Human nutrition and sport nutrition are closely related concepts. Nutrition is the process of nourishment of the human body through food, and whether in a non athletic, day-to-day existence, or for the purposes of high performance sport, proper nutrition has the same basic principles. Diet, as distinct from nutrition, is the composition of the various foods that are ingested into the body. Nutritional benefits may be derived from whole foods or through dietary supplements.
The difference between regular nutritional practices and those that pertain to sport is the fact that even the most minor departures from optimal nutritional practice can have a significant impact on sport performance; greater latitude in nutrition will not necessarily be noticed in circumstances where human performance is not measured.
The nutrients consumed through food are divided into two broad classifications: macronutrients and micronutrients. The macronutrients are carbohydrates, proteins, and fats. For the past 40 years, the generally accepted proportion of each of the macronutrients in a healthy diet was 60-65% carbohydrates, 12-15% proteins, and less than 30% fats. Sports-focused research has provided significant data about the ratio of carbohydrate, proteins, and fats for optimum macronutrient consumption for athletes. This research has confirmed that different sports will dictate different macronutrient consumption patterns for their participants.
Nutritional research has also been motivated by secondary factors in relation to sport performance. Nutritional guidelines are sometimes varied in consideration of health and fitness developments that indirectly impact on sports performance. The rapid rise in obesity rates in many countries, related in part of the equally dramatic rise in both juvenile and adult (type 2) diabetes, has spurred further examination of what constitutes optimal nutritional.
Carbohydrates are essential to athletic performance; athletes simply require more energy than do sedentary persons. A carbohydrate-restricted diet and effective athletic participation are incompatible concepts. Further, carbohydrates provide the energy for all brain and central nervous system activity. Carbohydrate consumption by athletes that is out of proportion to other macronutrients is also not necessarily a healthy choice. High-carbohydrate and low-fat diets, as are sometimes engaged in by endurance athletes such as marathon runners or by athletes seeking to remove the perceived weight gaining properties of dietary fat from their diet, will tend to reduce the production of high density lipoproteins, the so-called "good" cholestrol that negates the effect of the lower density, plaque-causing cholesterol that contributes to cardiovascular disease.
Dietary fats are crucial to athletic performance, as the fats, stored within the body as triglycerides and released into the bloodstream as the energy source, fatty acids, are also essential to the absorption of fat-soluble vitamins such as vitamin A and vitamin D. Without the proper absorption of vitamin D into the body, the companion absorption of the mineral calcium, essential to the formation and repair of bones, will be impaired. Proper sport nutrition requires a supply of fat in the athlete's diet; the adjustment of the precise quantity and quality of fats into the body is often essential. Dietary fats present in many diets are both saturated fats, the cause of the "bad" cholesterol, and the trans fats, created through the use of partially hydrogenated vegetable oils that make liquids solid. While a non-athletic person should limit consumption of these products, which have no nutritional value and which present well-established health risks, these fats in significant quantities will impair athletic cardiovascular performance.
Conversely, the fats can provide an athlete with a significant macronutritional benefit beyond the absorption of fat-soluble vitamins. Polyunsaturated fats are essential to the function of the body; there are two primary polyunsaturates, better known as omega-3 acid omega-6. In the formulation of a diet that addresses specific needs, the athlete should become familiar with food package labeling; in most countries in the Western world, and in regions such as Australasia, the identification of both the quantity and the quality of food ingredients such as trans fats and the relative percentages of other product components must be clearly marked.
Protein was long misunderstood in its application to sport performance, particularly in activities where musculoskeletal strength is crucial. Protein is the essential macronutrient in the building and repair of muscle and connective tissues, as well as essential to the formation of certain hormones and enzymes. The classic weight training programs encouraged the consumption of large amounts of dietary protein, such as animal meats, to contribute to muscle development. Modern sport research confirms that it is the type of proteins that consequently supply the correct essential amino acids that are as important as protein quantity. A healthy, non-athletic person will require a certain amount of daily consumption of protein to maintain muscle health; an athlete may consume only slightly more protein, even during intensive training, so long as the amino acid composition within the protein is correct.
Strictly speaking, fiber is not a macronutrient or a micronutrient, as it is not digested into the body; fiber tends to be present in both nutritional groups and it possesses significant sports nutritional benefits as a facilitator of the digestion and absorption of both types of nutrition sources. Dietary fiber has profound benefits in the proper and orderly digestion of foods and processing of waste products; regularity in both areas is essential to athletic performance. Dietary fiber is of particular benefit to the body in the maintenance of its blood glucose levels. Fiber that is not naturally occurring in a food product is described as functional fiber; studies confirm that while any fiber will assist in the digestive processes, dietary fiber is preferable.
