The People's Perspective on Medicine

Do Vitamin D Pills Lower Your Chance of Cancer?

A study from New Zealand showed no reduction in the chance of cancer for people taking pills with 100,000 IU of vitamin D each month.

Epidemiological studies have shown that people with low levels of vitamin D are more susceptible to various cancers. What can you do to reverse your risk? The answer is not clear.  We do not know if taking vitamin D pills to increase blood levels will lower your chance of cancer. Randomized controlled trials of vitamin D supplements have provided inconsistent results.

High-Dose Vitamin D Did Not Lower the Chance of Cancer:

The latest trial is from New Zealand (JAMA Oncology, online July 19, 2018). More than 5,000 people were randomly assigned to take vitamin D capsules or identical-appearing placebo capsules. Everyone in the study took a pill once a month for about four years. Each monthly dose was 100,000 IU of vitamin D3.

During the study, 400 participants developed cancer or died as a result of cancer complications. These people were in both in the vitamin D group and the placebo group. As a result, vitamin D pills don’t seem to have changed their chance of cancer diagnosis.

The investigators suggest that

“monthly high-dose vitamin D supplementation is not associated with reductions in cancer incidence or cancer mortality…”

Such big doses of vitamin D once a month do not reflect the body’s natural way of daily incremental dosing from the sun. Whether a different dosing schedule would have a different outcome remains to be determined. We will be watching for future studies with more physiologically normal dosing patterns to see if any of them can reduce the chance of cancer.

Learn More:

You can find out more about sources, doses and benefits of vitamin D in our Guide to Vitamin D Deficiency.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies. .
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Agree with comments, and also same questions and concerns as the others in the string! Flawed in so many ways.

Any study that concludes that “substance x” does not seem to help something should always be balanced out with a list of the things substance x DOES seem to help. Something that doesn’t help the heart, for instance, might be good for cancer, brain health, etc. And vitamin D is, in fact, good for many things!

Studies like this are akin to car commercials where they trumpet that Car A has more headroom than Car B — as if that alone seals the deal. Talk about smoke and mirrors!

This is a goofy study. Why is it even an issue?

I took 5000 units of D3/day Plus 1000 included in Calcium pill (for osteoporosis). My lab results after a year was only 1 point above minimum. My arthritis Dr wants me mid-scale to high. Since then upped dose to alternate 10000IU and 15000 every day. I have immune issues causing arthritis and mixed connective disease and adrenal problems. Feel better. Curious see my next lab results.

If the test population were people who were deficient in vitamin D, the results might have differed.

Vitamin D was found yo reduce infamations in addition to Ca inctement of blood+ boned…not more ot not lesd a moderate dose at aging ones seems a must.

From what I have read about Vit. D your levels should be between 70 and 100. I read this study and the treatment groups levels were just 20ng/ml above the placebo group meaning the treatment groups level could not be high enough. The treatment group received 100,000 units per month or only an average of 3333 units per day which is not adequate for high enough levels. I also look who funds these studies but could not find the source.

Good sleuthing, Jim from Florida. You had the pertinent questions and found some answers. I, too, thought the Vit D dosing in the study was peculiar. When my Vit D was low, several years ago, my doctor asked me to take 5,000 IU/day of over-the-counter D3. Now I’ve forgotten how long I did this, but the next time she tested my D levels, they were normal. I still take Vit D3 daily, 4,000 IU and have not experienced any ill effects. The peculiar regimen in this study makes me wonder, too, who funded it.

I always wonder why such studies are considered the ” gold standard.” There is a place near my city that does randomized trials. You stay there and they feed you and medicate you. A lot of the people who participate in the tests have been in many other tests. It seems to me that people who make money being in tests do not have normal, healthy lifestyles. As for testing megadoses of Vitamin D once a month– that is nuts. Were thay also taking Vitamin K? Are they on diets with enough fats? Vitamin D is fat soluble.
Cancer is big business. It sounds like this trial was designed to make people doubt the epidemiological studies. PS I always wonder what is in the identical looking capsules.

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