Carbohydrate Classifications

Simple or Complex?
Mono- and disaccharides are also classified as “simple” carbohydrates, and polysaccharides as “complex”. This is an outdated mode of carbohydrate classification and there is currently no use for characterizing carbohydrates in this manner. This classification system has been replaced by Glycemic Index, discussed below.

High Glycemic Index (HGI) or Low Glycemic Index (LGI)?
This newer classification system assesses the ability of the carbohydrate to elevate your blood glucose levels (glycemic response). The index uses either glucose dextrose) or white bread as the standard to which all other carbohydrates and foods are compared. On their respective scales, glucose (dextrose) or white bread is assigned an arbitrary value of 100. Therefore, using glucose (dextrose) as a reference standard of 100, a carbohydrate resulting in 70% of the elevation in blood glucose would be assigned a value of 70. Glycemic response tests are done by ingesting 50 grams of the carbohydrate/food in question, and measuring the blood glucose level at two hours.

Many factors influence the glycemic index of a carbohydrate, and include size of the molecule, type of component monosaccharides, degree of thermal processing, contents/timing of the previous meal and the make-up of other co-ingested foods. Because fructose and galactose must be converted to glucose by the liver first before they can elevate the blood glucose level, they have a low glycemic index i.e. this process takes time, resulting in slower increases in blood glucose. On a 100 point scale, fructose has a GI of 24, and galactose 22. These low GI scores mean that these substances are ‘slow burn’ carbohydrates. Use of these carbohydrates may lead to the body’s overdependance on using its’ glycogen stores, meaning eventual bonking. This concept is backed up by good research with respect to galactose, and the same problem can be reasonably inferred to exist with fructose (36). Carbohydrates, especially in the heat, must be able to supply quick energy, so the closer to 100 on the GI scale, the better. All high GI carbohydrates are immediately available and ready to use by the body once absorbed because they require no processing in your liver, giving you the energy you need now to fuel performance; they are therefore also called ‘fast burn’ carbohydrates. Dextrose is certainly in this category and also has the benefit of being easy to digest and absorb, with no remnants passing into the large intestine. Polysaccharides like maltodextrin, glucose polymers, amylopectin and amylose also have GI scores around 100, but may be associated with incomplete digestion, as discussed above, a process potentially detrimental in the heat.

Hyponatremia-Part 1

Hyponatremia, or reduced blood sodium concentrations, has been recognized as one of the most concerning potential health hazards of ultra endurance events. Hyponatremia has been reported in up to 20% of Ironman participants. When it occurs in triathletes, it usually happens during long course races performed in hotter temperatures, and especially so when combined with the one-two punch of heat and humidity. However, this problem may occur even in short course events in susceptible individuals, especially if these events are associated with relatively high heat and high humidity.

Sodium vs. Salt

Sodium is one component of salt (table salt). Salt, or sodium chloride, contains 1 part sodium to 1.5 parts chlorine. Your sweat on average contains anywhere from about 1.75 grams of salt (700 mg sodium plus 1050 mg chlorine) to 3 grams of salt (1200 mg of sodium plus 1800 mg chlorine) per liter. If you sweat an average of one liter per hour, you lose anywhere from 1.75-3 grams of salt per hour. Multiply this by a 12 hour Ironman (yes we do sweat in the water, albeit less than on land) , and you have 21-36 grams of salt lost (or 8.4-14.4 grams of sodium lost). Since a teaspoon of salt contains about 6 grams, this equals about 4-6 teaspoons of salt lost. Some might not think this seems like a whole lot, but if you consider that a 140 lb person only has about 40 grams (almost 7 teaspoons) of salt in his/her blood to begin with, you start to get a feel for how significant these losses can be!

According to one of the most respected textbooks in medicine, and a definite authority on the topic, relative to sweat, “these losses are almost entirely replaced by...solutions (including Gatorade) that have a much lower salt concentration. The net effect is water retention and, in some cases, symptomatic hyponatremia, with a fall in plasma sodium concentration...”

Quoted from Clinical Physiology of Acid-Base and Electrolyte Disorders-4th Edition, 1994. Chapter 23, pp 656. Edited by Burton David Rose.

It is important to understand the difference between amount and concentration of sodium. Amount refers to weight, and can be measured in milligrams (1/1000 gram) or grams. Concentration refers to weight in a given volume of water, and is measured in milligrams/litre or grams/litre. When speaking of ingesting a sports drink, concentration of sodium in the drink is the important issue when comparing different brands.


