases as we get older. Also, older people often stay indoors more and are in the sun less. Less sun means less vitamin D in the body.

For people with darker skin, they have a sort of "natural sunblock". This is due to the higher amount of dark pigment in their skin. The darker a person's skin, the less sunlight their skin "absorbs". Again, less sun means less vitamin D. In fact, research shows that up to 42% of African American women have low levels of vitamin D in the body. Up to 12% of these women have actual vitamin D deficiency (25).

Another reason for vitamin D deficiency is that in the winter the sun is weaker in the northern United States. If the sun isn't strong enough, the body cannot use sunlight to make vitamin D. People living in the northern part of the country cannot make vitamin D from sunlight during the winter months (25). Also, too much exposure to the sun will increase the risk of skin cancer (26). For this reason, it is not a good idea to lay out in the sun or rely on only the sun for all of your vitamin D needs.

Many health experts believe that the Recommended Dietary Allowance (RDA) or Dietary Reference Intake (DRI) for vitamin D needs to be raised (27,28). Government and medical health groups make these RDA and DRI recommendations for the amount of vitamins and minerals that people need every day for good health. Health experts are telling these groups that it is necessary to raise these numbers for vitamin D because so many people do not get enough of this nutrient.

Finally, we may not get enough vitamin D from food. Some foods are fortified with vitamin D. This means they have vitamin D added to them. Milk and some cereals have vitamin D added. However, many people don't eat enough milk or fortified cereal to get enough vitamin D. Other than this, vitamin D is not found naturally in many foods (29). Only oily fish, such as salmon, mackerel and sardines naturally contain plenty of vitamin D.

In summary, it is important to study vitamin D for several reasons :

• Many more people may be at risk of not having enough vitamin D in the body than previously thought.
• Many people are at risk of not eating enough vitamin D for good health. Only a few foods naturally contain vitamin D. For this reason, it is hard to eat enough vitamin D from food alone.
• Many people do not get enough sunlight to form vitamin D in the body naturally. Furthermore, too much sun increases the risk of skin cancer. For this reason, sunlight is not the best way to increase vitamin D in the body.
• Many people have darker skin. Having darker skin means that it is harder for your body to absorb enough sunlight to make vitamin D. Being older also makes it harder for your body to make enough vitamin D from sunlight.
• Researchers and health experts feel that the recommendations for how much vitamin D people need for good health should be increased.

Important Research on Vitamin D & Cancer

A group of cancer experts recently looked at all of the available research on vitamin D and cancer (30). They wanted to understand how vitamin D affects cancer risk. The researchers specifically looked at vitamin D and risk of colon, breast, prostate, and ovarian cancers. After reviewing more than 200 research studies on vitamin D and cancer, the researchers reached several important conclusions:

• Twenty out of the 30 studies on colon cancer and vitamin D suggest that vitamin D reduces the risk of colon cancer. In other words, two-thirds (67%) of available research agrees that vitamin D is likely to be protective against colon cancer.
• Nine out of 13 studies on breast cancer and vitamin D suggest that vitamin D reduced the risk of breast cancer. In other words, 69% or almost three-fourths of available research agrees that vitamin D is likely to be protective against breast cancer.
• Thirteen out of 26 studies on prostate cancer and vitamin D suggest that vitamin D reduces the risk of prostate cancer. In other words, half (50%) of available research agrees that vitamin D is likely to be protective against prostate cancer.
• Five out of 7 studies on ovarian cancer and vitamin D suggest that vitamin D reduces the risk of ovarian cancer. In other words, 71% or almost three-fourths of available research agrees that vitamin D is likely to be protective against ovarian cancer.

Why Don't All of the Studies Agree?

Many people wonder why only some of the studies show that vitamin D reduces cancer risk. There are many reasons for this. Sometimes studies are not large enough to get good results. In other words, there aren't enough people in the study to draw solid conclusions between a given factor, like vitamin D and risk of a disease, such as cancer. 

Also, the studies examined vitamin D in many different ways. For example, some of the studies looked at the amount of vitamin D that people ate. Other studies looked at the amount of vitamin D in the body (blood levels). Still other research looked at how much sun exposure a person had. Remember that when the skin is exposed to enough sun, the body can make vitamin D. For this reason, some research studies look at sunlight as a way to estimate how much vitamin D people have in their bodies.

Due to all of these issues, it is very difficult to get complete agreement between studies, even if the studies are on the same topic. In other words, it is very common that some studies show a connection and other studies do not show a connection between a give factor, such as vitamin D and a disease, such as cancer.

