Tag Archives: sun exposure

Lack of Sun Exposure increases Risk of Death from Lung Cancer and other Cancers in China.

By Marc Sorenson, EdD, Sunlight Institute…

A study from China demonstrates that residents who have the lowest sun exposure also have the highest risk of death.[1] The study obtained overall death rates and incidence rates from cancers per se from a national database during the years from 1998 to 2002) They compared those death rates to the quantity of sun intensity in the areas (263 counties) in which the residents lived.

The results were telling: Overall death risk for all cancers combined, and specifically for cancers of the esophagus, stomach, colon, rectum, liver, lung, breast and bladder were inversely correlated with increasing sun exposure. Lung cancer showed the greatest protection provided by sun exposure, with a 12% decrease in death risk for every 10 mW/(nm m2) increase in UVB irradiance (a measure of intensity of sun exposure).

Incidence rates of several cancers were also inversely correlated to sun exposure, namely cancers of the esophagus, stomach, colon, rectum and cervix. Only nasopharyngeal cancer and cervical cancer increased with sun exposure. The authors suggested the possibility that vitamin D provided the mechanism by which the overall cancer rates were reduced.

Dr. William Grant has confirmed that there are many cancers that correlate to low sun exposure and/or low vitamin D levels,[2] and there are dozens more diseases beyond cancer that have an inverse relationship with sun exposure. Dr. Grant and I will soon release a book that will delve into all of the diseases that sun exposure helps to prevent. Please world, let us back in the sun without making us feel guilty!

[1] Chen W, Clements M, Rahman B, Zhang S, Qiao Y, Armstrong BK. Relationship between cancer mortality/incidence and ambient ultraviolet B irradiance in China. Cancer Causes Control. 2010 Oct;21(10):1701-9.

[2] William B. Grant. Role of solar UVB irradiance and smoking in cancer as inferred from cancer incidence rates by occupation in Nordic countries. Dermato-Endocrinology 4:2, 203–211; April/May/June 2012.

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Does Lack of Sun Exposure contribute to deadly Sepsis?

By Marc Sorenson, EdD, Sunlight Institute…

Sepsis is a deadly disease, defined as infection of the tissues by bacteria. It can spread throughout the body and blood, where it is known as septicemia.  Sepsis accounts for 500,000 emergency-room hospital visits per year in the USA, and the typical stay is nearly five hours.[1] It is one of the most deadly of medical conditions and often results in multiple organ failure.[2] It is, in fact, one of the top-ten causes of death. It is more common than heart attack, and claims more lives than any cancer.[3] Yet, much of the population has never heard of it.

Antibiotics have not been effective against severe sepsis and in some cases may exacerbate the disease.1 Sepsis is also the most common cause of death in critical-care patients in non-coronary intensive care units.[4]

Does regular time in the sun act to protect against this deadly disease? The research indicates that it does. In both the USA and UK, the disease is more common in winter than summer and higher in the Northeast than in the Southwest.

It is likely that vitamin D, produced by sun exposure, is the mechanism by which sepsis risk is decreased in summer.[5] According to Dr. William Grant, reports have shown that vitamin D upregulates human cathelicidin, LL-37, which has antimicrobial as well as anti-endotoxin activity.[6] However, we must never lose sight of the other benefits of sun exposure beyond vitamin D, which is only one of the sun’s beneficial photoproducts. Staying out of the sun—and using deadly chemical sunscreens to block life-giving sun exposure—are two of the biggest blunders ever made in the history of health disasters.

It is also interesting to note that in Australia, melanoma rates skyrocketed between 1980 and 2000.[7] 1980 was the year when a massive anti-sun campaign, called “Slip, Slop, Slap” began. Sepsis rates jumped simultaneously with melanoma and coincided with the widespread use of sunscreens. During this campaign, there was also an increase in viral respiratory infections, most cancers, and congestive heart failure.[8]

Remember that hospitals are not sterile environments. Try to stay away from them except in cases of dire need. Get some moderate, non-burning midday sun exposure instead—without using sunscreens.

[1] Wang, H. et al.  National estimates of severe sepsis in United States emergency departments.  Crit Care Med 2007;35:2461-2.

[2] Mookherjee, N. et al.  Cathelicidins and functional analogues as antisepsis molecules. Expert Opinions on Therapeutic Targets 2007;11:993-1004.

