In January 2005, the government released new Dietary Guidelines for Americans (www.health.gov). The well-known "food pyramid" has now been subdivided into 12 pyramids, each one corresponding to a distinct food group. Unfortunately, it has not been warmly endorsed, mainly because many feel it is too complex for the average American (Kuehn BM. 2005).

In this discussion, I want to point out four nutrition concepts that differ when athletes (and active people) are compared to general dietary guidelines.

SODIUM

Most people have probably heard the medical profession's recommendation to limit the amount of sodium (salt) in our diets. This is because sodium causes fluid retention and raises blood pressure. Limiting sodium intake is especially important for people with conditions like hypertension, congestive heart failure, and certain kidney diseases. Blacks should also limit their sodium intake because they are more sensitive to its effects than other races.

The new Dietary Guidelines recommend a maximum of 2.3 grams of sodium per day. (NOTE: 2.3 g of sodium is equivalent to 5.8 g of salt.) For blacks, elderly, and individuals with hypertension, a limit of 1.5 g of sodium is suggested.

However, during strenuous exercise, athletes can lose 1 gram (or more) of sodium per hour. Thus, their sodium requirements can be much higher than 2.3 grams per day.

Further, if sodium loss is coupled with the consumption of large volumes of plain water, a condition known as "hyponatremia" can occur. (Translated, this term means "a low concentration of sodium in the blood".) Hyponatremia can cause confusion, disorientation, seizures, and can even be fatal.

While anyone who drinks too much plain water while perspiring can develop hyponatremia, especially at risk are cyclists (because it is easier to drink while riding a bike than while running), females, and marathon-walkers (because perspiration -- and water consumption -- occurs over a longer period).

So, athletes, and, for that matter, anyone who is perspiring heavily over a prolonged period of time, should not limit their sodium intake. In fact, they may need to increase it. However, check with your physician first if you fall into any of the special groups listed above.

WATER

Recently, a panel of experts from the US and Canada was convened on behalf of the Institute of Medicine. Their excellent report was made public in February 2004. Recommendations on fluid intake are listed below:

For healthy sedentary adults living in temperate climates:

• Men: 125 oz (3.7 liters) of water per day from all dietary sources
• Women: 91 oz (2.7 liters) of water per day from all dietary sources

For most people, this amount of water per day is a lot more than they normally drink. The requirement for men is roughly 1 gallon per day. How many of you men out there drink this much water every single day? For the women, 91 ounces is roughly 3 quarts.

However, an exercising athlete can lose enormous quantities of body water through perspiration. The recommendations listed above don't apply to endurance athletes.

So, then, how much should athletes drink? Unfortunately, there is no single answer that applies to all athletes because sweating rates for different sports can vary enormously. For example, researchers from West Chester University in Pennsylvania determined that cross-country runners should consume 4.6 liters of fluid per day and that football players require as much as 12.2 liters per day (Godek SF, et al. 2005).

In the past, the guideline was to "drink as much as you can". However, with over 70 cases of hyponatremia documented, the sports medicine community has recently changed their recommendations for hydration. Now, athletes are cautioned to be more moderate in the amount of water they consume (during competition or training). The International Marathon Medical Directors Association (IMMDA) released a statement in 2002 that marathon runners should drink no more than 400-800 ml per hour.

The best rehydration formula is based on an athlete's own specific sweat rate. This information is then used to determine how much to drink. The athlete records how much their weight changes and how much they drink during a specific duration of training, say, 60 minutes. (This formula can be obtained at the USA Track & Field web site, or, refer to the story Fluids and Electrolytes During Exercise.)

And because of the risk of hyponatremia, at least some of the fluid replacement should be with a sodium-containing sports drink. Several sports drinks are listed below, in descending order based on sodium content (all quantities are per 8-oz. serving, except as noted):

CARBOHYDRATE-BASED DIETS

During the past several years, there has been an attitude that carbohydrates are bad. While a little more sanity seems to have returned in 2005, there are still many who believe that carbohydrates should be avoided for one reason or another.

Carbohydrates are the easiest fuel for your body to utilize. For this reason, as exercise intensity increases, your muscles preferentially burn carbohydrates for energy.

Unfortunately, your body only stores about 2000 carbohydrate calories (compared to 50,000 or more for fat!). So, during strenuous exercise, you will run out of carbohydrate energy reserves long before you deplete your fat reserves.

