Sun Exposure and health by Marc Sorenson, EdD…
A very interesting study has been completed in a remote area of South America.
An indigenous tribe from the remote Bolivian Amazon jungle, known as the Tsimane, has been found to have the world’s healthiest arteries. People there survive on a diet low in saturated fats and high in non-processed foods. One of the researchers stated that “Our study shows that the Tsimane indigenous South Americans have the lowest prevalence of coronary atherosclerosis of any population yet studied.”
Here are some of the lifestyle habits and facts regarding the Tsimane.
- The diet is fiber rich.
- The diet is approximately 75% non-processed carbohydrates. Isn’t that supposed to make us fat?
- The diet includes rice, plantain (a type of banana), corn, nuts, and a very small amount of animal meat.
- Smoking is almost non-existent.
- Only three per cent of the people had moderate to high heart disease risk; two-thirds of them over 75 years of age had virtually no risk. The article states that only 14% of Americans had no risk, and that half had a moderate or high risk—about 5 times higher than the Tsimane.
- Men spend six to seven hours of their day being physically active, whereas women spend four to six hours. This, of course, means plenty of sun exposure.
During most of my professional career, I have advised people to live on this type of diet, but without the meat or any other animal product. In addition we helped them to exercise several hours daily outside. During that time, my wife and I have observed that people have recovered from diabetes, heart disease, arthritis and other maladies. That is no surprise, considering this new research and many other studies. Vitamin D and nitric oxide, both photoproducts, are exceptionally important to human health, but when it comes to heart disease, nitric oxide is probably the operative photoproduct. Here is a quote from Dr. Richard Weller, a common-sense dermatologist and great researcher:
“Sunlight may have beneficial cardiovascular effects, independently of Vitamin D production. Vitamin D could in these circumstances act as a marker for sunlight exposure and its postulated beneficial effects.” “These recent human data show the physiological relevance of photorelaxation. High blood pressure is the leading cause of disability adjusted life years lost worldwide and as a risk factor underlies 18% of all deaths.” The study noted: “The action spectrum of nitrite release shows that ultraviolet B is also involved in nitrite reduction to Nitric Oxide, and thus sunlight may be more effective than a pure UVA source.” The study concluded: “the prevalence of cardiovascular and cerebrovascular deaths is around 100 times higher than those from skin cancer. Interventions leading to small changes in the incidence of cardiovascular disease are thus of greater benefit to the health of the public even than large changes in skin cancer incidence.”
The Tsimane, therefore, are living (unknowingly) an almost perfect lifestyle for optimal health. To stay well, it is imperative that we do the same, although we don’t need quite that much sun exposure. Remember to build up a tan and be safe in the sun.
 Weller R. The health benefits of UV radiation exposure through vitamin D production or non-vitamin D pathways. Blood pressure and cardiovascular disease. Photochem. Photobiol. Sci. 2016, DOI: 10.1039/C6PP00336B.
By Marc Sorenson, EdD, for sun exposure.
According to a new study, people with MS feel better when they spend more time in the sunshine. Not only will they feel better, but they will have lower rates of fatigue, and a slower progression to disability. None of this should be a surprise, since similar results have been reported for decades. For example, in 1922 Dr. Charles Davenport wrote a paper entitled, “Multiple Sclerosis from the standpoint of geographic distribution and race. He analyzed the MS rate of military draftees and compared it to their states of origin. The highest rates were found in men who grew up in Michigan, Wisconsin, and the extreme northwest—all areas with low sun availability. There were few cases of MS among those who grew up in southern states, where sun availability is abundant. He also noted that those from urban areas, which have lower sun availability than rural areas, had 50% higher MS rates than those from rural areas. Similar studies confirm that relationship. 
Another interesting research paper demonstrated that sun exposure, while obviously being critical in the production of vitamin D, had its own profound influence in lessening the degeneration of nerves (neurodegeneration) in those with MS. By measuring whole brain volume (WBV) and grey-matter volume (GMV) by magnetic resonance imaging (MRI), the scientists determined that greater summer sun exposure predicted greater WBV and GMV in MS patients. Interestingly though, when vitamin D levels were measured, they had no influence on the positive effects of sun exposure with WBV or GMV. The researchers concluded: “Sun exposure may have direct effects on MRI measures of neurodegeneration in MS, independently of vitamin D.”
Be sure that you soak up your share of sunlight, without burning of course. It may indeed save your life!
