Carbohydrate, glucose specifically, is the preferred fuel source  for the body and the nerves system, in particular. As an energy source, carbohydrate provides 4  kilocalories per gram. Carbohydrates are classified by the number of sugar molecules they contain and can be divided into either simple or complex carbohydrates.

Simple carbohydrate refer to either a monosaccharide ( one sugar molecule) or disaccharide ( two sugar molecules). The most common forms of the monosaccharide’s include glucose, fructose, and galactose.

The most common disaccharides include sucrose, lactose, and maltose. Sucrose, more commonly referred to as table sugar, is composed of glucose and fructose and found primarily in sugar cane, honey, and maple syrup.

Lactose is composed of glucose and galactose and is the sugar most commonly found in milk. Lastly, maltose, a disaccharide composed off two glucose molecules, is a by product of complex carbohydrate digestion, starches in particular, and is frequently present in a variety of sport nutrition products .

Complex carbohydrates consist of three or more monosaccharide linked together. Depending on chain length, complex carbohydrates are referred to as either oligosaccharides or as polysaccharides.

Oligosaccharides are between 3 and 10 monosaccharieds in length and are found naturally in food such as legumes, onions, and bananas. Polysaccharides are complex carbohydrates greater than 10 monosaccharides  in length. The most common polysaccharides are glycogen and starch.  Glycogen, the storage form of glucose in humans, consists of numerous branched-chain of glucose molecules stored in both the liver and skeletal muscle. When necessary, glycogen is easily broken down under conditions where  glucose is needed. In particular, glycogen becomes the major source of glucose for the exercising muscle during prolonged endurance exercise events.

Fiber is another type of complex carbohydrate. Fibers are not digested in the human body and therefore are not absorbed. However, fiber consumption can have  beneficial effects on health, including improved gastrointestinal health, glucose homeostasis, and enhanced satiety. In addition, fiber consumption has been linked to reduced cardiovascular diseases risk by lowering hypertension and improving plasma cholesterol. Fiber has also been associated with reduced risk of cancer.

Fiber are classified based upon their solubility in water. Water-soluble and water-insoluble fibers are present in varying amount s in all plant sources.

Insoluble fibers are derived from the cell walls of plants and include cellulose, hemicelluloses, and lignins.  Insoluble fibers are most commonly found in vegetables  such as broccoli, carrots, green beans, celery, and potato skins. In addition, insoluble fiber are found in whole wheat, wheat bran, and flex seed lignins.

Insoluble fibers increase bulk, soften stool, and shorten intestinal transit time. In contrast, soluble fibers undergo a metabolic processing  via fermentation by bacteria in the large intestine. The end products of the bacterial fermentation is gas and short chain fatty acids, which can be absorbed. Soluble fibers, such as pectin’s, gums, and certain hemicelluloses, can be found within plants cells. Dietary sources of soluble fibers  include oats, apples, and beans. These soluble fibers, along with psyllium, have been shown to be beneficial in reducing blood cholesterol levels.

The glycemic response related to the rate at which carbohydrates are digested  and absorbed, what extent  they raise blood glucose, and for how long blood glucose remains elevated. This varies upon the type and amount of carbohydrate ingested, as well as the other nutrients with which the carbohydrate is consumed. Simple sugar, starches, and refined ( i.e., fiber has been removed) carbohydrates typically cause a greater glycemic response as reflected by a more rapid rise in blood glucose following their consumption.  Unrefined carbohydrates, which contain fiber, take longer to be digested and absorbed and therefore cause a lower glycemic response. Protein and fat, when consumed in conjunction with carbohydrates, can decrease the rate of carbohydrate digestion and absorption and subsequent appearance of glucose in blood.  The glycemic response of a specific food is calculated by its glycemic index. Glycemic index is a ranking of how  food affects blood glucose in comparison to an equal amount of a reference carbohydrate such as  white bread of glucose. The reference food is assigned a value of 100 and test foods are expressed relative to the test value. Food with glycemic indexes greater than or equal to 70 are considered high glycemic foods, whereas food with an index less than 55 are considered low glycemic foods.

Although the glycemic index can provide information regarding food sources effects on blood glucose, the glycemic index dose not predict the impact of consuming these food as a part of a mixed meal. In addition, the role of glycemic index with specific regard to glycogen replenishment after exercise continues to be debated.

Glycolysis is the first stage of glucose metabolism, which consists of a series of reactions involving highly regulated enzymes. Depending upon oxygen availability, glycolysis can be considered aerobic or anaerobic.  In the presence of oxygen, pyruvate is converted to acetyl-CoA  within the mitochondria, beginning the first stage of aerobic metabolism. However, when oxygen is limited, acetyl-CoA   is not formed, and pyruvate is converted to lactate. Lactate is a metabolic waste product of anaerobic glucose metabolism.

