The Sun: Balancing Risks and Benefits

Few things in life fall neatly into the category of "good" or "bad" for our well being. It is often the case that something can be beneficial in one respect (e.g. enhance our mood), but it might also be potentially harmful in another respect (e.g. high in calories, etc.).

Take something as simple as physical exercise. Recall, for example, my earlier post about the benefits of physical exercise. But there is some risk of harm associated with physical exercise, especially contact sports (e.g. sprains and strains, stress fractures, etc.). Determining what constitutes a sensible course of action requires us to responsibly pursue these benefits, so that we minimize, where possible, these risks of harm (though we cannot eliminate them completely).

Another obvious example are medically prescribed drugs, for they could remedy one's alignment but it is also possible that they could cause an adverse reaction (thus creating more problems for us). But when the likelihood of the benefits far outweigh the potential harms, it is sensible to pursue them. Much of our day-to-day activity involves such judgements (though we not even consciously think of things in these terms). The decisions we make concerning getting to work (via car, bike, etc.) has potential benefits and harms. Ditto for the food we consume.

And so life involves, for us as both individuals and collectively as societies, a complex balancing exercise. And thus it is always prudent, when faced with an argument that focuses exclusively on one purported harm or benefit, to step back and adopt the "big picture" perspective concerning the potential benefits and harms, and strive for some proportionality. And so reflecting on what constitutes responsible "risk management" should increase the likelihood that our lives will, on balance, go better.

Today I came across a great example that illustrates the complexities of potential harms and benefits- exposure to the sun. "Addressing the health benefits and risks, involving vitamin D or skin cancer, of increased sun exposure" by Johan Moan et. al. is published in the latest issue of PNAS. Here is the abstract:

Solar radiation is the main cause of skin cancers. However, it also is a main source of vitamin D for humans. Because the optimal status of vitamin D protects against internal cancers and a number of other diseases, a controversy exists: Will increased sun exposure lead to net health benefits or risks? We calculated the relative yield of vitamin D photosynthesis as a function of latitude with a radiative transfer model and cylinder geometry for the human skin surface. The annual yield of vitamin D is 3.4 and 4.8 times larger below the equator than in the U.K. and Scandinavia, respectively. In populations with similar skin types, there are clear latitude gradients of all major forms of skin cancer, indicating a north–south gradient in real sun exposure. Surprisingly, the incidence rates of major internal cancers also increase from north to south. However, the survival prognosis also improves significantly from north to south. Reasons for these findings are discussed in view of the role of vitamin D. In Norway, melanoma rates increased by a factor of 6 from 1960 to 1990, while the prognosis improved in the same period. After 1990, melanoma rates have remained constant or even decreased in age groups <50 years, whereas the prognosis has not improved further. These data, together with those for internal cancers and the beneficial effects of an optimal vitamin D status, indicate that increased sun exposure may lead to improved cancer prognosis and, possibly, give more positive than adverse health effects

And here is a sample from the article:

There is a controversy as to whether increased sun exposure to Western populations would prolong or shorten lifetime expectancy, result in fewer or more cancer deaths, and, in general, lead to health benefits or risks (1, 2). For years, emphasis has been placed on the increasing time trends of incidence and mortality rates of cutaneous malignant melanoma (CMM) (3, 4) and, in contrast, on the protective role of vitamin D regarding many types of internal cancer and other diseases (5–7). Too much sun exposure has been blamed for the high and increasing incidence rates of CMM. However, solar radiation is a major, if not the main, source of vitamin D in humans. Therefore, a population's increased sun exposure leads to improved vitamin D status. The observation that the incidence and mortality of several types of internal cancers decreases with decreasing latitude in the United States and other countries initiated the research on vitamin D–cancer relationships in the 1980s and 1990s. However, in some cases, there is an inverse gradient of the rates of internal cancer with latitude (1), with the rates being higher in regions with high annual UV fluences (New Zealand and Australia) than in countries with low annual UV fluences (Northern Europe, Scandinavia, and the U.K.), despite the fact that the populations of these regions are closely related genetically or, at least, have similar skin types, which is important for the photosynthesis of vitamin D.

These issues have health consequences far beyond those of cancer because a number of diseases are associated with inadequate vitamin D levels or low sun exposure: neurological, cardiovascular, metabolic, immune, and bone diseases (2, 7). Evolutionary arguments involving skin color also should be taken into account. A dark skin color is found among Africans and, possibly, early hominids who lived close to the equator (8). This pigment may protect against skin cancer and folate photodegradation (8, 9). A white skin color developed later in our history, as humans left Africa and went north. Because dark skin needs about 6 times higher solar exposure for vitamin D photosynthesis than white skin (10, 11) and because the fluence rate of vitamin D-generating solar radiation decreases with increasing latitude (Fig. 1A), one can argue that skin whitening may be related to the need for vitamin D and the lack of sunshine at high latitudes.

