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sunRead too many headlines and you might think that everything under the sun causes cancer. And, of course, the sun itself can increase your risk of the disease, because the ultraviolet radiation it puts out is the major cause of skin cancer.

But recently, some researchers have suggested that sunlight could also protect us from cancer – you’ve probably seen stories about it in the media. When sunlight shines onto our skin, we produce vitamin D and indeed, sun exposure is our main source of this chemical. We need vitamin D for strong, healthy bones but some studies suggest that it can also reduce the risk of many types of cancer.

Understandably, this is a fairly controversial issue – how do you balance the need for some sun exposure in order to make enough vitamin D with the need to stay safe in the sun and reduce your risk of skin cancer? And is it true that vitamin D can reduce the risk of cancer at all?

This month, the authoritative International Agency for Research into Cancer (IARC) have weighed in on the issue. By gathering a group of expert scientists, they have looked at all the available evidence and published a detailed report on vitamin D and cancer. The massive tome weighs in at 465 pages, but we’ll take a look at the key points in the first of two posts looking at the vitamin D debate.


Does vitamin D reduce the risk of cancer?

Possibly, according to IARC, although to a lesser extent than is commonly suggested. You’ll often see claims that vitamin D protects against a wide range of different cancers including very common types such as breast, bowel and prostate cancer. But the IARC report paints a different picture.

Much of the evidence that vitamin D could protect against cancer comes from studies looking at how rates of different cancers change depending on where in the world you live. These studies are called “ecological studies” and they have mostly found that the further north from the equator you go, the more likely people are to develop, or die from, many types of cancer.

The big idea is that the sun’s rays are weaker at higher latitudes, so people living in northerly places make less vitamin D. And it’s this that, in theory, accounts for their higher rates of cancer.

But the IARC report heavily criticises this type of research for several reasons:

  • These studies are based on a faulty assumption – that people have less vitamin D the further north they live. In fact, studies in Europe show the opposite trend; people living further north often have higher levels of vitamin D. And in North America, the link between latitude and vitamin D is a weak one.
  • These studies often don’t adjust for other things that vary with latitude and could also explain differences in cancer rates, such a what people eat, how active they are or how wealthy they are.
  • These studies don’t account for differences in the way people behave, such as their desire for a tan, whether they work indoors or whether they go on holidays in sunny places. These things have a much greater effect on a person’s vitamin D levels than simple geography does.

So ecological studies tell us very little about vitamin D and cancer – they are like looking at the issue through a fogged-up pair of glasses. For a clearer view, some studies have looked at individual people, actually measuring the vitamin D in their blood and comparing it to their risk of cancer.

These studies have found that people with higher levels of vitamin D in their blood are indeed less likely to get bowel cancer. So an association does exist. However, the evidence for breast cancer is “limited” – lots of studies have looked into a possible link and their results are so inconsistent that any protective effect could well be a fluke. And “there is no evidence” that vitamin D could reduce the risk of prostate cancer.

What does vitamin D actually do?

So all in all, there is growing evidence that vitamin D is linked to a reduced risk of bowel cancer in some way, but the jury’s very much out for other types. Even then, the IARC report says “The key question is to understand whether low vitamin D status causes an increased risk of cancer… or is simply a consequence of poor health status”. Is vitamin D directly influencing the biology of cells in our bodies, or are vitamin D levels a ‘proxy’ for something else?

There are certainly signs that a person’s levels of vitamin D could reflect their health in general. Many things that increase the risk of conditions like cancer and heart disease are also linked to low levels of vitamin D. These include old age, a high body weight, being inactive, smoking or an unhealthy diet. In at least one large study, the researchers adjusted their results to account for these other factors. They found that this weakened the link between vitamin D and cancer or heart disease.

On the other hand, studies using animals or cells in a laboratory have found that vitamin D could well have direct biological effects. The chemical is good at multi-tasking – it does a large number of jobs in our cells. And according to laboratory experiments, many of these – from stopping cells from growing to causing damaged ones to commit suicide – could help to prevent cancer.

But again, the IARC report advises us to interpret these experiment with care. What happens in laboratory cells may not apply to humans and all too often, researchers have been led down dead-ends by these types of experiments.

Other nutrients, such as beta-carotene or vitamin E, have shown similar anti-cancer abilities in a lab, but failed to deliver on this early promise when supplements were tested in humans. Indeed, in some clinical trials, people who received high-dose vitamin supplements actually had higher risks of cancer. It just goes to show that we have to be very careful when making assumptions about what happens in real people based on what happens in small samples of cells.

So…

So what does this mean for us? Should people be actively seeking out vitamin D supplements, or treating them with caution until more research is done? And should we still bother staying safe in the sun? We’ll see how the new report answers these questions in Part Two.

Ed

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Narek December 31, 2010

The Institute of Medicine (IOM), an advisory group established by Congress, was charged by the U.S. and Canadian governments to gather the existing evidence on the health benefits of vitamin D and calcium, and come up with revised guidelines to help the public and the medical community determine the recommend dietary allowance, or RDA, of each nutrient.

