Spectacular 2nd Edition of the World's Healthiest Foods is now complete and ready to order at the same low price of $39.95. You will also receive 2 free gifts valued at $51.95
To order and more. . .
The George Mateljan Foundation, a not-for-profit foundation with no commercial interests or
advertising, is a new force for change to help make a healthier you and a healthier world.


To fuel high-intensity exercise, the body needs increased amounts of calories and all nutrients, particularly, increased carbohydrates fuel sources, additional protein to maintain muscle mass, and additional iron and B vitamins to support the oxygen-carrying capacity of the blood. In addition, nutritional prerequisites for a well-nourished athlete include increased antioxidant nutrients to protect the cells in a highly active, highly-oxygenated body from oxidative damage.

Physical Factors

Exercise of all types requires energy in the form of calories. The amount of calories needed to fuel physical activity depends on several factors including your age, your gender, your level of conditioning, and the intensity and duration of the activity. For example, sports that require repetitive muscle contractions (running, rowing and swimming) use more energy than activities that require maintenance of muscle contractions (gymnastics and golf). Athletes need to consume large amounts of calories and carbohydrates to be sure they have enough fuel available to support high-intensity exercise.

Exercise causes loss of fluid through sweating and respiration. The fluid that is lost is taken from the blood, which can reduce blood volume. If fluid is not replaced during and after exercise, serious dehydration can result, causing an increase in body temperature and impairing heart function. Drinking water is probably the best way to replace fluids. However, some experts believe that it is also necessary to replace lost electrolytes. Electrolytes are minerals ' sodium, chloride, and potassium ' that are lost when we sweat. (Other minerals can be lost through sweat as well - including the antioxidant mineral, zinc). While many different 'electrolyte-replacement' sports drinks are available, you may not need to spend money on these expensive drinks to ensure adequate replacement of electrolytes. In most cases, a well-balanced diet rich in fruits and vegetables provides an appropriate amount of these important minerals.

If you exercise regularly for long periods of time or at a high level of intensity (for example, training for a marathon), you may find that you are more susceptible to infections, specifically upper respiratory tract infections. High-level physical activity does generate a significant amount of free radicals, which can tax and weaken the immune system, increasing your chance of catching a cold.

Nutrient Needs

Fluids: During strenuous exercise, athletes must drink enough water to maintain their pre-exercise weight. One pound of weight lost is equal to 2 cups of fluid that should be replaced. It is important to remember that thirst is not a dependable indicator of the need for fluids, and athletes must make a habit of drinking water frequently, both during and after exercise. Calories: Competitive endurance athletes have increased caloric needs. Female athletes may need 4,000 calories per day or more, while male athletes may require up to 6,000 calories or more. A nutritionist, trainer, or health coach can often help you determine exactly what your calorie needs will be. During periods of active exercise, however, as many as 10-15 calories additional intake per minute may be required.
Carbohydrates: Glycogen, the form in which carbohydrate is stored in muscle cells, is the primary source of energy used to fuel exercising muscles. It is well accepted that fatigue during exercise is caused primarily by depletion of glycogen stores. Most athletes' glycogen stores are depleted within 90 minutes of intense exercise, leaving muscles with inadequate energy sources to fuel activity. As a result, athletes who train daily often require large amounts of carbohydrate (more than 500 grams per day) to continue to perform at peak levels. Protein: Considerable debate exists among nutritionists regarding protein needs for athletes. Some nutritionists believe that physical activity does not increase protein requirements, and that athletes, like all other adults, need only 0.8-1.0 grams of protein per kilogram of body weight. Other nutritionists believe that daily protein requirements for athletes may be twice that of physically inactive individuals, reaching as high as 2.0 grams of protein per kilogram of body weight. Under the first scenario, a 175-pound athlete weighing about 80 kilograms would need about 65-80 grams of protein. Under the second scenario, this same athlete would need about 160 grams of protein. It is not yet clear exactly where in this range most athletes fall, but it is clear that amino acid balance and protein quality are equally as important as the total amount of protein. For this reason, athletes should be sure to obtain sufficient amounts of all the essential amino acids in their diet as well as the metabolic support amino acids. Included in this list would be the sulfur-containing amino acids cysteine, methionine and taurine, the methyl-containing amino acid methionine, and the detox-supportive amino acid glycine.