The maintenance of blood glucose

In conditions where blood glucose levels are low, such as fasting or low carbohydrate intake, many of the reactions of glycolysis are reversed to produce new blood glucose. The production of new glucose is referred to as gluconeogenesis. This process occurs primarily in the liver. The major substrates for gluconeogenesis are lactate, selected amino acids(i.e., alanine), and glycerol. Gluconeogenesis  is highly regulated, mostly  through the action of hormones such as insulin and glucagon.

Another source of glucose for the body is glycogen stored in the liver and muscle. Liver glycogenolysis supplies new blood glucose, whereas muscle glycogen is a source of glucose exclusive to the muscle. As glycogen stores decrease, adipose tissue is degraded, providing fatty acid as an alternative fuel and glycerol for the synthesis of glucose via gluconeogenesis. During an overnight  fast, gluconeogenesis and glycogenelysis work synergistically to maintain blood glucose. However, after approximately 30 hours of fasting, liver glycogen is depleted ; therefore gluconeogenesis becomes the only source of new blood glucose.

Fat, or lipid, is the most energy-dense macronutrient. Fats provide 9 kilocalories per gram_ more twice the energy content of both carbohydrate and protein. The most recognizable forms of fats in the diet are oils, butter, high-fat dairy products, and animal products. Although a negative perception often exists with regard to consumption of fat because of its implication in the development of cardiovascular diseases, some sources of dietary fats such as avocados, nuts , and certain oils confer many health benefits.

Fat is stored in the body in large amounts in adipose tissue. These fat stores represent a large energy reservoir utilized during resting conditions, certain  modes of exercise, and during energy- restricted states(i.e., weight-loss diets). In addition to being a source of energy, fat serves many vital role in the human  body such as insulation and protecting  vital organs. Fats are necessary for the production of steroid hormones such as testosterone and estrogen.

The primary fats in both food and in the body are in the form of triglycerides and cholesterol. Depending on their chemical structure, fats are classified as either saturated or unsaturated fatty acids ( which include mono- and polyunsaturated fatty acid). Unsaturated  fatty acids differ from saturated fatty acid : some carbon are not saturated with hydrogen and therefore contain carbon-carbon double bonds.

Unsaturated fatty acids are classified by the number of double bonds in the carbon chain, which can either  be monosaturated ( one double bond) or polyunsaturated ( more than one) fatty acids. The most common dietary monounsaturated fatty acid, oleic acid, is found primarily in olive and canola oil. Linoleic acid, found in the corn, safflower, and soybean oils, is the most common polyunsaturated fatty acid in the diet.

Dietary fat provides the essential fatty acids( EFAs), linoleic and linolenic acids. The most common omega 3 fatty acids are alpha-linolenic acid, eicosapentaenoic acid (EPA),  and docasahexaenoic acid (DHA), found in vegetable and fish oils. Linoleic acid, present in corn and safflower oil, and arachidonic acid, found in meat and fish, are the most common omiga6 fatty acid. These EFAs are required for growth, for healthy skin, and for producing elements of immune system. Although the body requires only small amounts of EFAs ( 2% to 3%  of total energy), obtaining sufficient amounts may require consuming a diet containing at least 10% of total energy from fat because the proportion of fatty acids in the diet is small.

The properties of unsaturated fatty acids are also affected by the position of hydrogen atoms around the carbon-carbon double bond. In general, most unsaturated fatty acids have both hydrogen atoms on the same side of the double bond, referred to as a cis configuration. Other unsaturated fatty acids with hydrogen atoms on opposing sides on the double bond are in the trans configuration, more commonly referred to as trans fatty acids. Trans fatty acids are less commonly found in naturally occurring foods. However, through a process known as hydrogenation, unsaturated fatty acids are altered from the  cis to trans configurations and become more saturated. Trans fatty acids have been shown to be deleterious to health by increasing the risk of coronary artery diseases(CAD) by negatively influencing blood cholesterol. It is now recommended that total intake not exceed approximately 3% of total energy intake.

