Complete Macronutrient Guide Part 2: Carbs

Complete Macronutrient Guide Part 2: Carbs

    No carb, low carb or a high carb diet? It Depends On A Few Things

Dakota Howe, B.S. in Food and Nutrition

     Carbohydrates are the body’s primary source of fuel. Without them we would have little to no energy because we need glucose, a sugar found in carbohydrates, in order to properly function. The recommendations for carbohydrates can be a little bit misleading; some people are under the impression that we should eat a low/no carb diet to achieve weight loss goals and optimal health; others recommend eating a diet rich in carbohydrates. While both of these statements do hold some truth, neither one of them is totally accurate. Just like not all calories are created equal, not all carbohydrates are created equal either. Healthy carbohydrates are a necessary part of the human diet because they provide our bodies and brain with the most instantaneous source of energy.

The Importance of Carbohydrates

     The consumption of carbohydrates is important for a number of reasons. To start, they are the first macronutrient that the body uses for energy before protein and fat. The sugars and starches in carbohydrates get turned into glucose after getting broken down by the body. Glucose is the simplest form of sugar and is the one that is most easily used by the human body for everything we do from the energy we need to run a marathon to simply relaxing and laying out on the beach.

     Of the three macronutrients, carbohydrates are the first one that the body breaks down to use as energy since glucose is the bodies main source of fuel. During the process of digestion carbohydrates get converted into glucose so they can be absorbed through the intestine walls and into the bloodstream1. After cells get filled with glucose and our bodies use what they need as energy, anything left over will go to the liver and muscles to get stored as glycogen (a storage form of glucose). About 100-200 grams of carbohydrates can be stored as glycogen in the liver and upwards of 400 grams of glycogen can be stored in the muscle tissues while the rest gets stored as body fat. When we are low on carbohydrates and all of our glycogen has been depleted, the body breaks down fat to be used as energy and in most cases, fats act as an efficient source of energy. However, our brain cells specifically need glucose from carbohydrates in order to properly function and cannot run off of fatty acids alone3. That is why when people go on very low carb diets they often feel sluggish and can have a hard time concentrating4. Simultaneously as the body is breaking down fatty acids to use as energy, it also breaks down the protein from our muscles. Therefore, it is necessary to consume an adequate amount of carbohydrates to prevent the breakdown of muscle tissues.

The Different Types of Carbohydrates

     Understanding the different types of carbohydrates is important because each one breaks down and digests differently in the body. Carbohydrates are broken down into two main categories, simple and complex carbohydrates and they are made up of three components – sugars, starches and fiber. Simple carbohydrates are made up of only one or two sugar molecules, no starches or fibers, and are easily digested by the body. Examples of simple carbohydrates include honey, molasses, glucose and fructose. These ingredients can often be found in products such as soda, fruit juice concentrate, some cereals and baked goods. Unlike simple carbohydrates, complex carbohydrates are made up of fiber and multiple sugar molecules known as starches - they require more energy and time for the body to break down and digest them. Examples of complex carbohydrates include oatmeal, brown rice, beans, fruits and vegetables.

     Sugars alone such as fructose, glucose, sucrose and lactose are simple carbohydrates. These sugars are naturally found in a variety of foods such as fruits, vegetables and milk and are often added to a number of packaged foods such as pastries, cookies, cakes, yogurt and cereals. When consumed, pure sugar is almost instantly absorbed into the bloodstream which causes a spike in insulin levels1. However, the body processes foods with naturally occurring sugars very differently than it processes foods with added sugars. For example, eating a candy bar with pure cane sugar will cause a higher spike in insulin levels when compared to a piece of fruit such as a pear. This is because a pear also contains fiber that slows down the rate at which sugar gets absorbed into the bloodstream. Some granola bars, for example, contain both fiber and added sugars. Therefore our bodies will process the granola bar in a similar way that it processes the pear; the only difference is that the pear has naturally occurring vitamins and minerals such as vitamin C and potassium. However, if the granola bar contains high amounts of sugar then it will inevitably get stored as body fat.

     Fiber, a crucial component of complex carbohydrates, is a plant-based nutrient that provides the body with numerous health benefits. You can find fiber in foods such as vegetables, fruits, whole grains, legumes, and beans. However, fiber is indigestible by the human body and is secreted via waste. Because of this, consuming fiber promotes healthy digestion by helping the body to relieve constipation and alleviate diarrhea. Studies have also shown that the consumption of fiber helps to reduce the risk of heart disease and lower the levels of bad LDL cholesterol. Additionally, eating foods high in fiber can aid in weight management and control by promoting feelings of fullness.

     The third component of carbohydrates are starches. By definition, starches are composed of multiple units of glucose molecules, making them complex carbohydrates. When consumed the body digests and absorbs starches at a slower rate because the sugars found in starches are slowly released into the bloodstream throughout the day, providing us with lasting and sustained energy.2 Because of this, there is not an immediate spike in blood sugar levels when we consume carbohydrates rich in starches. Next time you go food shopping, purchase foods that are made up of complex carbohydrates such as oatmeal, quinoa, brown rice, beans and legumes to help build a balanced and filling meal.

The Glycemic Index

     The glycemic index and carbohydrates go hand in hand. It is a system used to determine how much foods (specifically carbohydrates) raise blood glucose levels, also known as blood sugar levels. When blood glucose levels get too high, they can be toxic and can potentially cause weight gain, blindness, kidney failure and an increased risk of cardiovascular disease and diabetes. Those who are trying to lose weight are advised to consume foods that are low on the glycemic index such as oat bran, leafy greens, vegetables and tree fruits and advised to stay away from foods high on the glycemic index like candy, white bread, white rice, pastries and other processed foods with high amounts of added sugars. People who are eating to recover after an intense exercise are advised to eat healthy foods that are higher on the glycemic index including sweet potatoes, honey and dried fruit. Consuming healthy foods high on the glycemic index is beneficial because the goal after exercise is for a fast recovery, making it necessary to replenish blood glucose levels and to maximize glycogen stores5.

     Foods containing refined grains such as white bread, white rice, pasta, cookies, cakes, chips and candy are also higher on the glycemic index but should be consumed in moderation. These foods do not contain high amounts of fiber, so consuming them is merely consuming empty calories that provide the body with little to no nutritional value, as opposed to consuming healthy foods that are high on the glycemic index such as sweet potatoes which also provide the body with vitamins A and C and high amounts of fiber. The main difference between healthy foods that are higher on the glycemic index compared to unhealthy foods that are high on the glycemic index is their fiber, vitamin and mineral content. For example sweet potatoes are higher on the glycemic index but they are rich in fiber, potassium and vitamins A and C, as opposed to white bread which offers no nutritional support.

     While eating carbohydrates alone is not necessarily dangerous, it is the consumption of foods and drinks with high amounts of sugar that can lead to negative health consequences. Studies have shown that people who eat high amounts of sugar are twice as likely to suffer from heart disease, type II diabetes, weight gain, high blood pressure and dental cavities6.

     It is recommended that we consume between 45-65% of our calories from carbohydrates. However this recommendation varies from person to person depending on their height, weight, activity levels and own specific goals1. Thus, carbohydrates can and should be incorporated regularly into a healthy diet and just like anything else should be consumed in moderation but not in excess. Aim to consume healthy products containing high quality complex carbohydrates that are rich in fiber such as leafy greens, vegetables, fruit, beans, nuts and whole grains including oatmeal, brown rice and quinoa.


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