An Oldie Vies for Nutrient of the Decade

Vitamin D: An Oldie Vies for Nutrient of the Decade

The so-called sunshine vitamin is poised to become the nutrient of the decade, if a host of recent findings are to be believed. Vitamin D, an essential nutrient found in a limited number of foods, has long been renowned for its role in creating strong bones, which is why it is added to milk.

Now a growing legion of medical researchers have raised strong doubts about the adequacy of currently recommended levels of intake, from birth through the sunset years. The researchers maintain, based on a plethora of studies, that vitamin D levels considered adequate to prevent bone malformations like rickets in children are not optimal to counter a host of serious ailments that are now linked to low vitamin D levels.

To be sure, not all medical experts are convinced of the need for or the desirability of raising the amount of vitamin D people should receive, either through sunlight, foods, supplements or all three. The U.S. government committee that establishes daily recommended levels of nutrients has resisted all efforts to increase vitamin D intake significantly, partly because the members are not convinced of assertions for its health-promoting potential and partly because of time-worn fears of toxicity.

This column will present the facts as currently known, but be forewarned. In the end, you will have to decide for yourself how much of this vital nutrient to consume each and every day and how to obtain it.

Where to Obtain It

Through most of human history, sunlight was the primary source of vitamin D, which is formed in skin exposed to ultraviolet B radiation (the UV light that causes sunburns). Thus, to determine how much vitamin D is needed from food and supplements, take into account factors like skin color, where you live, time of year, time spent out of doors, use of sunscreens and coverups and age.

Sun avoiders and dark-skinned people absorb less UV radiation. People in the northern two-thirds of the country make little or no vitamin D in winter, and older people make less vitamin D in their skin and are less able to convert it into the hormone that the body uses. In addition, babies fed just breast milk consume little vitamin D unless given a supplement.

In addition to fortified drinks like milk, soy milk and some juices, the limited number of vitamin D food sources include oily fish like salmon, mackerel, bluefish, catfish, sardines and tuna, as well as cod liver oil and fish oils. The amount of vitamin D in breakfast cereals is minimal at best. As for supplements, vitamin D is found in prenatal vitamins, multivitamins, calcium-vitamin D combinations and plain vitamin D. Check the label, and select brands that contain vitamin D3, or cholecalciferol. D2, or ergocalciferol, is 25 percent less effective.

Vitamin D content is listed on labels in international units (IU). An eight-ounce glass of milk or fortified orange juice is supposed to contain 100 IU Most brands of multivitamins provide 400 a day. Half a cup of canned red salmon has about 940, and three ounces of cooked catfish about 570.

Myriad Links to Health

Let's start with the least controversial role of vitamin D ― strong bones. Last year, a 15-member team of nutrition experts noted in The American Journal of Clinical Nutrition that "randomized trials using the currently recommended intakes of 400 IU vitamin D a day have shown no appreciable reduction in fracture risk."

"In contrast," the experts continued, "trials using 700 to 800 IU found less fracture incidence, with and without supplemental calcium. This change may result from both improved bone health and reduction in falls due to greater muscle strength."

A Swiss study of women in their 80s found greater leg strength and half as many falls among those who took 800 IU of vitamin D a day for three months along with 1,200 milligrams of calcium, compared with women who took just calcium. Greater strength and better balance have been found in older people with high blood levels of vitamin D.

In animal studies, vitamin D has strikingly reduced tumor growth, and a large number of observational studies in people have linked low vitamin D levels to an increased risk of cancer, including cancers of the breast, rectum, ovary, prostate, stomach, bladder, esophagus, kidney, lung, pancreas and uterus, as well as Hodgkin's lymphoma and multiple myeloma.

Researchers at Creighton University in Omaha conducted a double-blind, randomized, placebo-controlled trial (the most reliable form of clinical research) among 1,179 community-living, healthy postmenopausal women. They reported last year in The American Journal of Clinical Nutrition that over the course of four years, those taking calcium and 1,100 IU of vitamin D3 each day developed about 80 percent fewer cancers than those who took just calcium or a placebo.

Vitamin D seems to dampen an overactive immune system. The incidence of autoimmune diseases like Type 1 diabetes and multiple sclerosis has been linked to low levels of vitamin D. A study published on Dec. 20, 2006, in The Journal of the American Medical Association examined the risk of developing multiple sclerosis among more than seven million military recruits followed for up to 12 years. Among whites, but not blacks or Hispanics, the risk of developing MS increased with ever lower levels of vitamin D in their blood serum before age 20.

A study published in Neurology in 2004 found a 40 percent lower risk of MS in women who took at least 400 IU of vitamin D a day.

Likewise, a study of a national sample of non-Hispanic whites found a 75 percent lower risk of diabetes among those with the highest blood levels of vitamin D.

