Senator George McGovern
Hoped that nutrition science would recommend a “best diet” for Americans.
Several senators following Nathan Pritikin favoured a vegetarian diet. The Seventh Day Adventist Church was strongly involved.
George V. Mann, and E.H. "Pete" Ahrens, said the science was immature and the guidelines proposed were inadequate.
The guidelines were adopted in 1980 in the USA, and similar legislation was passed in most English speaking countries about 1982 - 1983.
Standard American Diet Food Pyramid
A political statement. No scientific justification, the purpose was support for American agriculture. They hoped to reduce heart disease too (Ancel Keys).
The Women's Health Initiative reported “No health benefits.” (2006) (Existing CVD and cancer worse.)