Get ready for a big fracas among oncologists: "In June, U.S. researchers will announce the first direct link between cancer prevention and the sunshine vitamin. Their results are nothing short of astounding." (Globe and Mail, April 28). A lot of people are going to find this hard to swallow.
More the Globe's Martin Mittelstaedt:
A four-year clinical trial involving 1,200 women found those taking the vitamin had about a 60-per-cent reduction in cancer incidence, compared with those who didn't take it, a drop so large -- twice the impact on cancer attributed to smoking -- it almost looks like a typographical error.
...
One of the researchers who made the discovery, professor of medicine Robert Heaney of Creighton University in Nebraska, says vitamin D deficiency is showing up in so many illnesses besides cancer that nearly all disease figures in Canada and the U.S. will need to be re-evaluated.
I think the Globe exaggerates the newness of the story. For example, there's this from New Scientist two years ago, referencing a study on prostate cancer from 15 years before that:
Back in 1990, Schwartz noticed that people at a high risk of prostate cancer were similar to people at risk for vitamin D deficiency: they often lived in northern latitudes, had darker skin and were old. Vitamin D is produced in the skin as a reaction to ultraviolet light and it subsequently metabolised in the liver and kidneys to form "active" vitamin D.
Since then, numerous studies have unearthed a link between sunny lifestyles and reduced prostate cancer risk.
And again from New Scientist, back in 2003, a more general approach to the topic:
Every summer we are bombarded with official warnings to avoid all exposure to the sun's cancer-causing rays. But what if the official advice is wrong? A handful of dissidents around the world say that shunning sunshine actually increases our risk of cancer. They argue for a more balanced approach: as long as people don't go over the top, moderate sun exposure is beneficial, they say. (sorry, this one's subscriber only)
This is bad news for Canadians and other hyperborean dwellers. According to researchers, between March and October in the higher northern latitudes, the sun's radiation isn't powerful enough to produce Vitamin D (and it's vital hormonal breakdown product). I'm not sure I buy that for Torontonians, although it does make sense for those few who live above the Arctic Circle.
Read the whole thing. If you're pressed for time (appointment with the tanning salon perhaps?) the best lines come at the end:
Some may view the sunshine-vitamin story as too good to be true, particularly given that the number of previous claims of vitamin cure-alls that subsequently flopped. "The floor of modern medicine is littered with the claims of vitamins that didn't turn out," Dr. Cannell allowed.
But the big difference is that vitamin D, unlike other vitamins, is turned into a hormone, making it far more biologically active. As well, it is "operating independently in hundreds of tissues in your body," Dr. Cannell said.
Referring to Linus Pauling, the famous U.S. advocate of vitamin C use as a cure for many illnesses, he said: "Basically, Linus Pauling was right, but he was off by one letter."
- Log in to post comments
http://www.healthnewsreview.org/review/review.php?rid=880
I think this reviewer raises key points to think about when reading these sorts of news stories. Far too few of the recent spurt of vitamin D news stories fail to mention populations for whom supplementation might be risky.
I added this reference to the Wikipedia this morning, then in the talk page I did a back of the text-box calculation that a cancer rate in women of 300/10,000 annually, you might expect 14 cancers in a study of this duration, with a standard deviation of 3.8. There is certainly scope for the two sides of the study to divide 10 and 4 rather than 7 and 7 by chance alone, but not often.
As for the required UV radiation required for the skin to manufacture vitamin D, anyone who has ever watched a sunset knows that the low solar elevations eliminate the blue wavelengths (and even more the unseen ultraviolet) and turn the sun orange/red. The required solar elevation in the well-referenced Wikipedia article to produce the necessary UV spectrum is 45 degrees, which Toronto only achieves for six months of the year. Unfortunately for Torontonians, basking in your own arrogance doesn't count, but perhaps that solar gully beside that giant gold bank tower has its uses.
The recommended UV exposure is 15 minutes on the face and arms with the sun high in the sky twice a week. Anything more than this produces no additional vitamin D, but does continue to fry your skin. At high UV indexes, even 15 minutes is too much for one exposure.
I "buy" it for anyone north of Kansas City. rb
Regarding the time to make vitamin D in Canada. Much of the population of Canada lives at the latitude of Toronto (44 N). That is near the latitude of Hobart, Tasmania (41 S), so times to make vitamin D there can be a guide. However, the earth-sun distance in the Austral summer is a few percent less than during the Boreal summer and stratospheric ozone levels are lower and Tasmania is a few degrees to the south. With that in mind, it takes 14 minutes at noon in summer with 15% of a pale-skinned (type II skin), young body to generate 500-1000 IU of vitamin D3. We are now recommending 1000-2000 or more IU/day for optimal health, based on a number of studies. The paper by Samanek et al. can be obtained by searching www.pubmed.gov and making the appropriate clicks. Other work on UVB and vitamin D can be found there as well.
Solar UVB has been found inversely correlated with about 20 types of cancer and, more recently, with several types of viral diseases, explaining why they are more common in winter. Another risk factor associated with winter viral diseases is cold temperature.
