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We’re often cautioned to limit intake of sugars and sweeteners, as well as foods such as desserts and soda pop that are chock full of the stuff. And yet ironically, a major focus of the digestion and metabolism of all the carbohydrates we ingest is to produce a simple sugar: glucose. In fact, the glucose that courses through your bloodstream is so vital to survival that your body has elaborate mechanisms for ensuring that you always have enough of it available. Glucose is critical because it powers your brain, and without it, you can't survive. Glucose is also the primary fuel that your muscles rely on during endurance exercise.

So how do you square the fact that nutritionists tell us to steer clear of sugars, while our bodies work so hard to make it readily available? In this article, we dive headlong into sugars and sweeteners. You'll learn how sugars fit into the larger family of carbohydrates, why they are important to your body, and how and when to use them for performance and health advantages.

Sugars: the building blocks for making carbs
Carbohydrates come in different shapes and sizes. Just like amino acids serve as the building blocks for making proteins, sugars are the biological building blocks for making carbs. It's the individual component sugars and how they connect to each other that differentiate one carbohydrate from another. The simplest carbohydrate is known as a monosaccharide. Mono means single and saccharide means sugar, so a monosaccharide is a single sugar. When two or more single sugars bind together, they form a polysaccharide. Poly means many, so a polysaccharide is a carbohydrate made up of more than one sugar. The simplest polysaccharide is two sugars joined together to form a disaccharide. Carbohydrates can run the gamut from simple sugars made up of monosaccharides or disaccharides to complex carbohydrates that feature large numbers of sugars bound together to form complex branching chains.

• Glucose and its close cousin fructose are sweet-tasting monosaccharides found commonly in fruits
• Sucrose and lactose are examples of disaccharides. Sucrose is made up of glucose and fructose bound together, and sucrose is the chemical name for table sugar. It too is common in fruits, and it's the most abundant sugar found in nature. Lactose is the sugar found naturally in milk, and it's made up of glucose and another sugar, called galactose
• Starch is an example of complex carbohydrate that is found in foods from plants such as grains, beans, potatoes, other vegetables, and fruits. The human equivalent of starch is glycogen, a complex carbohydrate stored in your muscles and liver. Both starch and glycogen feature large numbers of glucose monosaccharide units joined together to form long chains

Carbohydrate digestion, absorption, and metabolism
Imagine eating a meal featuring a juicy orange, a hefty serving of steamed broccoli, and a thick slice of whole wheat bread warm out of the oven. This carbohydrate smorgasbord provides a mixture of both simple sugars and complex carbs. The primary site for digestion and absorption of the carbohydrates from this meal is the small intestine. It's here that the more complex polysaccharides are broken down into disaccharides and then monosaccharides. The simple sugars are then absorbed and moved to the liver. Both your digestive tract and the liver are able to convert monosaccharides like fructose and galactose into glucose. The resulting glucose then circulates in the bloodstream to tissues that need it immediately, such as your brain and your muscles. If your immediate glucose needs are met, the glucose sugars can be bound together as glycogen and stored in your liver and muscles for use later. Or, if your glucose supply exceeds your immediate and storage needs, the excess can be converted to fat and stored.

Vital role players in the digestion of carbohydrates are enzymes. You have a host of different digestive enzymes that can attack many of the different carbohydrates you encounter in your diet. The job of these enzymes is to break apart complex carbohydrate chains to free up the individual component sugars for absorption. However, digestive enzymes aren't always able to keep pace with the quantity or types of carbohydrates in your diet. This can be a problem in the case of lactose in milk, and a health benefit when it comes to a class of carbohydrates known as dietary fiber.

Digestion doesn't always measure up
Some people are able to consume multiple glasses of milk daily with absolutely no hint of digestive upset. However, for others, gas and diarrhea develop as soon as 30 minutes following the ingestion of even a small glass of milk.

Why the drastic difference in outcomes? The culprit is the lactose sugar in milk. Individuals who are lactose intolerant produce too little of an enzyme called lactase that is needed to break down lactose into its component sugars so that they can be absorbed. The undigested lactose sugar travels down the digestive tract to the colon where intestinal bacteria promptly gorge on the stuff. The copious quantities of gas these microbes produce as they metabolize undigested lactose results in the rapid-onset gas and diarrhea symptoms characteristic of lactose intolerance. Fortunately, the problem is readily solved by consuming milk treated with lactase. By adding the enzyme to milk, the lactose present is digested into its component sugars before ingestion.

