Experience From - Matt Mahoney#1 , Blake Woods , Karl King#1 , Karl King#2 , Tom Hayes , Karl King#3 , Dr. Bill Misner#1 , Dr. Bill Misner#2, Karl King#4, Unknown#1, Matt Mahoney#2, Gerry Wales, Unknown#2,
"Frozen" Ed Furtaw wrote:
"What are the differences if any (as related to their use before/during/after running an ultra) between "complex carbohydrates" and "glucose polymers"? Also, is "maltodrextrine" (or is it "maltodextrose"?) the same as either of those first two?Maltodextrine, or starch, is a glucose polymer, a complex carbohydrate, a large molecule made by linking together long chains of sugar molecules. In the stomach, the long chains are quickly broken down into simple sugars, so it doesn't make much difference what form you get your carbs from. The big difference is that sugar is sweet and starch is not, so drinks containing only complex carbohydrates (like Conquest) are artificially sweetened.
It is probably more important to distinguish glucose from fructose. Glucose is absorbed faster, so a high fructose drink (like Powerade) is more likely to cause stomach problems than a lower fructose drink (like Gatorade) if you consume it at the maximum rate of 200 calories per hour. Sucrose, (table sugar) is a polymer of length 2, consisting of one glucose and one fructose molecule. Starch, maltodextrin, etc., contains hundreds of glucose molecules (no fructose). Many drinks contain fructose because it's twice as sweet as glucose or sucrose. Also, most foods contain high fructose corn syrup because it's cheaper than sugar (at least in the U.S. because of the Cuban trade embargo and farm subsidies).
Maltodextrine is synonymous with "glucose polymer", and probably with "complex carbohydrate". It's three glucose molecules connected together. I've been told that this is the active ingredient in most specialty sports drinks, in addition to the high calorie drink powders they sell football players to bulk up at the beginning of the season. The one's you buy have other additives, the most significant of which I think is caffeine. I buy maltodextrine for $2-$3/lb at the local homebrew shop, add some crushed No-Doz, and have used this with some success in my workouts and hundreds. I like it because it's completely without taste and doesn't gum up my mouth or give me acid sores like some sports drinks do. Dave Cooper and I did some back-of-the-envelope calculations, and figured that this stuff supplied about 1000 calories/lb, or 60 calories/film can (1 fl. oz.), which is how I carry it.
"Glucose polymers" is a very inexact term for carbohydrates made from multiple glucose molecules ( stuck together like legos, for a crude analogy ).
Maltodextrin is a class of glucose polymers characterized by medium length, simple chains of molecules. When the chains get to be only a few glucose molecules long, the carbos are classed as sugars. When the chains get very long, they are classed as starches.
A glucose molecule has 6 carbon atoms, numbered 1 through 6 on a diagram of the molecule. Dextrins are formed by linking the 1-4 positions, forming a long chain. The molecules can also link at the 1-6 positions forming branching chains. Those are amylopectins.
As a simple generalization, "complex" carbohydrates have many glucose molecules arranged in a complex structure. These structures cannot be digested directly. From the mouth to the stomach, these structures are broken down into simple glucose molecules by the action of enzymes called amylases. This happens slowly, so that the carbohydrate energy is doled out over a long time. The production of insulin is correspondingly reduced. Simple sugars, such as glucose or sucrose ( a combination of glucose and fructose ) are absorbed very rapidly and produce a large insulin pulse if taken in quantity.
Before a long run, you'd like complex carbos to stick with you for a while.
During an ultra, if you can only eat every few hours, take complex carbos. If you can get carbos by drinking from a bottle whenever you like, simple sugars or maltodextrins are great, especially if you are pushing a pace. My personal preference is for maltodextrins because they have low sweetness, and I do not tire of them.
Drinks with fructose can cause big problems with some runners who get bloating and diarrhea from that sugar. Sucrose can cause the same problem because the sucrose molecule is glucose and fructose combined. Typical canned sodas have a large amount of fructose or sucrose, so may cause problems if used throughout an ultra. Some sodas also supply caffeine, and the combination of a lot of simple sugar with caffeine can give quite a pick-up in the later stages of a long run.
