Sugar: the Good, the Bad, and the Ugly

You have probably heard or been told to avoid/limit sugar in your diet. But why? What are the risks and what are the mechanisms? The word “sugar” is actually somewhat insufficient in the realm of nutritional biochemistry. It turns out there are actually many different forms that can affect your body and metabolism differently when ingested. This is important to understand because not all members of this so-called sugar family are created equal when comes to metabolic health. But before we deep dive into this subject, lets first define a few important terms. First, sugar is known in scientific vernacular as a “saccharide.” Furthermore, there are various subsets of saccharides that we will focus on in this article- monosaccharides, disaccharides, and polysaccharides. Next there are various molecules that fall into the saccharide family that you will need to know (these will likely ring a bell). Glucose, Fructose, Lactose, and Sucrose are some of the most well-known saccharides in the modern diet and the ones we will predominantly discuss in this article.

Glucose

Simply put, glucose is one of the most vital molecules in human energy consumption and is found in most naturally occurring carbohydrates. It is also often found as a part of many different saccharides much as lactose, sucrose, and high fructose corn syrup, all of which we will discuss later. Your body utilizes glucose to maintain healthy mitochondrial function and is constantly working to maintain steady levels in the blood i.e. Your blood sugar. If it gets too high, the pancreas will release insulin to bring it back down. Conversely if it gets too low, the pancreas will provide a hormone called glucagon which will enable the release of glucose to the body through a process called gluconeogenesis [1]. So what happens when we ingest glucose? When we consume a food containing glucose the body will first replenish energy stores in the organs and muscles in the form of glycogen (polysaccharide consisting of multiple glucose molecules, think of this as readily available energy), then store the excess as fat [2]. Just think, if your body did not have an efficient way of storing energy in the form of glycogen and fat, you would constantly have to be eating to maintain energy demands.

Fructose

While glucose is a central molecule in energy production within the body, fructose is not. Fructose can be found naturally in fruits and vegetables and as a sweetener in many processed foods, most notably HFCS but it is not essential to human energy production. Because it is not vital in the same way as glucose, our body processes it in a different way. Unlike glucose, fructose cannot be stored as glycogen and must be processed primarily in the liver. Fructose is converted to glucose in the liver to ultimately be able to be used by the body for energy, but in doing so, it also produces some other byproducts that can be harmful in high amounts to include, uric acid and triglycerides to name a few [3]. The liver is an amazing and resilient organ, but it has a limited capacity to process fructose. In short, excess fructose consumed in the form of processed foods (namely without fiber and other micronutrients found in fruit/vegetables) can lead to metabolic issues such as insulin resistance, inflammation, and a rather insidious ailment known as Non-Alcoholic Fatty Liver Disease (NAFLD) [3]. All three of these issues are known to heavily increase risk factors for Type 2 Diabetes [3]. The last thing to mention about fructose is that it can lead to a resistance to the satiety hormone known as leptin meaning chronic fructose consumption (again in junction with the absence of fiber and other micronutrients) will not fill you up thus potentially leading to the consumption of more calories than you may need [4].

Lactose

The third saccharide to cover is lactose. As you probably well know, lactose is a disaccharide found in dairy products and is made up of one glucose and one galactose molecule. Aside, from its presence in dairy products, lactose has many other uses in the food industry to include being added to sweeten and extend the shelf life of some processed foods [5]. So what happens when we consume lactose? This varies from person to person depending on the presence of lactase in the body (roughly 70% of the population have some sort of lactose intolerance due to a lactase deficiency [6]). Because it is a saccharide and contains glucose, it does raise blood glucose levels and incurs an insulin response although the intensity of the insulin spike will also vary from person to person. Despite being less clear on its effects to metabolic health, it is clear that lactose does not have the same adverse effects as fructose and if consumed in minimally processed foods (think dairy products with no added sugars) it likely won’t degrade metabolic health (barring any lactose intolerance).

Sucrose and High Fructose Corn Syrup

Sucrose, more commonly known as table sugar, is a disaccharide consisting of one glucose molecule and one fructose molecule [9]. Sucrose is found in processed foods as sweetener and naturally occurs in sugar cane, maple syrup, and some fruits and vegetables. Sucrose can lead to all the same issues as fructose (mostly because it contains fructose) especially when consumed in processed foods and without the presence of fiber and other micronutrients. Because of this, it is best to avoid added sucrose, especially in processed foods. Moreover, High Fructose Corn Syrup (HFCS) is another common sweetener found in processed food. HFCS contains 55% fructose and 45% sucrose [9]. Again, because of its presence of fructose and that it is typically found in highly processed foods, HFCS consumption should be avoided because of all the risks of consuming high amounts of fructose.

The Role of Fiber in Metabolizing Sugar

Where does fiber fit in to all this? Fructose, glucose, and sucrose, when consumed with fiber, (think fruits and vegetables) have a much different role in human energy production and consumption. Fiber, unlike other nutrients, does not get digested by the small intestine and thus moves to the large intestine where it ferments and then is eaten by the bacteria in your gut (this is why it is known as a prebiotic) [7]. Why does this matter? Because with the fiber goes most of the sugar, both limiting and slowing overall energy absorption by the body. This means that when you consume fructose, glucose, and sucrose in the form of fruits and vegetables, you likely will not experience the same spikes in blood glucose as with consuming it in the form of processed foods which is good because frequent blood glucose spikes contribute to insulin resistance which sets the stage for type 2 diabetes [8].

Bringing It All Together

The two biggest takeaways of this article are 1.) not all sugars are the same and thus are metabolized differently and 2.) it is best to avoid added sugars in processed foods (because they tend to be high in fructose and lack the fiber). With that said, here are a few tactics for optimizing energy levels when it comes to sugar consumption.

1.) As previously stated, limit sugar, namely fructose consumption to fruits and vegetables.

2.) Go for a 15–20 minute walk after consuming a meal especially if you do happen to eat a meal high in sugar. If this is not feasible you can substitute the walk for some sort of aerobic exercise (think 20-30 jumping jacks EMOM for 5-10 minutes, or a 5–10 minute dance party).

3.) Avoid eating large amounts immediately after waking up (60 minutes after) or before going to bed (2-3 hours before).

4.) Glucose in the form of honey or minimally processed foods/drinks can aid in maintaining energy levels during rigorous exercise (90-120 minutes or more, although this will vary from person to person).

5.) You can utilize a continuous glucose monitor (CGM) to observe how various foods affect your blood glucose levels.

6.) HbA1c blood tests conducted every 3 months can also aid in seeing how your diet effects your blood sugar levels.