In recent years, protein and amino acid supplements have become popular among athletes. Of special interest has been glutamine, an amino acid derived from glutamic acid. Glutamine is the most abundant amino acid in muscle cells and helps provide fuel to these cells when carbohydrate reserves are low. Glutamine also helps build muscle and can help prevent breakdown of muscle, which is advantageous to athletes. Heavy exercise, injury, and infection can deplete the body's glutamine stores, so some athletes find it helpful to supplement with glutamine. Glutamine is also easily obtained in the diet and is found in nearly all foods that contain protein. Dietary Fat: As is the case with protein, no consensus exists about exactly how much dietary fat an athlete needs. Like other adults, athletes should limit fat intake to no more than 30% of total calories and should include at least 4 grams of omega 3 fatty acids in their daily diet. It is important for athletes to remember that dietary fat slows digestion, so the best pre-event meals contain mostly carbohydrates and little or no dietary fat. B vitamins: B vitamins are important for energy production, red blood cell production, immune function, and synthesis of messaging molecules in the nerve cells. These vitamins are depleted rapidly any time the body is exposed to internal or external stress. For all of the above reasons, B vitamins are critical to a training athlete. In most cases, at least twice the RDA level would be needed by a a training athlete. Iron: As a component of the myoglobin, the oxygen-carrying compound found in muscles, iron plays a crucial role in delivering oxygen to muscle cells. As a result, athletes should be sure to obtain at least the Recommended Dietary Allowance of iron each day, 8 mg for men and 18 mg for women. Antioxidant nutrients: Athletes should ensure a high intake of the antioxidant nutrients, vitamin C, vitamin E, and carotenoids, to help the body deal with the free radicals that are produced as a consequence of high-intensity exercise. Some research points specifically to the benefits of vitamin C in preventing post-exercise infections. In addition, vitamin C may help reduce cortisol levels. Cortisol is a hormone that can increase breakdown of muscle components, and cortisol levels are often elevated after exercise. Double the RDA intake level for these antioxidant nutrients would be the minimal recommended starting point for many training athletes.

Dietary Choices

For optimal performance, meals should be eaten 3-4 hours before an athletic event or training session. Consequently, athletes who train for several hours a day sometimes find it difficult to time meals and snacks around their exercise routine, and because their calorie needs are so high, these athletes have difficulty obtaining enough nutrients.

Unfortunately, a significant number of competitive athletes have eating disorders such as anorexia nervosa and bulimia, which impacts the quantity and type of food eaten. For example, some athletes severely restrict calories and fat to prevent weight gain or to lose body fat, a dangerous and (in the long run) counterproducive behavior.

The World's Healthiest Foods offers athletes the means of accessing the information and developing the skills needed to choose and prepare food that will enable them to maximize their performance, while maintaining their health. The World's Healthiest Foods provide maximum nutrition, improving metabolism, energy, and the ability to gain muscle, while lessening cellular damage and recovery time. With the personalized information available on the World's Healthiest Foods website (Food Advisor), you can quickly determine which foods will best support your training goals. Then take advantage of the exceptional recipes specially developed to fit your needs. All recipes take a half hour or less to prepare, and each provides not only simple instructions, but video clips demonstrating the procedures involved. With the World's Healthiest Foods, you can quickly supply your body with the nutrition needed for optimal performance.