Immediately after an ultra ( 15 minutes ) your body will re-load carbo like mad, so give it simple sugars. The re-load capability ebbs after the first hour, so then it is better to go with complex carbos to trickle in a steady supply. It is also natural to crave fat after an ultra. [ My weird craving after a very long run is fried liver and onions, with mashed potatoes and salty gravy on the side. ]
Finally, though specific biochemical reactions can be very challenging to understand, the basics of good nutrition are not difficult. Anyone who is interested in quality of life should take the decision to study nutrition as a life-long project. Actually, the more you learn, the simpler the practice of healthy eating becomes. Knowing the fundamentals will also inoculate you against nutritional fads and snake oil sales pitches.
I can tell from my own training and racing that my dietary needs change greatly depending on what I'm doing. To try and force myself to follow one set of numbers in % fat, % protein and % carbo would be silly.
It is also silly to talk about %carbo as if all carbos are the same. Glycemic index plays an important part in insulin response. 70% carbo as glucose will give you a huge insulin response, while 70% carbo from legumes and vegetables will give a very low insulin response.
Consider the time before, during, immediately after, and following a long run.
Before the run, you'd like a lot of complex carbos. During the run, you'd like a steady infusion of glucose or glucose polymers. Immediately after the run you'd like easily digestible protein and glucose. Following the run, you'd like protein and complex carbos. Trying to describe this as X% is just too oversimplified to be correct.
The target of 30% protein doesn't make much sense either. Consider all of the vegetarians who run very well on far less. Even in an ultra, only 9% of the calories needed for running come from protein. If you eat 3000 calories per day, 30% would imply 900 calories from protein, or 225 grams. Ultra runners need more protein than body builders, and even at that, seldom need more than 100 grams per day. Excess protein will have to be broken down (ammonia produced ) and that is hard on the kidneys.
My experience is that I do well on a low-protein vegetarian type lunch, but a higher protein meal with a small amount of lean meat for dinner. Again, trying to force everything into a single set of numbers doesn't square with reality.
How much fat do you need? It depends on the quality. You have to have the right essential fatty acids. If your sources of fat are rich in those, you don't need much. Zero fat diets are a disaster waiting to happen. Your body will store quality fats and use them up over a long period of time if you get no fat. At some point those stores will be used up, and then the immune system can be seriously weakened. If the body is normally 10-30% fat, how can a zero fat diet be healthy?
Instead of worrying about percentages, I think it is more important to learn what constitutes quality food sources which provide the nutrition your body needs. I'm a great believer that most people will, given quality foods, select what is appropriate for their needs on average.
If you understand glycemic index, the role of anti-oxidants, and the role and sources of essential fatty acids, you will have most of what you need to eat healthy without concern for percentages.
I am a part time vegetarian, mainly trying to avoid fat, and a full time chemist. I am surprised that so many people are trying to argue this essential amino acid issue based on so little knowledge. We are still faintly instinctual beasts so our urges can be very roughly related to our needs. However, these urges are far more related to how we have conditioned ourselves. Hence it is a lousy argument to use while relating food to a body's ability to repair itself. Dana is almost entirely correct, those two amino acids cannot be produced by the body and they are necessary for the most efficient connective tissue reconstruction. But I believe there are some vegetable sources though it is not easy to find and bioavailability is arguable. I also believe your body can work around that lacking and can still construct connective tissue. It is not the same quality and some people undoubtedly do better than others so you may be able to get by. But I would have to agree with Dana that many, many injuries or slow recoveries can be attributed to lysine/methionine deficiency. So it is up to you, there are trade-offs to every diet but you need to be more educated about it than primordial urges and reasonable injury recovery history thus far.
Speaking of diets. I just had the following article sent to me by a four time Tevis Cup finisher who thought us runners might be interested.
Nutritionists like me have succeeded in convincing athletes to think of carbs as their best fuel source. What they may not recognize is that carbs cannot be lumped into one category. Most athletes have even heard that there are simple and complex carbohydrates. However, pardon the pun, carbs are more complex than that. When it comes to planning their training meals, athletes need to understand and use the glycemic index.
