I did some stalking of the authors a while ago. The second author is this guy: http://www.channing.harvard.edu/van_dam.htm
Dr. van Dam's primary area of research is the study of lifestyle determinants and health consequences of obesity and type 2 diabetes. His research is based on large-scale cohort studies (Nurses' Health Study, Health Professionals Follow-up Study, Black Women's Health Study), dietary intervention studies, and systematic reviews.
The first thing most people pick up on with this type of study is how inaccurate the data is. The Nurses' Health Study was based on self reported diets that are systematically wrong. People always under report what they think is bad and over report on what they think is good. Now this guy has built a career based on picking fly s#!t out of pepper using studies that are mostly fly s#!t. If he really stopped to look at how useless his life has been so far... The term cognitive dissonance comes to mind.