 Davenport, C. Multiple Sclerosis from the standpoint of geographic distribution and race. Arch Neurol Psychiatry 1922;8:
 Acheson ED, Bachrach CA, Wright FM. Some comments on the relationship of the distribution of multiple sclerosis to altitude, solar radiation and other variables. Acta Psychiat (Scand) 1960;35 (suppl 147):132-47. 51-58
 Norman JE Jr, Kurtzke JF, Beebe GW. Epidemiology of multiple sclerosis in USA veterans: 2. Latitude, climate, and risk of multiple sclerosis. J Chron Dis 1983;36:551-59
 Zivadinov R, Treu CN, Weinstock-Guttman B, Turner C, Bergsland N, O’Connor K, Dwyer MG, Carl E, Ramasamy DP, Qu J, Ramanathan M. Interdependence and contributions of sun exposure and vitamin D to MRI measures in multiple sclerosis. J Neurol Neurosurg Psychiatry. 2013 Oct;84(10):1075-81.
Benegits of sun exposure by Marc Sorenson, EdD…
For those who follow my writings, it should now be obvious that the risk of melanoma is decreased by regular sun exposure, and that the evidence for the health benefits of safe sun becomes clearer by the day. I opine that millions of lives could be saved yearly by regular, non-burning sun exposure for the entire population.
Another benefit of moderate sun exposure, or other ultraviolet radiation (UVR), is that it does not cause sufficient DNA damage to prevent efficient repair. A study published in the British Journal of Dermatology reviewed the impact of repeated low level sunlight exposures on vitamin D status and DNA damage/repair in light and brown skinned individuals. The UVR doses were equivalent to 13-17 minutes of midday exposure in the UK. The study reported that no evidence existed for these low-level exposures leading to accumulated DNA-damage, indicating that any damage was quickly repaired. The research also showed that the exposures led to sufficient vitamin D levels in the participants. In addition, it has been shown that “Regular exposure to UV leads to an almost complete disappearance of DNA damage in the basal and suprabasal layers of the epidermis, where the initiating of skin cancer occurs. It is no wonder that regular sun exposure is associated with less melanoma! Soak up some moderate, non-burning sun!
 Felton SJ, Cooke MS, Kift R, Berry JL, Webb AR, Lam PMW, de Gruijl FR, Vail A, and Rhodes LE. Concurrent beneficial (vitamin D production) and hazardous (cutaneous DNA damage) impact of repeated low-level summer sunlight exposures. Br J Dermatol. 2016 Jul 14. doi: 10.1111/bjd.14863. [Epub ahead of print]
 van der Rhee H, de Vries E, Coomans C, van de Velde P, Jan Willem Coebergh JW. Sunlight: For Better or For Worse? A Review of Positive and Negative Effects of Sun Exposure. Cancer Research Frontiers. 2016 May; 2(2): 156-183.
By Marc Sorenson, EdD, Sunlight Institute, for sensible tanning bed use
The online magazine, Life Science Daily, just posted an article regarding the health benefits of UV light from tanning beds. Surprisingly, they were quoting from research published in the British Journal of Dermatology. I say “surprising,” because so many dermatologists and dermatological organizations are vehemently opposed to a single ray of sunlight touching the skin. And heaven forbid someone should use a tanning bed.
Three times weekly, adult subjects were exposed to a tanning bed that emitted 95% UVA rays and 5% UVB rays, which is approximately the amount of UVA and UVB that midday summer sunlight emits. Each exposure lasted six minutes. Here are some of the salient points reported in the article:
- Any damage caused by the light exposure was repaired by the by the skin.
- One of the positive benefits of the light was the production of nitric oxide, which improves blood flow and reduces blood pressure.
- Another positive benefit was the productions of beta-endorphins, which reduce depression.
- A third benefit, of course, is the production of vitamin D, necessary for growth and bone strength, as well as asthma prevention.
Here is one of the important quotes from the article, from Dr. Michael Holick: “What this study shows is that you can get a reasonable amount of sunlight that would make enough vitamin D in your skin living in the U.K. Yes, the DNA is somewhat damaged, but because the body has adapted to its environment, it has the ability to repair it.” Dr. Holick also suggested that people become educated about the wide range of health benefits from modest sun exposure, which is superior to taking vitamin D supplements.
Step by step, the truth is overcoming the powers of darkness! Seek the sun, and let a tanning bed enhance your health in the winter.