For years, carbohydrate sources have been labeled as simple (containing sugars like glucose and sucrose) or complex (containing fiber and starch) based on the structure of the main carbohydrate. Simple carbohydrate foods have been charged with causing large and rapid changes in blood glucose. They are alleged to cause a rapid rise followed by a rapid and often greater fall - this is known as rebound hypoglycemia or the "sugar blues". Simple carbohydrates have also been considered to be lacking in nutrient value. On the other hand, it has been believed that the digestion and absorption of complexcarbohydrate foods is slower, producing a flatter and more sustained blood glucose and insulin response. Complex carbohydrate foods have also been regarded as being more "healthy" or "nutritious".
While this classification system may have been developed as a quick education tool for the lay person, it has become a major headache for nutritionists. Because we now know that the effect of specific carbohydrate foods on the blood glucose response is neither simple nor predictable. During the 1970s, diabetes specialists were amazed to find that simple carbohydrate foods did not always produce the high and short-lived blood glucose responses traditionally attributed to them. For example, fruit and sweetened dairy products produce a flattened blood glucose curve when they are eaten. The old no-no, sugar sucrose), has a medium blood sugar profile. Curiously, some foods high in complex carbohydrates (e.g. bread and potatoes) produce a rapid blood glucose response, similar to that following the ingestion of glucose itself. Even the presence of dietary fiber in foods does not always delay absorption and flatten the after-meal blood glucose curve. For example, blood glucose responses to whole-grain breads are similar to those after eating white bread. The glycemic index (GI) was introduced in the early 1980s to classify the real effects of carbohydrate-rich foods on blood glucose levels. The GI is a ranking of foods based on their measured blood glucose response compared to that following a standard food. In some laboratories the standard food is glucose, while other scientists prefer to use white bread.
Tables of the glycemic index of a large number of carbohydrate-rich foods have now been published internationally. The numbers vary according to who measured them and the exact type of food. For example, there are a lot of different types of "white bread" in the world. And even things like potatoes and rice come in a variety of plant types. Each has a slightly different GI. Generally, nutritionists now divide foods into those that have a high GI (bread, potatoes, breakfast cereal, glucose-based sports drinks), a moderate GI (sugar, soft drinks, tropical fruit) or a low GI (dairy foods, lentils, legumes, oats, cold climate fruits such as apples). Some foods sit on the borderline, but this is not really a problem. The real interest is in foods that are extremely different in their GI. And the real message is that there is no way to predict blood glucose responses to eating specific foods without these actual measures.
Now that we know the effect of specific food items on blood glucose responses, we can advise people who want to control their blood glucose profiles during the day or after meals. In other words, you can eat the same amount of carbohydrate, but manipulate whether you want blood glucose spikes during the day (eat high and moderate GI foods), or a more even level (low GI foods). Diabetics are a classic example of a population that benefits from tight control of blood glucose and low GI foods. People with high blood lipid levels may also benefit from being able to achieve a more even blood glucose profile that has smaller rises and falls during the day. The glycemic index may also be a useful tool in weight control, since low GI foods have recently been shown to produce a longer-lasting "satisfaction" after meals - you don't feel hungry quite so soon. A recently published book, The G.I. Factor, has made this information widely accessible.
Some people have quickly grabbed on to the idea that altering the GI of specific meals or the training diet may influence training and performance. The focus is on optimizing the muscle carbohydrate fuel sources, particularly for prolonged moderate-intensity exercise. Research at the Australian Institute of Sport, in conjunction with researchers at Deakin University and University of Melbourne, has examined the use of GI in sport.
The following guidelines are drawn from this research.
Brand Miller, J., Foster-Powell, K., & Colagiuri, S.(1996). The G.I. Factor: The Glycaemic Index Solution. Sydney, Australia: Hodder and Stoughton.
- The glycemic index may be useful in sport and deserves further attention. However, it is not intended to provide a single way to rank the virtues of carbohydrate foods. There are many other features of foods which may be of value to the athlete, such as nutritional value or practicality. Sometimes foods need to be chosen because they are tasty, portable, cheap, easy to prepare and unlikely to cause stomach upsets. These issue are specific to the individual and the exercise situation. In other words, foods must always be chosen to fit the "Big Picture" and not one single issue. In the case of food eaten before or during exercise, the athlete should practice any strategies in training so that they can be assessed and fine-tuned.
