To prevent cancer, everyone should bare off and take the noon-day sun for several minutes every day. . However, not so long that you burn (or even turn pink), and also go out WITHOUT a hat, sunblock, prescription glasses or sunglasses
Risk of developing several cancers increases with the latitude of where you live (i.e. the less sun you get in your location, the higher your risk for cancer). Including Hodgkin's lymphoma, colon, pancreatic, prostate, ovarian, and breast cancer. Holick MF, 2006
Maintaining a sufficiency of vitamin D in your blood protects against several common cancers. Several large cohort studies have now shown that CALCIDIOL, (precursor to CALCITRIOL, active vitamin D) levels<20 ng/mL (50 nmol/L) are associated with a 30 - 50% higher risk of colon, prostate, and breast cancer. A recent review of vitamin D in the prevention of colorectal cancer concluded that a CALCIDIOL level of 36 ng/mL (90 nmol/L) provided optimal protection against the development of colorectal neoplasia. Bischoff-Ferrari HA et al, 2006
Vitamin D deficiency linked to cancer back in the 1930's - A study of US navy personnel linking internal cancers with a lack of exposure to the sun / vitamin D deficiency was published in 1937. Since then several studies (referenced further in this article) have shown a lower risk for cancer for those living in sunnier states, at higher latitudes (with higher UV-B availability), and in rural areas (where people tend to spend more time outdoors). Attempts have been made to explain these geographic benefits as differences in other lifestyle factors, such as diet and socioeconomic status, however, the two main risk factors for cancer, i.e. smoking and diet, are not significantly different across the country.
CALCITRIOL (the active form of vitaminD) regulates cell growth and maturation. Exposing the skin to the sun's UV-B radiation produces vitamin D in the body, and it has been consistently demonstrated that activation of the vitamin D receptor by CALCITRIOL reduces cancer risk via fairly well defined mechanisms, which prevent cells from becoming malignant:
The cancers most strongly linked to low levels of vitamin D are:
Increased vitamin D3 levels could prevent 250,000 cases of colorectal cancer and 350,000 cases of breast cancer worldwide each year. According to researchers from the Moores Cancer Center at the University of California, San Diego (UCSD), especially in countries north of the equator (150,000 cancer cases in the U.S. could be prevented). Protective effects began when blood CALCIDIOL (25(OH)D) levels ranged from 24 -32 ng/ml. In the U.S., late winter CALCIDIOL levels ranged from only 15 - 18 ng/ml. Previous research has shown optimal cancer prevention value to be ~55 ng/ml.
Researchers concluded that a dietary intake of 2000 IU/day of vitamin D3, and very moderate exposure to sunlight (when possible), could raise serum CALCIDIOL to 52 ng/ml -a level associated with a 50% reduction in breast cancer incidence, according to observational studies. The Journal, 2007
U.S. study found 16 types of cancers (primarily epithelial, relating to surface) of the digestive and reproductive systems to be inversely correlated to UV-B exposure. These cancers included breast, endometrial, esophageal, ovarian, non-Hodgkin's lymphoma, prostate, bladder, gallbladder, gastric, pancreatic, rectal and renal cancers;
In males approximately 80% of the cancers attributable to low regional solar UV-B were digestive-system cancers
Other cancer correlations. 10 types of cancer were significantly correlated with smoking, 6 types with alcohol, and 7 types with Hispanic heritage. Poverty status was inversely correlated with 7 types of cancer. Since the results for alcohol, Hispanic heritage, and smoking for white Americans agree well with the literature Trapido et al., 1995; Thun et al., 2002, they provide a high level of confidence in the study's approach and results for UV-B radiation. Grant WB, 2002
Averaged annual solar radiation inversely correlated to mortality from digestive cancers (but not other cancers) in Japan. - i.e. Esophagus, stomach, colon, rectum, pancreas, and gallbladder and bile ducts - It is interesting that UV-B exposure makes a difference, since Japan's high fish consumption, would ensure high levels of dietary vitamin D. Mizoue T. Ecological study of solar radiation and cancer mortality in Japan. Health Phys 2004;87:532-8
A Norwegian study shows that breast, colon, and prostate cancer detection has a seasonal cycle correlated with vitamin D production by sunlight. The study also shows that vitamin D effectively fights cancer even in the later stages. Robsahm TE et al,2004