Click here to read the article. https://lifesciencedaily.com/stories/19743-study-shows-health-benefits-non-burning-exposure-uv-light/
Sun exposure and health By Marc Sorenson, EdD, Sunlight Institute…
New research shows that sunlight boosts the effectiveness of T-cells, an integral part of the immune system. T-cells are a type of lymphocyte that recognizes and binds to foreign invaders, thereby rendering them harmless. This is an important new finding, which demonstrates another beneficial effect of sun—one that has no relationship to vitamin D.
The key player in this action is the blue-light spectrum of sunlight that stimulates hydrogen peroxide production. The hydrogen peroxide (HP) causes T-cells to move to the site of infection, and it (HP) is also involved in the killing of noxious bacteria. Dr. Gerard Ahern, one of the primary investigators, stated it in this way: “T cells, whether they are helper or killer, need to move to do their work, which is to get to the site of an infection and orchestrate a response. This study shows that sunlight directly activates key immune cells by increasing their movement.”
Also interesting is the fact that the skin has a large share of the total T-cells in humans, about twice the number circulating in the blood. Think about this magnificent body of ours! It is programmed to immediately respond to any invasions that may occur in the skin, and sun exposure, if we take full advantage of it, immediately accelerates the process. Then, when the t-cells are activated by the blue light, they can move rapidly to other body areas where they can be utilized.
Sun exposure has also been found to have an exceptionally important and positive effect on autoimmune diseases such as lupus, MS, rheumatoid arthritis and others, many of which have been found to associate with low solar radiation and vitamin D. In this case, a different type of T-cell, called a regulatory T-cell, attacks the body’s own tissue, mistaking it for a foreign invader, and causes severe damage. The mechanism of autoimmune disease prevention by sunlight may be the suppression of regulatory T cells, in a manner that impedes the immune system’s attacks on its own tissues. 
Sunlight is one of God’s (or Nature’s) greatest miracles. Be sure to receive your full contingent of wonderful, non-burning sun.
 Thieu X. Phan, Barbara Jaruga, Sandeep C. Pingle, Bidhan C. Bandyopadhyay, Gerard P. Ahern. Intrinsic Photosensitivity Enhances Motility of T Lymphocytes. Scientific Reports, 2016;6:39479
 Schwalfenberg GK. Solar radiation and vitamin D: mitigating environmental factors in autoimmune disease. J Environ Public Health. 2012;2012:619381.
ArtukovićM1, Ikić M, Kustelega J, Artuković IN, Kaliterna DM. Influence of UV radiation on immunological system and occurrence of autoimmune diseases. Coll Antropol. 2010 Apr;34 Suppl 2:175-8.
Marsh-Wakefield F, Byrne SN. Photoimmunology and Multiple Sclerosis. Curr Top Behav Neurosci. 2015;26:117-41.
Sun exposure Information by Marc Sorenson, EdD. Sunlight Institute.
There are 62,700 cases of kidney cancer and 14,240 deaths annually. Kidney cancer incidence has tripled since the early 1980s, and some researchers have felt that environmental factors may have played a part in that worrisome increase. One of those factors may be sun exposure, which may be vital to the prevention of the disease. The newest research measured sun exposure, which was based on the average number of hours per day outdoors in the summer, during different periods of life. The researchers also took into consideration the age of the subjects and adjusted the data for other factors that may associate to kidney cancer.
These were some of the research results:
- Higher summer sun exposure at age 40+ years, but not at younger ages, was associated with a significantly lower risk of thyroid cancer. When comparing the highest quartile (fourth) of sun exposure to the lowest quartile, there was a 44% reduction in risk.
- Average lifetime sun exposure was not associated with thyroid-cancer risk.
- Recent summer sun exposure was closely associated with a decreased risk of thyroid cancer.
One of the salient points, in my mind, is that the best sun exposure is that which is habitual or consistent. In the case of kidney cancer, sun exposure in the past does not indicate that the disease will be avoided in the future. Only recent sun exposure provides protection. However, this is not necessarily true of other diseases; in the case of breast and prostate cancers, childhood sun exposure is associated with a lesser risk of the diseases in adulthood.
Previous research has also confirmed the importance of sun exposure on kidney-cancer prevention. There is a strong inverse correlation between sun exposure and kidney cancer. For example, one study that used NMSC as a measure of sun exposure, determined that sun exposure reduced the risk of several cancers, including kidney cancer, from 35% to 42%. Kidney cancer mortality rates were found to be strongly inversely correlated with solar UVB doses in Dr. William Grant’s 2002 and 2006 ecological studies. 