Vitamin D3 (cholecalciferol) supplements is a reliable way to obtain vitamin D on a regular basis.
Med J Aust. 2006 Apr 3;184(7):338-41.
Estimates of beneficial and harmful sun exposure times during the year for major Australian population centres.
* Samanek AJ, * Croager EJ, * Giesfor Skin Cancer Prevention P, * Milne E, * Prince R, * McMichael AJ, * Lucas RM, * Slevin T.
Genomics Directorate, WA Health, Perth, WA.
OBJECTIVE: To examine the influence of geographical and seasonal factors on duration of solar ultraviolet (UV) radiation exposure of skin to produce recommended vitamin D levels without producing erythema. DESIGN AND SETTING: An ecological study using daily Ultraviolet Index (UVI) data collected in major population centres across Australia for 1 year (1 January - 31 December 2001) to calculate sun exposure times for recommended vitamin D production and erythema. MAIN OUTCOME MEASURES: Sun exposure times to produce either serum vitamin D concentrations equivalent to an oral intake of 200-600 IU/day or erythema for people aged 19-50 years with fair skin (Fitzpatrick type II skin) exposing 15% of the body. RESULTS: In January, across Australia, 2-14 minutes of sun three to four times per week at 12:00 is sufficient to ensure recommended vitamin D production in fair-skinned people with 15% of the body exposed. However, erythema can occur in as little as 8 minutes. By contrast, at 10:00 and 15:00, there is a greater difference between exposure time to produce erythema and that to produce recommended vitamin D levels, thereby reducing the risk of sunburn from overexposure. From October to March, around 10-15 minutes of sun exposure at around 10:00 or 15:00 three to four times per week should be enough for fair-skinned people across Australia to produce recommended vitamin D levels. Longer exposure times are needed from April to September, particularly in southern regions of Australia. CONCLUSION: Our study reinforces the importance of existing sun protection messages for the summer months throughout Australia. However, fair-skinned people should be able to obtain sufficient vitamin D from short periods of unprotected sun exposure of the face, arms and hands outside of the peak UV period (10:00-15:00) throughout Australia for most of the year. The greater variability in sun exposure times during winter, means that optimal sun exposure advice should be tailored to each location.
Toulouse (S. of France) - latitude 43 degrees N
Toronto - Latitude 44 degrees N
London - Latitude 51 degrees N
Edinburgh - Latitude 55 degrees N
Toronto is hardly a 'northern' city. 90% of Canadians live within 100 miles of the US border, I believe.
I can tell you having lived in all 3 Anglo-Saxon cities that Toronto in a normal year has more cloud free or cloud partial days than the other two. And Toronto has snow (sometimes) which when it is not brown and grey, reflects even more sunlight onto skin.
*however* Toronto is very cold in winter, and very hot in summer, which encourages staying in climate controlled indoors.
I think the 'vitamin D' problem is more of a function of dark-skinned immigrant groups (particularly Asians and Afro-Carribeans) moving to places like the UK, plus the increased affluence of lifestyles (universal air conditioning) which tends to drive people indoors.
The shift away from fresh fruit and veg in the diet is also probably a problem. From memory, Canadian milk has vitamin D added.
This http//www.ajcn.org/cgi/content/full/85/1/6
Risk assessment for vitamin D should set anon's mind at rest.
www.vitamindcouncil.com/vitaminDToxicity.shtml have useful information on Vit D3 toxicity. Their links page also leads to some cheap suppliers of high strength Vit D3 that may be useful for those who are unable to get out into the sun when the UVB ratio to UVA is most beneficial.
www.ajcn.org/cgi/content/abstract/85/3/860 Hypovitaminosis D in British adults at age 45 y: nationwide cohort study of dietary and lifestyle predictors show a Vitamin d insufficiency in White UK adults is such that 60% remain insufficient throughout the year and it's about 9 out of 10 insufficient in Winter.
Several Vit d scientists are suggesting that levels under 100nmol/L probably all less than ideal so the goal posts are moving to an even higher minimum threshold.
Vitamin D insufficiency is defined as a 25OHD concentration of 20 to 30 ng/mL (50 to 75 nmol/L)(ng/mL times 2.5 gives nmol/L),
Mad dogs and ....
"How can vitamin-D deficiency exist despite lengthy sun exposure? This apparent paradox was raised in my last post. The medical community now recommends bloodstream vitamin D levels of at least 75-150 nmol/L, yet these levels are not reached by many tanned, outdoorsy people.[...]
Only mega-doses can overcome what seems to be a homeostatic mechanism that keeps bloodstream vitamin D within a certain range. Indeed, this range falls below the one that is now recommended. Curious isn't it? Why would natural selection design us the wrong way? [...]
In a wide range of traditional societies, people avoided the sun as much as possible, especially during the hours of peak UV (Frost, 2005, pp. 60-62). Midday was a time for staying in the shade, having the main meal, and taking a nap. Nor is there reason to believe that sun avoidance and clothing were absent among early modern humans. Upper Paleolithic sites have yielded plenty of eyed needles, awls, and other tools for making tight-fitting, tailored clothes."