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| | From:  JamieDH4 (Original Message) | Sent: 6/3/2007 12:43 AM |
Hans-
Why do people exposed to higher amounts of (unprotected) sunlight seem to have lower incidences of autoimmune diseases, and cancers? Is it just a correlation or is there actual evidence to support sunlights benefits? |
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Well, I can't imagine that people with AA in their cells who get a lot of sunlight have less skin cancer, for example. Have you read Peat's essays on sunlight and light in general? I would like to see the evidence for these claims, because that is the only way I can possibly get a sense of what mechanisms may be at work. It may be that the people studied (who get less cancer) are Asians who eat a lot of coconut - too many factors, so go ahead and cite the source of these claims and I'll take a look. |
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| I would comment here that the reason is VitD (a steroid hormone which is immunomodulatory and induces differentiation of cancerous cells). Depending on the complexion different levels of UV radiation are needed to manufacture VitD. One extreme are black men working in e.g. Canada closed all day long in offices with artificial illumination. Unless they heavily supplement with VitD they are set for prostate cancer (given AA is present in their cells to fuel the cancer growth). The other extreme would be white people living on refined vegetable oils in Australia. If they expose themself to sunlight to get burned occasionaly, skin cancer is almost guaranteed in the long run. Interestingly it seems also important that blue light doesn't reach the eyes during the natural sleep cycle everyday so the body can manufacture enough hormone melatonin which synchronizes all organs and stimulates selfrepair (females with night shift work have increased rates of breast cancer while blind females have less than average rates). |
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I'm going to post a bunch of them, but here is one that makes the point I am trying to ask about.
Sunlight, cholesterol and coronary heart disease.
Grimes DS, Hindle E, Dyer T.
Department of Medicine, Blackburn Royal Infirmary, UK.
We investigated the relationship between geography and incidence of coronary heart disease, looking at deficiency of sunlight and thus of vitamin D as a factor that might influence susceptibility and thus disease incidence. Sunlight deficiency could increase blood cholesterol by allowing squalene metabolism to progress to cholesterol synthesis rather than to vitamin D synthesis as would occur with greater amounts of sunlight exposure, and the increased concentration of blood cholesterol during the winter months, confirmed in this study, may well be due to reduced sunlight exposure. We show evidence that outdoor activity (gardening) is associated with a lower concentration of blood cholesterol in the summer but not in the winter. We suggest that the geographical variation of coronary heart disease is not specific, but is seen in other diseases and sunlight influences susceptibility to a number of chronic diseases, of which coronary heart disease is one. |
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Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease.
Holick MF.
Department of Medicine, Section of Endocrinology, Nutrition, and Diabetes, Vitamin D, Skin, and Bone Research Laboratory, Boston University Medical Center, Boston, MA 02118, USA. [email protected]
Most humans depend on sun exposure to satisfy their requirements for vitamin D. Solar ultraviolet B photons are absorbed by 7-dehydrocholesterol in the skin, leading to its transformation to previtamin D3, which is rapidly converted to vitamin D3. Season, latitude, time of day, skin pigmentation, aging, sunscreen use, and glass all influence the cutaneous production of vitamin D3. Once formed, vitamin D3 is metabolized in the liver to 25-hydroxyvitamin D3 and then in the kidney to its biologically active form, 1,25-dihydroxyvitamin D3. Vitamin D deficiency is an unrecognized epidemic among both children and adults in the United States. Vitamin D deficiency not only causes rickets among children but also precipitates and exacerbates osteoporosis among adults and causes the painful bone disease osteomalacia. Vitamin D deficiency has been associated with increased risks of deadly cancers, cardiovascular disease, multiple sclerosis, rheumatoid arthritis, and type 1 diabetes mellitus. Maintaining blood concentrations of 25-hydroxyvitamin D above 80 nmol/L (approximately 30 ng/mL) not only is important for maximizing intestinal calcium absorption but also may be important for providing the extrarenal 1alpha-hydroxylase that is present in most tissues to produce 1,25-dihydroxyvitamin D3. Although chronic excessive exposure to sunlight increases the risk of nonmelanoma skin cancer, the avoidance of all direct sun exposure increases the risk of vitamin D deficiency, which can have serious consequences. Monitoring serum 25-hydroxyvitamin D concentrations yearly should help reveal vitamin D deficiencies. Sensible sun exposure (usually 5-10 min of exposure of the arms and legs or the hands, arms, and face, 2 or 3 times per week) and increased dietary and supplemental vitamin D intakes are reasonable approaches to guarantee vitamin D sufficiency. |
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In the first study, the assume that "high cholesterol" is going to lead to higher rates of "heart disease," which is now known to be false. Oxidized LDL seems to be the biggest problem, so there is no reason to pay much attention to that study. In the second one, they are talking about vitamin D deficiency, and that is one possible factor for this claim, if it is in fact accurate. However, I prefer to supplement with small amounts of D than get a lot of sunlight. Native Americans had hardly any cancer, a hundred or so years ago, but their skin didn't look good as they got older (at least to me, judging from the old photos). |
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