  • Bazzarre TL, Scarpino A, Sigmon R, et al. Vitamin-mineral supplement use and nutritional status of athletes. J Am Coll Nutr 1993 Apr;12(2):162-9. 1993. PMID:19280.
  • Beltz SD, Doering PL. Efficacy of nutritional supplements used by athletes. Clin Pharm 1993 Dec;12(12):900-8. 1993. PMID:19260.
  • Bishop NC, Blannin AK, Walsh NP, et al. Nutritional aspects of immunosuppression in athletes. Sports Med 1999 Sep;28(3):151-76. 1999. PMID:19210.
  • Chen JD, Wang JF, Li KJ, et al. Nutritional problems and measures in elite and amateur athletes. Am J Clin Nutr 1989 May;49(5 Suppl):1084-9. 1989. PMID:19330.
  • Davis PA, Iwahashi CK. Whole almonds and almond fractions reduce aberrant crypt foci in a rat model of colon carcinogenesis. Cancer Lett 2001 Apr 10;165(1):27-33. 2001. PMID:16170.
  • DiPasquale M. Amino Acids and Proteins for the Athlete: The Anabolic Edge. CRC Press: Boca Raton, FL, 1997. 1997.
  • Economos CD, Bortz SS, Nelson ME. Nutritional practices of elite athletes. Practical recommendations. Sports Med 1993 Dec;16(6):381-99. 1993. PMID:19250.
  • Elmadfa I, Rupp B. Nutritional status of young athletes. Bibl Nutr Dieta 1994;(51):163-5. 1994. PMID:19240.
  • Fogelholm GM, Himberg JJ, Alopaeus K, et al. Dietary and biochemical indices of nutritional status in male athletes and controls. J Am Coll Nutr 1992 Apr;11(2):181-91. 1992. PMID:19300.
  • Hawley JA, Dennis SC, Lindsay FH, Noakes TD. Nutritional practices of athletes: are they sub-optimal?. J Sports Sci 1995 Summer;13 Spec No:S75-81. 1995. PMID:19230.
  • Lemon PWR. Beyond the Zone: protein needs of active individuals. Journal of the American College of Nutrition 2000; 19(5): 513S-521S. 2000.
  • Mahan K, Escott-Stump S. Krause's Food, Nutrition, and Diet Therapy. WB Saunders Company; Philadelphia, 1996. 1996.
  • Schmalz K. Nutritional beliefs and practices of adolescent athletes. J Sch Nurs 1993 Apr;9(2):18-22. 1993. PMID:19270.
  • Shephard RJ, Shek PN. Immunological hazards from nutritional imbalance in athletes. Exerc Immunol Rev 1998;4:22-48. 1998. PMID:19220.
  • Steinbaugh M. Nutritional needs of female athletes. Clin Sports Med 1984 Jul;3(3):649-70. 1984. PMID:19340.
  • van Erp-Baart AM, Saris WH, Binkhorst RA, et al. Nationwide survey on nutritional habits in elite athletes. Part I. Energy, carbohydrate, protein, and fat intake. Int J Sports Med 1989 May;10 Suppl 1:S3-10. 1989. PMID:19320.
  • Wittig E, Infante A, Suarez A, et al. [Functional evaluation of a nutritional energy supplement in athletes]. Arch Latinoam Nutr 1992 Sep;42(3):345-50. 1992. PMID:19290.

Printer friendly version

Send this page to a friend...


If you want to learn everything about how to eat and cook healthier, here's the book for you.
2nd Edition
Order this Incredible 2nd Edition at the same low price of $39.95 and also get 2 FREE gifts valued at $51.95. Read more

Newsletter SignUp

Your Email:

What You Should Know This Week

Find out what foods you should eat this week, the recipe and nutrient of the week, and the Smart Menu on our home page.

Healthy Eating
Healthy Cooking
Nutrients from Food
Website Articles
Privacy Policy and Visitor Agreement
For education only, consult a healthcare practitioner for any health problems.

We're Number 1
in the World!

35 million visitors per year.
The World's Healthiest Foods website is a leading source of information and expert on the Healthiest Way of Eating and Cooking. It's one of the most visited website on the internet when it comes to "Healthiest Foods" and "Healthiest Recipes" and comes up #1 on a Google search for these phrases.

Over 100 Quick &
Easy Recipes

Our Recipe Assistant will help you find the recipe that suits your personal needs. The majority of recipes we offer can be both prepared and cooked in 20 minutes or less from start to finish; a whole meal can be prepared in 30 minutes. A number of them can also be prepared ahead of time and enjoyed later.

World's Healthiest
is expanded

What's in our new book:
  • 180 more pages
  • Smart Menu
  • Nutrient-Rich Cooking
  • 300 New Recipes
  • New Nutrient Articles and Profiles
  • New Photos and Design
privacy policy and visitor agreement | who we are | site map | what's new
For education only, consult a healthcare practitioner for any health problems.
© 2001-2015 The George Mateljan Foundation, All Rights Reserved