No Evidence Tomatoes, Lycopene Cut Cancer: FDA

(HealthDay News) -- There's little hard evidence that a diet rich in tomatoes and the tomato antioxidant lycopene can ward off cancer, according to research from the U.S. Food and Drug Administration.

Reporting in the July 10 issue of the Journal of the American Cancer Institute, FDA experts lay out in great detail the evidence -- or mostly lack of it -- behind their November 2005 statement that tomato consumption is not linked to any reduction risk of tumors of the prostate, ovary, stomach and pancreas.

The agency had previously found no evidence that tomatoes could cut risks for lung, colorectal, breast, cervical or endometrial tumors, either.

The November 2005 statement contended that, "there is no credible evidence to support qualified health claims for lycopene, as a food ingredient, component or food, or as a dietary supplement, and reduced risk of any of the cancers in the petition."

The petition for approval of the claims was submitted by a supplement maker, American Longevity.

The FDA has now put the evidence behind its decision in print, said Paul Coates, director of the office of dietary supplements at the U.S. National Institutes of Health and the author of a related journal editorial.

The new data review "gives people some idea of what the process is," Coates said. That's important, he said, because "one of the things that people are concerned about is how are these decisions arrived at. Making the process transparent and open will be helpful."

As part of its review, the FDA pored over data from 107 observational studies comparing the level of consumption of either tomatoes or lycopene with people's general cancer risk.

They also looked at 23 studies that focused on blood levels of lycopene, although most of those trials were deemed unreliable, either because there were too many confounding factors or because most focused on cancer patients, not healthy people.

The agency also included dozens of studies comparing lycopene or tomato intake against the risk of individual cancers such as prostate, colon and breast malignancies.

The bottom line, according to the FDA: There's just not enough evidence to recommend that Americans boost their tomato intake to ward off cancer.

However, the new report is certainly not the last word on cancer-preventing claims for lycopene, Coates added.
"It just codifies the fact that the information about lycopene and cancer is not very robust," he said. "It may well be that if more studies are done, a greater effect might be found. But now, when you look at similar studies done by different people, they come to the same conclusion."

For its part, the American Cancer Society prefers to stay away from recommending any one food as a cancer preventive agent, said Marji McCullough, director of nutritional epidemiology for the organization.

"In our guidelines, we encourage people to eat a variety of foods, especially fruits and vegetables," she said. "Several studies have suggested a lower risk of cancer with some kinds of foods, including tomatoes, but we encourage variety."

The society encourages consumption of "dark deep-colored vegetables, because some studies have found an association between them and lower cancer risk," McCullough said.

The society also encourages fruit and vegetable consumption, because it helps prevent weight gain, she said.

But endorsement of specific foods won't come until research shows that they clearly are associated with lower cancer risk, McCullough said. As for supplements, "most of the evidence comes from studies of foods," she said.

More information
There's more on lycopene at the American Cancer Society.

Adjusting Cabin Pressure Eases Air Passenger Discomfort

(HealthDay News) -- The discomfort some passengers feel on airplanes could be due to the air pressure settings inside cabins, a new study finds.

Most aircraft cabins are pressurized to 8,000 feet above sea level, an altitude that lowers the amount of oxygen in the blood by about 4 percentage points, researchers say.

This decrease in oxygen saturation isn't enough to bring on acute mountain sickness, but pressurizing the cabin to 6,000 feet could help some passengers feel better when flying, concludes a study in the July 5 issue of the New England Journal of Medicine.

"We found that the altitudes did not affect the occurrence of acute mountain sickness syndrome, but it did affect discomfort," said the study's lead author, Dr. J. Michael Muhm, senior occupation physician for Boeing Commercial Airplanes in Seattle, which funded the study.

"There was no difference in the likelihood of discomfort at ground level and 6,000 feet, but the likelihood increased between 6,000 and 8,000 feet."

He added, "We concluded that passenger and crew comfort would be enhanced" if the cabin was pressurized to 6,000 feet during long-duration flights.

Most commercial aircraft are pressurized to 6,000 to 8,000 feet, not sea level.

"In order to pressurize at ground level, we would have to increase the weight of the aircraft tremendously, because the material as it exists right now couldn't tolerate pressure at ground level," explained Dr. Claude Thibeault, medical director of the International Air Transport Association in Montreal. "We would have to increase fuel, decrease passengers. So, it's an operational sort of factor."

And 8,000 feet, the maximum allowed, is also physiologically acceptable for "normal" people, he added.

"The average Joe in good condition could tolerate 8,000 feet without health effects," Thibeault said. But he noted, "They didn't say without discomfort."

