High-Carb Diets Improve Blood Sugar Control

Back in 1927, an Amer­i­can physi­cian named Shirley Sweeney recruit­ed some healthy male med­ical stu­dents for a study of how diet affects blood sug­ar con­trol. That study showed that you could make healthy young men seem dia­bet­ic by feed­ing them too much fat or too much pro­tein or noth­ing at all for only two days.

Sweeney divid­ed his vol­un­teers into four groups. He asked the mem­bers of each group to eat a par­tic­u­lar test diet for two days. One group ate main­ly car­bo­hy­drates (starch and sug­ar). Anoth­er ate main­ly pro­tein. A third group ate main­ly fats. The fourth group fast­ed for two days. On the morn­ing of the third day, before the sub­jects had eat­en or drunk any­thing else, they had a glu­cose tol­er­ance test. They drank a bev­er­age with a known amount of the sug­ar called glu­cose. Then, their blood sug­ar (blood glu­cose) lev­els were mea­sured over the fol­low­ing few hours.

Dur­ing the glu­cose tol­er­ance test, the men who had been eat­ing noth­ing but car­bo­hy­drates for two days had remark­ably sta­ble blood sug­ar lev­els. But the oth­er men’s blood sug­ar lev­els spiked to abnor­mal­ly high lev­els. The men who had been eat­ing noth­ing but fat got results that sug­gest­ed severe dia­betes. Remem­ber, these were healthy young men who had been eat­ing an abnor­mal diet for only two days.

From these results, Sweeney con­clud­ed that a high-car­bo­hy­drate diet helps to improve the body’s abil­i­ty to tol­er­ate car­bo­hy­drates. In con­trast, high-pro­tein diets, high-fat diets, and fast­ing under­mine the body’s abil­i­ty to con­trol blood sug­ar. In a fol­low-up arti­cle, Sweeney sug­gest­ed that some patients might have abnor­mal glu­cose tol­er­ance test results because of the diet that their doc­tors had been urg­ing them to fol­low, rather than because of some under­ly­ing med­ical prob­lem.

Sweeney was not the only researcher to show that high-fat diets cause prob­lems with blood sug­ar con­trol. In the 1930s, a British physi­cian named Sir Harold Per­ci­val Himsworth did sim­i­lar stud­ies and got sim­i­lar results.

Start­ing in the late 1930s, a Ger­man émi­gré physi­cian named Wal­ter Kemp­n­er start­ed apply­ing these lessons to the treat­ment of patients at Duke Uni­ver­si­ty. Kemp­n­er start­ed off by try­ing to find a dietary solu­tion to severe­ly high blood pres­sure. Back then, no effec­tive drugs were avail­able to reduce blood pres­sure. Kemp­n­er rea­soned that since heart and kid­ney dis­ease were rare in soci­eties that ate a rice-based diet, his patients should eat a rice-based diet.

Because his patients had kid­ney prob­lems and ath­er­o­scle­ro­sis, Kemp­n­er designed a diet to be as low as pos­si­ble in pro­tein and fat. So he told his patients to eat noth­ing but rice, fruit, and fruit juice. If they lost too much weight on that low-fat diet, they were told to add some pure sug­ar. This diet pro­duced dra­mat­ic improve­ments in patients with heart and kid­ney dis­ease. It also did won­ders for patients with dia­betes.

Patients with what is now called type 2 dia­betes, which is a com­pli­ca­tion of being over­weight, lost weight and became undi­a­bet­ic. Patients with type 1 dia­betes, which results when the immune sys­tem destroys the pancreas’s abil­i­ty to make insulin, had much bet­ter con­trol of blood sug­ar lev­els and could get by on much small­er insulin dos­es. Even their eyes were health­i­er. (Dia­betes is a major cause of blind­ness.)

The fact that high-carb diets are good for dia­bet­ics has been known since the 1920s. Nev­er­the­less, many doc­tors in the Unit­ed States are still urg­ing their over­weight and dia­bet­ic patients to avoid eat­ing carbs. Unfor­tu­nate­ly, a low-carb diet can make even a healthy young per­son look dia­bet­ic with­in a mat­ter of days. For­tu­nate­ly, a high-carb diet can cure the most com­mon form of dia­betes and can improve the health of peo­ple with the incur­able form of dia­betes.


Behind Barbed Wire_PrintUpdate: I explain the rela­tion­ship between car­bo­hy­drate intake and blood sug­ar in more detail in my book Thin Dia­betes, Fat Dia­betes: Pre­vent Type 1, Cure Type 2.