On 2017 Jul 30, David Keller commented:

This study can't tell whether avoiding sun exposure or the resulting low vitamin D levels were to blame

The authors state that "all-cause mortality is related to low vitamin D levels", and that "exposure to sunlight remains the main source of vitamin D". They did not have access to data concerning vitamin D levels or supplementation in their study. Therefore, they cannot control for vitamin D levels, nor prove that sun exposure confers any benefits beyond those associated with higher vitamin D levels, regardless of whether the vitamin D is obtained from sun exposure or by taking a supplement pill. We know that sun exposure leads to increased risk for malignant melanoma. It is unreasonable to risk a deadly skin cancer to obtain vitamin D, rather than take vitamin D in supplement form. This will not change until a study is performed which controls for vitamin D levels, and thereby demonstrates mortality benefit for sun exposure which is independent of sunlight's effect on raising vitamin D levels.

On 2017 Jul 31, David Keller commented:

Study subjects who exercise indoors, avoid solar radiation exposure & take vitamin D"

PubMed Commons commenters have difficulty responding to anonymous "unhelpful" votes which do not include any explanation or critique. I will have to guess that the study of spelunkers would be impractical (too few spelunkers) or biased (spelunkers are too distinctly different than non-spelunkers). So, instead of spelunking, substitute any form of moderate indoor exercise which includes social contact. For example, subjects who work out at indoor gyms and take vitamin D supplements at adequate doses could be compared with persons who exercise outdoors, to control for vitamin D levels and other confounding sources of bias associated with sun exposure of the skin. This is an important question, because the inherently limited findings of the Melanoma In Southern Sweden (MISS) study are being touted widely in the popular media by sunbathing advocates, which could lead to a future increase in malignant melanoma and even all-cause mortality, depending on the degree to which the MISS trial was confounded by unrecognized biases. The public generally are not informed that the MISS results do not prove that sunbathing promotes health or longevity, independent of vitamin D levels, or some other unrecognized and uncontrolled difference between sun-seekers and sun-avoiders.

On 2017 Jul 28, David Keller commented:

A proposed study to determine whether sun exposure promotes good health, or good health is a result of other factors associated with sun exposure, like sociable moderate exercise

Spelunking, the recreational exploration of caves, is an "outdoor" activity that promotes healthful cardiovascular exertion and social interaction, but zero sun exposure. The null hypothesis is that solar irradiation of the skin is not beneficial per se, and that the mortality benefits observed by Lindqvist and colleagues were due to factors associated with sun exposure, such as higher vitamin D levels, social interactions, and moderate exertion during hikes, volleyball games, etc. If sun exposure was, therefore, at best a "bystander" factor overall with regard to the mortality benefits observed in Lindqvist's study, then we ought to observe similar benefits in mortality among active spelunkers, despite the fact that they derive zero sun exposure from cave exploration. Is spelunking associated with the same benefits as sun exposure (or, are spelunkers equally self-preselected for good health) after correcting for vitamin D status? Spelunking mortality must also be corrected for the high rate of rabies from bat bites, and for trauma associated with spelunking, such as impalement injuries on stalactites and stalagmites, sudden drops into deep holes and other unseen hazards, and spelunkers who get lost in the caves and are never heard from again, who should be presumed dead, by intention to treat. Importantly, the serum vitamin D levels of spelunkers should be raised by oral supplementation until both groups exhibit equivalent levels. After those corrections, if spelunkers are found to be as healthy as those who sun-expose, we would have evidence supporting the null hypothesis, posed above.

On 2017 Jul 24, David Keller commented:

Swedes, and other depigmented peoples, should not engage in "daily, midday....sun exposure" of any duration

Depigmentation of northern peoples may seem like an evolutionary argument in favor of sun exposure to the skin. However, there is no safe threshold of solar radiation, especially for the fair-skinned, who are at the highest risk of melanoma. The risk of mutation accrues with each and every ionizing photon that hits the skin.

If there is benefit to sunbathing, then we should seek to identify and isolate the factors that provide such benefits, and advise the healthy how to maximize the benefits associated with sun exposure while minimizing its risks. The increased mortality from sunbathing is fully expressed over decades, not months or years. Older generations may have been too busy or too embarrassed to lay around near-naked in the sun. Today's generation suffers from no such inhibitions or lack of leisure time, and melanoma is now one of the fastest-increasing causes of cancer death.

My recommendation to patients, in "light" of the findings of Dr. Lindqvist and others, is as follows:

1) Avoid sun exposure to the skin. Never sunbathe. The best sunblock is clothing or shade.

2) Engage in outdoor activities that promote cardiovascular exertion and social interactions, which are healthy, while fully dressed and always seeking shade.

3) Evidence suggests that indirect light exposure can prevent or treat seasonal depression. This means that visual perception of bright light may be beneficial, but avoid direct solar radiation to the retina, which again causes melanoma. Outdoor activities in the shade safely provide this benefit.

4) Strict avoidance of sun exposure can lead to sub-optimum blood levels of vitamin D, which I suggest measuring with blood tests, and treating with vitamin D supplements. I aim for a high-normal vitamin D level.

If any other benefits of sun exposure are isolated, we should strive to find safer ways to attain those benefits. The increased risk of melanoma from sunbathing cannot be mitigated. Doctors who advise sunbathing violate the Hippocratic directive of "Primum non nocere" ("First, do no harm").

On 2017 Jul 18, P G Lindqvist commented:

Are we forcing people to choose health or melanoma? Or having a balanced discussion regarding pros and cons of sun exposure? In our observational study 2014 Lindqvist PG, 2014, we showed a strong inverse relationship between sun exposure and risk of all-cause death. Dr Keller is right that from an observational study we might not show causality. Even if we adjust for age, education, marital status, income, exercise, and smoking there might still be residual bias. The authors draw the conclusion that we might titrate a proper vitamin D dose, without raising the melanoma risk. This might be right, however, we still do not know that vitamin D is “the” mediator. Over exposure of solar radiation is a risk factor for melanoma incidence. However, as we show in our 2016 publication Lindqvist PG, 2016 using the same material. Incidence of melanoma increase with increasing sun exposure, but avoiders of sun exposure have a higher death rate if caching melanoma. Therefore, in Sweden, which is a country with scarcity of UV radiation we suggest daily, midday, short time sun exposure.

On 2017 Jul 07, David Keller commented:

Forcing a choice between vitamin D deficiency and elevated melanoma risk is a fallacy of the inevitable alternative

This observational study demonstrated that sun exposure was inversely associated with all-cause mortality. No epidemiological study, such as this, can distinguish whether lack of sun exposure caused increased mortality, or whether being destined to have increased mortality for other reasons caused reduced participation in outdoor activities that confer sun exposure.

Even if reduced sun exposure does increase mortality due to relative vitamin D deficiency, as the authors theorize, nobody would be forced to risk melanoma by exposing their skin to solar radiation. Vitamin D supplements can be titrated to match the blood levels of vitamin D achieved by sun worshipers, without raising melanoma risk.

The implication that people must choose to either raise their risk of melanoma by exposing their skin to solar radiation, or suffer morbidity and mortality from relative vitamin D deficiency is an example of the logical fallacy known as "the inevitable alternative".

Exposure of the skin to solar radiation is the number one modifiable risk factor for malignant melanoma, a cancer with rapidly rising incidence in the U.S.

The American Academy of Dermatology warns, "There is no scientifically validated, safe threshold level of UV exposure from the sun or indoor tanning devices that allows for maximal vitamin D synthesis without increasing skin cancer risk." [1]

1: American Academy of Dermatology, Position Paper on Vitamin D. Accessed on 7/5/2017 at:<br> https://www.aad.org/Forms/Policies/Uploads/PS/PS-Vitamin D Postition Statement.pdf

On 2017 Jul 07, David Keller commented:

Forcing a choice between vitamin D deficiency and elevated melanoma risk is a fallacy of the inevitable alternative

This observational study demonstrated that sun exposure was inversely associated with all-cause mortality. No epidemiological study, such as this, can distinguish whether lack of sun exposure caused increased mortality, or whether being destined to have increased mortality for other reasons caused reduced participation in outdoor activities that confer sun exposure.

Even if reduced sun exposure does increase mortality due to relative vitamin D deficiency, as the authors theorize, nobody would be forced to risk melanoma by exposing their skin to solar radiation. Vitamin D supplements can be titrated to match the blood levels of vitamin D achieved by sun worshipers, without raising melanoma risk.