The IOM stated: “That’s not to say that vitamin D will not at some point prove effective in preventing or alleviating conditions other than bone-related fractures; Dr. JoAnn Manson, committee member is currently recruiting for a multicenter study, the Vitamin D and Omega-3 Trial, or VITAL, that aims to do just that. VITAL will involve more than 20,000 healthy subjects who will be taking either vitamin D or a placebo and then followed over a number of years for their risk of developing cancer, stroke and heart disease.

VITAL will be the first such large-scale randomized study to analyze witamin D supplementation in this scientifically validated way, so until those results are released, in another five years or so, the IOM committee declined to make any recommendations about vitamin D’s role in anything other than promoting bone health.

The committee also established upper limits of intake per day, since some studies suggest that megadoses of the vitamin D may not provide any additional benefit, and may actually “cause” harm. Even when it comes to bone health, for example, a recent trial showed that high doses of vitamin D supplementation did not lower the rate of fractures and other studies showed high levels of D increased the risk of kidney stones and other renal conditions.

“This perception that more is better and that everyone should jump on the bandwagon of high doses of vitamin D is of concern until we have evidence from randomized clinical trials that the benefits of such dosing outweighs the risks,” says Manson.

William B. Grant December 30, 2010

The Institute of Medicine (IOM) was under the direction of the U.S. National Institutes of Health and the Food and Drug Administration to limit their review of vitamin D evidence to randomized controlled trials and nested case-control studies with several years follow up between blood draw for 25(OH)D measurement and disease outcome. Thus, they could not include in their review over 90% of the evidence that UVB and vitamin D reduce the risk of up to 100 types of disease. Results from case-control studies for breast and colon cancer indicate a strong inverse relation with respect to serum 25(OH)D level of about 40 ng/ml. Several reviews by vitamin D experts recommend 1000-2000 IU/d or more of vitamin D3 and serum 25(OH)D levels of 30-40 ng/ml. The IOM recommendations and those in the recent joint UK report
http://info.cancerresearchuk.org/prod_consump/groups/cr_common/@nre/@sun/documents/generalcontent/cr_052628.pdf
should be considered the results of bodies reluctant to endorse vitamin D since they benefit from the status quo. Those wishing to maintain optimal health will generally ignore these reports except, perhaps, the portion in the IOM report admitting that there are no adverse effects of vitamin D intakes of 10,000 IU/d.

Narek December 30, 2010

This is interesting: Tuesday, November 30, 2010, Time Magazine reported the findings for the new guidelines for vitamin D intake anounced by the Institute of Medicine (IOM), changed from 200 IU a day to 600 IU for the average adult. The new recommendations are based on data from more than 1,000 studies.

In addition, the report states that contrary to previous claims, most Americans are not lacking in vitamin D, and that the majority of adults are in fact well-supplied with the bone-building vitamin. The discrepancy can be traced to the lack of standardization among labs that test for blood levels of the vitamin.

Different facilities establish varying thresholds for what they consider to be sufficient levels of vitamin D and that can lead to a misleading perception that more people are deficient.

The mistaken belief that Americans are deficient in vitamin D has led some experts to suggest that adults spend more time in the sun, since UV exposure can trigger vitamin D synthesis in the skin. But the committee cautions against that practice, since UV exposure can increase the risk of skin cancer and that risk outweighs the need to boost vitamin D production in the body.

The committee’s advice also applies only to nutritionl requirements to maintain skeletal health, and should not, says committe member Dr. JoAnn Manson, be interpreted to suggest benefit for any other health condition. In recent years, studies have suggested a link between vitamin D supplementation and a lower risk of heart disease, as well as prevention of cancer, Alzheimer’s, diabetes and autoimmune conditions.

But after a thorough review of the existing evidence for those diseases, the committee determined that the data on such supplementation and non-bone conditions was “inconsistent, inconclusive as to the cause and effect, and insufficient to inform nutritional requirements. Most of the data drawing these correlations did not come from rigorous clinical trials that randomly assigned subjects to a vitamin or placebo group.”

vitamin d3 December 25, 2010

I just found out from new research that as yet there is no definitive scientific support for the new model of cancer development, the authors of the study say that maintaining adequate levels of vitamin D could potentially halt the development of cancer at its very earliest stages.

Vitamins for Skin & Hair - Health & Beauty Tips November 29, 2010

Some people argue that we all need a lot more vitamin D and that this is one of the reasons Scotland’s health is so poor

Narek April 22, 2010

Stuart: I am emotional but not biased. I’ve been studying the evidence for nearly 27 years. I sincerely think people, like my own Mom, believe what doctors write in print and don’t question the fact that doctors are just people and not necessarily smarter than anybody. And some, like Dr. Holick, are promoting themselves, selling ridiculous books and making money from the tanning bed industry.

The credible evidence comes from organizations like The American Cancer Society, The Cancer Institute, The Mayo Clinic and of course The Skin Cancer Foundation, among others.

