Posted on 04/05/2006 2:56:25 AM PDT by S0122017
Sunscreen chemicals disrupt thyroid in rats
Chemicals found in many sunscreens can disrupt the production of thyroid hormone in rats, researchers report.
Their study raises concerns that chemicals that absorb ultraviolet light could damage the thyroid in people. The thyroid gland is located in the neck and secretes hormones that affect growth and metabolism.
UV light from the Sun can potentially cause skin cancer. But studies on the chemicals that block UV have already raised concerns over side effects. In 2001 Swiss researchers reported that 4-methyl-benzylidene camphor (4-MBC), among other sunscreen chemicals, mimicks the reproductive hormone oestrogen and accelerates the development of the uterus in rats.
Experiments in animals had also suggested that 4-MBC could affect the thyroid, but did not reveal how much or why. Now German scientists say they have data from rats showing the extent to which this chemical can disrupt thyroid hormone and change the volume of the gland itself. Doubled hormone
Josef Köhrle of Charité University of Medicine in Berlin and his colleagues fed various amounts of 4-MBC to rats. They say that feeding the animals the compound makes sense because environmental surveys in countries such as Switzerland have detected it in lake waters.
Furthermore, Köhrle says Danish researchers recently reported that 4-MBC from topically applied sunscreen can enter the blood, though he stressed that no group has yet repeated and confirmed these findings.
Rats that received a daily dose of 33 milligrams of 4-MBC per kilogram of their bodyweight for five days showed a 15% increase in thyroid-stimulating hormone, which prompts the thyroid to produce metabolism-regulating hormones. Those that received 600 milligrams of the compound per kilogram of their weight each day had double the normal amount of thyroid stimulating hormone. There was also a 20% increase in the thyroid size of rats receiving a daily dose of 100 milligrams per kilogram of 4-MBC over five days in comparison with control rats. Iodine protection
Further experiments on rats and human cells in the lab showed that another major UV-blocking chemical, benzophenone 2 (BP2), also disrupted hormones that act on the thyroid. But the German team also found that the presence of element iodine in the mixture prevented this negative effect. Iodine has been previously shown to affect pathways involving thyroid stimulating hormone.
Medical experts say that further experiments are needed to explore the results from Köhrle's group. "I would view these findings with interest,” says Dennis Oh, who studies the effects of DNA damage in skin cells at the University of California, San Francisco, US. But he cautions against extrapolating the results to apply to humans and says: "The benefits of wearing sunscreen far outweigh the theoretical risks."
Köhrle also says that people should not interpret the findings from his study on rats as a reason to give up wearing sunscreen now. Instead, he says they should make sure that their diet includes enough iodine, which could protect against the effects of BP2. But if the effect seen in rats is found in people, he says, "we may have to rethink how we protect children and those with existing thyroid problems from Sun exposure".
Köhrle presents the findings at the European Congress of Endocrinology in Glasgow, UK on Wednesday 5 April 2006.
ping
this would explain why men going to tanning sessions are such you know what.
interesting!
Ofcourse oestrogen-mimics are also in plastic. Leading some controversial reasearchers to suggest that youknowwho are on the rise because of the huge amounts of female hormone mimics present in the human body thanks to chemical waste, plastics, sun-screen and perhaps additives.
I believe that male babies from mothers that where exposed to above acceptable levels of toxic waste in food showed braindevelopment more reminiscent to that of a female than that of a male. What influence that had on sexual preference wasnt tested. Guess they didnt wanted to wait 18 years.
Well, the estrogen studies bother me a bit. Those were dosed at levels that you would see in sunscreen.
On the other hand, 33 mg/kg of bodyweight seems like an awfully high concentration.
I'd have to see the actual studies on this one.
Here is a link to a cached report on 4-MBC from last year that seems to have similiar findings:
http://72.14.203.104/search?q=cache:5W5uo65QcpAJ:www.nrp50.ch/objectGallery/pdf/2127_01.pdf++%22Shining+a+Light+on+Sunscreens%22&hl=en&gl=us&ct=clnk&cd=7&lr=lang_en&ie=UTF-8
After being diagnosed with osteoporosis, I have been told by my new physician that small children, the elderly and especially small boned, fair skinned women over 40 are at a dangerous risk of bone loss due to complete lack of sunshine, which is one of only two ways to obtain Vitamin D - Calciferol.
Yes, here in Holland we have a lot of cases of orthodox muslim women getting shortage of vitamin D. This because they are often kept inside the house, and the rare times that they are allowed out of the house they wear burka's. Apparently they can live with this in arab countries as there is so much sun that even a little bit can give you enough (or maybe muslim women adapted to surviving on less sunlight) but in holland there is so little sun, that they are now getting insufficient amounts.
One of the best sunscreens in the world is liquid "foundation" makeup. Creates a physical barrier. Growing up, my sister was allergic to most sunscreens. My mom got a foundation close to her skin color and slathered it on. My sister never burned and hardly even tanned while wearing the foundation. The cheap stuff works well.
Wanted to add I also agree that sunshine is vital to health. People can go overboard avoiding it.
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