Walk into any sporting goods store and you'll see a plethora of endurance sports supplements in gel, liquid or chewable form, some with hefty price tags. These supplements are designed to provide a quick source of easily digestible carbohydrates to supply blood glucose for energy after an athlete exhausts his or her glycogen stores.
However, the humble raisin may perform just as well as a carbohydrate supplement for endurance sports. A 2012 University of California-Davis study examined the metabolic, performance and gastrointestinal effects of supplementing with raisins compared to commercial sports chews. Eleven male runners completed three randomized trials (consuming raisins, sports chews or only water) separated by seven days. Runners ran on the treadmill for 80 minutes at 75 percent of their maximal oxygen uptake to deplete glycogen stores before completing a 5-kilometer time trial.
Researchers found no significant differences in performance or GI issues between the athletes who consumed the sports chews and those who consumed raisins. Both raisins and chews enabled higher carbohydrate oxidation and better running performance compared to water alone.