The Bottom Line

Even though all the research doesn't agree 100%, we have learned some important things about the connection between vitamin D and cancer:

• Much of the research on vitamin D and cancer shows that having more vitamin D in the body reduces risk of several types of cancer, including colon, breast, prostate and ovarian cancers.
• Many people in the United States do not get enough vitamin D in the diet.
• There aren't very many foods in the diet that contain a lot of vitamin D. For this reason, it is difficult to eat enough vitamin D from food sources.
• Many people do not make enough vitamin D from sunlight exposure.
• Health experts now feel that the RDA or the official recommendation for vitamin D in the diet needs to be raised.
• Due to the difficulty of getting vitamin D from food, many people could benefit from using vitamin D dietary supplements.

Vitamin D For People Who Have Had Cancer

There are not a lot of studies on using vitamin D dietary supplements for people with cancer. However, the studies that have been done tell us that it is important for people with cancer to get enough vitamin D (5,7,19). It is difficult to get plenty of vitamin D from food, so it may be helpful to use a vitamin D dietary supplement.

Safe Use of Dietary Vitamin D Supplements

First, before you decide to take any dietary supplement, including vitamin D, please discuss this with your doctor and your entire health care team. Some dietary supplements can interfere with medications that are used to treat cancer. For this reason, please be sure you talk to your doctor BEFORE you start taking vitamin D or any other dietary supplements.

Use the chart below to focus on eating more foods that contain vitamin D. Use the guidelines below to safely add a vitamin D dietary supplement into your diet. Please keep in mind that too much vitamin D can be toxic. With vitamin D, more is NOT better!

Food Sources of Vitamin D (29)

Food	Serving Size	Amount of Vitamin D Per Serving In International Units (IU)
Salmon	3.5 ounces, cooked	360 IU
Mackerel	3.5 ounces, cooked	345 IU
Sardines, canned in oil, drained	3.5 ounces	270 IU
Shrimp, Mixed Types	4 ounces, cooked	162 IU
Milk, nonfat, lowfat and whole	8 oz (1 cup)	98 IU
Fortified Whole Grain Cereal Bars	1 bar	50 IU
Fortified Cereal	3/4 cup	40-50 IU
Egg (Vit D is in the yolk)	1 whole	25 IU

If you are interested in using a dietary vitamin D supplement and you have discussed this with your doctor to determine that it is safe, use the following tips to select a supplement that will provide a safe amount of vitamin D.

• The type of vitamin D that is used in many studies is cholecalciferol. Studies of using vitamin D supplements in people with cancer have used cholecalciferol too. Another name for cholecalciferol is vitamin D3. Cholecalciferol (vitamin D3) is well absorbed by the body. For best benefit, use a supplement that contains cholecalciferol, which is also called vitamin D3.
• If you take a multivitamin, it probably contains some vitamin D. Be sure that the amount of vitamin D in your multivitamin, any extra vitamin D from a separate dietary supplement and the vitamin D that you get from food do not exceed 2,000 IU of vitamin D per day. 
• When you look at a vitamin D dietary supplement label, the amount of vitamin D contained in the supplement will be listed in either International Units (IU) or micrograms (ug).
• One microgram of vitamin D is equal to 40 IU of vitamin D. This means that a supplement that contains 2,000 IU is the same as a supplement that contains 50 ug (1 ug = 40 IU, so 50 ug = 2,000 IU). Be sure to use this information to pick a supplement with the right amount of vitamin D, which will be listed as either IU or micrograms (ug).
• You may want to take your vitamin D in divided doses. For example, the vitamin D will be absorbed and used by your body more efficiently if you take one dose of 500 IU in the morning and a second dose of 500 IU in the evening.

For more information on good quality vitamin D dietary supplements, please see the following websites:

• ConsumerLab.com
• NSF International
• United States Pharmacopeia

This website list is not an endorsement by Caring4Cancer.com. It is provided for information purposes only.

Finally, please remember to talk to your health care team BEFORE you start taking vitamin D or any other dietary supplements!

If you are in cancer treatment, these diet changes may not be right for you. Dietary supplements can interfere with cancer treatments. For this reason, please discuss your use of any vitamins, minerals, herbs, or other dietary supplements with your health care team. This includes vitamin D supplements.