Definition

Hyponatremia is defined as a blood sodium concentration of < 135 mEq/liter (< 3.10 g/liter), with normal ranges usually falling between 138-142 mEq/liter (3.17-3.27 g/liter). In the most severe cases, blood sodium concentration may fall to below 120 mEq/liter (2.76 g/liter), a true medical emergency! As can be seen with these numbers, there is not much difference between normal and an emergency situation (about .50 g of sodium/liter, or 1/12 teaspoon/liter!). Symptoms of hyponatremia include nausea, muscular cramping, stomach upset, vomiting, dizziness, seizures and delirium. Coma and even death may result, and has been reported in several cases.

To be continued...see below for Part 2.

Hyponatremia-Part 2

Torn Between Two Ideals

Our bodies have many built in survival mechanisms that function without our conscious awareness or direction. Two important functions related to successful completion of races in the heat and humidity are maintenance of both hydration and normonatremia (normal blood sodium levels). Unfortunately, these functions are often in competition with each other.

Dehydration is not uncommon in the heat, and can cause a drop in our blood pressure. When dehydrated, pressure sensitive receptors located in our carotid arteries, called baroreceptors, sense a drop in our blood pressure. This in turn sets off a variety of counter measures, one of which is the release of Antidiuretic Hormone (ADH) from the pituitary gland in our brains, which tells the kidneys to conserve water, making our urine more concentrated, and reducing urination. Some triathletes experience “shutdown” in their ability to urinate during Ironman races, and this mechanism likely plays a major role in this phenomenon. The net effect is an increase in hydration and blood pressure. Unfortunately, this extra water reabsorbed by the kidneys also contributes to hyponatremia.

Hyponatremia, on the other hand, has the opposite effect in that this condition leads to reductions in the release of ADH, thus allowing the kidneys to excrete more water, making our urine more dilute, and increasing urination. Urinating more water will result in an increase in sodium concentration in the blood. Unfortunately, the loss of this water leads to further reductions in blood pressure. Some triathletes experience increases in urination of especially dilute urine after a Ironman, which is the body’s way of correcting a hyponatremia that evolved during the race.

In truth, the regulation of water and sodium is much more complex then what I have presented here. However, for the purposes of this discussion, two competing physiological processes are trying to maintain an optimum internal environment-one corrective process improves dehydration, but potentially makes hyponatremia worse, while the opposite occurs when trying to improve hyponatremia. So, which process wins when both are competing?

This is a complex question, and one that still has no firm answer. Research is ongoing, however. Suffice it to say, it is probable that dehydration plays a more significant role in stimulating protective responses, which may have a role in perpetuating hyponatremia.

To be continued...see below for Part 3.

Hyponatremia-Part 3

How to Prevent this Dilemma?

One principle of human physiology and medicine that is used as a “prime directive” is “for optimum health, replace what is lost at the rate of loss”. Some examples of this are:

1. You lose protein on a daily basis in the form of shed hair, nails, intestinal losses and skin. This amount must be replaced daily with dietary protein, at the same rate of loss, for optimal health.
2. In an average non-exercising day with comfortable temperatures, you typically lose about ½ liter of water in the form of sweat and respiratory losses. This must be replaced at the same rate to avoid dehydration.
3. If your daily energy expenditure is 2000 Calories, and assuming you neither want to gain nor lose any weight, you must eat 2000 Calories per day to balance your losses.

I could go on-there are hundreds of examples applicable to the human body. This same principle should be applied to your training and racing diet in general, and definitely should be applied to water and sodium balance. As mentioned earlier, your sweat contains on average anywhere from 700-1200 mg of sodium (1.75-3 grams of salt) per liter. Losing about 1 liter an hour means you need to replace both the water component of 1 liter and the sodium component of 700-1200 mg, per hour. If you strive to replace your water and sodium losses at the rate of loss, your odds of developing hyponatremia and dehydration will be drastically reduced. This is facilitated if you consider these two needs as totally separate. You must understand what your water requirements and your sodium requirements are, and ingest adequate amounts of each.

