ATHLETES
NUTRITION
1.1.
NUTRITION BASICS
This month's Nutrition section will cover the basic energy providing components of the food we eat. The 6 basic nutrient components of food are: protein, carbohydrates, fats, vitamins, minerals, and water. Of these, protein, carbohydrates and fats yield energy in the form of calories, to be used to fuel our body's many functions.
Protein
Protein is the component of food which contains the ingredients needed for growth and repair of the tissues of the body (called protein synthesis). Some proteins also function in chemical reactions in the body, and contribute to immune system function.
Proteins are molecules made up of smaller sub-units called amino acids.
Amino acids are composed of nitrogen, hydrogen, carbon and oxygen. These elements combine in different ways to make up the 22 different specific amino acids needed for human protein synthesis.
When protein is eaten, it is digested and broken down into the different amino acids, in varying amounts depending on the source of protein ingested. Animal protein sources and dairy products are called complete protein foods because they contain the 22 proteins needed for human protein synthesis, while vegetable protein sources are called "incomplete" protein sources because they do not. "In order to properly synthesize protein, all the essential amino acids must be present and in the proper proportions. If just one essential amino acid is missing, even temporarily, protein synthesis will fall to a very low level or stop altogether." (Kirschmann, et al. p.7-8) This is why it is important to consume protein from a variety of sources, to ensure that the spectrum of amino acids required by the body is complete.
The minimum daily protein requirement necessary for proper function of the body is a topic that is quite controversial. Many bodybuilders and current diet plans endorse a high-protein intake. the US RDA of protein is currently 10-12% of total daily calories. (Brown, p. 17-3)
Proteins contain approximately 4 calories per gram. This information can be used when designing your own diet plan. Proteins are often called the "building blocks of life". Make sure you are aware of your own protein intake!
CARBOHYDRATES
Carbohydrates are the main source of energy for all body functions, yielding 4 calories per gram. The major food sources of carbohydrates include fruits vegetables, grains and starches. When consumed, all carbohydrates are broken down into glucose, a simple form of carbohydrate usable by the body's cells for energy. Glucose can then be converted into glycogen, the fuel of our muscle cells.
When more carbohydrates are consumed than needed to meet the body's energy requirements, excess glucose is converted to and stored as bodyfat (lipogenesis).
Fat storage is stimulated by excess carbohydrate ingestion as follows: Insulin, a hormone secreted by the pancreas in response to the rise in blood glucose following ingestion of carbohydrates, facilitates uptake of glucose into body cells, especially the adipose (bodyfat) cells of the body. In other words, if more energy (in the form of sugars) is ingested than is needed by the body at that moment, the excess will be stored as fat.
Blood glucose rises as ingested carbohydrates are digested and absorbed into the bloodstream. Generally speaking, the more complex the carbohydrate molecule, the slower its absorption into the bloodstream, resulting in a slower rise in insulin secretion. Proteins and fats eaten at the same time as carbohydrate food sources can also slow the absorption of carbohydrates.
When designing your own diet plan, be sure to consider your energy requirements. It is important to supply the body with the fuel and nutrients it needs to function optimally, while avoiding the storage of excess energy in the form of bodyfat. For this reason, be aware of the foods in your diet that have a high-concentration of carbohydrates. Be sure to eat a variety of foods, making sure that the major source of carbohydrates in your diet is in the form of slower-to-absorb complex carbohydrate foods, to avoid an insulin spike, and increased fat storage. This means avoiding too many sugary foods, which often contain very little nutritional value for the amount of calories in them. ("empty" calories) Make sure that you are aware of not only the quantity, but also the quality, of your sources of energy! .
FATS
Fats are the most concentrated source of energy of the 3 energy-yielding nutrients. Each gram of fat gives us 9 calories. Fats are made of carbon, hydrogen and oxygen, and are insoluble in water. One of the basic functions of fats in the body is the transport of Vitamins A,D,E, and K. "By aiding in the absorption of vitamin D, fats help make calcium available to body tissues, particularly to the bones and teeth." (Kirschmann, p.6) In addition to being a concentrated source of energy, fats also provide food with flavor, and texture. The body needs fat for transport of vitamins, as mentioned above, in addition to development of nerve tissue, and contributing to the formation of some blood components.
Fats (also called lipids) are made up of a glycerol molecule, and fatty acid molecules, of which there are 2 types, saturated and unsaturated. The terms saturated vs. unsaturated refer to the ability of a fatty acid molecule to bond with hydrogen atoms. Saturated fatty acids are "saturated" with hydrogens. In other words, they have no room to bond further with hydrogen atoms. These types of fats are generally solid at room temperature. (lard, shortening, etc.) Unsaturated fatty acids (generally, plant oils, which are liquid at room temperature) have room on their molecular structure to bond with other hydrogen atoms.
The unsaturated fatty acids linoleic and linolenic acids, are known as the essential fatty acids, because they can not be synthesized in the body. They must be obtained through our diet, and are responsible for many of the contributions of fat to the body's developmental and metabolic processes.
Since fats are energy-rich, certain fats are useful in regards to performance, especially when your diet plan utilizes low-carbohydrates. Medium-chain triglycerides (MCT's) are shorter-length fat molecules, which are absorbed and available for use as energy much quicker than ordinary fats. It is important to monitor all fat intake, however, because all fats are calorie-dense, and intake of excess calories leads to storage as adipose tissue.
To summarize, some fat intake is necessary. The US RDA for fat intake is less than 30% of total calories. (Brown, 8-6) Depending on the nutrient profile of your diet plan, even less fat intake may be advisable. Be sure that your fat intake consists mostly of the unsaturated, essential fatty acids.
References:
Brown, J. Nutrition Now. Minneapolis/St. Paul: West Publishing Company, 1995.
Kirschmann, J., L. Dunne, Nutrition Almanac. New York: McGraw-Hill, 1984.
Van De Graaff, K., Stuart I. Fox. Concepts of Human Anatomy and Physiology. Dubuque, Iowa: Wm C. Brown Publishers, 1988.
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