References

1. News results for Vitamin D. Available at: http://news.google.com/news?q=vitamin+D&hl=en&lr=&sa=N&tab=nn&oi=newsr. Accessed Jan 18, 2006.

2. Holick MF. Vitamin D: important for prevention of osteoporosis, cardiovascular heart disease, type 1 diabetes, autoimmune diseases, and some cancers. South Med J. 2005;98(10):1024-27.

3. Morishita M, Ohtsuru A, Kumagai A, Namba H, Sato N, Hayashi T, Yamashita S. Vitamin D3 treatment for locally advanced thyroid cancer: a case report. Endocr J. 2005;52(5):613-16.

4. Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. Vitamin D and prevention of colorectal cancer. J Steroid Biochem Mol Biol. 2005;97(1-2):179-94.

5. Zhou W, Suk R, Liu G, Park S, Neuberg DS, Wain JC, Lynch TJ, Giovannucci E, Christiani DC. Vitamin D is associated with improved survival in early-stage non-small cell lung cancer patients. Cancer Epidemiol Biomarkers Prev. 2005;14(10):2303-09. 

6. Salazar-Martinez E, Lazcano-Ponce E, Sanchez-Zamorano LM, Gonzalez-Lira G, Escudero-DE Los Rios P, Hernandez-Avila M. Dietary factors and endometrial cancer risk. Results of a case-control study in Mexico. Int J Gynecol Cancer. 2005;15(5):938-45.

7. Porojnicu AC, Robsahm TE, Ree AH, Moan J. Season of diagnosis is a prognostic factor in Hodgkin's lymphoma: a possible role of sun-induced vitamin D. Br J Cancer. 2005;93(5):571-74.

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9. Bertone-Johnson ER, Chen WY, Holick MF, Hollis BW, Colditz GA, Willett WC, Hankinson SE. Plasma 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D and risk of breast cancer. Cancer Epidemiol Biomarkers Prev. 2005;14(8):1991-97. 
 
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11. Berube S, Diorio C, Masse B, Hebert-Croteau N, Byrne C, Cote G, Pollak M, Yaffe M, Brisson J. Vitamin D and calcium intakes from food or supplements and mammographic breast density. Cancer Epidemiol Biomarkers Prev. 2005;14(7):1653-59.
 
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13. Lowe LC, Guy M, Mansi JL, Peckitt C, Bliss J, Wilson RG, Colston KW. Plasma 25-hydroxy vitamin D concentrations, vitamin D receptor genotype and breast cancer risk in a UK Caucasian population. Eur J Cancer. 2005;41(8):1164-69.

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15. Kesse E, Boutron-Ruault MC, Norat T, Riboli E, Clavel-Chapelon F; E3N Group. Dietary calcium, phosphorus, vitamin D, dairy products and the risk of colorectal adenoma and cancer among French women of the E3N-EPIC prospective study. Int J Cancer. 2005;117(1):137-44.

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17. Peterlik M, Cross HS. Vitamin D and calcium deficits predispose for multiple chronic diseases. Eur J Clin Invest. 2005;35(5):290-304.

18. Lin J, Zhang SM, Cook NR, Manson JE, Lee IM, Buring JE. Intakes of calcium and vitamin D and risk of colorectal cancer in women. Am J Epidemiol. 2005;161(8):755-64.
 
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20. Miller EA, Keku TO, Satia JA, Martin CF, Galanko JA, Sandler RS. Calcium, vitamin D, and apoptosis in the rectal epithelium. Cancer Epidemiol Biomarkers Prev. 2005;14(2):525-28. 

21. Hartman TJ, Albert PS, Snyder K, Slattery ML, Caan B, Paskett E, Iber F, Kikendall JW, Marshall J, Shike M, Weissfeld J, Brewer B, Schatzkin A, Lanza E; Polyp Prevention Study Group. The association of calcium and vitamin D with risk of colorectal adenomas. J Nutr. 2005;135(2):252-59.

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26. Abdulla FR, Feldman SR, Williford PM, Krowchuk D, Kaur M. Tanning and skin cancer. Pediatr Dermatol. 2005;22(6):501-12.

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29. USDA National Nutrient Database for Standard Reference. Available at: http://www.nal.usda.gov/fnic/foodcomp/search/. Accessed January 17, 2006. 

30. Garland CF, Garland FC, Gorham ED, Lipkin M, Newmark H, Mohr SB, Holick MF. The role of vitamin D in cancer prevention. Am J Public Health. 2006;96(2):252-61.

Publish Date: 02/2006