Fiber is an example of a type of carbohydrate that none of us can digest. Fiber is the indigestible part of plant-derived foods that we eat. Fiber can't be digested because we lack the enzymes needed to break apart its component sugars. But unlike lactose, the lack of digestibility doesn't render fiber useless or a problem. Rather, a diet rich in fiber is associated with a host of long-term health benefits. One such benefit is that all that undigested roughage helps to keep digestive wastes moving through the colon and rectum faster. A faster transit time means that cells of the colon and rectum spend less time in direct contact with potentially toxic digestive wastes that could otherwise damage cells and possibly increase the risk of colorectal cancer. Another benefit is that some types of fiber form a gel-like state inside the digestive tract. This gel tends to trap and promote the excretion of digestive compounds called bile acids that are rich in cholesterol. The excretion of bile acids forces the body to use cholesterol to make more bile acids, and in doing so, blood cholesterol levels tend to fall. Thus, a diet rich in fiber often can help maintain a healthy cholesterol level in the bloodstream. Finally, although we lack the enzymes to digest fiber into its component sugars, each of us has colonies of friendly microbes residing in the colon that can gradually feed on fiber as a fuel source. In the process, these microbes produce various metabolic byproducts that are believed to help make the colon healthier. Thus, fiber itself doesn't necessarily provide the carbs you need to fuel muscles, but a diet rich in fiber does provide important long-term health benefits that you'll want to use to your advantage.

Fiber does come with some fine print that you should know about. A sudden large increase in the amount of fiber you consume can lead to temporary, yet uncomfortable, gas symptoms and possibly diarrhea. Here again, the culprit is the intestinal bacteria that feed on the fiber once it arrives down in the colon. You can largely avoid these symptoms by gradually increasing the fiber content of your diet.

When training or competing, think strategically about what carbs are best for the job
Slow-to-digest complex carbohydrates and indigestible fiber should make up the bulk of your daily diet. That being said, complex carbs and fiber don't make the cut when your goal is to fuel muscles just prior to or during exercise, or when you're trying to refuel rapidly just after exercise. Instead, this is where simple carbs get the nod.

When preparing for a training session or competition, a high-carbohydrate meal 2–4 hours before exercise is recommended along with a high-carb snack about an hour beforehand. However, the carbs you eat before exercise should be low in fiber. Why forgo fiber before exercise? There are two reasons: The first is that we don't digest fiber into its component sugars, and therefore it doesn't provide the glucose your muscles need for fuel. The second reason is ease of digestion. A digestive tract loaded with fiber or slow-to-digest complex carbs can leave you feeling uncomfortably full and bloated during exercise. Instead of complex carbs and fiber, the carbs of choice before exercise are those that are easily digested and absorbed, and that are familiar to you. Carbohydrate sources with these attributes will enable you to top off your glycogen stores, while leaving you feeling comfortable during exercise.

Simple carbs can also be required eating when you're carbohydrate loading in preparation for a long endurance event or an intense period of training. While whole grains, beans, and plenty of fresh fruit and vegetables are best for your long-term health goals, it can be tough to get in enough carbs each day when you're restricted to these bulky sources of carbs. Sometimes you need simple sugars to achieve the large quantities of carbs needed on a daily basis to maximally load up your glycogen stores.

Carbohydrates consumed during exercise need to meet an even more stringent easy-to-digest standard. The carbs you consume during exercise are intended to quickly replenish the glucose that is being depleted from your bloodstream and to help replenish glycogen stores if there are breaks and timeouts. Simple carbs offer the benefit of rapid absorption because they require no digestion, per se. This is key, because blood flow to the digestive tract during exercise is seriously curtailed in favor of circulation to the working muscles in your arms and legs. Thus, exercise is no time to challenge the digestive tract with a load of slow-to-digest complex carbs or indigestible fiber. Well-designed sports nutrition products like Ironman Perform™ sports drink, PowerBar® Peformance Energy bars, PowerBar® Energy Gels, and PowerBar® Energy Blasts gel filled chews not only deliver easy-to-absorb simple carbs, these products feature the innovative PowerBar® C2MAX dual source energy blend carbs that provide a unique 2:1 ratio of glucose to fructose for optimal carbohydrate absorption and fuel delivery to muscles. C2MAX takes advantage of the fact that glucose and fructose have separate transport systems within the digestive tract to carry out absorption of these carbohydrates. By providing both types of sugars, C2MAX is able to take advantage of both transport systems to deliver more carbohydrate fuel to muscles when they need it.

Carbs immediately after exercise are also best if they are simple rather than complex. This is especially the case if you need to promote rapid recovery after training or competing. A dose of simple carbohydrate taken right after exercise is readily absorbed, and this leads to a rapid boost in blood sugar level. The jump in blood sugar is then followed by a surge in insulin. Insulin is the natural anabolic hormone that drives the recovery process. With plenty of glucose available and a strong anabolic signal from insulin, the process of replenishing muscle and liver glycogen stores gets jumpstarted just as soon as exercise ends. In contrast, complex carbs are digested and absorbed more slowly, with not much of an immediate effect on blood sugar or insulin levels. The glycogen restoration process is fastest in the first few hours after exercise, so it's a window of opportunity that you'll want to maximize when rapid recovery is a must. To do this, stick to simple carbs right after exercise and then switch to more complex carbs once you resume your normal meals a few hours later.

Sleuthing for sugars
Understanding the amount and what types of carbs are in a food or beverage requires some label savvy. The Nutrition Facts panel on a product label lists the total carbohydrate content, the sugar content, and the amount of dietary fiber present.