What this means is that, if you are on a long bike ride, running (or walking) a marathon, or playing a 3-hr tennis match, you need to ingest carbohydrates while you are competing. Athletes know to eat carbs every 20-30 minutes during prolonged competitions like these. Carbohydrates need to be resupplied regularly because they are so easily depleted.

The 2005 Dietary Guidelines for Americans suggests the following calorie ratios:

• Carbohydrates: 45-65%
• Fats: 20-35%
• Protein: 10-35%

However, the 2005 Guidelines don't pertain to elite endurance athletes. In Food For Fitness - Eat Right to Train Right, Chris Carmichael (coach of Lance Armstrong) recommends a diet that provides 60-70% of daily calories from carbohydrates.

So, one source recommends a diet of 45-65% carbohydrates, while another source recommends 60-70% carbohydrates. Why?

One reason for the lower carbohydrate ratio suggested in the Dietary Guidelines is to acknowledge recent evidence showing that dieters can lose weight on higher-protein diets. By allowing for a higher percentage of calories from protein, the percentage of carbohydrates is less.

Another distinction is the total number of calories consumed per day. An overweight person who is dieting and not exercising vigorously may be consuming only 1500 calories per day. However, elite athletes like cyclist Lance Armstrong burn up as much as 9000 calories in a single day. To provide 9000 calories per day, a diet with less than 60% carbohydrates would contain too much fat and too much protein.

The final distinction to be made is that, for general health benefits, carbohydrates should be complex, eg., fruits, vegetables, whole grains, etc. However, during strenuous exercise, simple (rapidly-absorbed) carbohydrates such as glucose, sucrose, and fructose are needed.

So, to summarize, carbohydrate-based diets are still the best choice for both athletes and non-athletes. In sedentary people who want to lose weight, the carbohydrate portion of the diet can be as low as 45%, to allow for a higher ratio of protein-to-carbs. But, during vigorous exercise, carbohydrate intake should rise to 60-70% to provide the energy that exercising muscles need.

FRUCTOSE

If there is one dietary substance with a Dr. Jekyll and Mr. Hyde image, it might be fructose.

Over the past 40 years, food processors in the US have gradually shifted away from using sucrose (table sugar) as a sweetener in favor of using corn syrup. Corn syrup is easier for manufacturers to use and is cheaper. Further, fructose is sweeter to the taste than is sucrose. So, fructose was added to corn syrup, and in ever-increasing amounts. Today, corn syrup with 55% fructose (aka: "high-fructose corn syrup") is routinely used in many artificially-sweetened, fruit-flavored snacks and beverages (Elliott SS, et al. 2002). The dominant sweetener in soda pop is high-fructose corn syrup (HFCS). But, it is also found in foods that might surprise you, such as multi-grain bagels, spaghetti sauces, and even Fig Newtons.

As more and more data are collected on the obesity problem in the US, it appears that fructose -- in the form of high-fructose corn syrup -- is a major issue (Bray GA, et al. 2004) (Havel PJ. 2005). The 2005 Dietary Guidelines for Americans doesn't specifically address high-fructose corn syrup. However, other groups are very concerned about this food additive. On July 13, 2005, the Center for Science in the Public Interest (www.cspinet.org) filed a petition with the FDA requesting that "health notices" be placed on the labels of soft drinks.

The reason why obesity researchers believe HFCS is bad is because fructose does not stimulate an insulin response that typically occurs when you ingest other sugars such as sucrose, glucose, lactose, etc (Elliott SS, et al. 2002) (Teff KL, et al. 2004). Without triggering insulin output, another hormone known as leptin is not released. And without a normal insulin-leptin response, the brain does not receive the proper signal to stop eating. In other words, when you eat a 600-calorie meal, and 100 of those calories come from fructose, your brain perceives the meal as containing only 500 calories.

Now, if you look at the label for PowerBars, the first ingredient listed is "high fructose corn syrup". And, if you analyze the carbohydrate sources for sports drinks, you also find fructose. Elite endurance athletes like Lance Armstrong consume tons of PowerBars and sports drinks during competition. Besides, nature gives us fructose in such wholesome foods like bananas, so, what is going on here? Is fructose really bad for us?

First, for optimum performance, carbohydrates must be supplemented during prolonged exercise because glycogen stores can be depleted long before fat stores are. And, as mentioned above, these carbohydrates should be simple, not complex. Regarding the fructose found in sports drinks, four decades of research has revealed that using several different carbohydrates together allows for better absorption than if the product was formulated with only a single carbohydrate. For example, Gatorade® is made from a mixture of sucrose syrup and glucose-fructose syrup.