Short-haul flights are usually pressurized at 5,000 to 6,000 feet while long-haul flights are closer to 8,000 feet, according to Thibeault.

But acute mountain sickness, which can involve headache, nausea and vomiting, can occur at altitudes of 6,500 feet and higher.

The authors of the study wanted to see, among other things, if airplane travelers were prone to mountain sickness.

To that end, 502 adult volunteers participated in a 20-hour simulated flight to determine the effect of barometric pressures equivalent to altitudes of 650, 4,000, 6,000, 7,000 and 8,000 feet above sea level on arterial oxygen saturation and the occurrence of acute mountain sickness and discomfort.

Mean oxygen saturation went down as the altitude increased, eventually reaching a maximum decrease of 4.4 percentage points at 8,000 feet.

Acute mountain sickness occurred in 7.4 percent of participants, but the incidence did not vary between the different altitudes.

Discomfort rose with increasing altitude and was greater at 7,000 to 8,000 feet than at all the other altitudes combined. Discomfort became apparent 3 to 9 hours into the "flight."

Older people (over 60) were less likely to report discomfort than younger people, and men seemed more affected than women.

"There were no health effects, but the discomfort was there," Thibeault said. "What they were trying to do in this study is isolate one factor, which is altitude, so you can't blame these effects on other factors."

Next week, Boeing plans to launch its newest aircraft, the 787, with cabins pressurized to 6,000 feet.

"The 787 is one of our first airplanes with the fuselage made out of composites rather than aluminum, a structure that allows us to pressurize to 6,000 feet," said Jeanne Yu, director of environmental performance for Boeing. "The findings of this study, as well as the development of materials technology, enable us to fly the 787."

But she added, changing cabin pressures in existing aircraft is not that simple because of their aluminum structures.

"Airplanes are designed to withstand the continuous pressurization/depressurization cycles that occur in takeoffs and landings throughout their service life. To lower the maximum cruise cabin altitude, the pressure difference must be increased between the interior and exterior of the airplane. This change would fatigue (wear out) the structure more rapidly and impact the airplane's service life in an uncertain way, perhaps even compromising the design integrity of the airplane," she said.

More information
For more on staying healthy when you fly, head to the Academy of Family Physicians.

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Opening of Kidney Arteries Brings Dangers

(HealthDay News) -- Angioplasty and stenting can open blocked kidney arteries, but the procedure also throws off an immense amount of debris that can hurt kidney function, a new study shows.

It has been known that this procedure -- done primarily to relieve high blood pressure -- is messy, but "this is the first paper in humans to really demonstrate how much stuff there is and especially how much microscopic material there is," said Dr. Matthew Edwards, an assistant professor of surgery at Wake Forest University Baptist Medical Center and lead author of a report in the June issue of the Journal for Vascular Surgery.

Angioplasty and stenting for blocked kidney arteries involves the insertion of a balloon to open the artery, followed by the implantation of a tube to keep it open. The procedure doesn't get as much attention as a similar surgery done for heart vessels, but an estimated 40,000 to 80,000 Americans receive this intervention each year, Edwards said. The operation's primary purpose is to lower blood pressure caused by a blockage, and its ultimate goal is to prevent kidney failure, he said.

The new report described 28 angioplasty cases in which the physicians took blood samples after a stent was implanted.

Laboratory analysis revealed an average of 2,000 debris particles in the blood samples -- some pieces being big enough to block smaller vessels in the kidney.

The number of particles found in specific patients was directly related to their subsequent kidney function, the researchers found: more debris, worse kidney function.

That can bode ill for patient's longer term health, Edwards said, since "poor kidney function after kidney artery stenting has been previously demonstrated by our group to be associated with increased risk of heart attack, stroke or death in the future."

Post-angioplasty debris was also found to float freely in arteries, even though the surgeons used a protective device designed to trap it for removal. The Wake Forest surgeons used one of several protective devices now being tested. None have yet been approved by the U.S. Food and Drug Administration.

One or another of these protective devices may someday go into medical practice, Edwards said. "We certainly need a protection device," he said. His group used one designed by Medtronic. It is essentially a large balloon that traps the debris so that it can be collected and removed when the procedure is finished.

But Edwards also noted that certain kinds of fatty plaques could create more debris than others.
"The plaques that sit in these arteries are not all the same," he said. "Some might be prone to liberate more debris than others."

Edwards hopes that, in the future, this most dangerous form of debris could be identified before a procedure is done.

"There has been some work on that in the carotid artery," Edwards said, referring to the main artery to the brain. "Some MRI and ultrasound studies have identified plaque that is prone to release more debris."

Edwards said his group now is conducting a trial to explore that possibility.

More information
There's more on kidney angioplasty at the University of Southern California.