TUESDAY, Oct. 30 (HealthDay News) -- High blood levels of vitamin D did not lower the overall cancer death rate in a long-term study, researchers report.

However, they did note a marked reduction in colorectal cancer deaths linked to the vitamin.

The findings, by a team from the U.S. National Cancer Institute, run counter to some earlier data suggesting that vitamin D might help prevent malignancy.

"Over the past several years, a number of publications have suggested that vitamin D can reduce deaths from various forms of cancer," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "This is a further bit of evidence that leads us to call for further investigations before we make recommendations for the general population."

Even the finding that the vitamin might lower colon cancer risk merits further study, added Lichtenfeld, who was not involved in the research. "We have called for further research to see if vitamin D does or does not reduce deaths from cancer," he said. "We do not have sufficient evidence at this time to make a recommendation, for example, that people increase their intake of vitamin D to reduce the risk of colorectal cancer."

In their study, the NCI team looked at data on almost 17,000 participants in the third Health and Nutrition Examination Survey who were followed for anywhere from six to 12 years. There were 536 deaths from cancer in the group during that time.

The study found no relationship between overall cancer deaths and circulating blood levels of vitamin D, said the report, published in the Oct. 30 issue of the Journal of the National Cancer Institute.

However, people with higher levels of circulating vitamin D had a 72 percent lower risk of colorectal cancer mortality than those with lower levels, the report found.

These numbers can't be taken to mean that vitamin D prevents colorectal cancer because the study was not large enough and didn't run long enough to provide definitive information, said Cindy Davis, a program director in the NCI nutrition sciences research group and co-author of an accompanying editorial.

"Cancer is a very long process, and there is an even longer period between incidents of mortality," Davis said. "There was only a very small number of cancer deaths. If there is a relationship, this study is not large enough to show one."

Some other studies have given evidence that vitamin D may provide protection against colon cancer, but others have not, she noted.

In addition, Davis added, "We don't know what the optimum level of vitamin D is, we don't know whether genetics might affect the benefits, and we need to consider interactions with other dietary components. Some people may be put at risk. Evidence suggests an increase in kidney stones [with excess vitamin D], and while a kidney stone is not cancer, it is a problem."

The current recommendation for vitamin D is 200 International Units a day, Davis said, and "I believe that when possible, people are better off meeting their nutritional needs through diet rather than through supplements."

Some foods, such as milk, are fortified with vitamin D, and the nutrient can be found in some fish and fish oils, according to the U.S. National Institutes of Health. The skin also manufacturers vitamin D upon exposure to sunlight.

D. Michal Freedman, the NCI epidemiologist who led the study, said its main finding "was the lack of a relationship between total cancer deaths and vitamin D levels." Freedman downplayed the colorectal cancer data as "a secondary finding."

"The study doesn't address the issue of the effects of vitamin D in the blood," Freedman said. "The issue of what people should be taking in terms of vitamin D involves a lot of other factors."

In a related study published in the same issue of the journal, a team at the University of Texas M.D. Anderson Cancer Center, in Houston, found that treatment with a derivative of vitamin A might help reduce former smokers' risk of developing lung cancer.

Patients who received the derivative, called 13-cis-retinoic acid, displayed reduced lung cell growth of the type that might later form cancers, the team reported.

More information

There's more on vitamin D at the U.S. Office of Dietary Supplements.

FRIDAY, Oct. 26 (HealthDay News) -- Three months of daily, vigorous exercise can improve overweight kids' thinking, U.S. researchers report.

Physical activity can also lower their diabetes risk, reduce their body fat, and strengthen their bones, says a team that looked at about 200 overweight, inactive children, ages 7 to 11.

All the children learned about healthy nutrition and the benefits of physical activity. In addition, a third of the children exercised 20 minutes a day, and another third exercised for 40 minutes. During the exercise sessions, the children played running games and used hula hoops and jump ropes to get their heart rates to 79 percent of maximum -- considered a vigorous workout.

"Aerobic exercise training showed dose-response benefits on executive function (decision-making) and possibly math achievement, in overweight children," the researchers wrote in an abstract presented this week at The Obesity Society's annual scientific meeting in New Orleans. "Regular exercise may be a simple, important method of enhancing children's cognitive and academic development. These results may persuade educators to implement vigorous physical activity curricula during a childhood obesity epidemic," the researchers concluded.

"Is exercise a magic wand that turns them into lean, healthy kids? No. They are still overweight but less so, with less fat, a healthier metabolism and an improved ability to handle life," lead investigator Dr. Catherine Davis, a clinical health psychologist at the Medical College of Georgia, in Augusta, said in a prepared statement.

"We hope these findings will help persuade policymakers, schools and communities that time spent being physically active enhances, rather than detracts from learning," Davis said.

More information

The Nemours Foundation has more about overweight and obese children  .

THURSDAY, Oct. 25 (HealthDay News) -- What's good for your diet may also guard against skin cancer.

Scientists have discovered that an extract of broccoli sprouts protects the skin against the sun's harmful ultraviolet rays.

That's not the same as calling the extract a sunscreen, however.