....So far, epidemiological data for cancer argue for an overall positive role of sun-induced vitamin D. There may be more beneficial than adverse effects of moderately increased sun exposure, even for total cancer mortality (65). This message should be addressed to populations at risk for vitamin D deficiency. Trends need to be closely followed in the future. In view of the supposedly long latency times for cancer manifestation, decades are needed for final evaluation of the impacts of the antisun campaigns with respect to melanoma incidence, cancer prognosis, and other possible positive or adverse health effects. Authorities should pay attention not only to skin cancer research, but also to research on vitamin D–sun–health relationships occurring worldwide.

Cheers,
Colin

Interesting Globe Story on Vitamin D

When the weather is as cold and snowy as it has been this past week it is nice to think of the warm and sunny days to come. And so I want to blog (yet again!) about the importance of the sun for human health and well being. My previous posts have noted the purported benefits and harms of sun exposure. Today's Globe and Mail has this fascinating story on vitamin D. I find the story of vitamin D and sun exposure interesting for a number of reasons.

Firstly, it reveals how complex the relationship between our environment and our well being is. Of course there are often obvious ways in which we see the impact our environment can have, like when there is a drought and this destroys a harvest. But even the brutal snow storm Ontario experienced this past weekend can have an adverse impact on our health (e.g. increasing the number of serious falls, increased car accidents, delays getting to the hospital, impact on our mood, physical activity, etc.), not to mention the costs of snow removal, delays travelling, etc. For example, this story notes that, for the city of Toronto alone, the clean-up cost of this latest storm was about $4 million and as of late last week, the city had already spent $40 million of its $67 million snow budget for the year.

A second reason why I am really interested in the story of sun exposure and vitamin D is that it reveals how provisional we should be about complex empirical matters, even those things that are taken to be established parts of the medical orthodoxy. Too much exposure to the sun, for example, can be harmful. It can increase the risk of skin cancer. But we must also be aware of the possibility that harms (e.g. increased risk of other types of cancer) can result from lack of sun exposure. And the real challenge is to find what constitutes a reasonable balance between these two potential dangers. And this is were the story of taking vitamin D is interesting. When assessing the potential harms of pursuing something we must also consider the potential harms of not doing anything. So the story of vitamin D supplements illustrates the importance of evolutionary history and the complex challenges we face in trying to pursue responsible risk management.

Here is a sample from the Globe story:

In the summer of 1974, brothers Frank and Cedric Garland had a heretical brainwave.
The young epidemiologists were watching a presentation on death rates from cancer county by county across the United States. As they sat in a lecture hall at Johns Hopkins University in Baltimore looking at the colour-coded cancer maps, they noticed a striking pattern, with the map for colon cancer the most pronounced.
Counties with high death rates were red; those with low rates were blue. Oddly, the nation was almost neatly divided in half, red in the north and blue in the south. Why, they wondered, was the risk of dying from cancer greater in bucolic Maine than in highly polluted Southern California?

...It seems almost inconceivable that geography could damn someone to a life-threatening illness - that the mere fact of living in a northern country such as Canada could be a health hazard.

...The idea behind the research is simple: Humans evolved in a sunlight-filled environment near the equator, and still have countless biological processes exquisitely calibrated to the rich vitamin D levels we would have if we were still basking under the hot sun year-round.

But by migrating to higher latitudes, where strong sunlight is not present during the fall and winter, most humans upset their vitamin D metabolism, creating susceptibilities to chronic ailments that research is now linking to insufficiencies.

...One study, in the journal Circulation, found that those with low vitamin D status had a 62-per-cent increased risk of heart failure. Another, published in Archives of Internal Medicine, found that those who take vitamin D supplements cut mortality risk by 7 per cent. A third report, by scientists at the U.S. National Cancer Institute, found that, while vitamin D didn't affect overall cancer-death risk, those with relatively high levels of it in their blood had a 72-per-cent lower risk of dying from colorectal cancer.

Other studies have found that low blood levels are an excellent predictor of who goes on to develop cancer and heart disease and that people diagnosed with cancer during the vitamin D-rich summer have a better prognosis than those diagnosed during winter.

...But even though Ms. Logan says the Canadian Cancer Society agrees that all the science on vitamin D may not be in yet, evidence to date strongly suggests that not acting on the implications of the research is risky. Cancers affected include such big killers as breast, prostate and colon, which will claim more than 10,000 Canadians this year.

"You don't need to wait for every scientific question to be answered before you take action," Ms. Logan says. "Where there is evidence of harm, even in the face of scientific uncertainty, you should do something about it."

Cheers,
Colin

Vitamin D (update)

Today's Globe has this story about a new report on the recommended daily levels of vitamin D. The story is premised on this report published today by the Institute of Medicine of the National Academies.

The Institute's report, which was undertaken at the request of the US and Canadian governments, looked at both calcium and vitamin D. As I have noted in my previous posts on vitamin D, it is interesting to follow how things develop with this vitamin as an anti-aging intervention (that perhaps mimics the effects of CR) would likely face similar challenges.

The first challenge: figuring out what constitutes a safe and effective dose.

There are dangers with being too bold and with being too cautious. Prescribing people to take very high doses of a chemical (even a "natural" one) could be harmful. And yet prescribing people take a very low dose could also be harmful in that it won't realize the health benefits of a higher dose. How do we reasonably balance these different possible harms and benefits?