[3] World Sepsis Day web page. September 13, 2015. http://world-sepsis-day.org/?MET=SHOWCONTAINER&vCONTAINERID=11. Accessed February 25, 2016.

[4] Florian B Mayr, Sachin Yende, and Derek C Angus. Epidemiology of severe sepsis. Virulence 2014, 5:1, 4-11.

[5] Karin Amrein, Paul Zajic, Christian Schnedl, Andreas Waltensdorfer, Sonja Fruhwald, Alexander Holl,

Tadeja Urbanic Purkart, Gerit Wünsch, Thomas Valentin, Andrea Grisold, Tatjana Stojakovic, Steven Amrein, Thomas R Pieber and Harald Dobnig. Vitamin D status and its association with season, hospital and sepsis mortality in critical illness. Critical Care 2014, 18:R47

[6] Grant WB Solar ultraviolet-B irradiance and vitamin D may reduce risk of septicemia. Dermatoendocrinol. 2009 Jan;1(1):37-42.

[7] Montague M, et al. Slip! Slop! Slap! and SunSmart, 1980-2000: Skin cancer control and 20 years of population-based campaigning. Health Educ Behav. 2001;28:290–305

[8] Grant WB Solar ultraviolet-B irradiance and vitamin D may reduce risk of septicemia. Dermatoendocrinol. 2009 Jan;1(1):37-42.

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Nitric Oxide can have positive Effects on Cancer. Another Reason to seek the Sun.

By Marc Sorenson, EdD. Sunlight Institute…

Dr. Richard Weller has promoted sun exposure as a method of increasing nitric oxide (NO) in the vascular system, thereby lowering the risk of heart disease.[1] NO is a potent vasodilator that lowers blood pressure, which according to the World Health Organization, is the leading cause of premature death and disease worldwide.1 But NO may have other beneficial effects.

There is also research showing that NO, which is also an oxidant, has the ability to retard or reverse tumor growth, making it a potential anti-cancer therapy.[2] The problem with this of course, is that if it is used as an anticancer treatment, the oxidation has the potential to harm other systems of the body; After all, that is why we use antioxidants. However, the body beautifully controls the natural use of oxidants to specifically target tumors and leave healthy tissue untouched. As one group of researchers states: “…there is considerable controversy and confusion in understanding its role [NO) in cancer biology. It is said to have both tumoricidal as well as tumor promoting effects which depend on its timing, location, and concentration.[3]

The best way to use NO, in my opinion, is to let nature take its course and use sun exposure to produce NO. Then, the body’s natural physical process will use oxidation to destroy tumors and simultaneously reduce the risk of cancer.

Safely enjoy the sun.

[1] Richard B. Weller.  Sunlight Has Cardiovascular Benefits Independently of Vitamin D. Blood Purif 2016;41:130–134.

[2] Jordi Muntané and Manuel De la Mata. Nitric oxide and cancer. Nitric Oxide and Cancer. Journal List. World J Hepatolv.2(9); 2010 Sep 27.

[3] Sheetal Korde Choudhari, Minal Chaudhary, Sachin Bagde, Amol R Gadbail, and Vaishali Joshi. Nitric oxide and cancer: a review. World J Surg Oncol. 2013; 11: 118.

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A Positive Addiction: More on the Feel-Good Influence of Sun Exposure.

Nearly every article written on the addictive influences of sun exposure or other UV exposure takes a negative tack. We need to realize that some addictions are very good for us. Some runners are addicted to getting up every morning and going on the morning run. If one wants to be slim and fit, that is certainly a positive addiction. Hugging my wife is also a positive addiction; her touch helps to heal me and fills me with an addictive love. I’m also addicted to hiking in the pines and aspens near my Nevada ranch. There is little more exhilarating than being at 11,000 feet elevation and breathing the clear mountain air during a hike. You probably have your own positive addictions.

Sun exposure can certainly become an addiction, but is that all bad? In my opinion, no. When done habitually, sunning reduces the risk of melanoma and reduced the risk of myriad harmful diseases. It is therefore a positive and salubrious addiction.

A recent study, somewhat negative in tone, demonstrates that UVB light, contained in both sun lamp radiation and sun radiation, triggers the production of beta endorphins, one of the feel-good chemicals, sometimes called a “reward” chemical, that makes us want more.[i] The researchers used 12 healthy volunteers and used a UVB lamp to deliver a dose of narrow-band UVB light. Skin samples were taken before and after the exposure. After 24 hours, the skin samples showed an increase in endorphin levels in 11 of the twelve subjects.