The micronutrients are those components of diet that occur in smaller amounts than the broader carbohydrate, proteins, and fats that form the macro-nutrients. While no athlete will be able to compete at any significant sporting level if he or she does not consume proper proportions of the macronutrients, it is the effect of the micronutrients that often attract considerable sports science attention. It is the adjustment of micronutrient levels that may spell the difference between adequate and superb performance. Micronutrients include all vitamins, most minerals, and the class of substances known as the phytochemicals, or phytonutrients, which are present in many foods.
Vitamins are present in foods in one of two categories. Fat-soluble vitamins, which include vitamins A, D, and E, require the presence of fatty acids to be absorbed into the body. Fat-soluble vitamins are capable of being stored in the liver. Water-soluble vitamins, the most prominent of which are vitamin C and the vitamin B complex, are absorbed through the digestive process by the small intestine. Water-soluble vitamins cannot be stored within the body and each must be replenished through diet each day. Each vitamin is necessary to the function of one or more of the multitude of bodily systems.
A key example of vitamin absorption and athletic performance is that of the water-soluble vitamin B group. Different vitamins within the complex are essential to the regulation and function of carbohydrate absorption and the orderly storage of glycogen. Similarly, the presence of adequate levels of vitamin D is fundamental to the processes by which the bones are built, maintained, and repaired. Although the mineral calcium, along with phosphorous, is the prime construction material in bone cells, vitamin D must be present for the cell formation to occur. Both optimal glycogen storage and bone repair are fundamental to sport success.
Minerals, generally defined as substances that are produced from the Earth, are present in a wide variety of foods. Many minerals have a significant impact on general performance; many different mineral deficiencies are potentially catastrophic to effective athletic performance. There are over 20 minerals present in varying amounts in the body; key minerals are calcium, phosphorous, magnesium, and iron. A separate class of minerals with electrolytic properties includes sodium and potassium.
A sodium deficiency will create a chain reaction of increasingly serious problems in athletic performance. Sodium is essential to the maintenance of fluid levels and the acid/base balance within the body, as well as with respect to the transmission of nerve impulses into the muscles, in an electrochemical partnership with potassium. Calcium deficiencies will contribute to a loss of bone density and related structural problems, especially given the stresses of sport on the musculoskeletal system. Iron performs a number of important functions within the body, none more important than its presence within the hemoglobin of erythrocytes, the compartment of the red blood cells that transport oxygen.
The phytochemicals, like the fiber they are often contained within, have no caloric or energy value. Some common types of phytochemical actions and related food sources include antibacterial agents, the best known of which is allicin, the active ingredient of garlic that provides the vegetable with its characteristic strong odor. Allicin is a chemical that acts as an effective agent against bacteria entering the body. Antioxidants are found in a variety of plant sources. An antioxidant is a chemical that tends to seek out any molecules in the body that have an unpaired electron, known as free radicals, molecules that tend to form cancer-causing cells. Phytochemicals sources such as fruits, carrots, onions, and other vegetables are well-regarded antioxidants. Lycopene is a powerful antioxidant found in the skin of tomatoes that acts effectively in preserving the health of the cells in the cardiovascular system.
Alkaloids have phytochemical actions as well. The most important alkaloid is caffeine, the world's most consumed stimulant, possessing a powerful effect on the central nervous system. Digoxin is found naturally in the foxglove plant, and is used as a medication in the treatment of heart failure, as it acts to regulate and to strengthen a failing heart rate.
Flavanoids are chemicals found in a number of fruits, such as cranberries, raspberries, grapes, and blueberries that often act as antioxidants. Flavanoids also work to inhibit the progress of low-density lipoproteins in the cardiovascular system, the form of cholesterol that causes plaque and contributes to the narrowing of arteries and the development of arteriosclerosis. Red wine has been long regarded as possessing flavanoids.
Beta-sitosterol is a substance found in peanuts, wheat germ, and various rice products; these chemicals tend to reduce cholesterol levels, especially in men with prostate problems.
While phytochemicals can be added to an existing diet by way of dietary supplements, these substances are best absorbed into the body through a balanced diet that contains significant fresh fruits and vegetables. Two food types that are often overlooked concerning phytochemical benefits are the consumption of dried fruits, which lose little of their phytochemical effect in this form, and the liberal use of herbs and spices with meals. Most dried herbs, such as basil, thyme, and oregano, are rich in various phytochemicals. The active ingredient in many types of red pepper, capsicum, is an effective antioxidant agent.