- Despite early speculation, there is insufficient evidence to support the statement that all athletes will benefit from eating low GI carbohydrate meals prior to prolonged exercise. The idea is that a more sustained glucose response might sustain fuel and performance. In fact, in sports events where carbohydrate stores can become depleted, the typical way to sustain the carbohydrate supply during exercise is to consume carbohydrate during the event. The athlete should let practical issues and individual experience guide the choice of a pre-event meal. You may happen to like a carbohydrate food that is low GI (e.g. pasta), or you may find that your choices tend to foods with a high glycemic index such as rice, breakfast cereal, toast. Both choices can work.
- For specific individuals or during unique training situations, a low GI pre-event meal may be of particular benefit. Some athletes show an exaggerated and negative response when they eat carbohydrate foods in the hour before exercise. About 5% of the population experience a rebound hypoglycemia or blood sugar drop - and they feel terrible. Why this response occurs in some people is unknown. During unusual endurance sessions such as open water swimming where practical difficulties prevent the athlete from consuming carbohydrate during the session, the pre-event meal may have greater bearing on metabolism and fuel availability during the event, and a low GI carbohydrate meal may sustain blood glucose, and performance.
- Athletes performing prolonged exercise should consume carbohydrate during the event to supply additional fuel and thereby enhance their performance. Which carbohydrate drink or food to consume depends generally on their previous experience, the logistics of the event, gastrointestinal comfort and the need for fluid replacement. A carbohydrate source of moderate to high GI appears to be sensible - such as a glucose-based sports drink. However, practical issues and individual tastes are more important than GI when choosing a carbohydrate source for prolonged exercise situations.
- Moderate and high GI carbohydrate foods appear to enhance glycogen recovery after exercise compared with low GI foods. The reason for this is not clear. The most important point, however, in post exercise refueling is to eat enough total carbohydrate. We give recommendations to athletes about how much carbohydrate they should consume immediately after exercise and throughout the day to meet their refueling needs. Foods must be available and appetizing to the athlete so that these recommendations can be met. It is OK to let some favorite low GI carbohydrate foods contribute to total fuel intake - especially if these are foods that are handy and easy to eat. However, it makes sense to focus on carbohydrate foods and drinks with a moderate to high GI for glycogen recovery. The overall message: choose what is practical.
I never met a carbohydrate I didn't like.
Insulin is a wonderful substance, without which, we would die.
My personal preference is to eat meals with carbos that have a relatively low glycemic index. High GI meals taste good but leave me hungry a few hours later.
However, when I run, I want a drink with a moderately high GI, taken relatively frequently in small doses ( a swallow or two ). As soon after the run as possible, I like a drink or food with a very high GI. Right after running, the enzymes which assist re-loading muscle glycogen are very high. To make the most of that, I take a lot of simple carbs right away. A few hours later I'll eat again, but take carbs with a more moderate GI, as the enzyme activity is starting to wane.
Someone who is training a lot needs to eat plenty of carbs to keep their muscle glycogen restocked. For losing weight, I'd be far more concerned about fat calories in the diet and try to reduce that instead of carbs.
The major problem with eating a lot of sweet, sugary stuff is that it is frequently missing important vitamins and minerals. When it comes to vitamins and minerals, a can of soda is a total disaster.
As for giving up beer to save on carbohydrates, I consider that an unacceptable trade off. The Germans refer to beer as "liquid bread". So, I give up a slice of bread per day and have a beer instead. For those who don't like beer, giving it up is a moot point.
In the long run, I believe that the body will tell you what to eat, and imposing too many artificial restrictions may over-ride a healthy instinct.
Recommendations For Ultra Running (CHO Intake) Pre, During & After Exercise
(total grams complex-carbohydrates required/day)
|2 hrs Training
|4 hrs Training
Take 100-150 grams of complex carbohydrate glucose polymers 3 hours prior to exercise. Do not use simple sugars, fructose, honey, prior to or during exercise. If you must use simple sugars, use them after exercise.
