<h1 class= "pgc-h-arrow-right" > introduction</h1>
Understanding some of the basics of sugar metabolism can greatly improve athletic performance for both bodybuilders who want to gain muscle and for the average bodybuilder who wants to lose fat. Not only that, but the knowledge presented in this chapter will help athletes stay up-to-head in the face of a wide variety of nutritional supplement advertisements and speech in fitness magazines.
Carbohydrates are the most important source of energy for living organisms. Each gram of carbohydrate contains 4.1 kcal of calories, which is comparable to the calories contained per gram of protein, but there are many differences between the two basic nutrients. In addition to being able to burn rapidly to provide energy for living organisms, carbohydrates also assume countless other physiological functions. Due to space limitations, other physiological functions of carbohydrates are discussed only in individual cases.
The most interested in the metabolism of carbohydrates should be strength trainers. The metabolism of carbohydrates is closely related to one of the most influential hormones in the human body, which is insulin. We will elaborate on it below.
Carbohydrate derivatives include dietary fiber, sugar substitutes (including sweeteners), etc., which are described in this chapter. These derivatives are important for the nutritional balance of the diet of strength trainers.
<h1 class="pgc-h-arrow-right" > two, what are carbohydrates?</h1>
In order to avoid unnecessary misunderstandings in the following discussion, we will first clarify a few names of carbohydrates.
The first thing to say is "sugar." A wide variety of sugars appear in books and magazines, and what we call "sugar" in our daily lives refers to the ordinary crystalline sucrose used in cooking. In nutrition, "sugar" does not refer to the sucrose crystals often referred to in daily life, but to all short-chain carbohydrates, or to all carbohydrates involved in the human diet.
Don't be intimidated by the complex concepts above. The "sugar" in this column is the general term for all carbohydrates. It's important to keep this in mind, otherwise it can lead to misunderstandings in your reading.
< h1 class = "pgc-h-arrow-right" > third, the composition of carbohydrates</h1>
Let's first introduce the composition of carbohydrates. Don't worry, there will only be a few of the most important representatives of carbohydrates here. Knowing this knowledge has implications for both daily life and exercise: we can often infer the role of sugars in metabolism based on their structure.
In addition, as athletes who promote healthy eating, we often encounter some slippery words in our daily lives, such as glucose, dextrose, sucrose, maltodextrin, etc. The words sound very professional, not to mention that we can immediately put them in the seat. So let's start with the interesting background of these terms. You can understand and categorize the above terms after reading the following.
<h1 class="pgc-h-arrow-right" >1
</h1>
Monosaccharides, as the name suggests, are the basic units that make up the various sugar molecules. Monosaccharides are very important for living organisms because only monosaccharide molecules can be transported in the organism. All long-chain carbohydrates are broken down into simple sugars before they can be transported into the bloodstream.
Specialized tools ("molecular scissors", i.e. biological enzymes) that break down long-chain carbohydrates into simple sugars before they enter the bloodstream are present in the intestines below the stomach in the digestive tract. Figure 1 reveals the breakdown process of carbohydrates. For athletes who do strength training, the monosaccharides in the diet mainly include glucose, fructose and galactose.
Fig. 1 Principles of digestion of carbohydrates
1.1 Glucose is the most important monosaccharide
Glucose is the "sugar currency" in the human body, because all other carbohydrates obtained from food must be converted into grapes through the digestive tract before entering the bloodstream, and then they can participate in the process of energy metabolism. Various fruits contain a lot of glucose, and some foods are processed with glucose in the form of syrup.
Dextrose refers to the dextrose produced when long-chain carbohydrate starch is broken down in an organism. Dextrose can also be obtained by means of industrial manufacturing. We can usually take dextrose directly orally to quickly replenish energy.
Note: Although the names of the two terms above are different, in fact their molecular structure is exactly the same, and dextrose also belongs to glucose. Their role in metabolic processes and their effect on insulin secretion are exactly the same.
After reaching the intestines, glucose passes through the intestinal wall with the help of busy glucose transporters and provides the body with energy and is ready to perform other physiological functions in the shortest possible time. Therefore, after oral glucose, the body's blood sugar level will rise rapidly, and then it will drop significantly under the action of hormones. Some people may experience hunger and symptoms such as hypoglycemia after oral glucose, and the specific reactions vary from person to person.
1.2 Is there any benefit to fructose?
Fructose also comes from natural plant foods, and people can also buy refined fructose crystalline products on the market. The difference between fructose and glucose lies not only in the spatial structure of molecules, but also in the role they play in metabolism.
After entering the human body, fructose also enters the blood circulation through special transporters on the intestinal wall. However, the transport mechanism of fructose is very sluggish, so the rate of fructose into the human blood is significantly slower. Fructose also needs to be progressively converted into glucose or other metabolic molecules in the liver.
All the physiological and biochemical steps that fructose undergoes take a certain amount of time, so fructose provides energy to the human body at a significantly slower rate than glucose. This is also why fructose has become a specialty sugar for many diabetics: it causes blood sugar to rise significantly slower and more slowly, so it hardly triggers insulin secretion.
1.3 Lesser-known galactose
The chemical structure of galactose is half of the lactose molecule. Dairy products are the body's most important food source for ingesting galactose. Galactose metabolism does not affect insulin, and galactose is further processed in the liver first: galactose also needs to be converted into glucose if it is to participate in the body's energy balance. In addition to this, galactose has other physiological functions.
<h1 class="pgc-h-arrow-right" >2</h1>
Disaccharides (also known as disaccharides), as the name suggests, are made by combining two identical or different monosaccharides. The two monosaccharides of disaccharides can enter the bloodstream and participate in the body's metabolism after separation. For strength trainers, the most representative disaccharides are sucrose, maltose and lactose.
