A new study suggests eating a "stone age" diet consisting of fruit, nuts, vegetables and lean meat or fish could help people avoid diabetes.
Scientists found that patients with inadequate controls of their glucose levels greatly improved their ability to handle sugar after switching to prehistoric eating habits.
The diet given to the test subjects is similar to what early modern humans ate when they first walked out of Africa 70,000 years ago.
Cereals, dairy products, refined fat and sugar, which provide most of the calories of the modern diet, only became staple foods when farming began 9,000 years ago.
In the study, 14 glucose-intolerant heart patients were asked to copy the diet of their ancient ancestors for 12 weeks.
They were compared with a similar group of 15 patients who ate a supposedly healthy Mediterranean diet of whole-grain cereals, low-fat dairy products, fruit, vegetables and unsaturated fats.
All those taking part suffer from high blood sugar after consuming carbohydrates, and most have symptoms of type 2 diabetes.
After 12 weeks, the carbohydrate-linked blood sugar rises had fallen by 26% in the stone age diet group, the Swedish researchers found. In contrast, it barely changed for those on the Mediterranean diet, falling by only 7%.
Dr Staffan Lindeberg, from Lund University, whose results were released by the Swedish Research Council, said: "If you want to prevent or treat diabetes type 2, it may be more efficient to avoid some of our modern foods than to count calories or carbohydrates."