Take 70-90 grams glucose polymer complex carbohydrate in fluid solution every hour during exercise. An energy drink may be sipped 4 times per hour for constant replenishment energy substrate flow. This should be practiced in training-to-duplicate race conditions in order to establish what individual biochemistry tolerates best. Studies show that 100 grams or above of energy drink ingested may result in gastric stress. Costill's studies using 3.5 ounces water every 5 minutes or 35 ounces per 50 minutes also encouraged Dr. Colgan's studies to conclude the need for 35 ounces fluid intake per hour. Dr. Tim Noakes, who has done recent and more extensive hydration research with marathon and ultramarathon runners, suggests that most runners should take no more than 16 ounces fluids per hour during endurance events. His findings among athletes with hyponatremia indicated they were the victims of water intoxication(too much to drink-->evidenced by excess intakes above 1000 ml. or over 30 ounces fluid per hour)
Take up to 225 grams complex carbohydrates within 30 minutes optimal window time frame, include 30-50 grams easily digestible protein. Any more than 225 grams dietary carbohydrate intake may synthesize excess carbohydrates to body fat stores. Use of simple sugars may stimulate Insulin Growth Factor(IGF) for cellular uptake of post-exercise growth hormone...Which is, by the way-->good...as long as you do not take too much simple sugar. A tablespoon of fiber-rich raisins is ample to spark the IGF-factor mechanism from a post-exercise meal without introducing too much sugar into the bloodstream all at once.
The "Grazing" technique 4-6 small meals throughout the day rather than 1-2 meals at the end of the day has been shown to maximally elevate muscle glycogen stores with minimal to no increasing of adipose tissue sites. Fluid recommendations are 35 ounces(1 quart) per hour for rehydration.
This "simplified version" for adapting carbohydrate intake for the energy cycle has been time-tested at the Colgan Institutes with both endurance athletes and strength athletes. Provision for fuel-adaption to your specific biochemistry in the crucible of endurance exercise ideally should be tested in training runs before racing in competitive events.
What has been outlined above is definitively not "written in stone" and may be modified to creatively and efficiently to move your specific being through the time and space of what is otherwise known as "Ultra"...
Adenosine Triphosphate(ATP) is the fuel source from which the complex mechanism of long-term movement(ultrarunning) is generated by mitochondrial cells located within muscle fibers. The rate of ATP synthesis from carbohydrates is 1.0 mol/minute, while fats produce 0.5 mol/minute. Carbohydrates generate TWICE the rate of energy as fats converted to ATP! During anerobic activities, such as sprinting, energy expenditures of stored glycogen or body fats may jump up to as high as 2.4 mol/minute. At an aerobic pace, most of us use 10-12 calories of stored energy per minute. During an ultra run at the same aerobic pace pre-mentioned, consumption of carbohydrate-sourced calories from aid stations, crew, or whatever we can carry, will never meet the demand of expenditure, unless we stop running.
The problem is the liver can only replenish calorie expenditures at the rate of 4 calories per minute. This means that a deficit of 6-8 calories per minute during an ultra or endurance workout is created regardless of the type of carbohydrates we ingest. In the initial hour of an event the average caloric profile of spent calories is 65% glycogen(carbohydrates) to 35% fatty acids for ATP conversion. Then, as we continue, an interesting internal metabolic event occurs. As this increasing deficit(6-8 calories/minute) is depleted on mostly glycogen stores, somewhere around 90 minutes after initiating exercise, the profile of caloric selection reverses to 35% carbohydrates against 65% fatty acids converted! Up to a point, the more the athlete stresses this mechanism of energy expenditure during prolonged training bouts, the more efficient it will behave when future repeated sessions are demanded.
Karl King is correct in advising us to avoid simple sugars during an exercise event. Simple sugars characteristically have a high glycemic index, which tends to alert an insulin response from the beta cells of isles of langerhorns in the pancreas gland, sweeping blood sugars into cells as a survival response. Unfortunately when this "Sugar Crash" happens, we feel "low", shaky, and despondent. High Glycemic Index(GI)substrates also empty from gastric areas very slowly when compared to carbohydrates with a low GI. Low glycemic indexed long-chain complex carbohydrates empty the gastric area faster and with less insulin response resulting in a somewhat faster uptake for conversion within depleted tissue sites. The enzyme, Glycogen Synthase, is highest after one has spent glycogen stores. When this enzyme increases in blood serum volume, glycogen synthesis occurs at a rapid rate.The application for the endurance athlete is to utilize the optimal30-minute window after exercise by ingesting the carbs in order to replenish the glycogen without storing fat.
