According to a study published in Cancer Epidemiology, Biomarkers & Prevention, people whose diets included a large percentage of high-glycaemic foods (for example, white bread, potatoes, refined/processed foods) saw the risk for lung cancer (the number one cancer killer of women) increase by 49%.
Why would refined carbs and high levels of sugar do this? One theory says that high-glycaemic foods cause your blood glucose levels to spike. This then causes your body to release large amounts of insulin, the hormone that helps convert the sugar into usable energy to fuel your body’s processes. Higher levels of insulin can then spur an increase in proteins called insulin-growth factors, which have been linked to a greater likelihood of developing lung cancer.
For the study, researchers at the University of Texas Anderson Cancer Center in Houston recruited 1,095 newly diagnosed lung cancer patients and 2,413 healthy people from clinics nearby, and analysed their diets (both their dietary glycaemic index and their glycemic load, which looks at the amount of carbs in a given food), as well as other risk factors like smoking and physical activity levels. Each participant was interviewed by a medical staffer, had their vital stats recorded and completed a questionnaire about their diets and habits.
Those with the highest daily glycaemic index had a 49% higher risk for lung cancer than those with the lowest daily glycaemic index. Interestingly, non-smokers in the highest glycaemic index group were more than twice as likely to develop the disease than non-smokers within the lowest glycaemic group. And smokers in the highest glycaemic index had a 31% increased risk of lung cancer than their lowest glycaemic index group counterparts.
This is just one single study in one single ethnic population. MUCH more research is needed before we can blame carbs for cancer. Nevertheless, this indication seems to match the trend that excess amounts of refined carbohydrates and sugars in general are not part of a healthy diet or lifestyle.
A smart consumer would best try and stick to more natural foods which are rich in fibre and complex carbohydrates.