IOWA CITY — Obesity causes cancer — just like smoking causes cancer, and ultraviolet radiation causes cancer.
“I think the public isn’t aware of that link,” George Weiner, director of the University of Iowa Holden Comprehensive Cancer Center, said Tuesday while speaking about this year’s “Cancer in Iowa” report. “But there’s absolutely no question there is a link. It’s been well documented in multiple different populations. It’s been well documented in the research lab.”
Obesity-related cancers include kidney, thyroid, pancreas, and breast cancer, according to Weiner, who also serves as president of the board of directors for the Iowa Cancer Consortium and head of the Association of American Cancer Institutes.
“The poster child for metabolic cancer is uterine cancer in women,” according to Andrew Nish, interventional radiologist and director of the John Stoddard Center in Des Moines. “That is the cancer with the strongest metabolic link to obesity.”
And uterine cancer rates in Iowa — as with many of the other obesity-related cancers — have been on the rise. This year’s Cancer in Iowa report — released Tuesday by the State Health Registry of Iowa, based in the UI College of Public Health — shows 336 women per 100,000 got breast cancer in Iowa between 2011 and 2015, up from 261 per 100,000 between 1976 and 1980.
Kidney rates for the same time periods jumped from 5 per 100,000 women to 12 per 100,000 women and from 10 per 100,000 men to 23 per 100,000 men, according to the report. Those figures — along with spikes in pancreas, thyroid, and liver cancers — mirror a rise in obesity in Iowa, which reports the nation’s 13th highest obesity rate, a figure that’s doubled from 15 percent in 1991 to 30 percent.
“We have epidemiologic data — so we follow populations over time — that was our first clue,” Nish said about the connection between obesity and cancer. “But now we actually have the basic science to tell us somewhat what’s going on.”
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Overall in Iowa, an estimated 6,300 people will die from cancer this year — 18 times more than will die in auto accidents and 100 more than were predicted for 2017, according to the state report. An estimated 17,800 new cancers will be diagnosed in Iowa this year, 400 more than predicted for 2017.
Lung cancer is projected to continue to be the most deadly cancer for both men and women in Iowa — causing 1,640 cancer deaths, or one of every four, according to the report. Prostate cancer will remain the most common diagnosed among men this year, while breast cancer — one linked to obesity — will remain the most common among women.
Although not all “obesity-related” cancers are caused by obesity, researchers now can explain — at least in part — how the condition can spawn and fuel the disease. Scientists know, for example, that “highly active” fat tissue produces large amounts of hormones like estrogen and insulin, which have been associated with increased risk for breast, endometrial, ovarian, colon, kidney, and prostate cancers.
Fat cells also produce something called “adipokines,” which are hormones that can affect cell growth, according to the report.
“It has also been proven that people with obesity often have chronic low-level inflammation, which can cause DNA damage to cells over time, leading to cancer,” the report states.
Inflammation from acid reflux can cause esophageal cancer, and inflammation from chronic ulcerative colitis and hepatitis can cause liver cancer. Obesity increases the risk for gallstones, which cause inflammation and increase the chance of developing gallbladder cancer.
And Nish implicated one of this country’s dietary staples as fueling obesity.
“Sugar is a poison,” he said. “At the right dose, sugar is toxic, and we far exceed the dose of toxicity in our daily lifestyle.”
The average American consumes 82 grams of sugar a day — or about 19.5 teaspoons, according to the U.S. Centers for Disease Control and Prevention. American Heart Association recommendations cap consumption at six teaspoons of added sugar a day for women and nine for men. Recommended limits for children range from three to six teaspoons, according to the guidance.
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“We live in a food supply that I consider toxic,” Nish said. “It’s fast. It’s cheap. And it’s loaded with processed carbohydrates and sugar. It’s no good for us. So we need to shift back to a plant based diet. Fresh fruits, fresh vegetables.”
And, he urged, “You can do it.” Doing so, he said, will “change the trajectory of cancer.”
Donna Reihman, 59, said she’s living proof. While working at the university in 2013, she was diagnosed with breast cancer. The doctors caught it early, and she beat it with chemotherapy and radiation. But, Reihman said, she also made significant lifestyle changes — fine-tuning her diet to her specific needs and cutting out junk.
She also changed exercise, sleep, and stress management habits, which experts on Tuesday emphasized are part of the overall healthy-lifestyle view of cancer prevention — or cancer formation, in cases where individuals make poor choices.
“Depending upon how you look at the data … anywhere between 10 and 30 percent of cancers are thought to be actually caused by obesity and poor lifestyle choices,” UI director Weiner said.
Nish said the battle against obesity is just beginning, and he equated corporate convenience food and beverage manufacturers to the tobacco industry, which have fought community health messages harmful to their bottom lines.
“They’re always going to try to plant doubt,” he said. “But from a scientific aspect, from a practicing physician aspect, there is no doubt.”
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