Low exposure to UV-B is associated with increased risk of endometrial cancer in an ecological study reported in "Preventive Medicine": "Is ultraviolet B irradiance inversely associated with incidence rates of endometrial cancer: an ecological study of 107 countries". Interestingly, additional factors found positively associated with (i.e. associated with an increase risk of) endometrial cancer included high intake of energy from animal sources (i.e. eating a lot of meat), proportion of population overweight, and per capita health expenditure . Mohr SB et al, 2007
More sunlight reduces colon cancer mortality. The key to understanding this geographic pattern was provided by Cedric and Frank Garland in 1980. They reasoned that sunlight, through the production of vitamin D, reduced the risk of colon cancer in the sunny areas compared to that in the darker areas. They performed an ecologic study of annual solar irradiance versus colon cancer mortality rates and found a strong inverse correlation, i.e. the more sunlight, the less cancer. (An ecologic study treats entire populations defined geographically as entities, with values for disease outcome and environmental or dietary factors averaged for each entity.) Garland CF, Garland FC, 1980
In 1941, Dr. Frank Apperly demonstrated an association between latitude and cancer mortality. Apperly FL, 1941
U.S. cancer mortality rates higher in Northeast than Southwest. An explanation involving environmental factors is required to explain why mortality rates for a number of internal cancers are ~ twice as high in northeast's highly-urbanized states than in the southwest's more rural states. Devesa SS et al, 1950-1994
Smoking and diet are known risk factors for cancer neither of which vary significantly throughout mainland U.S. Doll R and Peto R, 1981
Lifetime exposure to sunlight may reduce your risk of some of the most common types of cancer. In an analysis of death certificates from 24 U.S. states between 1984 and 1995, National Cancer Institute (NCI) researchers found that people who lived in the sunniest parts of the country, and those exposed to the most sunlight through their jobs, had significantly lower rates of breast and colon cancer than matched controls.They only included people who were born and died in states in the same solar radiation range. Overall, people who lived in the highest solar radiation range (E.g. in Arizona, Hawaii, Florida, and Texas) had less risk of dying of breast, ovarian, prostate, or colon cancer than those who lived in the lowest range (E.g. in Maine, New Hampshire, Ohio, and Washington).
People who worked outside had 20-25 % less risk of breast and colon cancer. Across all levels of solar radiation and even after adjusting for physical activity level.
Study found that rural residence was inversely correlated to breast, colon, endometrial, esophageal, ovarian, and non-Hodgkin's lymphoma. This suggests that urban living is associated with reduced UVB exposure compared to living in a rural environment. The study estimated 45,000 Americans die from cancer annually as a result of inadequate vitamin D levels. Of these, 22,500 urban Americans die as a consequence of indoor lifestyle and lack of exposure to the sun's UVB light, and another 22,500 based on residential location due to unavailability of UV-B. Grant WB. 2002
As early as 1937, Peller and Stephenson hypothesized that sunlight exposure lowered the risk of cancer. A study of US navy personnel linked those with skin cancer and actinic keratosis with lower risk for internal cancers . Peller S, Stephenson CS, 1937
In 1941, Frank Apperly reexamined the evidence produced by Peller. Apperly FL, 1941
The campaign to discourage sun exposure and urge the use of sun block began about 30 years ago. Dermatologists noticed that skin cancer rates were increasing, and wrongly assumed that excess sun was causing this increase. In the 90's, already aware that lack of sunlight / vitamin D could cause rickets, scientists began to realize that vitamin D had multiple roles in all the body's cells, and suspected that lack of vitamin D was increasing certain cancer rates, including breast and colon cancer.
Two studies run by the Harvard School of Public Health found that high vitamin D levels reduced risk for colon cancer. The Nurse's Health Study and the Health Professionals Study (1986-2006), have been following tens of thousands of people for decades:
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