In the last post, we talked about the new report on vitamin D and cancer from the International Agency for Research into Cancer (IARC). In this one, we’ll summarise what the report has to say on the balance between getting enough vitamin D through sun exposure and reducing the risk of skin cancer by being SunSmart.
First, a quick recap:
- Our skin makes vitamin D when exposed to sunlight, which is the major source of this chemical.
- BUT too much exposure to the sun can cause skin cancer.
- Having enough vitamin D is essential for healthy bones, among other things.
- There is growing evidence that bowel cancer is less common in people who get enough vitamin D, but the jury’s still out for other types of cancer.
So the big question is: do vitamin D’s benefits mean that staying safe in the sun will actually do more harm than good? Should people be actively trying to tan for the sake of their health? The answer, according to the new IARC report, seems to be no.
Vitamin D and sun exposure – casual exposures are enough for most people
There is no doubt that vitamin D is important but we need to work out the safest way to increase someone’s vitamin D levels. Encouraging them to spend more time in the sun is unlikely to be the right approach for several reasons, (unless they currently get very little exposure either through dress or not going out of doors when UVB is around).
For a start, the link between skin cancer and ultraviolet radiation from the sun is “well-established” and the rates of this cancer are still on the rise.
Our skin’s ability to create vitamin D peaks after a relatively short burst of UVB, and is always less sunlight than the amount that causes reddening or burning. This is important, and actually very reassuring – it means that, amid all the confusion about sun and vitamin D, the main thing to do is to get some sun exposure, but avoid sunburn. By doing so, it’s possible for everyone to reap the benefits of vitamin D without incurring the risk of skin cancer.
Our skin’s ability to make vitamin D isn’t infinite either. It has a natural cut-off point, to prevent toxic levels from building up, so after a brief amount of UV exposure, extra sunlight does no good.
The report says that light-skinned people reach this point after 5-10 minutes. Beyond that, soaking up more sunlight will not increase vitamin D levels, but will increase the risk of skin cancer. As the report says, “for children and adults, everyday casual exposure to sunlight provides [enough] vitamin D.” But of course, there are so many variables that it’s virtually impossible to make useful estimates of actual times for individuals.
Vitamin D and supplements
IARC say that vitamin D supplements would probably represent the safest way of increasing your levels of this chemical. But they don’t recommend that people actually take these supplements. Why?
We don’t actually know what would happen if you gave well-fed healthy people high doses of oral vitamin D and kept it up for several years. According to the report, it’s “practically never been studied”. Most studies have been limited to weeks or months. They also tended to look at young, healthy people who are most likely to tolerate high doses of vitamin D, rather than elderly people who have the greatest need for it.
On the surface, this seems like unnecessary nit-picking, but IARC is justified in its concern. Sadly, experience has taught cancer scientists to be very cautious when it comes to prescribing vitamin or mineral supplements.
Many studies in the past have found that high doses of vitamin supplements – from beta-carotene to selenium to vitamin E – could actually do more harm than good. While lab studies suggested that they would be beneficial, clinical trials found that they either had no effect or could even increase the risk of cancer and other chronic diseases. And some studies have found that people with very high levels of vitamin D could be just as detrimental as very low levels.
So…
IARC calls for more trials to really pin down the effects of vitamin D supplements – either positive or negative – depending on how much vitamin D people already have in their system.
Until then, they feel that there is no solid basis for changing any existing recommendations about vitamin D.
As such, Cancer Research UK’s line remains the same. Vitamin D is important, but you should be able to make enough through casual, ‘everyday’ sun exposures, and certainly before the point at which your skin starts to redden or burn. Trying to get enough of this vitamin shouldn’t stop you from taking steps to avoid sunburn and protect yourself against skin cancer.
Ed
Comments
Rufus Greenbaum May 19, 2010
A high level of Vitamin D in the blood (25-hydroxyvitamin D) has been shown to be protective against many forms of cancer.
Professor Cedric Garland of UCSD has published scientific papers explaining the protective mechanism.
The key is to get your blood serum level of Vitamin D above 100 nmol/L (40 ng/mL) and preferably above 150 nmol/L (No toxicity below 500 nmol/L)
You can read more about this at: http://www.grassrootshealth.net
This includes a “Call to Action” by a large group of scientists who support this statement.
.
Kaitlynn December 30, 2008
No no no! Everyone has the wrong impression of their health. You do not get any vitamin source from taking a supplment!!! A study has shown that supplments help your health 0% and are a leading profit maker in the US. Shouldent one wonder why the US has the worst health in the world however were consumed with fad diets and supplments that are supposivly good for you? Also, you only need one hour of sun to get enough vitamin D per year. Believe it or not, your body synthesises (makes its own) vitamins A,D,E,K. So those “one a day” pills or whatever your taking, stop using them because you are just peeing out your money!
