Some 20 percent of cancer-related deaths in the U.S. can be attributed to obesity, making it the number-one preventable cause of cancer death in the country. But with myriad metabolic and inflammatory changes associated with obesity, determining the mechanisms that underlie the obesity-cancer link has proven challenging.
The human large intestine (colon), in healthy individuals, has extremely low oxygen concentrations, and over 90% of its microbiota are strict anaerobes. Researchers taking metagenomic fecal microbiota surveys of adult Europeans could assign about 0.8% of the genes in their dataset to archaea [9], and similar numbers (0.2%-0.3%) were reported for Amerindians and Malwaians [10], while North Americans had much lower fractions (<0.05%).