Effects of carrot consumption on intestinal cancer risk

Abstract

Intestinal cancer is a leading cause of death, and epidemiological studies associate high intakes of fruits and vegetables to reduced risk of the disease. This study investigated the effects of carrot consumption on intestinal tumourigenesis in the Apcmin/+mouse model, homologous to the human Familial Adenomatous Polyposis mutation. Mice were fed either standard RM3 mouse feed (control) or diets enriched with 20% freeze-dried carrot powder prepared from blanched carrots. In Experiment 1, both diets were fed as pellets, manufactured by SDS Diets by mixing, extruding and drying at 90-120oC for 20-30 minutes, while in experiment 2; both diets were fed to the mice as unprocessed powder. Dams were fed either carrot enriched or control diets from two weeks prior to mating with Apcmin/+ sires and throughout pregnancy and lactation. At weaning, all offspring were randomised to either carrot enriched diet or control diets. At 15 weeks post-natal, intestinal tumour number, size and location were recorded alongside body and organ weights. Using tissue from tumours and normal intestinal segments from min and wild-type mice in experiment 2, Total RNA was isolated, reverse transcribed and Real-time PCR performed, to assess expression of 6 potentially cancer related genes: Retinoid X receptor beta, (RXRb); Retinoid acid receptor alpha, (RARα); Cyclin D; ββ-Carotene 15,15-monooxygenese-1, (BCMO1); Cyclooxygenase-2, (COX-2); and Metrilysin-7, (MMP7). In experiment 1, consumption of carrot pellets post weaning increased total gut tumour number by 42% (P = 0.038) whereas in experiment 2, carrot powder feeding post weaning reduced the total gut tumour number by 21% (P = 0.037). The control diet tumour numbers did not differ between experiments and maternal/pre weaning diets did not affect tumour numbers in offspring significantly. Powdered diets did not affect expression of the measured genes. So while powdered carrot as expected reduced cancer severity, pellets had the opposite effect. According to Duan and Barringer, (2012) paper, using high temperature for drying of carrot causes formation of the volatile carcinogen furan, providing a possible explanation for this difference.