Get Clever About Carbohydrate

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Thursday, 16 October 2008 19:55

Johanna Shiu, our resident sports scientist casts her eye over diet this month - specifically carbohydrates and what they mean to stand up paddle surfing performance.

Carbohydrate - what does it do?

While the body’s cells contain a very small store of their “immediate” energy source (this is called ATP for the people who want to know), this gets used up in less than the time it takes to run 100 metres. Carbohydrate, along with both fats and proteins, provides the body with a way to regenerate ATP, allowing the muscles to keep on working and crucially, carbohydrate also provide energy to the brain – so it’s pretty vital stuff!

A plentiful supply of carbohydrate allows high intensity exercise (think 400 metre sprint) and also allows people to endure lengthy exercise of relatively high intensity (eg, soccer match, marathon and SUPing). Anyone who has ever run out of carbohydrate will know about it….”bonking” “hitting the wall” “a hypo” “sugar crash”…whatever you call it, it’s an experience to be avoided. Your body and mind go blank and if you’re out on your SUP, it’ll be a struggle just to get it together and head back to shore, let alone carry on in a competition. The good news is, you’re currently arming yourself with the knowledge to avoid it happening to you….

What foods contain carbohydrate?

Clearly, I can’t list them all, but when most people think of “carbs,” the common ones that come to mind are bread, pasta, rice and potatoes. These are indeed all carbohydrate-rich foods, as are cous cous, sweet potato, oats, cereals, noodles, squash and eddoe, but carbohydrates are also present in nearly all fruit and vegetables, many sodas, fruit juices and sports drinks, dairy products, candy, pulses and legumes (beans, lentils, chickpeas etc), cakes, biscuits, pastry and even nuts.

Some fruit and vegetables contain very little, such as celery and cucumber, due to their largely water-based make-up.

Foods that either don’t contain any carbohydrate or negligible amounts include meat, offal, eggs, fish, seafood, oils, butter, lard and margarine.

Just so that you know, 1g of pure carbohydrate gives you 4kcal of energy.

How much carbohydrate?

Traditionally, before sports science really got going, athletes used to have a fried breakfast or steak and peas before a soccer or rugby match – full of protein and fat! Some time ago, scientists found that carbohydrate is probably the more important energy source, and for some time a very high carbohydrate diet was recommended – with 70-80% of energy coming from carbs.

More recently, there has been a move away from this, and some now recommend considerably lower carbohydrate diets, with a higher fat/protein content to ensure a “steady release” of the carbohydrate supply – ensuring a more balanced amount of carbohydrate available to your body, rather than a sudden surge and high, with a crashing low once exercise has started.

However, every person is different, and you may have to just find what suits you best.

While there is good evidence to show that a low carbohydrate, high fat/protein diet can be very useful for overweight/obese people, it would not be my recommendation for anyone involved in high amounts of sport….you simply can’t get the revs/throttle you need for speed and dynamic movement.

So, roughly around 50-60% of energy in your diet coming from carbohydrate would seem suitable. To put this in context, for an average male regularly involved in exercise and consuming around 3,000kcal per day, approximately 1,500-1,800 kcal should come from carbohydrate. This is equivalent to 375-450 grams of carbohydrate per day.

These days, you only need to look at the labels on most foods to work out how many grams of carbohydrate you’re getting from what you eat.

Working out how much energy you need to consume overall will be the focus of another article.

Which carbohydrate to have? - the glycaemic index

You may have heard about glycaemic index (GI) – a rating of how quickly the carbohydrate you eat causes a rise in your blood sugar, with 1 being the fastest. While a rapid rise in blood sugar can be good if you need sudden energy (eg, trying to reverse a “hypo” in someone with diabetes, or if you’ve just bonked on a training session), it’s not that great for sustained exercise purposes. You’re better off with steady-release carbohydrates that will help to keep your blood sugar at a consistent level while you are also using up your carbohydrate stores from the muscle and liver.

That said, don’t get too worked up about the GI of your foods, because by combining carbohydrate with fats and proteins, as will be my recommendation in further articles, you alter how quickly the carbohydrate is released anyway. For instance…

  • white rice = high GI and rapid appearance of glucose in your blood
  • white rice + chicken + cashew nuts = medium GI and slower appearance of glucose in your blood

So, if you have hit the wall and are hanging out to get some energy back quickly, get some jelly beans or a sugar-loaded soda/sports drink down you...but if you’re just ticking over and want to sustain another hour of exercise, you’ll be looking to eat either a tailor-made sports bar that contains appropriate carbohydrate/protein/fat ratios or perhaps your own concoction that incorporates roughly 50-60% carbohydrate, 30% protein and 10-20% fat.

Still to come amongst others...... Probing into Protein”; “Fat Facts”; “Find out about Fluids”; “Estimate your Energy Needs”; and “Pulling It All Together – Planning Your Training, Pre-Race, Race and Post-Race Nutrition”.

 
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