Gert Schuitemaker, Netherlands December 16, 2008
Your argumentation ‘We stress again that many of the scientists who wrote the new report were chosen for their expertise in the methods used in scientific studies.’
is according to the argumentation theory ‘ad verecundiam’.
My suggestion is to have these experts look at your statement ‘Many studies in the past have found that high doses of vitamin supplements – from beta-carotene to selenium to vitamin E – could actually do more harm than good.’
This meta-analysis where you refer to, have been qualified by peers as follows (NYT, March 13, 2007):
Dr. Stampfer and others say its analysis is methodologically flawed, because it includes data from widely heterogeneous studies, excludes data from hundreds of others for unclear reasons and does not try to detail the causes of increased mortality among supplement users.
Dr. Bernadine Healy, former director of the National Institutes of Health, gives her comment on: http://www.michaelmooney.net/AOStudyUSNewsWR.html .
Bottomline of my comment is that, refering to such a meta-analysis shows bias of the author. Moreover anioxidant supplements do not say anything about vitamin D (as Crestor doesn’t say anything about Aspirin).
Ed Yong December 16, 2008
To answer your points:
In a randomized controlled trial (RCT) (2), a 35% reduction in cancer incidence was associated with increasing serum 25(OH)D from 29 ng/mL to 38 ng/mL.
As stated in the comments in the previous post, on the surface, the results from this trial seem to support the idea that vitamin D supplementation could reduce the overall risk of cancer. But the IARC report concludes that “the statistical analysis of the trial was not correct” and the “design of the trial was biased”. The group who received a placebo had unusually high rates of cancer, which would have increased the chances of finding that vitamin D supplements have a protective effect. The trial also found that calcium supplements alone reduce the risk of cancer to a similar extent as vitamin D and calcium supplements combined. The trial’s results were actually “negative for vitamin D”. We stress again that many of the scientists who wrote the new report were chosen for their expertise in the methods used in scientific studies.
Also, meta-analyses of observational studies of cancer incidence with respect to serum 25(OH)D found that srum [sic] levels of more than 33 ng/mL were associated with a 50% reduction in risk of colorectal cancer (3) and 52 ng/mL for breast cancer (4).
Once again, the report noted that the statistical methods used in the two studies you have cited “were not appropriate”. As said in our earlier post, IARC’s own (and more up-to-date) analysis of the evidence acknowledges that higher vitamin D levels are associated with lower risks of bowel cancer, but that the “evidence for breast cancer is limited”.
Unfortunately, messages from well-meaning organizations to use sunscreen and avoid solar UV irradiance as much as possible seem to have reduced serum 25(OH)D levels in the United States population by 2-4 ng/mL (5).
Your interpretation of the study by Looker et al is disingenuous as they cited sun protection as just one of three behaviours that could have contributed to lower vitamin D levels – the other two are increasing obesity levels and falling milk consumption. Indeed, the IARC report notes that the obesity epidemic could lead to vitamin D deficiency as overweight and obese people have very low levels of this vitamin. Cancer Research UK reiterates that our SunSmart campaign does not advise people to “avoid [UV] as much as possible”, but to take sensible precautions. And we are funding research to find out if following sun protection advice will actually lead to vitamin D deficiency.
Given all the health benefits of vitamin D (6,7), this is unfortunate. In addition, it was reported that use of sunscreens at latitudes greater than 40˚ increases the risk of melanoma (8).
The link between sunscreen and melanoma is often misconstrued. Some studies have unexpectedly found that sunscreens fail to lower the risk of melanoma or could even increase this risk. But this can be explained very simply through the behaviour of sunscreen users. Trials and observational studies have shown that people tend to use sunscreen to increase the time they spend in the sun, eventually exposing themselves to more UV radiation than they would normally receive, and increasing their risk of burning.
As for the recommendation for additional RCTs, they would be useful but, in my opinion, unnecessary. Vitamin D is not an artificial pharmaceutical drug but a molecular substance required for optimal health with which man and other animals have lived forever. Thus, numerous properly designed ecological and observational studies have determined many of the health benefits of solar UVB and vitamin D and have shown few adverse effects for vitamin D at doses of less than 10,000 IU/day. Thus, the call for additional RCTs before changing health policies can only be viewed as an effort to further delay changes in vitamin D recommendations. The sooner that the vitamin D recommendations are changed, the more lives will be saved.
We are not debating that vitamin D is essential for good health. It is clearly vital for good bone health and preventing bone diseases such as rickets and osteomalacia. In the earlier paragraph, you argue that man and other animals have lived with vitamin D “forever”. However, we have also evolved ways of preventing toxic build-ups of vitamin D after intense sun exposure, by limiting the amount of the vitamin that is produced in the skin after a certain time. And this is the key point here. This inbuilt defence does not appear to apply to doses of vitamin D taken through oral supplements. In the light of this, and trials showing that high-dose supplements of other nutrients can increase the risk of some cancers, we support IARC’s call for caution and the need for further clinical trials. The goal is not, as you claim, to “delay changes in vitamin D recommendations” but to amass high-quality evidence to justify such changes, and to show that they will be safe for the general population.
