Lab Rat
Cornstarch as Performance Booster?
You feel it coming on – the first stomach cramp that signals an impending gastrointestinal disaster. No matter what you do, this is not a battle you’re going to win. Even worse – what if your body fails you at the 35k mark in a marathon and you bonk? The secret to endurance fuelling is carbohydrates that provide energy without a spike in blood sugar or GI distress, and sometimes the solution comes in a mundane package – like that container of cornstarch at the back of your pantry.
Scientists have known about the benefits of cornstarch as a slow-releasing, low glycemicindex carbohydrate for a long time. In the 1980s, researchers discovered that uncooked cornstarch could help children suffering from glycogen storage disease to maintain their glucose levels overnight. Then the Connecticut-based ucan company created a race fuel made with SuperStarch, or modified cornstarch.
Many people find cornstarch effective at preventing the blood sugar spikes and crashes and GI discomfort caused by some other fuels. Sarah Sellers, the Arizona nurse-anesthetist who finished second at the 2018 Boston Marathon, is a Generation ucan athlete and finds the product works well. “I’ve had GI issues while training and doing long workouts,” she says, adding that she was also keen to find ways to consume less sugar during marathon training.
In particular, a slow-releasing carbohydrate like cornstarch could be advantageous over ultramarathon distances, according to Trent Stellingwerff, director of performance solutions, Canadian Sport Institute Pacific. But there are few alternatives to shelling out for a commercial cornstarch-based product like ucan, since mixing simple cornstarch with water doesn’t make a very palatable race fuel – and the verdict is still out on whether cornstarch offers any real performance benefit at shorter distances.
Stellingwerff says the research points strongly to sucrose – a 50/50 blend of glucose and fructose – as the best fuel for marathon training. And while sports drink companies spend millions combining ingredients to come up with products that both fuel well and taste good, sometimes the best solution is as close as the nearest convenience store. In October 2018, when Cam Levins of Black Creek, B.C., broke Jerome Drayton’s 43-year-old Canadian men’s marathon record, running 2:09:25 at the Scotiabank Toronto Waterfront Marathon, he used a sucrose-based drink that he had practised with in advance to make sure it agreed with his stomach: Country Time Black Cherry Sweet Tea. “If you look at the label, it has a profile that is similar to all the major brands’ sports drinks,” says Stellingwerff. “Sometimes we need to keep it really simple, and it worked for him.”
Stellingwerff points out that there is a wealth of research showing that a blend of carbohydrates (referred to as multiple transportable carbohydrates) provides better fuelling than glucose or fructose on its own. “Your body has two separate intestinal transporters, one for glucose and one for fructose, and if you have this blend during exercise, you can increase carbohydrate oxidation,” he says. Burning more carbs means delivering more energy to the muscles, and there is less left over in the GI tract to upset your stomach.
Most importantly, athletes should develop a personalized fuelling plan with the guidance, collaboration and expertise of their coach, and practise fuelling during training to be sure the system they choose will work well for them on race day.