Fuel for Thought

Weekly Column By Barb Bryan, BSc(Pharmacy), BSc(Nutrition) APA PRESCRIBING RIGHTS

Macronutrients – aka “Macros” – Part 1 in a 6-part series

 Ever wonder what macronutrients are?

It’s a great time to get to know them – at the start of the triathlon base building season. By having a foundational understanding of this it will better prepare you to understand why and how we fuel for training and race day. So, let’s begin by understanding Macronutrients- the kinds of calories we eat – food is fuel.

First, we must know that all foods are basically considered to be one of three (macro- or big) nutrients: Carbohydrates, Protein and Fat. Each one has a unique set of properties that influence our growth, repair, immune function, and overall health. But, all three are a source of energy (calories). Many whole foods have two or all three of these macronutrients but are predominately one. Oats, for example, are seen as a carbohydrate food, although the actual macronutrient content of 100g oats is carbohydrate 66.3g, protein 16.9g, and fat 6.9g. Balancing these three macronutrients in our diet will not only protect our overall health but also offer optimum energy, injury prevention, muscle and tendon repair, regulation of sleeping cycles, and much more.  Macronutrient balance is the foundation of physical growth and repair and overall progression in terms of performance.

As mentioned, there are three types of macronutrients:

1.Carbohydrates– Our main source of energy and spares proteins

2.Fats (Lipids)– Protect our organs, a source of fuel, absorb certain vitamins and insulate us

3.Proteins– Building blocks of human life

Macro – means a large amount – Indicating we need these three nutrients in relatively large doses on a daily basis. The amount of Macronutrients we need in a day depends on many factors including age, gender, body weight, activity level, and certain medical conditions. The first three parts of this series of articles will be focused on carbohydrates.

Quick facts about Carbohydrates:

  • All carbohydrates are broken down in the body as a monosaccharide– a single sugar molecule – with the most abundant being glucose. One exception, however, is fiber which is not digested at all.
  • The difference between a simple carb(sugar) and a complex carb(starch) is the speed at which your digestive system converts them into a monosaccharide. (This will be covered in Part 2 of this series)
  • The glycemic index (GI) is a measure of how quickly different foods raise the blood sugar levels. A higher GI indicates a faster-digesting carbohydrate. This is key to be aware of for recovery and race strategy (This will be covered in Part 3 of this series)
  • Fiber is a carbohydrate. It is long chains of glucose molecules, but they are bound in a way we cannot digest. Therefore, fiber does not contribute to calories or energy. All naturally fiber-rich foods are also rich in carbohydrates. We need fiber to keep bowel regularity and most importantly to get ample phytochemicals, naturally occurring compounds that protect us from chronic disease.
  • Glycogen is the storage form of glucose in humans and other animals. It’s not a dietary source of carbohydrate. Glycogen is stored in your liver and skeletal muscle. When your blood glucose drops, as it does when you’re sleeping or fasting, the liver will break down glycogen via glycogenolysis and release glucose into your blood. Muscle glycogen fuels your activity. The body can store just a limited amount of glucose, so when empty you will experience lethargy. And, if glycogen stores are full, extra glucose is stored as fat and can be used as energy when needed.

Carbohydrates are essential for good health but often get a bad rap. They’re blamed for everything from obesity to diabetes to heart disease. The misconception that carbohydrates are bad prevents people from consuming a properly balanced macronutrient rich diet. They are the preferred fuel source for your brain, nervous system, red blood cells and for a placenta and fetus. The best carbohydrates to include in your diet for your well-being are unprocessed, high-fiber carbohydrates that get digested slowly. Some carbohydrates have an excellent nutritional value, and some have little to no nutritional value. It’s important to understand and navigate the difference if you wish to construct a diet that places optimal health as its primary goal.

Carbohydrates are found in plant, animal and processed based foods such as fruits, vegetables, grains, lentils, potatoes, dairy, pastries, and candy to name a few. More specifically, carbs are sugar molecules that are a union of carbon, hydrogen, and oxygen (CHO). Think of carbs as one, or more sugar molecules that are bound together and broken down by the body to be used as fuel. They are classified into two main forms—simple and complex carbohydrates. Both play a unique role in providing the body energy, but accomplish this at different rates of digestion and absorption due to their chemical makeup.

The Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates is 45-65%. One gram of carbohydrates equals about 4 calories, so a diet of 1,800 calories per day would require about 202 grams (808 calories) on the low end and 292 grams (1,168 calories) of carbs on the high end of the AMDR.

When we touch on Glucose stores (aka Glycogen) – it is similar to the limited fuel tank of a car. The human body can only store so much carbohydrate as glycogen within the liver and muscle—approximately 1,400-2,000 calories worth. This amount dictates how fast and how long we are able to go before we “bonk” (aka experiencing low blood sugar) without refueling or without going into a race topped up per se.

Over the next five parts in this series, I will talk more about carbs and how we should train to be excellent at burning or oxidizing carbs and fat – they’re not mutually exclusive. In an endurance event, we are using both energy pathways and the ratio of fats and carbs that are used depends on the intensity as well as some other factors, (sleep quality, hydration, training, nutrition an etc.) The higher the intensity and longer the race the higher the ratio of carbs to fat.

More on this in my next installment – stay tuned! 😀