Sunscreen {and the tension with cancer prevention}

I know everyone is probably sick of hearing about sunscreen by now, so I promise this is the last post about it.  There were just so many different aspects to cover-- many more than I had originally thought of.

The more I'm reading, the more I'm learning that skin cancer really is a concern, and I ought not to brush it off as something that doesn't affect me.  Melanoma rates are rising every year in the United States, and overexposure to sun, especially in youth, appears to be linked to an increased risk of developing cancer later in life (1).

If the the melanoma rates really are related to sun exposure, I'm curious what has changed.  For example, common sense would tell me that, in general, the population spends less time in the sun today than 100 years ago, not more.   But yet, the population certainly did not liberally apply commercial sunscreen 100 years ago (2).

I found a few interesting speculations for why sun exposure might be more dangerous today then it was in past decades, and I think this could contribute to the rising rates of skin cancer.  In The Five Paradoxes of Vitamin D (2), Chesney states that between 1600 and 1960 the skies in general where simply darker because of the amount of coal in the air.  Coal and coke were the primary fuel used to heat both homes and industry, and this contributed greatly to hazy skies, especially over cities.  However, between 1950-65 the types of fuels the world used diversified--populations starting using nuclear energy, hydroelectricity, and other non-coal hydrocarbons (2).  In the last several decades there has also been aggressive campaigns to reduce many kinds of emissions from industrialized countries and to promote "clean air".

Another environmental factor that might contribute  to the change of intensity from the sun is atmospheric dimming due to volcanic ash. Four catastrophic volcanoes erupted between 1815 and 1902: Tambora, Krakatoa, Santa Maria, and Mount Pelée.  Tambora, which is in Indonisia, erupted in 1815 and was the most explosive eruption in 1300 years (170 times stronger than the Mt. St. Helens eruption in 1980).  The atmospheric dimming was so noticeable that the following year, 1816 ,is known as "the year without a summer".  Apparently, volcanoes in the 20th century have been less intense and the ash has been more localized which could be one reason dimming has fallen since 1990 (2).

One last environmental factor to consider when thinking about environmental changes is the presence of CFC's in the stratosphere.  When CFC's reach the stratosphere certain chemical reactions cause the depletion of the ozone layer. With the depletion of the ozone layer,  a higher number of UVB rays hit the earth (2) and this could contribute to an increased need for protection from the sun.

To be honest, I'm nowhere near an expert at environmental science.  One question I have about atmospheric dimming is that if it didn't start declining until 1990 (and I believe it's been a pretty gradual decline), then would that really contribute to the increase in skin cancer we see today?  As Mr. L pointed out, that would depend on how long it takes for skin cancer to develop.  Are the effects that noticeable within a 23 year window?  I just don't know enough about the etiology of skin cancer to answer this question.

So, to conclude this series on sunscreen and vitamin D, it appears that it probably is important to protect ourselves from the sun, but this doesn't diminish the importance of vitamin D.  Some studies have associated a deficiency in vitamin D with autoimmune disease, fractures, cancer, and cardiovascular disease (1). A prior NHANES suggested that low vitamin D levels were even associated with all-cause mortality (1).  When thinking about how I should ensure that my family receives enough vitamin D this is a big tension for me, since I prefer not to rely on supplements for essential parts of our diet, but I also don't want to significantly increase our risk of skin cancer (yes, there are dietary sources of vitamin D, but I think it's unlikely that we would get enough from our diet).

I do plan on being more consistent with sunscreen (since at least in one large study it didn't appear to be associated with vitamin D deficiency), but until I'm more convinced that moderate, non-sunburning sun exposure is a significant risk factor for developing skin cancer, I'm still not planning on slathering it on every day.

(1) Dart H, Wolin KY, Colditz GA. Commentary: eight ways to prevent cancer: a framework for effective prevention messages for the public. Cancer Causes Control. 2012 Apr;23(4):601-8. doi: 10.1007/s10552-012-9924-y. Epub 2012 Feb 26. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3685578/?report=reader.  Accessed 7/11/2013.
(2)Chesney, RW. The five paradoxes of vitamin D and the importance of sunscreen protection. Clin Pediatr (Phila). 2012 Sep;51(9):819-27. doi: 10.1177/0009922811431161. Epub 2011 Dec 12. http://www.ncbi.nlm.nih.gov/pubmed/22166748. Accessed on 6/3/13.
(3)Linos E., et al.. Sun protective behaviors and vitamin D levels in the US population: NHANES 2003-2006. Cancer Causes Control. 2012 Jan;23(1):133-40. doi: 10.1007/s10552-011-9862-0. Epub 2011 Nov 2.http://www.ncbi.nlm.nih.gov/pubmed/22045154. Accessed on 7/9/13.  

