Cereal in the morning, a sandwich at lunch and pasta at dinner. Starchy, sugary carbohydrates are a staple in most Canadians’ diets but new research is warning that they may increase the risk of lung cancer dramatically. Do the findings check out, though?
Earlier this week, a new study warned that a diet with a high glycemic index — bread, rice, crackers — could increase the risk of lung cancer by a whopping 49 per cent.
Then came the headlines that warned that bagels were the latest cigarettes or that your corn flakes were upping your cancer risk.
Global News looks at the study’s findings, the counter-arguments and the verdict from Canadian experts.
The study: Researchers out of the University of Texas MD Anderson Cancer Center say that a high-GI diet raises lung cancer risk even in people who don’t smoke.
Keep in mind, smoking is the No. 1 cause of lung cancer, but it doesn’t account for every case, lead researcher, Dr. Xifeng Wu told Global News.
“Most people think lung cancer is caused solely by smoking and it is surprising to hear that a high glycemic index diet may also increase lung cancer risk,” she said.
“What we showed in our study is that lung cancer patients are more likely to have a high GI diet compared with [their healthy peers]… I would recommend limiting the consumption of foods and beverages with high glycemic indexes as a general health tip,” she advised.
The glycemic index is a 100-point scale in which foods are ranked based on how quickly they raise blood sugar levels. Food that’s higher in GI raises our blood sugar levels faster.
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Prime examples include white bread, puffed rice, bran flakes, instant oatmeal, white rice and pasta, russet potatoes, saltine crackers, pretzels and popcorn.
It isn’t the first time a high GI has been tied to cancer risk. Its link to lung cancer is relatively novel. But it’s the first time scientists found a pronounced link between GI and lung cancer risk in specific groups, such as people who don’t smoke.
The Houston scientists looked at 1,905 people who were just diagnosed with lung cancer next to another 2,415 people without cancer. Their eating habits were taken into account along with income and lifestyle habits like smoking and drinking.
Turns out, those who ate the most food with a high GI ended up in the lung cancer group. Those on the other end of the spectrum were least likely to have lung cancer.
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The doctors aren’t sure what’s at play but they guess that high GI foods could encourage the body to produce more insulin. That, in turn, leads to cell growth — cancer is triggered when cells begin to grow out of control.
Wu says her next steps are to look at whether starches and carbs could be tied to other cancers, such as bladder, kidney and colorectal.
They also want to zero in on other factors — age, gender, smoking status, exercise levels, lung function — to build a risk prediction model for lung cancer.
Canadian experts weigh in: Eighty-five per cent of lung cancer cases are tied to cigarette smoking, according to Alice Peter, director of population health and prevention at Cancer Care Ontario. Exposure to radon gas and asbestos are other factors that could cause cancer.
Right now, it’s too early to say that a high glycemic index diet could be to blame for lung cancer, she suggests.
“We know healthy diets, especially those high in non-starchy fruits and vegetables, can prevent cancer and if you’re not eating healthy you put yourself at a greater risk, but the idea that bagels cause lung cancer is definitely premature,” she told Global News.
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The scientific community has been steadfast in its research linking processed meat to colon cancer, for example. Last year, when the International Agency for Research on Cancer (it’s part of the World Health Organization) said processed meat can cause cancer in humans, its claim was based on a review of thousands of studies, Peter noted.
There are some holes in the research too, according to Dr. Natasha Leighl, an oncologist at the Princess Margaret Cancer Centre.
The data is based on self-reporting. In her experience, healthy volunteers may not thoroughly report their eating habits compared to patients with cancer who may not have a clear explanation as to how they developed their disease.
Factors, such as exposure to asbestos and radon weren’t taken into consideration, too.
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Still, the findings build on research tying diet to cancer risk. What we eat is already tied to risk of obesity, diabetes and heart disease.
“This is not something we should ignore and we should look at it further. I don’t think it shows bagels cause lung cancer or a high glycemic index diet causes cancer but there’s no question it’s risky for our health from a number of perspectives,” Leighl said.
Food with a high glycemic index include: white bread, bagels, corn flakes, puffed rice, bran flakes, instant oatmeal, white rice, pasta, macaroni and cheese from mix, potatoes, pumpkin, pretzels, rice cakes, popcorn, saltine crackers, melons, pineapple and energy drinks.
Food with a low glycemic index include: 100 per cent stone-ground whole wheat or pumpernickel bread, steel-cut oats, oat bran, muesli, barley, bulgur, sweet potatoes, corn, yams, butter beans, peas, legumes and lentils and most fruits and non-starchy vegetables.
Wu’s full findings were published this week in the journal, Cancer Epidemiology, Biomarkers and Prevention.
carmen.chai@globalnews.ca
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