By Marcus John Marlow, MD
In this article, we will attempt to bring better understanding to dietary carbohydrates. Carbohydrates are molecules that contain carbon, hydrogen and oxygen. Carbohydrates are derived from plants. In a process called photosynthesis, plants combine water (H2O) and carbon dioxide (CO2) with energy from the sun to form glucose as well as fructose, the simplest forms of carbohydrate. However, it is not always that simple. For example, a glucose molecule can be linked with fructose to form sucrose (table sugar). Glucose can also be linked into long chains for energy storage (starch) or structural support (fiber). Although starch is readily digestible (broken down into its constituent glucose molecules), in fiber, glucose molecules are linked in a manner which is not broken down by humans.
We have all heard someone mention that they’re on a diet and are avoiding “carbs” (short for carbohydrates). Well, all carbohydrates are not created equally. With respect to risk for chronic disease, evidence suggests that the total amount of carbohydrates consumed as a percentage of dietary intake is much less important than the type of carbohydrate. In other words, when it comes to carbs, how much you eat is less important than what you eat. For instance, refined grains (such as white flour), drinks sweetened with sugar and potatoes are all implicated in increasing the risk for chronic disease. Whole fruits, vegetables, minimally processed grains (such as whole wheat or steel-cut oats), and legumes are associated with a decreased risk for chronic disease.
Two very useful measures have been created in order to rank foods according to their effects upon blood glucose. The two measures are called glycemic index and glycemic load. Glycemic index provides a comparison of foods based on the amount of available (or readily digestible) carbohydrate. The higher the glycemic index (high glycemic), the more rapidly blood glucose levels rise when that particular food item is consumed. For glycemic index, glucose is given a value of 100 and foods are ranked relative to that standard. Glycemic load is the glycemic index multiplied by the amount of carbohydrate in a typical serving. Therefore, glycemic load uses information obtained within the glycemic index and combines it with practical information regarding serving size. With both glycemic index and glycemic load, lower values are generally considered better.
|Glycemic Index||55 or less||56-69||70 or higher|
|Glycemic Load||10 or less||11-19||20 or higher|
Consuming high glycemic foods (for our purposes those with glycemic indexes of 70 or higher) results in very high blood glucose levels shortly after eating. Insulin is the hormone that is responsible for drawing glucose out of our bloodstream (where glucose goes following digestion) and into our bodily tissues for use as fuel. High blood glucose triggers the release of large amounts of insulin as a countermeasure. Similar to the story of the boy who cried wolf, when high blood glucose levels and the consequent increased insulin release occurs often, the receptors on our body’s tissues that are responsible for responding to insulin, either stop responding or produce a diminished response. If this process continues unchecked, the result is type 2 diabetes.
Type 2 diabetes is also referred to as insulin insensitivity. Of the many chronic diseases associated with poor carbohydrate consumption choices, diabetes is the most common. Both of the two main types of diabetes involve the inability to draw glucose into the body’s tissues from the blood. Type 1 diabetes is generally thought of as genetic and mainly occurs in childhood. Type 2 diabetes is far more common, accounting for 95% of all diabetes in the U.S., and more commonly occurs in adolescence or adulthood. When our tissues are insensitive to insulin, blood glucose levels will remain elevated unless glucose is drawn out of the bloodstream by another mechanism.
That other mechanism is exercise. Skeletal muscle, when active, has the ability to directly draw glucose from our bloodstream without the help of insulin. However, if left unchecked, diabetes can contribute to a plethora of other problems, ranging from heart disease and stroke to kidney disease, as well as visual and other sensory abnormalities.
How do we prevent/combat type 2 diabetes and thereby increase the likelihood of eliminating associated comorbidities? It appears as though proper diet and regular exercise would be the most logical starting point and this leads us to an even broader contextual understanding of recent events.
The recent COVID-19 outbreak underscores the importance of eating a healthy diet from a number of different perspectives. Trendy diets seeking to promote weight loss by eliminating carbohydrates have also eliminated the protective effects of those whole fruits, vegetables, minimally processed grains and legumes. Current evidence suggests that those most severely affected by the virus are those with chronic health conditions such as diabetes, heart and lung disease. From that information, we can surmise that given proper dietary habits and regular exercise, that those vulnerable to the most harmful effects of COVID-19 would likely be much less numerous.
During a recent trip to the grocery store, I was surprised to see individuals hoarding not only tissue paper but also nonperishable food items. Many people have appropriately questioned the tissue paper hoarding, but stocking up exclusively on nonperishables is only slightly more sensible. The fresh produce section was relatively untouched. While I completely understand why individuals are concerned about the uncertainty presented by COVID-19, the irony is that most of the nonperishable survival-type food items being hoarded are the very same food items that have contributed to creating such a large population of vulnerable people, namely those with chronic diseases.
As discussed above, whole fruits, minimally processed grains, vegetables and legumes have a protective effect in terms of chronic disease. In addition, plants also provide our bodies with the vitamins, minerals, antioxidants and phytochemicals needed in the short term to keep the immune system strong and ward off infection should one be unfortunate enough to contract it. Survival foods are fine; however, let us not consume them to the extent that we lead ourselves to a place where we actually need to consume them. All carbs are not created equally, nor are they all bad. Eat more fresh fruits and vegetables and less of the rest.