Sun exposure enhances health. A twenty-year study demonstrated that the risk of death among people who were sun-seekers was only half that of those who received little sun.[ii] The researchers made this statement: “In both models the summary sun exposure variables showed a ‘dose-dependent’ inverse relation between sun exposure and all-cause death.”

Obviously, habitual sun exposure produces a positive addiction, and that is good! God (or nature if you prefer) has programmed our bodies to seek the sunlight in order to help provide a healthful and rewarding life. “Habitual” is the operative word here. An occasional blast of sun that causes burning is definitely not recommended. Be careful and enjoy your positive addictions.

[i] Jussila A, Huotari-Orava R, Ylianttila L, Partonen T, Snellman E. Narrow-band ultraviolet B radiation induces the expression of β-endorphin in human skin in vivo. J Photochem Photobiol B. 2016 Feb;155:104-8.

[ii] Pelle G. Lindqvist, Elisabeth Epstein, Mona Landin-Olsson, Christian Ingvar, Kari Nielsen, Magnus Stenbeck & Håkan Olsson. Avoidance of sun exposure is a risk factor for all-cause mortality: results from the Melanoma in Southern Sweden cohort. J Intern Med. 2014 Jul;276(1):77-86.

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Embrace the Sun, and your Kidneys will Love You.

By Marc Sorenson, EdD, Sunlight Institute…

Kidney cancer is nothing to take lightly. Any protective measures you take will be worthwhile and potentially life-saving. Nearly 65,000 Americans are diagnosed with kidney cancer annually, accounting for roughly 4% of newly detected cancers and 2% of cancer deaths.[i]

Research demonstrates that kidney cancer, also known as renal cancer, is reduced among people who have the greatest sun exposure. Dr. Sara Karami and her colleagues, in 2010, showed that among European men, there was a 24-38% risk reduction in renal cancer with the highest levels of sun exposure.[ii]

These same researchers, in 2015, showed that U.S. women with the highest two quartiles (fourths) of sun exposure had a 33% reduction in risk.[iii]  Interestingly, the data was adjusted for vitamin D intake, and the results still showed sun exposure to have a stand-alone protective influence on kidney cancer—another indication that sun exposure has protective effects beyond vitamin D.

Other studies on kidney cancer, using different designs, have produced similar results. A study of Swedish construction workers showed a significant 30% decreased risk among men with the highest sun exposure,[iv] and in a study of approximately 451,000 adults, followed for nine years, increasing sun exposure was associated with a significant reduction in kidney cancer and several other cancers.[v]

Embrace the sun, and your kidneys will love you for it. Remember not to burn.

[i] Siegel R, Ma J, Zou Z, et al. Cancer statistics, 2014. CA Cancer J Clin 2014;64:9–29.

[ii] Karami S, Boffetta P, Stewart P, Rothman N, Hunting KL, Dosemeci M, Berndt SI, Brennan P, Chow WH, Moore LE. Occupational sunlight exposure and risk of renal cell carcinoma. Cancer. 2010 Apr 15;116(8):2001-10.

[iii] Sara Karami, Joanne S. Colt, Patricia A. Stewart, Kendra Schwartz, Faith G. Davis, Julie J. Ruterbusch,

Wong-Ho Chow, Sholom Wacholder, Barry I. Graubard, Mark P. Purdue and Lee E. Moore. A case–control study of occupational sunlight exposure and renal cancer risk. Int J Cancer 2015;138:1626–1633.

[iv] Håkansson N, Floderus B, Gustavsson P, Feychting M, Hallin N. Occupational sunlight exposure and cancer incidence among Swedish construction workers. Epidemiology 2001;12:552–7.

[v] Lin SW, Wheeler DC, Park Y, et al. Prospective study of ultraviolet radiation exposure and risk of cancer in the United States. Int J Cancer 2012;131:E1015–23.