How much Carbohydrate and what kind? Complex carbohydrates, Glucose Polymers, especially amylopectins, are more near like the chemical structure of human glycogen than their distant simple sugar relatives, and may lend somewhat of an advantage to glycogen conversion by the liver. Ivy(1988 J APPL PHYSIOL) demonstrated that the maximum rate of carbohydrate synthesis occurs by ingesting 225 grams of glucose polymers within a 4-hour window post exercise. Above 225 grams the advantages do not occur and the body may begin to store excess carbs in adipose tissue sites. Colgan(1990) recommends from 600-900 grams carbohydrate replenishment for intense athletic workouts, which figures out to be 2.0-3.0 grams carbohydrate per 2 hours workout per pound of body weight.
All dietary fat(9 calories/gram) ingested takes only 3% of it to process it in to the fat storage areas, while 27% of all complex carbohydrates(4 calories/gram) are burned during the resynthesis-replenishment process. Several of the Costill late 1970 studies demonstrated dramatically the arguments supporting high carbohydrate intake during endurance training. The same scientist(Yudkin 1953) who caused us all to rethink our position on dietary fat as its harms to health and longevity also published an equal warning-concernas to the immediate danger of dietary simple sugars and their intake correlation rate with the advent of coronary heart disease(CHD) in the 20th century. This distinguished scientist's warning on dietary fat was heeded, but few of us are aware of his precautionary note regarding use of simple sugars. Coronary heart disease(CHD) was unheard of 85 years ago. As Americans began to increase their intake of sugar, the death rate(CHD) per 100,000 people increased to 60 from a person ingesting up to 20 pounds of dietary sugar per year. The average American today consumes over 120 lbs. sugar per year, raising our mortality rates(from coronary artery disease) to 300 per 100,000 deaths, or 5 times the former CHD death rate! For the damage to health that appears to occur from ingesting simple sugars, it may be best to choose complex carbohydrates and leave the sugars(Sucrose, corn syrup solids, glucose, and fructose) to small dose intake. The 7-calorie alcohol carbohydrate gram, if taken post-exercise behaves much like the simple sugar model, but in addition, it also suppresses the post-workout growth-hormone response entirely, and thus enters into the "Poor Choice" category.
The "Sugar Buster" dietary protocol(suggested in the original post by Chip Marz) may also not supply or support an Ultrarunner's classic carbohydrate-caloric energy demand, however, it may serve as a plausible method for losing body fat stores. My experience with ultra endurance athletes is that weight-loss diets for diets that produce body-fat-burning-efficiency training are incompatible. If you have read this far, it is my wish that you found some useful dietary application that may effect your training choices into personal bests.
Adding some thoughts to the subject of Dr. Bill Misner's post...
One thing I enjoy ( when there's time ) is cooking. Most enjoyable for me are Chinese and Nepalese styles. One common thread in these styles is the general lack of simple sugars. Chinese cooking regards sugar not as a major ingredient, but something to be used in small amounts as a "harmonizing" ingredient.
The sportsdrink(s) I use are based primarily on maltodextrins and contain simple sugars in small amounts, only as an agent to harmonize with the flavor. Accordingly, I never use any drink with fructose during or after an event.
The only time I purposely take a drink with fructose or high fructose corn sweeteners is soon after rising from bed. During the night, the body uses liver glycogen as a significant energy supply. One of the quickest ways to recharge liver glycogen is to take 100-200 carbohydrate calories, primarily from fructose, upon rising. Starting an ultra with low liver glycogen is asking for trouble, so I'll get some quick calories right after rising. Then I get dressed and prepared for the run.
I'll eat on the way to the race site. Some of my best runs have come after eating fatty foods along with a cup of coffee. That protocol raises levels of plasma free fatty acids. The concept is that if fat levels are high from the start of the run, muscle glycogen is spared early on.
The observation that alcohol blunts the body's growth hormone response is interesting. While I enjoy a beer or a glass of red wine, I prefer to have such drinks with or just after dinner. Beer right after a run will sometimes give me a headache.
