Captain Carbs to the rescue!

In the sports world, nutrition is very much in vogue. However, it hasn’t really taken root; for instance, runners training for a marathon rarely think about what dietary changes to make. Even fewer consider their carbohydrate intake.

The human body relies on two energy sources: fats and carbohydrates. It constantly burns a combination of the two, rarely just one or the other. The ratio depends mainly on intensity: the harder the effort, the more carbohydrates we use.

Our body’s fat reserves—stored in both adipose tissue and muscle—are relatively abundant. Carbohydrate stores—found in the liver and muscle—are much more limited, enough for just one to one-and-a-half hours of exercise, depending on intensity and starting levels. Beyond this window, carbohydrate intake is necessary to sustain the same level of exertion.

Adequate carbohydrate intake really makes the difference in endurance sports like cycling. The feeling of “hitting a wall” stems directly from the depletion of glycogen, the carbohydrate stored in muscles. People tend to blame a lack of training, the wind, the heat, the hills and so on before admitting it could simply be a lack of sugar, the simplest form of carbohydrate.

Carbs are often scorned and their importance underestimated. They’re laden with deeply rooted myths and misconceptions—they’re bad for your health, they cause diabetes, and other social media 'truths'.

Today, nutrition guidelines recommend 60 to 120 grams of carbohydrates per hour for sporting activities lasting over two-and-a-half hours. While there seems to be no upper limit, and some elite athletes reportedly exceed 120 grams, more research is needed to establish a general recommendation. In practice, we take a case-by-case approach.

Yes, it can cause digestive issues, such as intestinal discomfort, diarrhea or delayed gastric emptying. So the challenge is to avoid overwhelming intestinal absorption.

To achieve this, the digestive system needs training, too. This involves gradually increasing food intake, training immediately after a meal and increasing fluid intake. External factors like heat and stress can also reduce absorption. So it’s important to have a personalized nutrition plan.

I think it’s just a marketing gimmick. I’m tired of seeing them. I even spotted protein-infused candy recently. It’s over the top. People think they aren’t getting enough protein, but a balanced diet provides plenty; it’s actually rare for active adults to have a protein deficiency. But it’s common for clients to walk into my office convinced they do, whereas no one ever comes in saying, “I’m not getting enough carbs!”

The body doesn’t need protein during athletic performance. In fact, protein is not an efficient energy source for the body. Among other things, protein makes you feel sated, which is counterproductive during exertion because you have to consume so many carbs. Furthermore, since protein takes longer to digest, it can slow down the digestive process and increase the risk of discomfort.

It’s best to save protein for after physical exertion. That’s when it provides the amino acids your muscles need to repair and rebuild after intense effort. 

It’s becoming clear that gut bacteria affect an athlete’s health (and therefore performance) and, conversely, that physical activity affects gut bacteria. However, research is still in its early stages, especially for elite athletes.

We know that a healthy gut microbiome requires a varied, fibre-rich diet. But during competition, athletes have to ingest a lot of carbs, while avoiding fibre to prevent intestinal discomfort. So they compensate by eating plenty of fruits, vegetables and whole grains between competitions. But what effect does constantly switching between a low- and high-fibre diet have on the gut microbiome?

We also know that moderate exercise strengthens the immune system by boosting blood circulation and white blood cell activity, compared to being sedentary. However, elite athletes who train intensely, sometimes twice a day, become more vulnerable to infection because of the physiological stress and high cortisol levels caused by the exertion. Could there be a similar effect on the microbiome? For now, we know very little, largely because elite athletes are such a small population to study.