SHR # 2920:: The Role of the Microbiome in Immunity - Donna Gates, M.ED., ABAAHP and author of "The Body Ecology Diet" - If you have gut problems you have immune system problems. Period. AARP did a survey 7 years ago and stated 60% of older Americans claim they have digestive problems, GERD, and bloating. That's 60% of older Americans that we can say unabashedly have immune system problems.