These concerns are what we see in this report on vitamin D. The recommended dietary allowance of vitamin D has been raised to 600 IU/day. This triples the recommended levels. Health Canada had prescribed that 200 IU/day were recommended, and that this level could be reached by simply drinking two cups of milk a day. But the new, higher levels will mean some people should take a daily supplement.

In addition to revising recommended daily dosage of vitamin D, this report has also increased the upper intake level from 2000 IU to 4000 IU. The purported benefits (lower rates of internal cancers) of taking higher doses of vitamin D is, at this stage, inconclusive. This presents a second challenge: what to do when the findings are still inconclusive?

Daily dosages of vitamin D between 600 IU and 4000IU are still an "unknown" in terms of health benefits. These levels have been deemed safe, but does a dosage above 600 IU confer any health benefit? And what is it reasonable to do when such uncertainty exists? Should one take a higher dose, a dose that is deemed safe, just in case it has benefits? Or should one wait to see if conclusive evidence emerges about the alleged health benefits before increasing one's dosage? It's a tricky dilemma. I have my own views on this issue, but I'll leave it up to readers to make their own decisions about what levels of vitamin D they should take.

Now that the vitamin D max dosage has been increased, more studies on their purported health benefits will take place. So it will be interesting to see how things unfold in the years to come.

Cheers,
Colin

Vitamin D and Children

I've been following the debates on vitamin D for some time now. Today's Globe has this story about a study on the health risks in children who are deficient in vitamin D. Here is a sample:

The first Canadian study to investigate vitamin D levels in toddlers has found that more than 80 per cent of the children tested didn't have enough of the sunshine vitamin and nearly a third had such low amounts that doctors classified them as deficient.

...."Vitamin D deficiency is associated with a number of chronic medical conditions," observed Jonathon Maguire, a researcher at Toronto's Hospital for Sick Children and lead author of the study, who called the results "concerning."


....There has been a flurry of medical interest in vitamin D because of tantalizing hints that it plays a far wider role in promoting good health than just helping ensure proper bone development, for which it is well known. New research has linked deficiencies to many cancers, heart disease, to such autoimmune conditions as MS and diabetes and even influenza.

Cheers,
Colin

New Vitamin D Recommendations

The latest issue of the CMAJ has this article on the new guidelines for the (adult) daily supplements of vitamin D.

For adults who are at a low risk of osteoporsis, the recommended daily intake of vitamin D is 400–1000 IU.

EurekAlert! also has the scoop here.

Cheers,
Colin

Cancer Study in Canada

The latest issue of Science has this report about the ambitious Canadian Partnership for Tomorrow Project. Here is a sample from the story:

Canada has joined the global stampede of countries gathering biological data over decades on a large population cohort in hopes of better understanding the genetic, social, and environmental factors that affect human health.

The Canadian Partnership for Tomorrow Project, launched last week, will follow 300,000 adults over the age of 35 for 30 years, gathering saliva, blood, urine, fecal, and toenail samples as well as answers to questions about the health effects of influences including diet, physical fitness, and environmental conditions. The goal is "a comprehensive data set for research into the causes of cancer," says Heather Bryant, vice president of cancer control for the Canadian Partnership Against Cancer in Toronto, a federally funded organization helping to lead the study. But she says the project will also "provide a platform for numerous other research topics."

The project builds on a cancer-risk study in Alberta that examined the interaction of lifestyle, behavioral, environmental, and genetic factors. Five provincial public health agencies have kicked in an initial $82 million to recruit participants in what is expected to be a $3.5-million-a-year effort. Researchers have already obtained funding to probe the effects of vitamin D in northern climes, measure compliance with public health recommendations for physical activity, and chart the effects of dietary supplements as varied as alcohol, vitamins, and traditional native diets, notes Phillip Branton, head of the Canadian Institutes of Health Research's Institute of Cancer Research, who will oversee research.

And this info sheet contains some useful data on the toil of cancer in Canada:

Cancer incidence and mortality
• Cancer incidence continues to rise annually in Canada by two to three per cent, while the number
of people living with cancer is growing at least twice that rate2
• This year approximately 166,400 Canadians will be diagnosed with cancer
• An estimated 40 per cent of Canadian women and 45 per cent of Canadian men will develop cancer during their lifetime2
• Canada’s growing and aging population is leading to an increase in cancer cases
• Approximately one out of every four Canadians will die from cancer
• This year approximately 73,800 Canadians will die from the disease

Cost of cancer
• At more than $12.2 billion annually, cancer is the most costly illness in losses due to premature
mortality (assessed as lost labour productivity, including wages, CPP/QPP, EI and workers
compensation)
• In 2002, cancer accounted for about $17.9 billion in costs (direct and indirect) in Canada
• Hospitalization of cancer patients costs approximately $2.1 billion a year, in addition to physician
costs and drug treatment costs
• In 1998, $210 million was spent on drugs for cancer treatment

Cheers,
Colin