Plant-rich, low-carb diet linked to reduced CRC-specific mortality
A plant-rich, low-carbohydrate diet may reduce the risk of mortality associated with nonmetastatic colorectal cancer (CRC), according to results of a recent study.
The study cohort comprised 1,542 patients with stage I–III CRC who were enrolled in the Nurses’ Health Study and the Health Professionals Follow-up Study and had completed a food frequency questionnaire between 6 months and 4 years post-diagnosis (median, 2.1 years). A total of 185 CRC-specific deaths occurred over the median 9-year follow-up period.
Patients who consumed a low-carbohydrate diet rich in plant-based fat or protein had a reduced risk of CRC-specific mortality (hazard ratio [HR], 0.37, 95 percent confidence interval [CI], 0.25–0.57; ptrend<0.001), as well as a reduced risk of all-cause mortality (HR, 0.70, 95 percent CI, 0.58–0.84; ptrend<0.001). [JNCI Cancer Spectr 2018;2:pky077]
Conversely, a diet rich in refined starch- or sugar-based carbohydrates was associated with an increased risk of CRC-specific mortality (HR, 1.36, 95 percent CI, 1.14–1.62; ptrend<0.001 per 1-SD increase), while the risk of CRC-specific mortality was reduced when carbohydrates were substituted with plant-based fat (HR, 0.81 [per 1-SD increase], 95 percent CI, 0.69–0.95; ptrend=0.01) or plant-based protein (HR, 0.77 [per 1-SD increase], 95 percent CI, 0.62–0.95; ptrend=0.02).
Following CRC diagnosis, patients who increased their intake of plant-based fat and protein had a lower risk of CRC-specific mortality (HR, 0.78; ptrend=0.005 and HR, 0.76; ptrend=0.004, respectively, per 1-SD increase), while a higher carbohydrate intake post-diagnosis was associated with an elevated risk of CRC-specific mortality (HR, 1.22; ptrend=0.03).
There was no apparent association between an overall low-carbohydrate diet score or an animal-rich low-carbohydrate diet score and the risk of CRC-specific mortality, though the risk of all-cause mortality was increased among patients with an animal-rich low-carbohydrate diet score (HR, 1.21, 95 percent CI, 1.00–1.47; ptrend=0.02 for the highest vs lowest quartile).
Previous studies have pointed to a potential link between hyperglycaemia and poor outcomes of CRC. [Int J Cancer 2016;139:2705-2713; Oncotarget 2016;7:18837-18850]
An increase in carbohydrate intake and elevated “dietary glycaemic load” lead to elevations in blood glucose levels and subsequently increased insulin production which can increase cell proliferation and prevent apoptosis, said the authors of the present study. [Eur J Clin Nutr 2012;66:1146-1152; Am J Clin Nutr 2007;86:s836-s842] Furthermore, a high-fibre diet, which is linked to improvement in insulin sensitivity, has been associated with reduced all-cause and CRC-specific mortality. [JAMA Oncol 2018;4: 71-79]
“These findings … support the hypothesis that high intake of carbohydrate, primarily from refined starches and sugars, may promote cancer cell proliferation and inhibit apoptosis of micrometastases by increasing glucose availability and insulin production,” they added.
“[G]iven that cancer patients are at particularly high risk of developing insulin resistance and hyperglycaemia … it is possible that replacing carbohydrate, especially that consumed from refined food sources, with plant fat and protein may improve glycaemic control and mitigate cancer-related metabolic disturbances, leading to a better survival after CRC diagnosis,” they said.