Did you know that, until the final quarter of the twentieth century, public health dietary advice in the US and the UK focused on minimum intakes, to ensure that populations consumed adequate nutrients? The US 1950s-1970s “Basic Four Foundation Diet” recommended four or more bread and cereal portions daily, two cups or more of milk and two or more servings of meat (Ref 1). The UK favoured micronutrient recommendations; until the first macronutrient guideline was introduced in 1950 with British Medical Association advice that dietary fat intake should provide a minimum of 25% of daily calories (Ref 2).
The first public health dietary guidelines to set maximum intakes were those announced by the US Select Committee on Nutrition and Human needs in 1977 (Ref 3). These were followed by(Carter, 1977) UK public health dietary advice issued by the National Advisory Committee on Nutritional Education in 1983 (Ref 4). Dietary recommendations in both cases focused on one macronutrient, fat, and a component part of that macronutrient, saturated fat. The specific targets were to i) reduce overall fat consumption to 30% of total energy intake and ii) reduce saturated fat consumption to 10% of total energy intake.
As there are only three macronutrients (carbohydrate, protein and fat), and since protein tends to stay fairly constant in either a plant or animal based diet at approximately 15%, if fat is restricted, carbohydrate increases (and also – if carbohydrate is restricted, fat increases). Fat and carbohydrate are the two most dependent variables in the diet. As human diets restricted fat to c. 30%, therefore, carbohydrate increased to 55-60% of our dietary intake. Since these guidelines were introduced, epidemics of obesity and type 2 diabetes have developed: coincidence or cause?
The 1980 Dietary Guidelines for Americans
The first issue of the famous American publication, issued every five years, came out in 1980. It presented the views of the 1977 Select Committee in a form intended to be digestible (excuse the pun), by all Americans. The 1980 publication, jointly written by the United States Department of Agriculture and the United States Department of Health, Education and Welfare, had seven dietary guidelines as follows: