A few words on Carbohydrates

First I’ll discuss the role carbohydrates play in the body and then give some basic guidelines for daily carb consumption.

Carbohydrates in the Body

Carbohydrates serve four important functions related to energy metabolism and exercise performance.

1) Main Energy Source
The main function of the carbohydrate is to serve as an energy fuel, particularly during exercise. Energy, strictly speaking, is derived from the breakdown of blood-borne glucose and liver and muscle glycogen is ultimately used to power the contractile elements of the muscle as well as other forms of biological work.   In short, daily carbohydrate intake must be adequate to maintain the body’s relatively limited oxygen stores.

2) Protein Sparing
Adequate carbohydrate intake helps preserve tissue proteins.  Normally, protein serves a vital role in tissue maintenance, repair, and growth and to a lesser degree, as a nutrient source of energy.

3) A “primer” for lipid metabolism
Carbohydrate is essential for the proper functioning of the central nervous system.

4) Balance during exercise
Our “fuel mixture” in exercise depends on the intensity and duration of effort, as well as the fitness and nutritional status of the individual.  The energy contribution from nutrients during physical activity is vital in the following:

  • Intense exercise: With strenuous exercise, neural-humoral factors increase the hormonal output of epinephrine, noepinephrine, and glucagon and decrease insulin release. These actions have a stimulating effect on the enzyme.  Glycogen phosphorylase facilitates glycogenolysis in the liver as illustrated in my previous blog entry.
  • Moderate and prolonged exercise:  Almost all energy in the transition from rest to submaximal exercise is supplied from glycogen stored in the active muscles.

Carb Consumption and recommended daily intake

A question I’m commonly asked by my clients is –- What is the difference between good carbs and bad carbs?

In the past several years the talk on carbohydrates has varied greatly. Carbs have been feared in several popular fad diets. And some carbs have also been promoted as a healthy nutrient associated with lower risk of various diseases/conditions.  So which is it? Are carbs good or bad? Well, the answer is both. 

  • Reap the benefits of good carbs by choosing carbohydrates full of fiber. These carbs that get absorbed slowly into our systems, avoiding spikes in blood sugar levels. Examples: whole grains, vegetables, fruits, and beans.
  • Minimize the health risk of bad carbs by eating fewer refined and processed carbohydrates that strip away beneficial fiber. Examples: white bread and white rice.

According to Webmd.com,  the National Academies Institute of Medicine recommends that people focus on getting more good carbs with fiber into their diet.  To meet the body’s daily nutritional needs while minimizing risk for chronic disease, adults should get 45-65% of their calories from carbs, 20-35% from fat, and 10-35% from protein.

There is only one way to get fiber — eat fruits and vegetables.  Evidence suggests that fiber in the diet helps to prevent colon cancer and promote weight loss.

The recommendations:  

  • Men aged 50 or younger should get 38 grams of fiber a day.
  • Women aged 50 or younger should get 25 grams of fiber a day.
  • Because we need fewer calories and food as we get older, men over aged 50 should get 30 grams of fiber a day.
  • Women over aged 50 should get 21 grams of fiber a day.


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