Recent research by Dr. Sara Karami and colleagues, demonstrates that in women, there is a significant reduction in kidney cancer with high levels of sun exposure. Those women with the highest fourth of sun exposure showed a 33% reduction in risk. 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 production.
Remember that a lifetime habit of non-burning sun exposure will always provide the best health outcomes.
 Rachel D Zamoiski, Elizabeth K. Cahoon, D. Michal Freedman, et al. Prospective study of ultraviolet radiation exposure and thyroid cancer risk in the United States. Cancer Epidemiol Biomarkers Prev Published Online First December 2, 2016.
 Tuohimaa P, Pukkala E, Scélo G, Olsen JH, Brewster DH, Hemminki K, Tracey E, Weiderpass E, Kliewer EV, Pompe-Kirn V, McBride ML, Martos C, Chia KS, Tonita JM, Jonasson JG, Boffetta P, Brennan P. Does solar exposure, as indicated by the non-melanoma skin cancers, protect from solid cancers: vitamin D as a possible explanation. Eur J Cancer 2007;43(11):1701-12
 Grant WB. An estimate of premature cancer mortality in the U.S. due to inadequate doses of solar ultraviolet-B radiation. Cancer. 2002 Mar 15;94(6):1867-75.
 Grant WB, Garland CF. The association of solar ultraviolet B (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates. Anticancer Res. 2006 Jul-Aug;26(4A):2687-99.
 Karami S, Colt JS, Stewart PA, Schwartz K, Davis FG, Ruterbusch JJ, Chow WH, Wacholder S, Graubard BI, Purdue MP, MooreLE. Short Report: A case-control study of occupational sun exposure and renal cancer risk. Int J Cancer. 2015 Oct 27.
By Marc Sorenson, EdD. For sun exposure…
It should be well-known by now, but the relationship between sun exposure and myopia (nearsightedness) is still being studied. And as before, the answer is the same: sun deprivation is associated to a greater myopia risk. The difference in this research was the study population, which was a random sample of participants 65 years and older from Europe. Among the factors that the researchers considered important, were vitamin D blood levels, vitamin D polymorphisms, ultraviolet B radiation (UVB), and years in education. Of these factors, only ultraviolet B radiation (UVB) was associated with reduced odds for myopia, especially if higher UVB exposure occurred during adolescence and early adulthood. This is another research paper that shows sun exposure to be protective against a disease, independent of vitamin D.
The authors of the study made this conclusion: “This study, while not designed to determine cause and effect relationships, suggests that increased ultraviolet B exposure, a marker of sunlight exposure, is associated with reduced myopia.
This is one in a long line of studies that show the relationship of sun exposure to myopia, and it doesn’t take a rocket scientist to determine that myopia is caused by lack of sun exposure. The evidence has been building for years. For example, one of the studies showed that the lowest risk of myopia among 12-year-old students was found among those who reported the highest levels of outdoor activity. Some might surmise that the key ingredient was exercise, but that idea was refuted by the fact that there was no association between indoor activity and myopia. Something besides exercise had to be leading to the lower risk of myopia among children who were actively outdoors; it had to be sun. The lower risk of myopia persisted after adjusting for genetic factors, ethnicity and the amount of near work. This is important, because for many years there was an assumption that long hours of study indoors, staring closely at books (near work) and never focusing on distant objects, led to myopia. This study belied that error.
This same research showed that the prevalence of myopia among Chinese children living in Singapore was 29.1%, whereas Chinese children living in Sydney, Australia, had a prevalence rate of only 3.3%. The children in Sydney spent about 13.8 hours per week outdoors compared to 3.05 hours in Singapore. In other words, the children who spent most or their lives indoors had 9.5 times the risk of developing myopia!
Depriving either adults or children of their time in the sunlight leads to myriad illnesses, only one of which is myopia. When will we learn?
 Katie M. Williams, FRCOphth; Graham C. G. Bentham, MA; Ian S. Young, MD; et al Association Between Myopia, Ultraviolet B Radiation Exposure, Serum Vitamin D Concentrations, and Genetic Polymorphisms in Vitamin D Metabolic Pathways in a Multicountry European Study. Published Online: December 1, 2016. doi:10.1001/jamaophthalmol.2016.4752
 Rose KA, Morgan IG, J, Kifley A, Huynh S, Smith W, Mitchell P. Outdoor activity reduces the prevalence of myopia in children. Ophthalmology 2008 Aug;115(8):1279-85.