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Sun Exposure and Athletic Performance, Part 2

By Marc Sorenson, EdD, Sunlight Institute

Almost no one realizes the dramatic improvement that sun exposure can make on athletic performance. I helped Dr. John Cannell obtain translations of many esoteric and decades-old studies that had been forgotten, probably due to the fact that sun lamps were used to create some of the improvements in athletics, and have fallen out of favor due to the sunscare movement. I co-authored a paper with Cannell, called Athletic Performance and Vitamin D.[1] That paper is the source of much of the material covered here, and it demonstrates the remarkable, positive effect of sun or other ultraviolet (UV) exposure on human performance. I would also strongly suggest that the readers avail themselves of Dr. Cannell’s book on the subject, called The Athlete’s Edge, which discusses in far greater detail the materials introduced here.

One of the salient studies on UV exposure took place in 1957 and assessed the influence of sun exposure on strength and performance over a two-year period.[2] During that time six subjects were able to increase athletic performance and muscle trainability through systematic UV exposure. But when vitamin D3 was used, it not only did not work, it inhibited the performance-enhancing effect of the UV. I sometimes fear the public is beginning to believe that if sun exposure is proven to enhance human health, one needs only to take a vitamin D pill. Don’t get pulled into that idea. Sun exposure will always be more important than any of the photoproducts whose production it stimulates.

Here are some of the other salient studies on sun exposure and performance. In 1938, Russian researchers demonstrated that a series of four UV treatments improved speed in the 100-meter dash compared to four non-irradiated students, when both groups were undergoing daily physical training.[3] The times improved from 13.51 seconds to 13.28 seconds in the non-irradiated group and from 13.63 to 12.62 seconds in the irradiated group. In other words, the UV-treated group improved by three-fourths of a second more than the non-UV group. That may seem like a relatively small improvement, but three-fourths of a second better time in a 100-meter dash could be the difference between first and last place!

German research from 1944 showed that the exposure of 32 medical students to UV, twice weekly during for six weeks, associated with a 13% improvement in endurance, whereas performance of a control group was unchanged.[4]

Other German research shows that the ability of a muscle to gain strength (trainability) is much better in summer than winter, and peaks in September.[5] In fact the trainability was 2½ higher that the average monthly trainability for the entire year.

Reaction time has also been shown to improve significantly in the sunnier months.[6] [7]

When we consider reaction time, muscle and bone strength, speed and endurance, we should realize that these measurements are not only important for athletes; they are important for all aspects of living for all people. Everyone wants to be stronger, quicker, and faster, as well as have more endurance in daily activities. So embrace the sun, but do it safely and do not burn.

[1] Cannell JJ, Hollis BW, Sorenson MB, Taft TN, Anderson JJ. Athletic performance and vitamin D. Med Sci Sports Exerc. 2009 May;41(5):1102-10.

[2] E. Seidl and Th. Hettinger. The Effect of Vitamin D3 on the Strength and Performance of a Healthy Adult. International Journal Physiology, including Industrial Physiology, Vol. 16, Pages 365-372 (1957).

[3] Gorkin Z, Gorkin MJ, Teslenko NE. [The effect of ultraviolet irradiation upon training for 100m sprint.] Fiziol Zh USSR. 1938;25:695-701.

[4] Lehmann G, Mueller EA. [Ultraviolet irradiation and altitude fitness.] Luftfahrtmedizin. 1944;9:37-43. [Article in German].

[5] Hettinger T, Muller EA.  Seasonal course of trainability of musculature.  Int Z Angew Physiol. 1956;16(2):90-4.

[6] Sigmund, R. The effect of ultra-violet rays on the human reaction time.  Strahlentherapie.1956;101(4):623-9.

[7] Seidl E. [The effect of ultraviolet irradiation on reaction time.] Int Z Angew Physiol. 1958;17(4):333-40.

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Sun Exposure, bone strength and shaved heads.

By Marc Sorenson, EdD, Sunlight Institute

After coming across some research having to do with sun exposure and the seasonality of fractures, I thought it wise to share it with my readers.

