There are many guidelines printed discussing the increasing consumption of vegetables, fruit and whole grains. There are few regarding sources of dietary fiber and starch. Everyone talks about the carbohydrate intake. This was told to me for years when working closely with the late Robert Atkins MD .One should realize that the different carbohydrates as sugar , starches and fibers perform different roles in the body. It is not that simplistic to the total amount of carbohydrates. Much needs to be considered.
So more studies need to be done. Also the clinical outcomes were studied using systematic reviews and meta analysis of all prospective studies up to April 2017
A lot of information was obtained. In a nutshell ( no pun intended) those eating more dietary fiber and whole grains protects against noncommunicable diseases such as coronary heart disease, stroke , type II diabetes and cancer, specifically colon cancer. A simple increase in whole grains changed outcomes. For every 15 gram of increase in whole grains there was a 2%to 19% decrease in incidence of coronary heart disease, type II diabetes and colorectal cancer