Vitamin D is a fat-soluble vitamin that when consumed or made in the skin can be stored in body fat. In summer, as little as five minutes of sun a day on unprotected hands and face can replete the body's supply. Any excess can be stored for later use. But for most people during the rest of the year, the body needs dietary help.

Furthermore, the general increase in obesity has introduced a worrisome factor, the tendency for body fat to hold on to vitamin D, thus reducing its overall availability.

As for a maximum safe dose, researchers like Bruce Hollis, a pediatric nutritionist at the Medical University of South Carolina in Charleston, maintain that the current top level of 2,000 IU is based on shaky evidence indeed ― a study of six patients in India. Hollis has been giving pregnant women 4,000 IU a day, and nursing women 6,000, with no adverse effects. Other experts, however, are concerned that high vitamin D levels (above 800 IU) with calcium can raise the risk of kidney stones in susceptible people.

Giant Sheets of Dark Matter Detected

Giant Sheets of Dark Matter Detected

CLICK TO VIEW Cloaked Giants A dark matter ring is seen in a galaxy center. An international team of astronomers peering into the deep Universe said they had mapped the biggest-ever structure of the enigmatic substance known as dark matter.

The most colossal structures in the universe have been detected by astronomers who tuned into how the structures subtly bend galactic light.

The newfound filaments and sheets of dark matter form a gigantic features stretching across more than 270 million light-years of space--three times larger than any other known structure and 2,000 times the size of our own galaxy.

Because the dark matter, by definition, is invisible to telescopes, the only way to detect it on such grand scales is by surveying huge numbers of distant galaxies and working out how their images, as seen from telescopes, are being weakly tweaked and distorted by any dark matter structures in intervening space.

"We measured the shapes of millions of galaxies and then mapped the stretching of their light," explained astronomer Ludovic Van Waerbeke of the University of British Columbia. The international team from France and Canada studied the galaxies with the Canada-French-Hawaii Telescope Survey's MegaCam telescope in Hawaii.

The resulting map of distorted galaxies reveals the locations of the vast dark matter structures, with more dark matter located where the greatest distortions are seen, he explained. A paper describing the discovery by Van Waerbeke and his colleagues appears in the latest issue of Astronomy and Astrophysics.

The dark matter of the giant structures can distort the appearance of distant galaxies because dark matter has gravity, which can alter the course of light--or "lense" it--as it flies through space. So although the galaxies themselves are not affected, their images are distorted as seen from Earth when their light passes near significant concentrations of dark matter. The distortion is very small, on the order of 0.1 percent.

It's sort of like there were vast strings or sheets of glass prisms out there messing up the images of the galaxies, with more distortion corresponding to a greater number of prisms.

"If we were able to see the dark matter from Earth it would be a very complex network of filaments and sheets," Van Waerbeke told Discovery News.

That sort of cobwebby structure matches computer models which predict that the visible matter in the universe--clusters and super clusters of galaxies--are just the small lights in much vaster clusters of dark matter. All of it is expanding and in some places still connected by filaments of dark matter--rather like very stringy Mozzarella cheese pulled from a hot pizza.

"They're picking up these really large filaments," said astronomer Bhuvnesh Jain of the University of Pennsylvania. The filaments are 10 to a 100 times less dense than the clusters where filaments meet and things like galaxies collect, he explained.

The filaments are of special interest to cosmologists studying the early universe because unlike in the clusters of light and dark matter where things have smashed together a lot, the filaments are relics of much earlier times, said Jain.

"The structures that are providing all this action are still forming," Jain said. The filaments contain regular matter as well, he said, but so little that few stars or galaxies can form – thus far in the history of the universe, anyhow.

Mysterious Haze Found on Venus

Mysterious Haze Found on Venus

CLICK TO VIEW Venus’s atmosphere, taken by the Venus Monitoring Camera (VMC) during Venus Express orbit number 459 on 24 July 2007. The view shows the southern hemisphere of the planet. CLICK TO VIEW Venus’s atmosphere, taken by the Venus Monitoring Camera (VMC) during Venus Express orbit number 465 on 30 July 2007.

Bright hazes that mysteriously appear and then disappear on Venus in a matter of days have revealed a new dynamic feature of the planet's cloudy atmosphere that is unlike anything on Earth.

The European Space Agency's Venus Monitoring Camera (VMC) captured a series of images showing the development of a bright haze over the southern latitudes of the planet in July 2007. Over a period of days, the high-altitude veil continually brightened and dimmed, moving towards equatorial latitudes and then back towards the south pole.

These transient dark and bright markings indicate regions on the cloud-covered world where solar ultraviolet radiation is being absorbed and reflected by sulfuric acid particles, mission scientists said this week.