"This is not a sunscreen, because it does not absorb the ultraviolet rays of the sun," explained Dr. Paul Talalay, a professor of pharmacology and molecular sciences at Johns Hopkins University School of Medicine in Baltimore. "We don't want people covering their bodies with broccoli and going to the beach. They will have no protection whatsoever."

Exposure to ultraviolet or UV rays is the primary cause of most skin cancers. The incidence of skin cancer in the United States is on the rise as men and women who had too many sunburns earlier in life get older and develop the disease.

Talalay started working on skin cancer prevention about 25 years ago. "Cells contain an elaborate network of protective genes that code for proteins that protect against four principal injurious processes to which all of our cells are exposed and which are the causes of cancer, degenerative disease and aging," he explained.

Those four processes are: oxidation; DNA damage; inflammation and radiation, namely ultraviolet radiation.

The cells' protective system normally operates at about one-third capacity, so the real question is what would ramp up that system.

"Our strategy has been to find things that will boost the system," Talalay explained. Broccoli, in particular, has previously reported to have some anti-cancer effects.

"We looked in vegetables, and it turned out they had a rather large quantities of a compound that induced this system, particularly in cruciferous vegetables such as broccoli, cabbage, Brussels sprouts, et cetera," Talalay said.

The compound, called sulforaphane, is found in broccoli sprout extracts and was first identified by Talalay and his colleagues more than 15 years ago. Sulforaphane has been shown to inhibit tumor development in animals.

For this study, Talalay and his colleagues tested the compound in both mice and humans.

The human experiments involved six healthy volunteers. Each participant was exposed to UV radiation on two circles on their back that were either treated or not treated with different doses of broccoli extract.

The highest doses of the extract reduced UV-induced redness and inflammation (erythema) by an average of 37 percent, although protection varied from 8 percent to 78 percent.

"If you apply an extract of broccoli sprouts that contains high levels of sulforaphane to regions of human skin, you can protect them very substantially," Talalay said. "We believe, to the best of our knowledge, that this is the first demonstration of protection against a known human carcinogen in humans."

One expert was excited by the discovery.

"There is some interesting data here," said Dr. Vijay Trisal, an assistant professor of surgical oncology at the City of Hope Cancer Center, in Duarte, Calif. "Sulforaphane compounds have been known to boost the immune system locally. This has some basic science behind it."

"The same thing happens with interferon, which we use for melanoma. It boosts the natural killer cells," Trisal explained.

The findings do need to be replicated, Talalay noted.

"It's going to take a little while to work out how this should be applied," Talalay said. "We would need to have a preparation rich in sulforaphane that would be easily absorbed through the skin, and this is not yet a reality. But, since we're dealing with a food, we're not dealing with anything likely to have a toxicity."

The study is published in this week's issue of the Proceedings of the National Academy of Sciences. Talalay and a co-author are unpaid consultants to Brassica Protection Products LLC (BPP), which licenses the technology to produce broccoli sprouts. These two authors, along with Johns Hopkins University, are equity owners in BPP. Antony Talalay, son of Paul Talalay, is chief executive officer of BPP.

More information

Visit the National Cancer Institute for more on skin cancer.

WEDNESDAY, Oct. 24 (HealthDay News) -- Cigarette smoking and a family history of alcoholism can both affect how a person perceives sweet-tasting foods, U.S. researchers say.

Women who smoked were less sensitive to sweet tastes than women who did not smoke, according to a study in the November issue of the journal Alcoholism: Clinical & Experimental Research.

The study included 27 current smokers (18 with a family history of alcoholism) and 22 women who'd never smoked (9 with a family history of alcoholism), ages 21 to 40. All of the participants were tested for their sensitivity to sweetness.

"Cigarette smoking and having a family history of alcoholism had different effects on sweet-taste perception and food cravings," study co-author Julie A. Mennella, a senior researcher at the Monell Chemical Senses Center in Philadelphia, said in a prepared statement.

"Women who smoked cigarettes were less sensitive to sweet taste than women who never smoked. This means that women who smoke required higher concentrations of a sweet solution in order to detect sweet taste; we also found that the more years a woman has smoked cigarettes, the less sensitive she will be to sweet taste," Mennella said.

"The study suggests that cigarette smoking dulls sweet-taste detection and is associated with increased food cravings, especially for starchy carbohydrates and foods high in fat," co-author M. Yanina Pepino, a researcher at Monell, said in a prepared statement.

The study also found that women with a family history of alcoholism preferred higher levels of sweetness and craved sweet-tasting foods more often. That confirms previous findings that a pleasurable response to sweet taste is associated with a genetic risk for alcoholism.

"We may now use this knowledge to, one, identify individuals at high risk for alcoholism and, two, study biological mechanisms involved in the development of alcohol-use disorders," said Alexei B. Kampov-Polevoy, a research assistant professor of psychiatry at the University of North Carolina at Chapel Hill, said in a prepared statement.

Future studies looking at the effects of smoking on food habits and cravings should take into account family history of alcoholism, Mennella and Pepino said.

More information

The American Academy of Otolaryngology -- Head and Neck Surgery has more about taste and smell  .