Understanding Carbohydrates 

Carbohydrates are the sugars, starches and fibers found in fruits, grains, vegetables and milk products. Though often maligned in trendy diets, carbohydrates — one of the basic food groups — are important to a healthy diet.

"Carbohydrates are macronutrients, meaning they are one of the three main ways the body obtains energy, or calories," said Paige Smathers, a Utah-based registered dietitian. The American Diabetes Association notes that carbohydrates are the body's main source of energy. They are called carbohydrates because, at the chemical level, they contain carbon, hydrogen and oxygen.

There are three macronutrients: carbohydrates, protein and fats, Smathers said. Macronutrients are essential for proper body functioning, and the body requires large amounts of them. All macronutrients must be obtained through diet; the body cannot produce macronutrients on its own.

The recommended daily amount (RDA) of carbs for adults is 135 grams, according to the National Institutes of Health (NIH); however, the NIH also recommends that everyone should have his or her own carbohydrate goal. Carb intake for most people should be between 45% and 65% of total calories. One gram of carbohydrates equals about 4 calories, so a diet of 1,800 calories per day would equal about 202 grams on the low end and 292 grams of carbs on the high end. However, people with diabetes should not eat more than 200 grams of carbs per day, while pregnant women need at least 175 grams.

Good carbs vs. bad carbs

Carbohydrates are found in foods you know are good for you (vegetables) and ones you know are not (doughnuts). This has led to the idea that some carbs are "good" and some are "bad." According to Healthy Geezer Fred Cicetti, carbs commonly considered bad include pastries, sodas, highly processed foods, white rice, white bread and other white-flour foods. These are foods with simple carbs. Bad carbs rarely have any nutritional value.

 The Pritikin Longevity Center offers this checklist for determining if a carbohydrate is "good" or "bad."

Good carbs are:

  • Low or moderate in calories

  • High in nutrients

  • Devoid of refined sugars and refined grains

  • High in naturally occurring fiber

  • Low in sodium

  • Low in saturated fat

  • Very low in, or devoid of, cholesterol and trans fats

Bad carbs are:

  • High in calories

  • Full of refined sugars, like corn syrup, white sugar, honey and fruit juices

  • High in refined grains like white flour

  • Low in many nutrients

  • Low in fiber

  • High in sodium

  • Sometimes high in saturated fat

  • Sometimes high in cholesterol and trans fats

Carbohydrates and Sugars in the Diet

  • Metabolism: Once ingested, most carbohydrates and complex sugars are broken down into the simple sugar glucose. However, in the digestion of sucrose, both glucose and fructose are released into the bloodstream. Glucose is the primary fuel utilized by the brain and working muscles. To protect the brain from a potential fuel shortage, the body maintains a fairly constant glucose level in the blood. Dietary glucose can be stored in the liver and muscle cells in units called glycogen. When the level of glucose in the blood starts to drop, glycogen can be converted to glucose to maintain blood glucose levels. Several hormones, including insulin, work rapidly to regulate the flow of glucose to and from the blood to keep it at a steady level. Insulin also allows the muscles to get the glucose they need from the blood supply. In the process of breaking down carbohydrates into glucose, the body is unable to distinguish between sugars that are added to foods and sugars that occur naturally in foods, since they are chemically the same.

  • Carbohydrates, Sugars, and Weight Control: Calories are needed for normal body processes. However, people will gain weight when they eat more calories than they use up in daily activities and exercise. These excess calories can come from all macronutrients—fats, proteins, carbohydrates, and even alcohol. Carbohydrates or sugars eaten within daily calorie needs, by definition, do not cause weight gain. According to the 2010 Dietary Guidelines Advisory Committee Report, “healthy diets are high in carbohydrates”—45-65% of calories should come from carbohydrates depending on activity level.  Regarding sugars, recent 2015-2020 Guidelines suggest limiting the intake of added sugars to less than 10%  of total calories per day. 

  • Diabetes: Diabetes is a metabolic disorder that occurs when the body cannot regulate blood glucose levels properly. In diabetes, either the pancreas does not make enough insulin (type 1 diabetes) or the body cannot respond normally to the insulin that is made (type 2 diabetes). The causes of diabetes continue to be a mystery, although both genetics and environmental factors seem to play a role. Obesity and lack of exercise are important in susceptibility to type 2 diabetes. Interestingly, sugars are not “off limits” for people with diabetes. In fact, the American Diabetes Association (ADA) has stated that, “the myth that sugar causes diabetes is commonly accepted by many people”. Regarding sugars, the ADA states that diabetics do not need to avoid sugars, but should focus on portion control and serving sizes of both carbohydrates and sugars to keep blood glucose levels on track.  Additionally, the ADA also recommends limits on dietary fat and dietary saturated fat for diabetics.

  • Dental Health: Sugars and cooked starches (e.g.: bread, pasta, crackers, and chips) are fermentable carbohydrates that contribute to the risk for dental caries. The degree of risk from a carbohydrate-rich food is related to several factors such as exposure time and frequency of consumption. However, according to the American Dental Association, risk can be decreased through several practices, the most important being proper oral hygiene and the use of topical fluorides, fluoridated toothpaste, and fluoridated water. Regarding sugars, the ADA recommends “limiting between meal sipping and snacking on sugary beverages and foods. If you must eat a sugary food or drink, consume it with a meal”. Also important in reducing the risk of caries is eating a balanced diet in line with current dietary guidelines.

Carbohydrate deficiency

  • Not getting enough carbs can cause problems. Without sufficient fuel, the body gets no energy. Additionally, without sufficient glucose, the central nervous system suffers, which may cause dizziness or mental and physical weakness, according to Iowa State University. A deficiency of glucose, or low blood sugar, is called hypoglycemia.

  • If the body has insufficient carbohydrate intake or stores, it will consume protein for fuel. This is problematic because the body needs protein to make muscles. Using protein for fuel instead of carbohydrates also puts stress on the kidneys, leading to the passage of painful byproducts in the urine, according to the University of Cincinnati.

  • People who don't consume enough carbohydrates may also suffer from insufficient fiber, which can cause digestive problems and constipation.

The Bottom Line

As the main energy source for the body, carbohydrates are an important part of a healthful diet. Currently, experts agree that carbohydrates and sugars in foods and beverages can be enjoyed in moderation as part of a balanced diet and active lifestyle.