Gaseous sulfur dioxide and small amounts of water vapor are usually found below altitudes of about 43 miles (70 kilometers) in Venus' carbon-dioxide rich atmosphere. These molecules are usually shrouded from view by cloud layers above that block our view to the surface at visible wavelengths.

ESA scientists think the sulfuric acid particles that make up the bright haze are created when some atmospheric process lifts the gaseous sulfur dioxide and water vapor high up above the cloud tops where they are exposed to ultraviolet radiation from the sun.

The UV radiation breaks up the molecules, making them highly reactive. The fragments of the molecules eagerly seek each other out and combine to form the sulfuric acid particles.

"The process is a bit similar to what happens with urban smog over cities," said mission team member Dmitri Titov of the Max Planck Institute for Solar System Research in Germany.

Exactly what causes the sulfur dioxide and water vapor to well up is not known, but Titov says it is likely some internal process of Venus' atmosphere.

The transient dark markings on the VMC images are even more of a mystery. They are caused by something that absorbs UV radiation, but scientists don't yet know what the chemical is.

Some Women Do Not Have G-Spots

Small Study Concludes Some Women Do Not Have G-Spots


The debate has raged for some time as to whether or not the fabled G-spot exists.


But one scientist has concluded that the much-talked-about area believed to be the point of origin for the female "vaginal" orgasm does exist but only in some women, according to a small study published in the Journal of Sexual Medicine.

Emmanuele Jannini of the University of L'Aquila in Italy used an ultrasound to scan the area of the vagina where the G-spot, also called the Gräfenberg spot after Ernest Gräfenberg, the man who discovered it, is located.

Jannini determined that the tissue on the front vaginal wall located behind the urethra was noticeably thicker in the women who reported having vaginal orgasms. The thicker tissue, the study concluded, demonstrates the presence of a G-spot.

"For the first time, it is possible to determine by a simple, rapid and inexpensive method if a woman has a G-spot or not," French news agency AFP quoted Jannini as saying. "Women without any visible evidence of a G-spot cannot have a vaginal orgasm."

Click here for more on this story from the Journal of Sexual Medicine.

Did Martian Oceans Bubble From Below?

Did Martian Oceans Bubble From Below?

View image details Gusev Crater This image taken in 2005 by the Spirit Rover shows the sunset casting a blue glow above the rim of Gusev Crater on Mars. Fan-shaped deltas at the edge of huge basins scattered across Mars were probably formed by a titanic influx of water, gushing from the bowels of the Red Planet, according to study released.

Fan-shaped deltas at the edge of huge basins scattered across Mars were probably formed by a titanic influx of water, gushing from the bowels of the Red Planet, according to study released Wednesday.

The origin and morphology of the deltas, studded with curious step-like terraces, have perplexed scientists since they were first observed three years ago.

Today the surface of Mars is bone dry, but a growing body of evidence suggests as much as a third of its surface was at one time covered with oceans.

But scientists have differed -- sometimes sharply -- as to exactly where the water came from.

A quartet of researchers at Utrecht University in the Netherlands led by Erin Kraal, using satellite images and topographical data from the Mars Orbiter, hypothesized that these unique formations could only have originated from a single, massive basin-filling event.

Their study, published in Nature, also concluded that the water rushed in over a period measured in tens of years, not millions, as many scientists had thought.

And not just a little bit, either.

"Water volumes would be that of the Mississippi River over the course of 10 years, or the Rhine River flowing for 100 years into a 62-mile-wide basin," said Krall.

Rainfall could not have accounted for so much water over such a short timespan, which means that it must have come from deep within the planet.

Krall's findings bolster research, published last year, suggesting that Mars once had a criss-cross underground water system that may have latticed the entire planet.

Still unexplained, however, were the strange fan-shaped geological formations studded with steps leading into the basin. Were they consistent with the theory of a massive flow of liquid from the planet's interior?

To find out, the researchers refined an experiment that they had first conducted as part of a high school science class.

"There are no fans with steps on Earth, so we had to build one," said Kraal, who is now a geoscience researcher at Virginia Tech University.

The scientists dug a mock crater in a roomful of sand, then simulated water flow into the crater.

As the fan, created by the incoming stream of water, intersected with the rising water level in the basin, steps -- much like the ones observed on Mars -- appeared.

"As the water flows in through a channel, it erodes the sediment," explained Kraal. "The water fans out and deposits the transported sediment as deltas, building steps down into the basin."

Kraal points out that there were likely other sources of water on Mars, and that his theory only explains the dozen or so large basins -- averaging 60 miles across -- with fans seen on satellite images and data collected by a laser altimeter aboard the U.S. orbiter.