The implication that people must choose to either raise their risk of melanoma by exposing their skin to solar radiation, or suffer morbidity and mortality from relative vitamin D deficiency is an example of the logical fallacy known as "the inevitable alternative".

Exposure of the skin to solar radiation is the number one modifiable risk factor for malignant melanoma, a cancer with rapidly rising incidence in the U.S.

The American Academy of Dermatology warns, "There is no scientifically validated, safe threshold level of UV exposure from the sun or indoor tanning devices that allows for maximal vitamin D synthesis without increasing skin cancer risk." [1]

1: American Academy of Dermatology, Position Paper on Vitamin D. Accessed on 7/5/2017 at:<br> https://www.aad.org/Forms/Policies/Uploads/PS/PS-Vitamin D Postition Statement.pdf

On 2017 Jul 18, P G Lindqvist commented:

Are we forcing people to choose health or melanoma? Or having a balanced discussion regarding pros and cons of sun exposure? In our observational study 2014 Lindqvist PG, 2014, we showed a strong inverse relationship between sun exposure and risk of all-cause death. Dr Keller is right that from an observational study we might not show causality. Even if we adjust for age, education, marital status, income, exercise, and smoking there might still be residual bias. The authors draw the conclusion that we might titrate a proper vitamin D dose, without raising the melanoma risk. This might be right, however, we still do not know that vitamin D is “the” mediator. Over exposure of solar radiation is a risk factor for melanoma incidence. However, as we show in our 2016 publication Lindqvist PG, 2016 using the same material. Incidence of melanoma increase with increasing sun exposure, but avoiders of sun exposure have a higher death rate if caching melanoma. Therefore, in Sweden, which is a country with scarcity of UV radiation we suggest daily, midday, short time sun exposure.

On 2017 Jul 28, David Keller commented:

A proposed study to determine whether sun exposure promotes good health, or good health is a result of other factors associated with sun exposure, like sociable moderate exercise

Spelunking, the recreational exploration of caves, is an "outdoor" activity that promotes healthful cardiovascular exertion and social interaction, but zero sun exposure. The null hypothesis is that solar irradiation of the skin is not beneficial per se, and that the mortality benefits observed by Lindqvist and colleagues were due to factors associated with sun exposure, such as higher vitamin D levels, social interactions, and moderate exertion during hikes, volleyball games, etc. If sun exposure was, therefore, at best a "bystander" factor overall with regard to the mortality benefits observed in Lindqvist's study, then we ought to observe similar benefits in mortality among active spelunkers, despite the fact that they derive zero sun exposure from cave exploration. Is spelunking associated with the same benefits as sun exposure (or, are spelunkers equally self-preselected for good health) after correcting for vitamin D status? Spelunking mortality must also be corrected for the high rate of rabies from bat bites, and for trauma associated with spelunking, such as impalement injuries on stalactites and stalagmites, sudden drops into deep holes and other unseen hazards, and spelunkers who get lost in the caves and are never heard from again, who should be presumed dead, by intention to treat. Importantly, the serum vitamin D levels of spelunkers should be raised by oral supplementation until both groups exhibit equivalent levels. After those corrections, if spelunkers are found to be as healthy as those who sun-expose, we would have evidence supporting the null hypothesis, posed above.

On 2017 Jul 30, David Keller commented:

This study can't tell whether avoiding sun exposure or the resulting low vitamin D levels were to blame

The authors state that "all-cause mortality is related to low vitamin D levels", and that "exposure to sunlight remains the main source of vitamin D". They did not have access to data concerning vitamin D levels or supplementation in their study. Therefore, they cannot control for vitamin D levels, nor prove that sun exposure confers any benefits beyond those associated with higher vitamin D levels, regardless of whether the vitamin D is obtained from sun exposure or by taking a supplement pill. We know that sun exposure leads to increased risk for malignant melanoma. It is unreasonable to risk a deadly skin cancer to obtain vitamin D, rather than take vitamin D in supplement form. This will not change until a study is performed which controls for vitamin D levels, and thereby demonstrates mortality benefit for sun exposure which is independent of sunlight's effect on raising vitamin D levels.