The Skin Cancer Foundation writes: “The latest figures confirm that skin cancer, the world’s most common cancer, is truly an epidemic. There are more new cases annually than the combined incidence of cancers of the breast, prostate, lung, and colon. While skin cancer, particularly nonmelonoma skin cancer, is usually very treatable when caught early, it should not be taken lightly. Skin cancers have a high rate of recurrence, and anyone who has had one runs an increased risk of developing another skin cancer, including melanoma. Additionally, people who have had nonmelanoma skin cancer have twice the risk of developing other malignancies, such as lung, colon, and breast cancers. Melanoma, the deadliest skin cancer, may metastasize(spread) to distant tissues or organs, and can be life-threatening, if not detected and treated quickly.”

If these organizations are not credible to you, then you are the one that is biased.

Stuart April 13, 2010

Narek

With respect, you come across as emotive and biased. Relating anecdotal “evidence and discussing friends/relatives appears out of place in scientific debate.

Narek January 14, 2010

Steve: No disrespect, I don’t think your information is BS. My oldest son is very intelligent with a very lengthy education and has argued with me about UVR for years. He agrees with you on all acounts. I think the bottom line to this arguement is: Is vitamin D3, aquired from the sun only, superior to food or supplements? I think not! There is no evidence of that.

Why get more UVR, which is cumulative, when the safe alternative doesn’t cause cancer? Most of us have already had way too much UVR; why keep getting more?

I know for me, I would be stuck in that cancer world if I had followed the UVR route to get Vitamin D3. Once you get skin cancer, you will most certainly get more. People my age are getting cancers cut off over and over. It’s no big deal to them but I think it means they are also more likely to get other kinds of cancer.

Also, Oxygen is not on the government cancer list. The reason is obvious. And how do you know what goes on behind closed doors in Hamilton’s life? He has the money to get the best fake tan available.

I have an aunt whom was also noted for her dark tan. What most people don’t know about: she has had numerous plastic surgeries to undo the horrible damage the sun did to her skin.

Maybe I am making too big of a deal about this because most people are going to get that glorious tan like I did many years ago but I think if I can get one person to think about what I’m presenting, it’s worth it..

Steve January 14, 2010

Narek: Let’s not fall prey to comparing UV to tobacco, arsenic, 1,2,3-Trichloropropane or any other such item listed on the HHS Report on Carcinogens. Their order of appearance (sequence) has nothing to do with their severity. More importantly… there is NO dose relationship with their inclusion on the list.

Oxygen and water are toxic in high enough dosages. We do not “need” any tobacco or arsenic for survival… but we do need UV light in appropriate dosages (J/m2 Eeff). I take 5mg of rat poison (Coumadin) every day so my artifical aortic heart valve won’t clot. It’s all about dose – not dose rate – regarding UVR or warfarin or beer or everything else in life..

Is George Hamilton in mortal danger after 60 years of tanning without burning. I don’t think so. Was Dean Martin in mortal danger (like the Marlboro man was)for 60 years of cigarettes? Of course!

I sincerely hope your dad didn’t die of internal cancer metastasized from CMM. If so I certainly understand your position re UVR. Mine died from complications of surgery for a broken hip. If we’d taken him out in the sun more as he grew old… maybe his bones would have remained stronger. Albeit he’d probably have grown some more BCC’s.

Speaking of studying UV for many years… me too. If you google (or bing or yahoo) solarmeter or uv meters you will see my website ranked #1 after the paid ads. I know exacty what nm of UVR is effective for what response… EAS weighted or unweighted.

After 20 years of attending NIST/NOAA UV instrument intercomparisons in Boulder, CO… measuring UV on the roof of NIST in Gaithersburg, MD… and working with FDA re tanning bed regulations, etc, etc, I can assure you my replies re UVR are not BS.

Narek January 13, 2010

Steve: The average lifespan only 100 years ago was about 40 years old. Mother nature creates numerous life killing elements and occurrences, from H.I.V. to volcanos. And how many lifeguards do you know personally, to know what the sun did to them?

Being born in 1953, I know way too many people who have had skin cancers and then other cancers after the skin cancer. I just watched my Dad die a painful, horrible death from cancer at the age of 78. He was still young and was not ready to die.

He had the same attitude about the sun that you do and I honestly believe he would be alive if he had just worn a hat while in the mountains he loved so much..Good for you if you have genes that protect you from the same fate but cancer, especially skin cancer, is an epidemic.

I’ve studied about UVR for many years and I’m certain these facts about it’s dangers are not sensationalized, unlike the tanning bed industry and quacks like Dr. Michael F. Holick and Dr. Mercola.

I’ve had way too much sun and paid a big price for it. Back in 1968 my dermatologist recommended sun exposure for my acne. Now days they say it makes it worse.

People are going to believe what they want but in the end, the truth is still the truth…Did you ever wonder what happened to the Marlboro man? The cigarette companies had doctors and scientists saying that tobacco did not cause cancer. How ironic is that?