Second, ingesting excessive amounts of anything, even a naturally-occurring substance such as fructose, is never a good idea (though, high-fructose corn syrup is hardly what one would call a "natural" substance!). Note that non-diet sodas contain 80% more sugar -- as high-fructose corn syrup -- than sports drinks like Gatorade®.

So, the bottom line is this: if you are attempting to lose weight, you should definitely try to avoid food products sweetened with HFCS. Athletes and others who exercise regularly don't need to worry about the fructose in bananas or sports drinks.

SUMMARY

Athletes have a much different requirement for the following four nutrients compared to the average adult:

• Sodium: For the general population, a daily maximum of 2.3 g of sodium is recommended (1.5 g for blacks, elderly, or people with hypertension). However, during exercise that lasts longer than 60 minutes, especially if you are a "salty sweater", sodium requirements will be much greater than 2.3 g per day.

• Water: In general, most adults need to increase the amount of water they drink each day. However, athletes need to drink an amount that matches their sweat rate, which can be substantially greater than the recommendations in the new 2005 Dietary Guidelines. Further, in athletes, at least some of the fluid intake should come from sports drinks that contains sodium. Or, alternatively, athletes should try to eat some salty pretzels.

• Carbohydrates: The key to a good diet is balance. Carbohydrates are not bad, though too little, or too much might be. Whether you are an endurance athlete or not, carbohydrates should represent the largest percent of your daily calories. Shoot for 45-65% at a minimum, and up to 60-70% during periods of regular, strenuous exercise.

• Fructose: Because fructose does not trigger the normal insulin-leptin response, dieters should attempt to avoid all food products sweetened with high-fructose corn syrup. However, athletes and other active people should not worry about energy bars or sports drinks that might contain fructose, unless that particular product causes GI intolerance.

FOR MORE INFORMATION

One of the best sports nutrition books I have read is Food For Fitness - Eat Right to Train Right by Chris Carmichael (2004). Chris Carmichael is the coach of Lance Armstrong. Even though this book is intended for serious endurance athletes, it provides a lot of solid, common-sense information. The book is very easy to read, so average people don't need to worry about trying to understand a lot of complex biochemistry. I can highly recommend this book for anyone who wants solid, practical information on sports nutrition, and, healthy eating in general (see Book Reviews).

For more information on fluid requirements during exercise, go to USA Track and Field at: www.USATF.org.

The 2005 Dietary Guidelines for Americans can be found at: www.health.gov. The web site for the new food pyramid is: www.MyPyramid.gov.

Readers may be interested in the following related stories:

• Fluids and Electrolytes During Exercise
• Sports Drinks and Recovery Drinks
• Glycemic Index: Should Athletes Care? (coming soon)
• Low-Carbohydrate Diets and the Athlete (coming soon)

PERSONALIZED FITNESS COUNSELING

If you'd like some help designing your personal fitness program, or have questions regarding exercise, or simply want some regular motivation, sign-up for our Fitness Counseling Service. It may be the best investment in your health that you'll ever make.

REFERENCES

Bray GA, Nielsen SJ, Popkin BM. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. Am J Clin Nutr 2004;79:537-543. Abstract

Elliott SS, Keim NL, Stern JS, et al. Fructose, weight gain, and the insulin resistance syndrome. Am J Clin Nutr 2002;76:911-922. Abstract

Godek SF, Bartolozzi AR, Godek JJ. Sweat rate and fluid turnover in American football players compared with runners in a hot and humid environment. Br J Sports Med 2005;39:205-211. Abstract

Havel PJ. Dietary fructose: implications for dysregulation of energy homeostasis and lipid/carbohydrate metabolism. Nutr Rev 2005;63:133-157. Abstract

Kuehn BM. Experts charge new US dietary guidelines pose daunting challenge for the public. JAMA 2005;293:918-920. Abstract

Teff KL, Elliott SS, Tschop M, et al. Dietary fructose reduces circulating insulin and leptin, attenuates postprandial suppression of ghrelin, and increases triglycerides in women. J Clin Endocrin Metab 2004;89:2963-2972. Abstract

ABOUT THE AUTHOR

Stan Reents, PharmD, is a former healthcare professional. He holds Personal Trainer and Lifestyle Counselor certifications from the American Council on Exercise and has been certified as a tennis coach by USTA. He is the author of Sport and Exercise Pharmacology (published by Human Kinetics).  He can be reached at: Editor@athleteinme.com.