Sun exposure By Marc Sorenson, EdD… Sunlight Institute…
Nearly thirty years ago, I talked to many “experts” who told me that our mostly vegetarian diet could not help those who suffered from arthritis, because “diet has nothing to do with arthritis.” However, I was able to find one or two pieces of research that indicated that arthritis was indeed associated with poor nutrition and could be ameliorated or reversed by proper nutritional habits.
Then, during our many years in the health and fitness resort business, we observed many seeming miracles with our arthritic attendees. One woman, who could not play piano due to her arthritic hands, was able to play again in less than two weeks. Her reduction in inflammation was visible and her increase in range-of motion was remarkable. Her husband, who could not walk more than about a hundred yards when they arrived, was walking a mile after two weeks as his arthritic hips recovered range of motion and his muscles gained strength.
Through serendipity, a few days ago, a piece of research appeared to me—a study that I wished I had known about 30 years ago. It was published in 1935, and was titled, THE TREATMENT OF CHRONIC ARTHRITIS BY DIET AND SUNLIGHT. The author studied a group of seventy-two arthritic patients whom he treated with diet, calling his program the “depletion diet.” The diet was bulky and very high in protective foods, but contained very little protein and fat. He stated that “Thus in seventy-two cases treated by diet, five were not improved, thirteen were slightly improved, thirty-nine were much improved, and fifteen were completely relieved.”
Other treatment included sunbathing, and the doctor considered it so important that he had his patients move to an area where they could sunbathe for at least eight weeks per year. He felt that it was almost indispensable.
Our program was somewhat similar, although our diet was much stricter. We were fortunate that we already operated our resort in an area where the sun shines about 260 days per year.
Other research has shown a correlation between arthritis and sun exposure. A paper by Dr. Viera and colleagues demonstrated that at high latitudes, where sun exposure is considerably less available, the rate of rheumatoid arthritis (RA) is much higher than at lower latitudes. RA is also more severe in winter, a time of less sun exposure.
So give up the junk food and safely embrace the sun. Your joints will love it!
 Langsworth, L. THE TREATMENT OF CHRONIC ARTHRITIS BY DIET AND SUNLIGHT. CALIFORNIA AND WESTERN MEDICINE. March, 1935.
Vieira VM, Hart JE, Webster TF, Weinberg J, Puett R, Laden F, Costenbader KH, Karlson EW. Association between Residences in U.S. Northern Latitudes and Rheumatoid Arthritis: A Spatial Analysis of the Nurses’ Health Study. Environ Health Perspect. 2010 Mar 25. [Epub ahead of print]
Cutolo M, Otsa K, Uprus M, Paolino S, Seriolo B. Vitamin D in rheumatoid arthritis. Autoimmun Rev 2007;7:59-64
By Marc Sorenson, EdD… Sun exposure benefits…
A very important paper regarding the necessity for sun exposure has recently been published by the journal Medical Hypothesis. It is entitled Regular sun exposure benefits health, and it discusses the pros and cons of sun exposure. One of the salient statements in the paper is that intermittent sun exposure may increase the risk of skin cancer, whereas regular exposure to sunlight might benefit health. For those of us who have for years studied the beneficial effects of sun exposure, the use of the word “might” is the only drawback to the statement. There is no doubt that for the majority of the population, regular sun exposure absolutely protects and enhances health.
Among the diseases mentioned as being reduced or prevented by regular sun exposure are the following:
- Cancers: Colon, breast, prostate and non-Hodgkin lymphoma
- Multiple sclerosis
As the authors mention, most of these positive effects of sun exposure were previously ascribed to Vitamin D, but they point out that immune system function is enhanced by sun exposure beyond the effects of vitamin D, and list other non-vitamin D benefits of the sun, including:
- Production of nitric oxide
- Production of melatonin
- Production of serotonin
- Regulation of the circadian clock
I have discussed most of these items on the Sunlight Institute web site, but it was good to see new research that, in particular, separated the health benefits of sun exposure from vitamin D production. The idea that has become popularized during the past decade, that all benefits of sun exposure come from increased vitamin D production, is simply not true and can lead to the supplementation of vitamin D as a “cure” for diseases that may not be influenced by that hormone.
Of course, vitamin D is an exceptionally important photoproduct, and the only natural way to attain it is by exposure to the sun or to other sources of UVB light (such as a sunlamp or a tanning bed). The beauty of using these sources, rather than a vitamin-D capsule, is that all of the benefits of nitric oxide, melatonin, serotonin and circadian entrainment are included in the package.
