CHICAGO  A new TV commercial shows kids eating hot dogs in a school cafeteria and one little boy's haunting lament: "I was dumbfounded when the doctor told me I have late-stage colon cancer."

It's a startling revelation in an ad that vilifies one of America's most beloved, if maligned, foods, while stoking fears about a dreaded disease.

But the boy does not have cancer. Neither do two other kids in the ad who claim to be afflicted.

The commercial's pro-vegetarian sponsors say it's a dramatization that highlights research linking processed meats, including hot dogs, with higher odds of getting colon cancer.

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But that connection is based on studies of adults, not children, and the increased risk is slight, even if you ate a hot dog a day. While compelling, it is not conclusive.

So what exactly is the truth about hot dogs?

The 33-second ad launched last month in several U.S. cities provides the perfect opportunity to separate fact from fiction about this mysterious yet so familiar meat. It is to run in September in Chicago and Denver.

The bottom line from several nutritionists familiar with the ad is this: Hot dogs are not exactly a "health food," but eating one every now and then probably won't hurt you.

"My concern about this campaign is it's giving the indication that the occasional hot dog in the school lunch is going to increase cancer risk," said Colleen Doyle, the American Cancer Society's nutrition director. "An occasional hot dog isn't going to increase that risk."

Americans as a whole eat hot dogs more than occasionally. According to the National Hot Dog & Sausage Council, U.S. consumers spent more than $4 billion on hot dogs and sausages last year. That includes more than 1.5 billion pounds (680 million kilograms) of hot dogs and sausages bought at retail stores alone.

The health concerns primarily come from their high fat and salt content and sodium nitrate and nitrite, commonly added preservatives and color-enhancers. Nitrate-related substances have been reported to cause cancer in animals, but there is no proof they do that in people.

Hot dogs typically contain muscle meat trimmings from pork or beef. Contrary to legend, they do not contain animal eyeballs, hooves or genitals, according to the Hot Dog Council's Janet Riley. But the government does allow them to contain pig snouts and stomachs, cow lips and livers, goat gullets and lamb spleens. If they have these byproducts, the label should spell out which ones, a U.S. Department of Agriculture spokeswoman said.

Some also are made with leaner meats, including turkey, as well as tofu or soy protein.

Check the label of a name-brand hot dog, and chances are fat provides around 80% of total calories, more than double what's often advised. What's more, saturated fat and trans fat — the fats most strongly linked with artery-clogging — are common ingredients, in some cases providing at least half the fat content.

The hot dog council called the new ad an alarmist scare tactic, but the promoters, a group called The Cancer Project, defend their campaign.

Dr. Neal Barnard, president of the Physicians Committee for Responsible Medicine, called the ad "a way to raise appropriate concern about a deadly concern." Barnard also heads The Cancer Project, an offshoot of his anti-meat advocacy group.

Hot dogs may be considered as American as apple pie, but Barnard said it's time to change that tradition.

"Children are born with no traditions whatsoever," he said. "You or I might think a hot dog, that just goes with baseball ... We can always change our traditions to be healthful."

The new ad is based on an analysis of five studies in adults by scientists working with cancer research groups not affiliated with Barnard's.

Their report last November said eating 50 grams a day of processed meats for several years increases colorectal cancer risk by 21%. That equals about one hot dog a day or two deli slices of bologna or five slices of bacon.

The duration of daily consumption linked with that higher risk is uncertain. Colorectal cancer was diagnosed between three and 19 years after the studies began, but participants could have been eating processed meats for years before that, said dietitian Karen Collins, nutrition adviser with the American Institute for Cancer Research, a group that analyzed the studies.

For a U.S. adult, eating one hot dog daily for several years would increase the average risk of getting colorectal cancer, which is 5%, to 7%. On a population level, it would increase the number of people nationwide who get colorectal cancer each year from 50 per 100,000 people to 60 per 100,000, Collins said.

"It's not the kind of impact on risk that, say, tobacco smoking has on lung cancer. But on the other hand, colon cancer is one of our most common cancers, so small changes still affect a lot of people," Collins said.

She said the level of risk is smaller for eating a hot dog once or twice a month but that it can't be precisely quantified. It would not mean up to a 1.4% increase in colon cancer risk, as she had indicated.

"The risk we get from things like lack of physical activity, excess body weight, lack of adequate vegetables and fruits, these are much more important to work on."

Scientists who analyzed the studies recommend avoiding processed meat — advice that makes sense, said Lilian Cheung, of the nutrition department at Harvard's School of Public Health.

Cheung is not connected to Barnard's group, but called its campaign "a good spark plug" to improve school foods and raise awareness.

The ad is part of a campaign to improve foods in schools and get the government to stop providing processed meats. The government provides some, such as ham and processed turkey. However hot dogs, pepperoni pizza, bacon and other popular processed meats are bought from local vendors, not the federal government, according to the USDA.

Cancer Project promoters want all processed meats off school menus. They recently issued a report analyzing menus from one month last spring at 28 large school districts. Half got failing grades for serving too much processed meat.

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