For Parents, Nutrition, Science

Why You Should Never – EVER – Eat a Low-Carbohydrate Diet

As part of my Nutrition for Sports Performance course, I was recently assigned to create a project (anything other than a written report) about a topic of my choice related to nutrition for a sport of my choice.  Of course, there was no choice of a sport other than soccer, and the topic I decided on was carbohydrate intake for high performance players.  I decided to make a “funny” video, with some useful information that applies specifically to university varsity soccer players on game days.  Here is a link to the video which I just posted on our Youtube page:

In my career, I have had a lot of experience with this particular topic, from being a university varsity athlete myself, to taking undergraduate kinesiology courses in nutrition and post-graduate courses in fitness and weight management, and finally to the work I did later at the higher levels of the game (including the Canadian Women’s U17 National Team and the Toronto FC Academy teams) that involved very specific nutritional education and player monitoring.  Throughout all this time, I have noticed that in the field of nutrition, many trends and “fad diets” come and go, from the Atkins diet in the early 2000’s to the more recent “Paleo” and “de-tox” type fads.  Unfortunately, one central theme among a lot of these fad diets has been recommendations for low – or even no – carbohydrate intake.

I don’t really have a problem with people in the “general population” (non-athletes) reducing their carbohydrate intake, even if I don’t necessarily agree with it.  This is because people who are not competitive athletes typically consume too many calories in general, and since a significant portion of their caloric intake is likely to be carbohydrates, they will likely experience some weight loss simply by reducing and/or eliminating carbohydrates from their diet.  The problem with low/no carbohydrate diets when applied to athletes – and specifically, soccer players – is that they simply do not provide soccer players with enough energy to perform the work they need to do on the pitch.  Here is a simple breakdown of scientific facts (not my personal opinions) about carbohydrates and soccer:

  • Professional soccer players cover, on average, between 9-12 kilometres per game
  • Included in this distance covered is an average of 2-3 kilometres of high intensity running (fast running and sprinting)
  • The average heart rate of professional soccer players in games is 170-180 beats per minute, or roughly 60-80% of age-predicted maximum heart rate
  • The ONLY nutrient available in the human body to provide the energy needed to perform work at these intensities is carbohydrate, which are stored in the body (in the muscles and in the liver) as a compound called “glycogen”
  • A large body of scientific evidence exists which demonstrates the relationship between stored muscle glycogen and physical performance in soccer, including:
    •  A linear relationship between resting muscle glycogen levels pre-training/game, and time to exhaustion in soccer (thus, the more energy a soccer player has stored, the longer he/she will last in training/games)
    • An inverse relationship between muscle glycogen used, and resting muscle glycogen levels in soccer (thus, the longer a soccer player plays the game, the more of their energy gets used up)
    • A linear relationship between high carbohydrate intake post-training/games, and muscle glycogen re-synthesis (thus, the more carbohydrates a soccer player eats, the better their will be able to replenish its energy stores)
    • A linear relationship between muscle glycogen re-synthesis, and increased physical performance (including muscular strength, power, and endurance) in soccer (thus, the better job a soccer player does of restoring his/her energy levels, the better he/she will perform physically in training/games)

Adding to the overwhelmingly strong argument for soccer players to eat a high carbohydrate diet is the fact that there is not one government-regulated organization in North America (including Health Canada, the Canada Food Guide, the Food and Drug Administration and the United States Department of Agriculture and Department of Health and Human Services) that recommends healthy adults to get less than 45% of their total caloric intake from carbohydrates.  Most of these organizations recommend a range of 45-65% of total daily caloric intake to be from carbohydrates, and that is for the “general population” of non-athletes, not elite soccer players.

Taken together, this information presents soccer players with an easy and clear message that they should eat a lot of carbohydrates each day, to optimize both performance, and recovery.  How much carbohydrates should you eat if you are an elite level soccer player?  A great study done by Burke et. al. in 2001 determined that elite soccer players should follow the following guidelines:

  • Consume 5-7 grams of carbohydrate per kilogram of body weight per day on non-training/game days
  • Consume 7-10 grams of carbohydrate per kilogram of body weight per day on training/game days

I think it’s time we take a science-based approach to carbohydrate consumption in soccer.  Unless the advocates of low/no carbohydrate diets can come up with a way to provide soccer players with the energy to run 12 kilometres, with 3 kilometres being run at high speeds, and an average heart rate of 175 beats per minute, for 90+ minutes per game, without using carbohydrates, then a diet high in carbohydrates is the only science-based solution.  I hope that any elite level soccer player (or their parents/coaches) who read this article will think twice before they consider a low carbohydrate diet in the future.

I’d love to hear your thoughts about this topic.  Drop me a line here to get the conversation started.

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