Sports Nutrition Lesson 19

Carbohydrates Carbohydrates are organic compounds that contain carbon, hydrogen and oxygen in various combinations. They are one of the least expensive forms of calories. They are a major food supply for the vast majority of the world’s people.

Carbohydrates Carbohydrates can be divided into 3 categories: simple carbohydrates complex carbohydrates dietary fiber

Carbohydrates Simple Carbohydrates - usually known as sugars. Sugars are subdivided into disaccharides monosaccharides (Saccharide means sugar or sweet)

Carbohydrates The 3 major monosaccharides are: glucose, fructose and galactose. Glucose is often called dextrose or grape sugar. Fructose is known as levulose or fruit sugar. Galactose in found in milk as part of lactose.

Carbohydrates The combination of 2 monosaccharides yield a disaccharide. (double sugar) maltose, also known as malt sugar lactose is milk sugar sucrose in cane sugar or table sugar

Carbohydrates Trisaccharides and higher saccharides exist. High-fructose corn syrup is a manufactured carbohydrate derived from the conversion of glucose in corn starch to fructose. https://www.youtube.com/watch?v=6-uL2oW4dcY

Carbohydrates Complex Carbohydrates, commonly known as starches are generally formed when 3 or more glucose molecules combine. Polysaccharide in when 10 or more glucose molecules combine. The vast majority of CHO’s exist in the world in polysaccharide form.

Carbohydrates Dietary Fiber consists of nondigestible carbohydrates that have beneficial effects on humans. Soluble fiber dissolves or swells in water and may be metabolized by bacteria in the lg. intestine.

Carbohydrates The RDA for carbohydrates is 130gm/day. (You can survive on 0 if you have enough protein and fat, but you might develop a micronutrient deficiency.) The 130 number is based on the average minimum amount of glucose used by the brain.

Carbohydrates The brain is 2% of body mass, but it’s metabolism accounts for 50% of total body glucose utilization.

Carbohydrates Sports nutritionists recommend a high-carbohydrate diet for those in a training program. For athletes consuming 3000 calories a day, 55-60% (the amount generally recommended) would be 1,650-1,8000 calories or 400-450 gms.

Carbohydrates Many endurance athletes reveal a CHO intake lower than recommended. This can have a negative effect on performance.

Carbohydrates In order for food to be used in the body, it must be digested and absorbed. Carbohydrates are usually ingested in the forms of polysaccharides and disaccharides.

Carbohydrates The enzyme that digests complex carbohydrates in amylase. It is secreted in the salivary glands and pancreas. Most of this digestion is done with the pancreatic enzyme in the small intestine.

Carbohydrates After amylase has broken polysaccharides down into disaccharides, enzymes further break it down into monosaccharides. It is then absorbed by specific receptors in the villi.

Carbohydrates Composition of CHO affects its absorption. Some sports drinks containing CHO and sodium may enhance water absorption.

Carbohydrates High concentrations of simple sugars, particularly fructose may have a reverse osmosis effect in the intestine, drawing water from the circulatory system into the intestinal lumen. This can cause what is called the “dumping syndrome”. Symptoms include weakness, sweating and diarrhea.

Carbohydrates Research: What is the glycemic index. How is it measured? What does it mean for an athlete?

Carbohydrates Most CHO is absorbed into the bloodstream as glucose. Normal blood glucose levels range from 80-100 milligram/deciliter of blood. The human body has variety of mechanisms, mostly hormones, to keep blood glucose levels under precise control.

Carbohydrates http://www.getbloodsugarcontrol.com/how-insulin-works/insulin-and-your-body Insulin is a hormone that facilitates the uptake and utilization of glucose. This glucose is mostly taken up by and adipose (fat) tissue.

Carbohydrates Insulin can activate the cells to take up glucose. Exercise also activates the receptors that uptake glucose independently of insulin.

Carbohydrates The glycemic index - is an ranking system. It measures how fast your body’s blood sugar goes up after eating that food. 50gms of CHO in 2 hr = 100 is the measuring system.

Carbohydrates 70 or more - High GI foods 55-69 - Medium GI foods 55 or less - Low GI foods. There are a number of things that can make account for variables.

Carbohydrates Foods with a high GI may lead rapidly to hyperglycemia (high blood glucose). This causes enhances secretion of insulin from the pancreas. High levels on insulin will then lead to a rapid, and possibly excessive transport of blood glucose into tissue leading to hypoglycemia.

Carbohydrates Effects of varying levels of blood glucose: blood glucose is used by the brain and other parts of the nervous system. Hypoglycemia can impair the normal function of the brain. As a condition this is rare, but in very prolonged endurance exercise, it can happen.

Carbohydrates Effects blood glucose can be converted to adipose when caloric intake exceeds use blood glucose can be excreted in urine if an excessive amount occurs in the blood because of rapid ingestion of simple sugars.

