Greger is Director of Public Health and Animal Agriculture at The Humane Society of the United States. An internationally recognized lecturer, he has presented at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial. Greger is a graduate of the Cornell University School of Agriculture and the Tufts University School of Medicine.