Example:

Based on before and after weights of many training sessions, Scott knows that he loses about 1 liter of sweat per hour in conditions predicted for the upcoming Ironman (see www.eload.net/eCalculator for a detailed explanation on determining fluid requirements). He also knows that his sweat is usually quite concentrated, leaving a lot of salt stains on his clothing. He guesses his sweat contains sodium at the higher end of the normal range, about 1200 mg/liter, so with a sweat rate of 1 liter per hour, ideally he should replace 1200 mg of sodium per hour. Scott uses eload, which contains 740 mg of sodium per litre. Each gel he is consuming contains 50 mg of sodium, and each bar he consumes contains 100 mg of sodium. The following summarizes Scott’s water and sodium intake per hour:

eload Heat Endurance Formula Sports Drink: 1 litre of water; 740 mg of sodium
Gels: negligible water; 50 mg sodium per gel; 2 gels per hour = 100 mg sodium
Bar: no water; 100 mg sodium per bar; 1 bar per hour = 110 mg sodium
Total water = 1 litre; total sodium = 950 mg

Based on this basic Ironman diet, Scott ingests enough water every hour, but his sodium intake is below what he actually needs, about 250 mg per hour short, considering he needs 1200 mg/hour. Multiply this by 12 hours, and you have 3 grams of sodium, or 7.5 grams of salt! Most likely, Scott is headed for hyponatremia.

Scott can do several things to bump up his sodium intake:

1. Increase ingestion of other foods that contain sodium.
2. Use salt tablets/capsules. For example, let’s say that Scott used Zone Caps, which contains 50 mg of sodium per capsule. He would therefore need about 5 capsules (250 mg) per hour to balance sodium losses.

Overhydrating

A lot of talk about “overhydration” has been occurring of late. It is important to understand that this concern is most relevant when you are not matching sodium losses with replenishment. Yes, you can overhydrate, and if you do so with dilute sports drinks, failing to match the rate of sodium loss, and replacing relatively too much water, you may run into trouble with hyponatremia. This problem cannot occur if you are balancing your sodium intake with losses, as illustrated above.

In conclusion, hyponatremia is a relatively common occurrence in ultra endurance events like the Ironman. Using the strategy of separating water from sodium ingestion to figure out needs, and replacing each as they are lost, your risk of hyponatremia will be drastically reduced.

Carbohydrate Digestion and Absorption

During exercise, for the most part, carbohydrates are broken down to their component monosaccharides during the process of digestion, resulting in release of fructose, galactose and mostly glucose (dextrose) in the small intestine. These sugars are then absorbed through the intestinal wall into the bloodstream, and then are taken to the liver. Glucose (dextrose) requires no processing, and is released into the bloodstream for use as quick energy Fructose and galactose are converted to glucose in the liver before they are released into the bloodstream. This process takes time, however, and therefore fructose and galactose are not ideal carbohydrates for use in sport, especially in the heat, where a steady supply of readily available carbohydrate is a must.

Furthermore, regarding fructose, this carbohydrate is a known irritant to the gastrointestinal tract. A lot of sports drinks and sports nutritional products contain this carbohydrate, contributing to gastrointestinal distress, especially in the heat.

Finally, some carbohydrates escape full digestion, passing into the large intestine. This contributes to flatulence, abdominal cramping and bloating. It can also cause diarrhea, and hence contribute to dehydration. The carbohydrates most likely to be associated with this phenomena are polysaccarides such as maltodextrin, glucose polymers, amylopectin and amylose.

Stay tuned to find out about a newer classification system for carbohydrates. You may also subscribe to this site in order to get automatic updates.

Product Concentration Guidelines for Triathlons and Marathons

Many customers have been asking about the best way to use their favorite product (eLoad(TM)) on race courses which are not sponsored by eLoad(TM). The following are some basic guidelines for using a concentrated solution so that you don't have to go without.

Here's the setup:

JetStream/Triathlons
Assuming you have a jetstream bottle on your bike as well as two bottle cages on the frame, mix an eLoad(TM) concentrate in one of your water bottles, using one scoop/e-pak per 500 ml (16 fl oz) that you will need on course (you may want to confirm your needs using our fluid calculator at www.eload.net/eCalculator.htm). Add however many Zone Caps(TM) you need (www.eload.net/eCustomizing.htm. Finally, add enough water to make the concentrate.

Mix two additional bottles of normal strength eLoad(TM) as you normally would prepare them. On race day, dump one of the regular bottles in your jetstream and mount the other one and the concentrate in the cages. When the first jetstream is finished, refill it with the other standard bottle. For all additional jetstream refills, combine a big squirt of the concentrate with enough supplied course water to achieve your desired dilution/taste.

Fuel Belt/Running
Mix a concentrate of eLoad(TM) as above, and place in 2 Fuel Belt containers, loading other containers with normal strength eLoad(TM). When the normal strength eLoad(TM) has been consumed, use concentrate with supplied course water. Squirt the concentrate into your mouth, and ‘chase’ with course water. You will have to experiment with the ratio of concentrate to water that ultimately produces the desired dilution/taste. These systems work out very well, and enable you to keep using your preferred beverage!

Hope this helps!