Sunscreen {protection methods}

Sunscreen is one of many ways we can protect ourselves from the sun, but it's not the only way.  Shade, long sleeves, and hats also work well in protecting us.  I was surprised to learn that people who tend to seek shade and wear long sleeves where more likely to be vitamin D deficient than people who reported regularly using sunscreen (1).  Part of the reason this surprised me is that for years I've thought in the back of my head that sunscreen was greatly contributing to the epidemic of vitamin D deficiency, but inasmuch as my reading has shown me, this is probably not the case.  

The CDC started The National Health and Nutrition Examination Survey (NHANES) in the early 1960's to conduct nation-wide surveys to gather statistics of various population groups and health topics.  In 1999 the program became an ongoing survey that examines about 5,000 people each year regarding emerging health and nutrition topics.   The data NHANES collects is available for researchers to analyse and use, or for agencies to utilize in evaluating and implementing health policy.  One example of NHANES data in use is the growth charts that doctors use to see how well babies and children are growing (2).

Between 2003-2006 NHANES collected data regarding sun protection habits and the levels of vitamin D in participants' blood.  Linos, et al., analysed this data and published a paper examining what they found (1).  Below is a graph from their paper that illustrates part of what they found-- that for all races combined, two factors, staying in the shade and wearing long sleeves, were significantly associated with lower vitamin D levels, while frequency of wearing hats or using sunscreen were not associated with lower vitamin D levels.

The NHANES data is a survey intended to gather information about the population at a specific point in time--this study design is called a cross-sectional study.  Cross-sectional studies are the simplest of all study designs, but also one of the weakest(3).  This type of study is often used to asses prevalence; for example, in this paper the authors measured the prevalence of vitamin D deficiency in different subsets of the population.  The major weakness of this design, however, is that because of the lack of any time dimension (all data is gathered at the same time) it is extremely difficult to establish any semblance of causality (3).  Because of this major design limitation we need to be careful not to make too strong of a conclusion from this study.

I think what they found is interesting-- I wouldn't have guessed that sunscreen was not associated with  vitamin D deficiency, but that shade and long sleeves were associated.  Although we certainly can not say that shade and long sleeves cause deficiency it is instructive to consider this association when thinking about our sun protection options.  We should realize that it's possible that protective clothing may be much more effective at protecting us from the sun than sunscreen-- this may be good or bad depending on what your goals are.

Although causality can't be established by this study, I still think it makes a fairly strong case that sunscreen is not single-handedly causing the epidemic of vitamin D deficiency.  For me, I think this means that I'll worry less about using sunscreen, but also that in certain situations I'll be more likely to seek shade, since that is apparently one good way to protect myself from overexposure to the sun.

Photo Credit: Sanny Hauck

References:
(1)Linos E., et al.. Sun protective behaviors and vitamin D levels in the US population: NHANES 2003-2006. Cancer Causes Control. 2012 Jan;23(1):133-40. doi: 10.1007/s10552-011-9862-0. Epub 2011 Nov 2. http://www.ncbi.nlm.nih.gov/pubmed/22045154. Accessed on 7/9/13.  
(2) National Center for Health Statistics.  National Health and Nutrition Examination Survey 2013-2014 Overview: Let's Improve Our Health. http://www.cdc.gov/nchs/data/nhanes/nhanes_13_14/2013-14_overview_brochure.pdf. Accessed on 7/11/2013
(3) Elwood, M. Critical Appraisal of Epidemiological Studies and Clinical Trials: Third Edition. Oxford: Oxford University Press, 2008.  p. 25-6, 46. 

Sunscreen {a historical perspective}

I've always thought that sunscreen smells bad, feels bad, and is just generally inconvenient. Since I also know that vitamin D is important for many reasons, and your body synthesizes it from the sun, I generally use the excuse of “getting my vitamin D” for not applying sunscreen as often or as liberally as recommended.

Since sunscreen season is fully upon us, I thought a post (or perhaps a series of posts)
looking at what the evidence has to say about sunscreen would be timely. Today we’ll start with a historical perspective.

In The Five Paradoxes of Vitamin D and the Importance of Sunscreen Protection, Russell Chesney takes time to look at the history and relationship between vitamin D and sunshine. Below is a short summary and review of his journal article published in Clinical Pediatrics.

