Most of us are familiar with warnings to go easy on the carbs, and especially the unhealthy, processed ones, to avoid weight gain and other health problems. Now it seems that cutting out sweet drinks and processed foods can also reduce the risk of cancer.
The findings are being presented at the American Society for Nutrition Scientific Sessions and Annual Meeting during Experimental Biology 2016 in San Diego, CA.
They suggest that consuming sugary drinks and eating processed lunch foods can double or triple the chance of developing prostate cancer, while eating legumes, fruits and vegetables can cut the risk of breast cancer by two thirds.
Prostate cancer is one of the most common types of cancer and the second leading cause of cancer-related death in men, while breast cancer is one of the most common cancers among women.
Previous research has linked excessive intake of refined carbohydrates with a number of adverse health effects, due to the impact on body fatness and the dysregulation of insulin and glucose, potential factors in cancer risk.
Lead author Nour Makarem, a PhD student at New York University, and colleagues examined health data for 3,100 volunteers.
'Bad' carbs linked with 88% higher rate of prostate cancer
Data collection started in the early 1970s, and tracking of diets began in 1991. Participants provided dietary information by completing detailed food frequency questionnaires.
The team categorized the subjects' food sources by glycemic index (GI) and glycemic load (GL).
GI measures the quality of a dietary carbohydrate based on an item's relative impact on blood sugar levels, compared with a reference food. GL measures the quantity and quality of carbohydrates in a specific food item.
The researchers then looked for correlations between carbohydrate intake and cancer rates, adjusting for other cancer risk factors.
Results revealed some strong associations between the consumption of highly processed carbohydrates and prostate cancer. Regular consumption of foods with a higher GL correlated with an 88% higher prostate cancer risk. Consumption of low-GI foods was associated with a 67% lower prevalence of breast cancer.
Low-GI foods include legumes, non-starchy vegetables, most fruits and whole grains.
'Good' carbs offer protection
The team noticed a lower rate of breast cancer among women whose total calorie intake involved a proportionally higher level of carbohydrates.
Those with the highest levels of carbohydrate intake also ate more fruits and vegetables, whole grains and legumes.
This suggests that the type of carbohydrate matters more than the quantity.
Legumes such as beans, lentils and peas were associated with a 32% lower risk of breast, prostate and colorectal cancers, all of which are more likely to affect people who are overweight or obese.
"One of the most important findings here is that the type of carbohydrate-containing foods you consume can impact your cancer risk. It appears that healthy carbohydrate sources, such as legumes, tend to protect us from cancer, but non-healthy ones, such as fast foods and sugary beverages, seem to increase the risk of these cancers."
Most at risk were those who routinely consumed processed lunch foods such as pizza, burgers and meat sandwiches, or sugary beverages, including fruit juices, which are naturally high in sugar and often contain added sugars.
Makarem adds, "Americans consume almost half of their added sugars in beverages. Sugar-sweetened beverages have been shown to increase the risk of obesity and diabetes, and our study documents that they may also have a detrimental impact on cancer risk."
The authors point out that results do not prove any causative link, only evidence of associations.
However, they appear to support previous study outcomes suggesting that malignant cancer cells feed on sugar.
One limitation is that 99% of the volunteers were white. Further research could reveal whether these associations apply to other ethnic groups.