As an example, a Wild Berry-flavored PowerBar Performance Energy bar features 45 total grams of carbohydrates per bar, including 25 grams as sugar and 1 gram of dietary fiber.

Ingredients on a label are listed in descending order of predominance. If you're looking for a snack that will provide you with readily digestible carbs prior to your next event, carbohydrates should be one of first ingredients listed in the ingredient deck, and the snack should be a source of simple carbs.

With the Wild Berry-flavored PowerBar Performance Energy bar example, the first group of ingredients listed is the C2MAX carbohydrate blend, featuring evaporated cane juice syrup, maltodextrin, fructose, and dextrose.

Sugars or caloric sweeteners don't always get listed simply as "glucose" or "sucrose." Below is a list of many of the common names for sugars or caloric sweeteners that you'll see as ingredients in foods and beverages. All of these ingredients are utilized as sources of monosaccharides or disaccharides:

• Sugar
• Sucrose
• Glucose
• Dextrose
• Corn Syrup
• Raw sugar
• Brown sugar
• Honey
• Evaporated cane juice
• Fructose
• Glucose syrup
• High-fructose corn syrup
• Fruit juice concentrate, e.g., white grape juice concentrate
• Invert sugar
• Lactose
• Maltose
• Malt syrup
• Molasses

Sweet doesn't always mean sugar
Just because a food or beverage tastes sweet doesn't always mean that sugar is present. There are a number of sugar substitutes that are added to foods and beverages in place of sugars. In many cases, these compounds have a sweetness that is many times that of common table sugar or sucrose. In the United States, five artificial sugar substitutes have been approved for use in foods or beverages, including saccharin, aspartame, sucralose, acesulfame-potassium, and neotame. A sixth sugar substitute, cyclamate, was banned in the United States in 1970, but it is still approved for use in 50 countries around the world.

• Saccharin is 200–700 times sweeter than sucrose and is found in beverages, jams, and baked goods
• Aspartame is available commercially as Equal, Nutrasweet, and Spoonful, and is 200 times sweeter than table sugar. Made from two amino acids, a packet of this sweetener is equivalent in sweetness to 2 tbsp or 32 calories' worth of white sugar, while weighing in at just 4 calories. This sweetener is used as a tabletop sweetener and can be found in candies, baked goods and mixes, carbonated beverages, nonalcoholic beverages, and malt beverages
• Sucralose is available commercially as Splenda and is 600 times sweeter than sugar. It is excreted in the urine virtually unchanged. This sugar substitute is used as a tabletop sweetener and is found in desserts, beverages without alcohol, and confections
• Acesulfame-potassium is comparable to aspartame in its sweetness and is marketed as Sunette, Sweet One and Diabetisweet. It is used in soft drinks, beverage mixes, and chewing gums
• Neotame is the most recently approved sugar substitute with a sweetness 7,000–13,000 times that of sucrose. At present, there are no commercial products that feature neotame
• Cyclamate is 30 times sweeter than sugar and is used as a table top sweetener and in pharmaceutical preparations in countries other than the United States

Sugar alcohols are sometimes used as a substitute for sucrose in chewing gum and candies. Sugar alcohols include xylitol, mannitol, sorbitol, and maltitol. They tend to be comparable or a bit less sweet than sucrose, but they are metabolized more slowly than sucrose. While food and beverage products with these sugar substitutes may help you get your sugar fix, the substitutes themselves don't deliver carbs. In some cases they may be blended with sugars and caloric sweeteners to offer lower-carb foods and beverages. So don't just assume that something sweet is delivering a full load of carbs, especially when you're relying on these foods as a carbohydrate source before or during exercise for fueling purposes, after exercise to promote rapid replenishing of glycogen stores, or when you're carbohydrate loading.

The final word
Simple carbs or sugars are the best strategy for meeting your immediate fueling needs just before and during exercise, and for recovery just after exercise. They also come in handy in helping to get in enough carbs when you are carbohydrate loading. Complex carbohydrates and fiber are generally your carbs of choice the rest of the time. Fruits, vegetables, whole grains, and beans are great sources of complex carbohydrates and fiber that are vitally important for long-term health, including the prevention of diseases like obesity, diabetes, heart disease, and cancer. You give yourself the best shot at better athletic performance and better health when you understand the different types of carbohydrates, sugars, and sweeteners in foods, and how to use them to your advantage.

References:
1. Coleman EJ. Carbohydrate and exercise. In: Sports Nutrition: A Practice Manual for Professionals. 4th ed. Sports, Cardiovascular, and Wellness Nutritionists Dietetic Practice Group. Dunford M, ed. American Dietetic Association. 2006:14–32.

2. American College of Sports Medicine; American Dietetic Association; Dietitians of Canada. Joint Position Statement: Nutrition and athletic performance. American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada. Med Sci Sports Exerc 2000;32:2130–2145.


Topics: C2MAX, Research, Carbohydrates, Dieting, Nutrition, Nutrition advice, PowerBar products

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