A high-carb diet may raise your risk of lung cancer, according to a study carried out by the University of Texas.
However, the study has not proved a link between carbs and cancer risk (see our expert verdict below).
Researchers found that food with a high glycaemic index — for example, white bread and rice — appeared to increase the risk of lung cancer by as much as 49 per cent. They surveyed 1,900 lung cancer patients, along with 2,400 healthy controls, and found a significantly higher risk of the disease in those with the highest daily gross intake of poor-quality carbohydrates, compared to the group with the lowest intake.
The glycaemic index measures the rate at which a given carbohydrate raises blood sugar levels. Researchers believe that a diet high in such foods creates higher levels of insulin-like growth factors (proteins similar to insulin). Raised IGF levels are believed to be associated with an increased lung cancer risk.
The study, which has been published in the journal Cancer Epidemiology, Biomarkers and Prevention, found that carbohydrate quality, rather than quantity, was the culprit. Foods with a lower glycaemic load were found to have no significant association with lung cancer.
The study’s lead author, Dr Stephanie Melkonian, said: ‘We observed a 49 per cent increased risk of lung cancer among subjects with the highest daily GI compared to those with the lowest daily GI.
‘Diets high in glycaemic index result in higher levels of blood glucose and insulin, which promote perturbations [disturbances] in the insulin-like growth factors (IGFs).
‘Previous research suggests increased levels of IGFs are associated with increased lung cancer risk.
‘However, the association between glycaemic index and lung cancer risk was unclear.’
We can’t say definitely that high-carb foods cause cancer without an in-vivo lab study demonstrating metabolic effects. Nor can we say that decreasing low-carb foods will decrease cancer incidence compared to a normal carb intake, as no randomised trial has been done.
Research score: N/A (full paper not seen)