2.1 Sucrose is the most common disaccharide
The sucrose molecule consists of one molecule of glucose and one molecule of fructose. Sucrose comes from certain plants in nature, such as sugar beets, sugar cane, etc., and is the most commonly used sugar in our lives, commonly known as white sugar.
Another familiar form of sucrose is brown sugar. However, brown sugar does not refer to a specific sugar alone, according to the different manufacturing processes, brown sugar can be divided into different types, it covers many derivatives of sucrose. The color of brown sugar may be specially made, or it may be naturally produced during the production process (caramelization can also bring sucrose
brown appearance). Although there are many folk sayings about the benefits of brown sugar, in fact it has no special effect on people.
Sucrose has many different forms in life, such as white sugar, refined sugar, sugar cubes, icing sugar, sugar gum, rock sugar, brown sugar, powdered sugar, tongs candy, jam candy, decorative sugar, vanilla sugar, etc.
Like glucose, sucrose has a variety of names, but there is always only one molecular structure. Therefore, the body's metabolism of these sugars is exactly the same — no matter what form sucrose is ingested into the human body, it is the same thing for the enzyme responsible for metabolizing it. Enzymes do not recognize a variety of names, only the spatial structure of the ingested sugar.
In daily life, sucrose is used as a preservative as well as natural colors and flavors in addition to mainly providing sweetness. A more typical example is beet syrup, which can provide a brown appearance for some foods (including bread), and consumers will think that the food is rich in dietary fiber when they see the dark appearance of the food, thus stimulating the desire to buy.
Sucrose and starch are the largest carbohydrates consumed in the daily lives of ordinary consumers. What we want to emphasize here is that the vast majority of high-calorie soft drinks contain sucrose, such as fruit water. Judging from the molecular composition of sucrose, half of the calories in fruit water come from the fructose components it contains and half from glucose. As a result, people who regularly drink fruit water soft drinks will consume a lot of these two carbohydrates — their intake is much higher than the sugar they consume when eating solid foods such as fruits.
2.2 Maltose can cause a large amount of insulin secretion
Maltose consists of two glucose residues that are connected to each other and are rapidly broken down into glucose by an enzyme in the small intestine. After that, the efficient glucose transport mechanism in the small intestine is triggered, and blood glucose levels rise rapidly, even more rapidly than eating a meal of pure glucose food.
Maltose can also exist as a decomposition product of starch, and is also found in ordinary beer and alcohol-free beer.
2.3 Common side effects of lactose
As the name suggests, lactose is mainly found in dairy products, so it plays an important role in the daily lives of most athletes. Lactose is recognized as a sugar that has the least effect on blood sugar and insulin levels.
There is no strong scientific basis for the claim that increased lactose in the body causes subcutaneous water retention (puffiness) in bodybuilders. Perhaps this misconception stems from the well-known fact that controlling carbohydrate intake can make exercisers look tougher.
The lactose molecule consists of one molecule of glucose and one molecule of galactose. Lactose is broken down into the above two monosaccharide molecules in the intestine (see Figure 1 for the principle). The enzyme that catalyzes this decomposition reaction is the so-called lactase, which is a lactose decomposition tool located in the intestine.
An important concept associated with lactose is "lactose intolerance". For most people, after breastfeeding, lactase activity in the body drops to 1/10 of the initial level. However, there are obvious differences between different races. For example, many Caucasians still have the ability to digest and absorb large amounts of lactose even as adults.
This is not the case for lactose intolerant patients. Lactose intolerance is not an allergic reaction (allergy to dairy products refers to an allergy to milk protein, not lactose), but an abnormal decline or even complete disappearance of the activity of enzymes in the intestine that break down lactose.
The cause of lactose intolerance may be congenital (very rare) or acquired (caused by a viral infection). The symptoms and treatment of lactose intolerance are diverse, mostly related to the digestive tract.
Lactose that is not broken down will reach the posterior segment of the intestine, where it is broken down into different metabolites by the intestinal flora. When these metabolites are overdose. It can cause a range of discomforts, such as bloating and farting, abdominal cramps and diarrhea. But. The severity of these symptoms is not directly related to the amount of lactose consumed. That is to say, some people have to consume a lot of lactose to cause serious problems, while some people only need a little lactose to do so. How much lactose each person can bear, can only rely on their own groping, the official can not give reference values.
In real life, lactose intolerant patients can try to eat a small amount of fermented dairy products (such as yogurt, curd, etc.). In these fermented dairy products, the lactose originally contained has been converted into lactic acid by fermentation, and the remaining lactose is very small. If the activity of lactase in a person's body has not completely disappeared, he is fully capable of digesting the small amount of lactose left in yogurt. Lactose intolerant patients can also boldly try a certain amount of soft cheese or hard cheese. In addition, there are low-lactose dairy products and lactase preparations for sale.
Only when the symptoms of lactose intolerance are severe should athletes completely abandon milk and other dairy products, because for athletes, dairy products are extremely nutritious foods. Milk contains high-quality protein, and most people who don't consume a certain amount of dairy products a day will have a hard time getting enough calcium from their daily diet unless they take calcium supplements for a long time. From the point of view of calcium supplementation, soy milk simply cannot replace milk – although soy products contain many other nutrients. Especially for female athletes, chronic under-consumption of dairy products increases the risk of osteoporosis in old age. If they also adopt a low-calorie diet for a long time, the situation will be even worse.
In addition, a large number of follow-up studies have found that people who consume a lot of dairy products are less likely to be overweight and develop type 2 diabetes. We will elaborate on this later.
(Based on Chapter 2, Sections 1-3 of the Complete Book of Sports Nutrition)