The optimum dietary device for distance running is the employment of complex carbohydrates. When many simple sugars are join together forming longer chain lengths of each the result is a "Complex Carbohydrate". An example of longer chain-length complex carbohydrates are "Glucose Polymers", which are described on the ingredient lists of the better energy drinks, energy gels, and energy bars as "Maltodextrin". When ingested, complex carbohydrates do not throw the endocrine system into a wild "tizzy" like their simple-sugared short-chain cousins do. Complex carbs taste do not taste as sweet as simple sugars. Corporate manufacturers sweeten energy products for taste and for resale. When a simple sugar(sucrose or corn syrup solid) enters the human digestive system, blood sugar levels peak dramatically above baseline within 20-25 minutes, but then "crashes" below fasting baseline within the hour! Fructose, also a simple fruit sugar found in corn syrup, honey and fruit, is diverted from the stomach to the liver. Fructose raises blood sugar levels meagerly peaking at 25 minutes after eating, but also "crashes" below baseline around 70-75 minutes post. Fructose ingestion also has been shown to raise blood serum triglycerides. Liver glycogen stores are replenished from fructose intake.If possible, the ultrarunner who is concerned with optimal performance and health may want to avoid excessive intake of simple sugars both during the run and at mealtime. Every year I field dozens of questions regarding problems experienced during an ultra, from athletes who accepted a sugared energy drink-bar-gel "hand-out" from an aid station, or whose dietary practices include too much simple sugar.
Observing a 53-year old man clad in a robe-like garment and tire-tread sandals literally "destroy" a talented field of some of the best ultrarunners in the USA over a tough 100-mile trail course stirs my curiosity vehemently to ask," How did he do that?" Does what one eats support endurance performance? The dietary choices this Tarahumara legend practices may have had some influence upon his incredible performance. The antithesis is, had he "fasted" food and water before this 100-mile ultramarathon, he may have remarkably hindered his performance results.
Since the textbooks that describe cellular and molecular synthesis and resynthesis have generally stated that 98% of what we are today(in terms of bone, muscle, and fat cell tissues) was constructed from the foods that we ate over the past 6-month time period. Two distinguished researcher, Dr. David Costill's late 70's works and Dr. Tim Noakes' mid 80's to mid 90's research well-established the importance of complex carbohydrates and fluid replacement before, during, and after endurance exercise.
In 1978, W.E.Connor examined the dietary practices of 523 Tarahumara Indians over a 3-year period(American Journal of Clinical Nutrition, 31:1131, 1978). The Tarahumara were found to possess extremely low blood cholesterol levels(136mg/dl average for men vs. 117 mg/dl for women). Amercians tend to be above 200 mg/dl for both men and women! Connors conclusions were that these values occurred because of their extremely low dietary cholesterol intake of 71mg average per day compared to our +625mg/day in the USA. Their dietary fat intake accounted for 11% of their total caloric residue compared to between 34-40% in North American diets. Saturated fat intake was found to be 2% of the Tarahumara daily diet, while 15% is typical in the United States. Simple sugars accounted for 5% of the Tarahumara diet, while we in the States consume a whopping 25% of our diet in processed sugars. Vegetable sources provided 96% of their dietary protein, averaging 79-96 grams protein per day, more then meeting the RDA for protein synthesis(+236%-1221%). Corn and Beans are the staples which these people utilize to synthesize complex carbohydrates to muscle glycogen stores, low lipid concentrations for membranes or cell wall structures, and dietary protein for lean muscle mass resynthesis. The Tarahumaras' high physical activities, such as "kickball" games that last 1-2 days and may cover nearly 200 miles, could not be performed unless they had a cardiovascular foundation from repetitive high endurance training, low body mass indecies, a superlative cardiovascular system, and a superb supportive dietary protocol. Their dietary practices are a model for the ultrarunning community, exemplary of the importance of a high intake of fiber-rich complex carbohydrate diet, moderate vegetarian protein, and little to no saturated fat and cholesterol from meats or animal byproducts.
The use of ergogenic glucose polymer-based drinks(maltodextrins)during an ultra event is supported by myriads of research studies dating back to the late 1970's. What's so special about maltodextrins? Maltodextrins are simply processed long-chain corn sugars with a glycemic index of below 20. The Tarahumaras simply leave the "husks" on their glucose polymers, e.g. "corn or beans". Their culture and performance in ultras favor the use of complex carbohydrates before and during extreme energy expenditure.