Carbohydrates CHO Storage CHO’s are stored in blood - about 5 gm. or 20 calories CHO’s are stored in liver glycogen - 75-100 gms. or 300-400 calories CHO’s are stored in muscle glycogen - 300-400 gms. or 1,200 -1,600 Calories

Carbohydrates CHO’s are used in the body for energy. They have a few other functions, but their main use is fuel. CHO supplies about 40% of the body’s total energy needs during rest.

Carbohydrates During light exercise, fat is an important energy source. When the body is working intensely at 65-85% of capacity, CHO becomes the preferred energy source. At max or supramax levels, CHO is used almost exclusively.

Carbohydrates Yanis Kouros won the 600 mile marathon from Sydney to Melbourne, Australia in 5 days and 5 hours running 114 miles per day. He consumed 13,400 calories/day, 98% from CHO.

Carbohydrates Endurance training and CHO metabolism. Because CHO is the main fuel for exercise, as you initiate an endurance program, a major proportion of your energy will come from muscle glycogen stores. Exercise can activate the genes that produce receptors that transport glucose into muscle.

Carbohydrates As you continue training tissues adapt to better accommodate the exercise stress. After several months of endurance training: you will increase your VO2 max. you will be able to work at a greater % of your VO2 max without fatigue

Carbohydrate you will use less glucose at low-intensity but have the capacity to use more during max as muscle cell mitochondria density increase the enzymes that metabolize CHO will increase More glycogen is stored in the muscle. Synthesis of muscle glycogen may be 2x faster in trained athletes.

Carbohydrates What does this mean? You may be able to run a 10K at 7min/mile instead of 8min/mile You can use high gear longer because of the increased ability to produce energy from CHO You can use lower gear longer without becoming hypoglycemic.

Carbohydrates Hypoglycemia Blood glucose is in short supply. It must be replenished from liver glycogen. If liver glycogen is depleted hypoglycemia may result

Carbohydrates Hypoglycemia is known to impair the functioning of the central nervous system. You may have acute feelings of dizziness, muscle weakness and fatigue. In order to compensate for this, the body will release hormones.

Carbohydrates Epinephrine is secreted from the adrenal gland during exercise. It stimulates the liver to release glucose. It speeds up the use of glycogen in muscle.

Carbohydrates Glucagon is released from the pancreas and increases the rate of gluconeogenesis in the liver.

Carbohydrate Cortisol is secreted from the adrenal gland and helps break down and release amino acids from muscle tissue to provide for gluconeogenesis.

Carbohydrates How the body uses the CHO eaten. It can be ready for use within 5-10 minutes. Peak use is at 75-90 minutes. It will delay fatigue Studies suggest that endurance tasks seem easier. Glucose in the brain and muscle reduce the rate of perceived exertion.

Carbohydrates Because the body can store CHO in the muscles and liver, the usefulness of glucose and other CHO intake before or during exercise depends on the supplies already in the muscle and liver. For Competition the supplies should be enough. The critical point is to consume CHO a day or 2 before the event and decrease the duration and intensity of traianing

Carbohydrates Exercise Intensity and Duration. The potential benefits of CHO supplementation depend on the intensity and duration of the exercise. The most common activities that may benefit from carbohydrate feedings are those that last 90-120 minutes. Marathons, cross-country skiing.

Carbohydrates CHO intake 60-240 min. before exercise lasting more that 90 min. may help performance. 1.8-2.3gm/pound of body weight easily digested CHO’s low in fiber

Carbohydrates 1 hour before exercise Studies found that CHO intake 1 hour before exercise either improved performance or had no effect. There is no need to stay away from CHO ingestion. Much depends on the individual.

Carbohydrates Immediately before exercise If the event is 90 min. or less, CHO consumption just prior to the event will not enhance performance.

Carbohydrates During Exercise Maximal exercise lasting less than 45 minutes - none required. Maximal exercise lasting about 45-60 min - less than 30gm/hr. Team sports lasting about 90 min. - up to 50gm/hr.

Carbohydrates Submaximal exercise lasting more than 2 hours - up to 60gm/hr Near maximal lasting more than 2 hours - up to 50-70gm/hr Ultraendurance events - 60-90gm/hr

Carbohydrates Key Concepts -CHO is the most important energy source for moderately high to high-intensity exercise. - Low levels of blood glucose or muscle glycogen may be contributing factors in the premature onset of fatigue in prolonged exercise.

Carbohydrates Regular training increases the ability of muscles to store and use CHO for energy production. Low levels of muscle glycogen may contribute to impaired performance in prolonged, moderate to high-intensity endurance exercise.

Carbohydrates Given the recommendation to consume about 1.0-1.5gm of CHO/kg of body weight/4-5hrs after exercise in order to rapidly replenish muscle glycogen, calculate how much CHO you would need per hour and list specific foods and amounts that you might need to consume each hour.