Kiwifruit Skin and Flesh Contributions to Fecal Bulking and Bacterial Abundance in Rats

Changes in fecal bulk and bacterial abundance due to separately consumed skin and flesh of four kiwifruit cultivars was determined using a rat model designed to estimate the fecal bulking potential of human foods. Dry matter contribution by skin to 100 g of fresh kiwifruit was less than 5% in all cultivars, whereas flesh dry matter contributed up to 20% of fresh fruit weight. Dietary fiber was 35-49% of skin compared with 8-23% of flesh on a dry weight basis. The skin significantly increased whole fruit fecal bulking, but the total bulk per 100 g kiwifruit was less than 10% of daily fecal bulk recommended for optimal gut health. Kiwifruit (skin or flesh) substantially increased the abundance of Lachnospiraceae and Lactobacillus spp. within the gut. Fermentation and prebiosis therefore probably play a greater role than fermentation-resistant dietary fiber in gut health benefits of kiwifruit.