In high latitude areas, which have far less sun availability than lower latitude areas, we would expect rates of hip fracture to be high, and such is the case. Sweden is a country that has large differences in latitude, and in research performed there it was shown that the higher the latitude and the lesser the sun exposure, the greater was the risk of hip fracture.[1] In other words, significantly more hip fractures occurred in the northern part of the country compared to the middle and southern parts. Another Swedish investigation demonstrated that in men, hip fracture risk was 37.5% lower in summer than winter. Women had a 23.5% reduced risk in summer.[2]

Research from Norway showed similar results. Hip fracture risk in men was 40% higher in winter than summer, and in women the risk was 25% higher.[3]These fluctuations in seasonal hip fractures indicate a loss of bone mass during periods of low sun exposure (winter) and an increase in bone mass during periods of high sun exposure (summer). In other words, sun exposure is able to reverse bone loss, or osteoporosis. Other studies show similar patterns of bone strength based on sun exposure or lack thereof.[4]

The importance of sunlight in maintaining and producing strong bones has been known since antiquity. Dr. Richard Hobday, author of The Healing Sun, writes the following comments and a history in an online article.[5] “Traditionally, sunlight deprivation has been linked with weak or brittle bones. One of the earliest references to this was made more than two thousand years ago by the Greek historian Herodotus (480-425 BC), who noted a marked difference between the remains of the Egyptian and Persian casualties at the site of battle of Pelusium which took place in 525 BC:

‘At the place where this battle was fought I saw a very odd thing, which the natives had told me about. The bones still lay there, those of the Persian dead separate from those of the Egyptian, just as they were originally divided, and I noticed that the skulls of the Persians were so thin that the merest touch with a pebble will pierce them, but those of the Egyptians, on the other hand, are so tough that it is hardly possible to break them with a blow from a stone. I was told, very credibly, that the reason was that the Egyptians shave their heads from childhood, so that the bone of the skull is indurated by the action of the sun — this is why they hardly ever go bald, baldness being rarer in Egypt than anywhere else. This, then, explains the thickness of their skulls; and the thinness of the Persian’s skulls rests upon a similar principle: namely that they have always worn felt skull-caps, to guard their heads from the sun.’ Herodotus, ‘The Histories’

The message is this: Don’t hide yourself from the sun; rather, embrace it in a safe manner, and that will protect your bones.

[1] Nilson F, Moniruzzaman S, Andersson R. A comparison of hip fracture incidence rates among elderly in Sweden by latitude and sun exposure. Scand J Public Health. 2014 Mar;42(2):201-6.

[2] Odén A, Kanis JA, McCloskey EV, Johansson H. The effect of latitude on the risk and seasonal variation in hip fracture in Sweden. J Bone Miner Res. 2014 Oct;29(10):2217-23.

[3] Solbakken SM1, Magnus JH, Meyer HE, Emaus N, Tell GS, Holvik K, Grimnes G, Forsmo S, Schei B, Søgaard AJ, Omsland TK.

[4] Grønskag AB1, Forsmo S, Romundstad P, Langhammer A, Schei B. Incidence and seasonal variation in hip fracture incidence among elderly women in Norway. The HUNT Study. Bone. 2010 May;46(5):1294-8.

[5] Richard Hobday. The Healing sun: Sunlight, Brittle Bones, and Osteoporosis. http://sunlightenment.com/the-healing-sun-sunlight-brittle-bones-and-osteoporosis/. (accessed February 5, 2016)

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Lack of Sun Exposure is an important Factor in Premenopausal Breast Cancer

By Marc Sorenson, EdD, Sunlight Institute…

Case-control research from Iran indicates that lack of sun exposure is a major risk factor for breast cancer.[1] Two groups of women, one that had breast cancer (cases) and another that was normal (controls), were assessed by questionnaire regarding lifestyle choices and the risk for breast cancer. When assessing sun exposure habits, those who had the lowest level of sun exposure had nearly three times the risk of being a cancer victim as those who had the highest level.

This is the second Iranian study I am aware of that showed a remarkable difference in breast-cancer risk based on sun exposure. Another case-control study showed that women who covered themselves completely had more than 10 times the risk breast cancer compared to those who were not totally covered.[2] Of transcendent importance was the unexpected finding that vitamin D levels were nearly identical in cases as controls, meaning that the protective mechanism could not have been vitamin D. Some other factor must have protected them from the disease. We have mentioned on this blog many times that sun exposure leads to higher levels of serotonin, endorphin, nitric oxide and other potentially helpful products.

Whatever the mechanism, it seem wise to get plenty of non-burning sunlight.

[1] Salarabadi A, Bidgoli SA, Madani SH. Roles of Kermanshahi Oil, Animal Fat, Dietary and Non- Dietary Vitamin D and other Nutrients in Increased Risk of Premenopausal Breast Cancer: A Case Control Study in Kermanshah, Iran. Asian Pac J Cancer Prev. 2015;16(17):7473-8.