Where we seem to differ is...that these people do not have the opportunity to eat from packages pumped full of additives for extended shelf life, or, at places that serve rich meats, hydrogenated fats, and simple sugars mixed in caramel-flavored-carbonated water. Most of their pre-energy substrates are from raw/cooked vegetarian foods, rich in fiber, low in salt, and almost nil in bad fats.
The obvious differences between the Tarahumaras and American ultrarunners is that they are healthier, and, looking at the finish results...They define the art of ultrarunning.
Dr. Bill wrote:
"When ingested, complex carbohydrates do not throw the endocrine system into a wild "tizzy" like their simple-sugared short-chain cousins do."That is true at rest but not during exercise. When you are running, simple sugar is burned faster than it is absorbed, so there is no overproduction of insulin and no overshoot as blood sugar level returns to normal. The rate of absorbsion of sugar by the digestive system is 200 calories/hour. The rate of usage is 100 calories/hour at rest and 500-1000 calories/hour during exercise. When you are running, it doesn't matter what form your carbohydrates come from.
I find that the best thing for me is both. By the time I get to the aid station, I need a quick sugar high and then the more complex for in between stations. I will take candy or cookies at the aid stations and then follow that up with a GU type product and, if the aid stations have them, a bit of fruit. I remember when I got stomach upset last year at BAUS what I threw up was the watermellon I had been eating. Figure that one out.
Optimal solution osmolality(mOsm.) for rapid fuel gastric-emptying must be between 280-303 mOsm., which is the same osmolality as body fluids. Dextrose reaches the body fluid osmolality level at 4-5% solution.(4 parts dextrose to 96 parts water, by weight) Sucrose-glucose reaches body fluid osmolality at 8% solution.(8 parts sucrose to 92 parts water by weight) Glucose Polymers are said to be at body fluid levels for immediate absorption at 20% solution.(20 parts Glucose polymers to 80 parts water by weight)
Twice the quantity of Glucose Polymer carbohydrate calories pass through gastric channels as do those calories originating from fructose, sucrose, or glucose.
The Iso-Osmotic solutions of calories provided by a solute mixture at 280-300 mOsm(body fluid equivalent) are as follows:
Glucose..........0.2 calories/ml...5% solution
Fructose.........0.2 calories/ml...5% solution
Sucrose..........0.4 calories/ml...8% solution
Glucose Polymer..1.2 calories/ml..20% solution
If the energy solutes exceed body fluid osmolality, gastric emptying is absolutely halted until the body draws from it's internal fluid and electrolyte stores enough of each for lowering osmolality of the sucrose, fructose, or dextrose solutions to body fluid levels(for eventual gastric emptying). This is why an athlete should drink fluids that have been formulated to osmolality equivalences of 280-300 mOsm.(This is especially true during thermic conditions, if dehydration/electrolyte imbalances are also symptomatically in question, sudden intake of a sugar-fructose-dextrose energy drink may cause complete cessation of exercise.
After gastric emptying is accomplished, then the liver must reprocess glucose polymers, some of the simple sugars, or starches(Tarahumara) back into tissue sites for replenishment of muscle glycogen stores. As I stated in a previous post, the liver can produce a gram per minute no matter what form of carbohydrate emptying from the gastric area. While we run selectively at chosen 70-90% VO2 Max pace, slow-twitch fibers burn the highest percentage of stored muscle glycogen, at perhaps 3-4 grams per minute. Running, therefore, creates an energy deficit of 2-3 grams per minute minimal, even when gastric emptying is optimal, using an abundant income of the optimal 20% caloric solution of Glucose Polymers. Simply put, more than twice as many calories from glucose polymers are able to pass through the stomach to the liver in the same time frame than those from simple sugar derivatives.
B.J.M Jones(1983, GUT 24:1152-1160, and in 1987, CLINICAL SCIENCE 72:409-414.) showed that glucose polymers empty faster than glucose type sugar solutions. The question then becomes whether to run an ultra with a minimal 2-3 gram/minute deficit using glucose polymers...or, eat the "sugars" for higher deficits from their slow gastric-emptying rate, enjoy the sweets, resulting in the inevitable, a premature "bonk".
Once gastric channels have slowly released ingested simple sugar into an ultrarunners blood stream, what other mechanisms may systemically contribute to a DNF?