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What's the fastest way to fuel your ride?

Fast fuel pizza
James Witts
15 Feb 2016

When you need energy on a ride, should you eat a bar, down a gel or sip a drink? Let science make the choice for you.

During a stage, I might take in six or seven gels. I’ll also have four or five bars and of course I’ll sip on energy drinks. You need a lot to get through the Tour.’ That’s Trek-Segafredo’s Bauke Mollema offering a snapshot of what he consumes during a day of the Tour de France. But which of those will get Mollema the energy he needs fastest? And is there a best time to consume each of them? Let’s examine the science. 

‘In one study we showed that an energy gel, if taken with water, is as fast at delivering energy as a drink,’ says Asker Jeukendrup, a sports nutritionist who works with Lotto-Soudal. ‘That’s not surprising because you’re consuming a similar amount of carbs but, instead of diluting it in a bottle, you’re diluting it in your stomach.’

With a drink or gel, glucose appears in the bloodstream in around five minutes, a bar around ten

Exactly how long carbs take to enter your bloodstream for use by the muscles is influenced by several factors, more of which later. Broadly speaking, though, you’ll feel the benefits quickly.

‘With a drink or gel, glucose appears in the bloodstream in around five minutes,’ says Jeukendrup. ‘With a bar we’re talking 10 minutes, so still pretty fast. That said, we’re talking tiny traces of glucose. For all three, the bulk comes through after around 60 minutes.’

Jeukendrup should know, as he could rightly be tagged as the carbohydrate king, having had numerous carb-specific studies published as well as having worked with Gatorade and PowerBar.  

‘In one study we had riders cycle for two hours at moderate intensity, and every 15 minutes they’d ingest either drink, gel or bar. We used a “label” in the carbohydrate – carbon-13 – so we could gauge how much glucose was oxidised by measuring the expired gases of the respective subjects. As you exercise, you produce carbon dioxide and some of that CO2 will contain the carbon-13. That way, we accurately measured that the gels and drink were being used by the muscle quicker than the bars.’

Jeukedrup stresses that the breakdown of the bar, in particular, is affected by macronutrient composition. But glucose delivery can reach that 10 minute figure if it’s low in fat, low in protein, low in fibre and high in carbs. That’s because fat, protein and fibre slow down carbohydrate delivery – something to remember when planning your race-day menu. 

Chewing the fat

As you face that Sunday morning climb and knock back a drink, gel or bar, digestion starts in the mouth via an enzyme called amylase. ‘Of course, that’s after chewing when it comes to the bars, which increases the surface area of the food for more contact with the enzyme,’ says Tim Lawson, founder of Secret Training nutrition.

Next, the oesophagus transports the food to the stomach, which senses the carbohydrate composition. If it’s a more complex solid content, such as a bar, it will sit in the stomach while the stomach acids dilute the composition. If it’s fluid
it can move on almost immediately. In both cases, this is into the small intestine, which is where most absorption of sugars to the bloodstream takes place. ‘The small intestine can only absorb carbohydrate as glucose, fructose or galactose,’ says Jeukendrup, adding that further glucose transporters are involved in dragging glucose from the bloodstream to skeletal muscle. But it’s that movement of glucose from the small intestine to the bloodstream that’s key to the speed of delivery.

You want more?

Fast fuel gels

Glucose uses a sodium-dependent transporter called SGLT1 to move from the small intestine to the bloodstream. A significant body of research concludes that this transporter becomes saturated at 60g each hour – the equivalent of two gels, one large energy bar or around 750ml of energy drink. However, a group of sports scientists, including Jeukendrup, has observed that by adding fructose to the energy product, you can tap into the fructose transporter GLUT5 and deliver more energy. 

‘This elevates how much you might be able to consume to around 90g per hour [or 360kcals],’ says Jeukendrup. ‘That might still be too much for some people – there’s no blanket figure.’ What’s clear is that cycling at high intensity sends more blood to the working muscles and away from the intestines for use in digestion, so 90g of carbs per hour might result in stomach issues.

Genetics plays a role in how much carbohydrate you can stomach but, like strength and stamina, it’s trainable. A study by Cox et al in 2010 showed that carbohydrate oxidation rates were higher after a 28-day high-carb diet, following a similar template to the tactic of consuming a high-fat diet to increase energy derived from fat metabolism.

I’d also recommend having gels around 15 minutes before a stiff climb.

No matter what your carb limit is, there’s a logical order to consuming gels, drinks and bars according to Peter Hespel, an exercise physiologist who’s worked with Etixx-Quick-Step. ‘Early on in a ride, especially if it’s flat, I would rely more on solid foods,’ says the Belgian. ‘You can easily sip energy drinks throughout, as that obviously has a hydration value, too. I’d also recommend having gels before a more intense part of the course, like a stiff climb. Around 15 minutes before should be fine.’

The morning after 

Constant feeding is key to maintaining glucose levels, ideally around every 15 minutes without going over your upper limit. Mind you, it’s not all about feeding your metabolism. 

Studies have shown that swilling carbs in your mouth and then spitting out results in similar performance improvements to carb ingestion. Research suggests this is down to oral receptors in the mouth detecting sugars and stimulating a positive performance response in the central nervous system. This could be useful if you’re suffering with a dodgy tummy.

‘There’s also evidence that your body reacts not just to your pre-race breakfast but what you had the night before,’ says Lawson. ‘Studies show that consuming foods high in resistance starch the night before can improve your energy fuelling at the races.’

Here’s how it works: many starchy foods, like pearl barley, bulgar wheat and brown rice, contain a modicum of resistant starch. This goes all the way through the small intestine without being digested. When it reaches the colon, it’s used for fuel by bacteria in a process called fermentation, producing short-chain fatty acids like butyrate, which studies have shown increases glucose tolerance the next day. It’s known as the ‘second-meal effect’.

‘It’s an exciting area of research that will influence your energy stores on race day,’ says Lawson.

Whether this will impact on how much energy you can absorb from gels, bars and drinks remains to be seen – these are early days. One thing is clear, however – hyperbole can make cyclists suspicious of nutrition manufacturers’ claims but the evidence is strong that events over an hour benefit from carbohydrate feeding. And the fastest-acting are gels and fluids.

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