The Science of Sugar and its Effects on the Body

Most of us know that sugar can be detrimental to our metabolic health, but how bad can it really be? 

Sugar has been one of the basic nutrients of the human diet for as long as time. Sugar is abundant in fruits and vegetables, grains, and even in dairy. Humans have been tuned by evolution to crave sweet and sugary foods, as sugar is energy-rich and requires limited processing by our bodies. Simple sugars, including glucose, fructose, sucrose, maltose, and lactose, consist of one or two sugar molecules bound together. These are the easiest forms of sugar for our bodies to process and therefore have the highest yield of energy per molecule consumed. Complex carbs are made up of long chains of sugar molecules. They require more energy to metabolize, resulting in a net reduction in the energy we can obtain from them. The most common complex carbohydrates in our diet are starches, found in grain-based foods like pasta, rice, and bread. 

Although most people consume sugar daily, it is not an essential nutrient. Humans have the ability to synthesize sugar from other nutritional sources like lactate and amino acids through a process called gluconeogenesis. Evolutionary pressures gave our ancestors a craving for sweet sugary foods because these were the energy-rich foods they needed to survive in their harsh environments. Our taste buds act as nutrient sensors that signal to our metabolic system to prepare for the specific nutrients in the foods that we have ingested. These cravings were beneficial for our ancestors as a driving factor to seek out the foods they needed to survive. Unfortunately, we still have these cravings today, which can be dangerous in the modern world where sweet treats are ample and easily obtainable. 

When we consume sugar, our pancreas secretes a hormone called insulin as a signal to our cells to uptake the sugar in our blood to be utilized for energy production. Excess dietary sugars cause insulin to be excreted constantly and in much greater amounts, to shuttle the excess sugar out of the blood. Blood sugar must be maintained at a set point between 4.0 – 10.0 mmol/L. If it goes above or below this range for too long, it can cause long-term health complications such as cardiovascular disease, kidney failure, or retinal damage (diabetic retinopathy). Insulin exists primarily to maintain this blood sugar range. When insulin is elevated chronically, we can eventually become desensitized to it, a condition commonly known as insulin resistance. In response to this, our body continues to elevate levels of insulin production to elicit a response. This is known as Type 2 diabetes, one of the most common metabolic syndromes in the world.

When it comes to blood sugar management, the best advice is to avoid spiking blood sugar too high or too frequently. The best way to do this is to avoid foods with high amounts of simple sugars or processed sugars. Sugars that are dissolved in liquids tend to be more readily digested by our metabolic system and can cause a greater spike than solid foods. Although this seems like a simple solution, blood sugar responses are highly variable between individuals. A bowl of rice can cause a huge spike in some individuals while barely shifting glucose levels in another individual. Fortunately, an up-and-coming new technology has made it possible to measure blood sugar levels in real-time and monitor how they fluctuate in response to meals. Continuous glucose monitors (CGM) are small sensors that are implanted into our skin that can measure serum glucose levels every 5 minutes and send data to your phone for you to track. CGMs can be an incredible tool for assessing your individual blood sugar response to different types of food. They even have the added benefit of informing you when your blood sugar is too high, so you can take action to reduce it. In healthy individuals, all it takes to combat a blood sugar spike is a brisk walk or burst of activity to help shuttle the glucose into our muscles.  

Although fruit is generally healthy, excess fruit intake can dramatically affect our blood sugar metabolism. Fruits predominantly contain a different type of sugar known as fructose. These sugars undergo a different metabolic process involving a very important enzyme, fructokinase, that uses energy (ATP) to metabolize fructose. Interestingly, unlike so many other enzymes in our body, fructokinase is unresponsive to cellular energy levels and will initiate the first step of metabolism as soon as fructose enters our cells. This mechanism exists to put our body in a state of hibernation in response to the bountiful fall harvest to prepare for winter. This mechanism has become maladaptive as we no longer need to hibernate. Additionally, fructose metabolism produces a by-product called uric acid. Too much uric acid can cause dysfunction in the tissues that line our heart and blood vessels (endothelium) – which increases risk of heart disease and causes oxidative stress to our mitochondria – lowering our metabolic efficiency and promoting fat accumulation. Cardiovascular exercise can be a potent method to improve overall metabolism and utilization of sugar. The cellular metabolism laboratory at the Colorado School of Medicine focuses on understanding why athletes with healthy mitochondria stave off the large majority of age-related decline and disease, and they have made some groundbreaking observations. Many people know that lactate is produced when we exercise and can cause muscles to feel sore. Interestingly, lactate is also used for cell signaling and can be metabolized into energy. When studying world-class athletes, Dr. Inigo San-Milan observed that extremely healthy mitochondria have the ability to convert the by-products of aerobic activity (lactate) into energy. This research group has concluded that by increasing the amount of time one spends doing zone II cardiovascular exercise, we can improve our mitochondria’s ability to metabolize fuels like lactate and therefore bolster their ability to combat oxidative stress – acting to lower the prevalence of metabolic syndrome and dysfunction. With frequent blood testing, nutrition management, and exercise protocols, we strive to have our patients achieve peak metabolic health. Being metabolically healthy does not have to be about sacrificing all the foods we love. With a balanced approach, you can occasionally enjoy a treat while maintaining a healthy metabolism and having the energy to stay active daily.

Dr. Rohan Bissoondath,
Medical Director

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