Rickets, a vitamin D deficiency disorder, first emerged in England around the start of the industrial revolution and reached epidemic proportions by 1650. At first, it was puzzling that rickets was much less prevalent in the tropics and in rural areas, but as the link between vitamin D and rickets and the sources of vitamin D became known, this observation made sense. By 1930, it was well understood that vitamin D deficiency caused rickets and that there were 2 “sources” of vitamin D, a substance found in cod liver oil, and sunshine. Due to the nature of extreme latitudes, the coal in the air above cities to filter the sunlight, and the habits of city dwellers, it made sense that those who lived in cities would receive less sunlight, and therefore be more susceptible to vitamin D deficiency and rickets.

In 1931, The Children’s Bureau strongly advised parents to suntan infants and give them cod liver oil. At this time in history, the value of sunlight exposure was highly stressed, while there was little thought given to potential skin damage. (How far we have swung to the other side, when we now recommend little to no sun exposure for the first 6 months!)

Around 1985 it was observed that skin cancer rates were increasing. With this observation came the real fear of developing skin cancer from exposure to sunlight. Sun exposure recommendations therefore changed, and today the AAP and the American Academy of Dermatology recommend shelter form sun and liberal sunscreen use. However, adhering to these recommendations necessitates vitamin D supplementation by mouth in order to prevent deficiency.

It is interesting to me, but not surprising, that opinions of whether vitamin D should be absorbed from the sun or ingested through diet/supplements are highly influenced by the current opinion concerning the potential harmfulness of the sun.

It’s estimated that a large percentage of the United States is vitamin D deficient, and I’m curious if this could be related to our sun protection behaviors. Also, is there any reason that the sun might be stronger today and consequently require more “protection” from than in the past? Or is this obsession with sun protection just a result of our safety obsessed society? Next week, I hope to address some of these questions.

But enough of me talking, what is your relationship to sunscreen? Do you practically hate it too?

References:
Chesney, RW. The five paradoxes of vitamin D and the importance of sunscreen protection. Clin Pediatr (Phila). 2012 Sep;51(9):819-27. doi: 10.1177/0009922811431161. Epub 2011 Dec 12. http://www.ncbi.nlm.nih.gov/pubmed/22166748. Accessed on 6/3/13.

Vitamin D and Baby

The other day I finally did it, I bough a vitamin D supplement for Baby.  I still feel slightly guilty both for buying it, and for the fact that I hadn't bought it sooner (he'll be 6 months this week).

You see, I've known for some time that the both the American Academy of Pediatrics and the Center for Disease Control recommend a 400 IU vitamin D supplement for exclusively breastfed infants.  We were also sent home from our stay in the NICU with multivitamin drops I was theoretically supposed to mix with formula or milk and then feed to Baby.  Well, I wasn't going to give Baby formula, and it just seemed so inconvenient to pump just to turn around and immediately give a bottle-- it seems like so many extra, and unnecessary steps.  I know our wonderful pediatrician mentioned the need for vitamin D at one point as well.  So, yes, if my son has a vitamin D deficiency it is solely my responsibility.  And therefore, as you could guess, this is why I feel guilty for not having bought it sooner.

But, I'm stubborn.  I don't like supplements-- you could say it's a pet peeve of mine.  I feel like I ought to be able to get all the vitamins I need from my diet and a healthy lifestyle (spent anytime outside lately for your vitamin D?).  The only time I've even semi-consistently taken vitamins or other supplements is during pregnancy.  I suppose all of the hype surrounding neural tube defects and folic acid influenced me and I decided the potential benefits outweighed the risks.

To take the time and thoroughly research vitamin D supplementation has been on my mental to-do list since shortly before Baby was born, but to be honest I still haven't really gotten around to it.  By purchasing the supplement I feel like I caved in to pressure and am conforming to the norm without knowing if this is really best.  I know this is silly, but this is how my mind works...I want to know why, and just knowing that it's recommended isn't enough.

On an unrelated note, the supplement contains artificial coloring.  I asked the pharmacist if it were possible to find one without artificial coloring, and she seemed skeptical.  Even the supplements she had behind the counter contained artificial color.  Perhaps there is some available somewhere -- I'd love a link if you know of a place that sells some.

That said tough, after considering what I know of the benefits and risks, I've decided to swallow my pride and add the vitamin D supplement to Baby's diet, even without actually doing the research myself.  Perhaps this is keeping with my evidence based theme, or perhaps not.  I could see it both ways.  At least I've 'fessed up to it.

Here's hoping Baby will swallow the drops!