Safely enjoy the sun, and you then will also safely enjoy better health. Remember not to burn, and to gradually develop a good tan.
 van der Rhee H, de Vries, E, Coebergh, J. Regular sun exposure benefits health. Medical Hypotheses 97 (2016) 34–37
The importance of sun exposure for colon cancer
By Marc Sorenson, EdD, Sunlight Institute…
In 1980, Cedric and Frank Garland published a seminal paper showing a relationship between colon cancer and geographical location. They observed dramatically higher rates of colon cancer in the Northeast, where there is a paucity of sun exposure, compared with the South and West where sun is more prevalent. They hypothesized that vitamin D, stimulated in the skin by sun, reduced the risk of colon cancer. They pointed out the correlation between colon cancer and UVR exposure, stating particularly that “New Mexico and Arizona had the highest statewide mean solar radiation values (500 gm-cal/cm2). These states experienced colon cancer rates for white males of 6.7 and 10.1 per 100 000 population, respectively, over the period 1959–61. New York, New Hampshire, and Vermont had the lowest statewide mean solar radiation values (300 gm-cal/cm2) and experienced colon cancer rates for white males of 17.3, 15.3, and 11.3 per 100 000 populations, respectively, during the same period.”
Other studies have corroborated the correlation between high sun exposure and low colon cancer rates. Japanese research demonstrated that people in the areas of highest solar radiation exhibit the lowest rates of colon cancer, with those living in the areas of highest sun exposure having about half the colon cancer rate as those living in the lowest.A significant aspect of this research is that sun correlated to a reduced risk of cancer even where vitamin D consumption was high, indicating that sun exposure (as noted with prostate cancer and breast cancer, above) may have beneficial influences on cancer beyond its stimulation of vitamin D production, or that vitamin D produced in the skin by sun exposure may have advantages over that consumed through food or supplements.
The research by Dr. Mizoue is not the only investigation that differentiated the effects of UV light exposure and vitamin D/colon cancer. A six-week study by Dr. Rebel and colleagues used mice with intestinal tumors—tumors that often progress to cancers. It was shown that the mice given either UV radiation or vitamin-D supplementation reduced the tumor load when compared to mice who received no treatment. However, only the UV treatments prevented the tumors from progressing to cancer. Still other recent research has demonstrated that sun, not vitamin D, may produce all of the positive effects on colon cancer. The researchers performed a 140-day investigation involving rats that had colon adenomas (a precursor to full-blown colon cancer) induced in their colons. The rats were given either vitamin D3 as supplements, or the stored form of vitamin D, 25(OH)D3, in differing amounts. With low dose vitamin D in either form, no reduction in either existing adenomas or emerging tumors were seen. In higher doses, there was a dose-dependent increase in colon tumor numbers in both male and female rats. The researchers said the following in their concluding statement: “Thus, the association between sun exposure and the incidence of colon cancer may involve factors other than vitamin D concentrations. Alternative hypotheses warrant investigation. Furthermore, this study provides preliminary evidence for the need for caution regarding vitamin D supplementation of humans at higher doses, especially in individuals with sufficient serum 25(OH)D3 concentrations.” The takeaway from this research is this: sun is protective against colon cancer in rats (and probably in humans), independent of vitamin D—another reason to safely embrace the sun.
These studies again demonstrate that we cannot substitute vitamin D pills for sun in many cases. UV light from sun or sun lamps is always the best option to cover all prevention and healing possibilities.
 Garland CF, Garland FC. Do sun and vitamin D reduce the likelihood of colon cancer? Int. J. Epidemiol 1980;9:227–31.
 Mizoue, T. Ecological study of solar radiation and cancer mortality in Japan. Health Phys 2004;87:532-38.
 Rebel H1, der Spek CD, Salvatori D, van Leeuwen JP, Robanus-Maandag EC, de Gruijl FR. UV exposure inhibits intestinal tumor growth and progression to malignancy in intestine-specific Apc mutant mice kept on low vitamin D diet. Int J Cancer. 2015 Jan 15;136(2):271-7.
 Irving AA, Plum LA, Blaser WJ, Ford MR, Weng C, Clipson L, DeLuca HF, Dove WF. Cholecalciferol or 25-hydroxycholecalciferol neither prevents nor treats adenomas in a rat model of familial colon cancer. J Nutr. 2015 Feb;145(2):291-8.