In summary, IARC – an internationally respected organisation – have convened a group of world-class experts across the fields of vitamin D and research methods and have published the most comprehensive publication to date on vitamin D and cancer. Their conclusions are that it is premature to change existing recommendations on vitamin D based on the current evidence.
William B. Grant December 14, 2008
Casual UVB exposures are not enough for most people.
An excellent study of serum 25-hydroxyvitamin D [25(OH)D] levels in British adults throughout the year was recently published (1). Levels ranged from near 15 ng/mL in winter to 30 ng/mL in summer. Since the vitamin D production rate decreases with age due to less 7-dehydrocholesterol in the epidermis, older people would not make as much vitamin D in summer as the 45-year olds did. In a randomized controlled trial (RCT) (2), a 35% reduction in cancer incidence was associated with increasing serum 25(OH)D from 29 ng/mL to 38 ng/mL. Also, meta-analyses of observational studies of cancer incidence with respect to serum 25(OH)D found that srum levels of more than 33 ng/mL were associated with a 50% reduction in risk of colorectal cancer (3) and 52 ng/mL for breast cancer (4).
Unfortunately, messages from well-meaning organizations to use sunscreen and avoid solar UV irradiance as much as possible seem to have reduced serum 25(OH)D levels in the United States population by 2-4 ng/mL (5). Given all the health benefits of vitamin D (6,7), this is unfortunate. In addition, it was reported that use of sunscreens at latitudes greater than 40˚ increases the risk of melanoma (8). The effects of low serum 25(OH)D for England and Scotland have been assessed by Oliver Gillie (9,10).
As for the recommendation for additional RCTs, they would be useful but, in my opinion, unnecessary. Vitamin D is not an artificial pharmaceutical drug but a molecular substance required for optimal health with which man and other animals have lived forever. Thus, numerous properly designed ecological and observational studies have determined many of the health benefits of solar UVB and vitamin D and have shown few adverse effects for vitamin D at doses of less than 10,000 IU/day. Thus, the call for additional RCTs before changing health policies can only be viewed as an effort to further delay changes in vitamin D recommendations. The sooner that the vitamin D recommendations are changed, the more lives will be saved.
Disclosure
I receive funding from the UV Foundation (McLean, VA), the Vitamin D Society (Canada), and the European Sunlight Association (Brussels).
References
1. Hypponen E, Power C. Hypovitaminosis D in British adults at age 45 y: nationwide cohort study of dietary and lifestyle predictors. Am J Clin Nutr 2007; 85:860-8.
2. Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr. 2007;85:1586-91.
3. Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. Optimal vitamin d status for colorectal cancer prevention a quantitative meta analysis. Am J Prev Med. 2007;32:210-6.
4. Garland CF, Gorham ED, Mohr SB, Grant WB, Giovannucci EL, Lipkin M, Newmark H, Holick MF, Garland FC. Vitamin D and prevention of breast cancer: Pooled analysis. J Steroid Biochem Mol Biol. 2007;103:708-11.
5. Looker AC, Pfeiffer CM, Lacher DA, Schleicher RL, Picciano MF, Yetley EA. Serum 25-hydroxyvitamin D status of the US population: 1988-1994 compared with 2000-2004. Am J Clin Nutr. 2008;88:1519-27.
6. Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357:266-81.
content.nejm.org/cgi/content/short/357/3/266
7. Schwalfenberg, G., Not enough vitamin D: health consequences for Canadians. Can Fam Physician, 2007;53:841-54.
8. Gorham ED, Mohr SB, Garland CF, Chaplin G, Garland FC. Do sunscreens increase risk of melanoma in populations residing at higher latitudes? Ann Epidemiol. 2007;17:956-63.
9. Gillie O. Sunlight Robbery. http://www.healthresearchforum.org.uk/reports/sunlightrobbery.pdf
10. Gillie O. Scotland’s Health Deficit: An Explanation and a Plan. August 2008. Oliver Gillie. Health Research Forum Occasional Report #3. http://www.healthresearchforum.org.uk/reports/scotland.pdf
Ingrid Sherman December 11, 2008
So it makes sense to take at least the daily requirement of vitamin D. Also it seems like a good idea to take a supplement with calcium and vitamin D as this would also strengthen and thicken your bones.
Rufus Greenbaum April 1, 2011
There will be a conference about Vitamin D & Cancer on May 18th at BMA House
More at: http://vitamindassociation.org/events.html