[2] Bidgoli SA, Azarshab H. Role of vitamin D deficiency and lack of sun exposure in the incidence of premenopausal breast cancer: a case control study in Sabzevar, Iran. Asian Pac J Cancer Prev. 2014;15(8):3391-6.

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Sun Exposure, Chronic Fatigue and Vitamin D

By Marc Sorenson, EdD, Sunlight Institute…

A recent post by an online paper called The Korea Bizwire talks of research by Dr. Emad Al Duzahiri, in which he concludes that those who are suffering from chronic fatigue may really be suffering from sun deficiency.[1] The article mentions that vitamin D, preferably from sun exposure, is essential for reducing the risk of the disease.

There is at least one additional study indicating that optimization of vitamin D improves the severity of symptoms in those who suffer from fatigue.[2]

Remember that sun exposure is the best way to obtain your vitamin D, because it also comes along with serotonin, nitric oxide, endorphins and perhaps dopamine, and it profoundly improves the mood—just what the doctor ordered for chronic fatigue.

So when your get-up-and-go has gotten up and gone, don’t forget the sun!

[1] Emad Al Duzahiri. Quoted in The Korea Bizwire, January 19, 2016. http://koreabizwire.com/lack-of-exposure-to-sunlight-may-lead-to-chronic-fatigue/48480 (accessed January 20, 2016)

[2] Roy S, Sherman A, Monari-Sparks MJ, Schweiker O, Hunter K. Correction of Low Vitamin D Improves Fatigue: Effect of Correction of Low Vitamin D in Fatigue Study (EViDiF Study). N Am J Med Sci. 2014 Aug;6(8):396-402.

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Sun Exposure, Nitric Oxide and Vitamin D for improved Athletic Performance

By Marc Sorenson, EdD  Sunlight Institute…

A most interesting research paper demonstrates that nitrate supplements, combined with exposure to sunlight, increases performance of cyclists.[1] The researchers state that “dietary nitrate supplementation has been shown to increase nitric oxide (NO) metabolites, reduce blood pressure (BP) and enhance exercise performance.” And, as we have discussed in this blog, sun exposure reduces BP by increasing the production of NO. It was theorized that sun exposure might enhance the athletic performance induced by the dietary nitrate supplementation.

The theory proved to be correct; although sun exposure did not improve cycling times by itself, when combined with the nitrate supplementation, cycling times improved significantly.

It may surprise some people to realize that ultraviolet radiation (UVR) from sun beds or sun lamps has been used since before 1950 to enhance athletic performance.[2] As early as 1938, Russian researchers reported that a course of UVR significantly improved speed in the 100-meter dash among four students when compared with controls that did not have the radiation, although both groups were undergoing identical daily training.[3] The non-irradiated group improved by 1.7% but the irradiated group improved by 7.4%. Another study conducted over ten weeks showed that cardiovascular endurance improved remarkably among athletes in training who were irradiated vs. those who were not.[4] The irradiated athletes improved by 19.2% compared to 1.5% among the non-irradiated group.

There are numerous studies from Germany showing the efficacy of UVR on athletic performance, most of them from the early days before the idea of sun-lamp produced UVR fell into disrepute because of the attack on tanning beds. What a shame. This method of athletic assistance could produce an impressive improvement in sports performance for so many people, athletic or not. Strength improves, stamina improves, quickness improves and speed improves with UVR radiation, which of course is also part of sunlight. The mechanism for this improvement is likely a combination of vitamin D and nitric oxide.

Safely enjoy the sun!




[1] Muggeridge DJ, Sculthorpe N, Grace FM, Willis G, Thornhill L, Weller RB, James PE, Easton C. Acute whole body UVA irradiation combined with nitrate ingestion enhances time trial performance in trained cyclists. Nitric Oxide. 2015 Aug 1;48:3-9.

[2] Cannell JJ, Hollis BW, Sorenson MB, Taft TN, Anderson JJ. Athletic performance and vitamin D. Med Sci Sports Exerc. 2009 May;41(5):1102-10.

[3] Gorkin Z. Gorkin MJ, Teslenko NE. The effect of ultraviolet radiation upon training for the 100-meter sprint.

[4] Allen R, Cureton T. Effects of ultraviolet radiation on physical fitness. Arch Phys Med 1945;10:641-4.

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