Cholesterol is a waxy, fat-like substance found in foods of animal origin. It is found in the membranes of all cells and performs a number of essential anatomical and physiological functions; it is necessary for bile acid and steroid hormone formation. It is not found in plants or plant products. Cholesterol, produced by the liver, is transported in the blood by distinct particles containing both lipids and protein(i.e., lipoprotein). There are three major classes of lipoprotein: a- low- density lipoprotein (LDL), b- high density lipoprotein(HDL), and c- very-low density lipoprotein(VLDL). In general, the liver produces sufficient amounts of cholesterol to meet  requirements. Therefore, dietary consumption is unnecessary. However, cholesterol is found in many food sources. Thus, recommendations regarding dietary cholesterol intake suggest consuming no more than 300mg per day. Although monitoring cholesterol intake is important, dietary saturated and trans fatty acids have a more substantial negative impact on blood cholesterol, a risk factor for CAD.

During periods of excess energy intake ,the body stores excess calories as  fat in adipose tissue .calories from dietary fat have the most efficient and direct route  to store .age when energy intake is higher than energy expenditure (i.e., fasting)the body can utilize dietary fat to produce energy. During endurance exercise ,the body also utilize stored fat as an energy source.

Of the macronutrients, protein is unique because of the nitrogen(N) content of its constituent amino acid. Similar to carbohydrate, protein provides 4 kilocalories per gram. When  proteins are oxidized for energy purposes or when dietary intake exceeds recommended amounts. CO2 and water are produced, whereas the N component is (a)- incorporated into urea and eliminated from the body in urine or (b)- used in the synthesis of dispensable amino acids and other nitrogen-containing compounds in the body. Proteins are considered  a required and vita nutrients that serves both structural and functional components of muscle, bone, tendons, and ligaments, proteins function as enzymes critical in energy producing reactions, hormone that regulate metabolism, transporter s of other critical nutrients , and as an energy source in energy-deprived conditions. The latter function is the least desirable for this particular macronutrient. Both dietary and body proteins are composed of amino acid, which are classified as either essential( indispensable) or nonessential( dispensable). Nonessential amino acids (NEAAs) are amino acids that can be made by the body, whereas essential amino acids (EAAs) cannot be synthesized in the body and therefore must be consumed in the diet. All amino acids are needed to maintain optimal protein utilization in the body  such as health, growth and development, and tissue maintenance and repair are promoted.

The branched chain amino acids (BCAA: leucine, isoleucine, valine) are a unique class of essential amino acids used almost exclusively by skeletal muscle.

Protein is abundant in meat and dairy products and it’s found in significant level in cereals, grain, nuts, and legumes. In addition, certain fruits(i.e., apples, blueberries, and apricots) and vegetables (i.e., green beans and asparagus) contain small amounts of protein. Protein quality is determined by both amino acid content and digestibility of the protein. Protein derived from plant foods are approximately 85% digestible; those in a mixed diet of meat products and refined carbohydrates are approximately 95% digestible. Protein quality also considered the “ completeness” of the dietary protein. Complete, or high quality proteins, contain all of the EAAs. Plants proteins are generally classified as incomplete and considered to be of less quality than animal protein. Plants do contain all of the amino acids, but in lower amounts than animal proteins. Thus, one needs to eat more of a plant protein sources t obtain adequate amounts of the amino acids, particularly the EEAs. In some cases, one must consume more than one source of plant protein to obtain a sufficient amount of the EAA. Grains tend t lake lysine, for example, and legumes tend to lake methionine. Consuming both plant protein sources simultaneously allow for complementary amino acid combinations( such as soybeans and rice, wheat bread and peanut butter, pinto beans and corn tortillas) so that sufficient amounts of EAAs are derived from the diet.

Although not a macronutrients.

Alcohol does provide 7 kilocalories per gram.

Alcohol is readily absorbed by simple diffusion along the gastrointestinal tract, with the majority of absorption occurring in the small intestine. Rapid absorption of alcohol is responsible for deleterious effects on mental and physical function. Body weight, gender, the type of alcohol, rate at which an alcoholic beverage is consumed, and the consumption with other food determine blood alcohol levels. The majority of alcohol is metabolized by the liver. The reminder is lost in the urine or exhaled. Excess alcohol consumption can cause acute alcohol intoxication, malnutrition, and chronic diseases, live damage in particular. However, moderate consumption ( i.e., one and two drinks per day for women and men , respectively) of some alcoholic beverage, in particular red wine, may confer health benefits such as improved lipoprotein profiles and reduced cardiovascular diseases risk.

The effect of alcohol consumption persist for up to 48 hours and compromise a number of factors related to athletic performance. Alcohol metabolism by the liver interferes with carbohydrate utilization, ultimately interfering with glycogen synthesis and glucose metabolism. In addition, immune function, recovery from exercise or injury, and hydration status can be impaired with alcohol consumption. Therefore, athletes are discouraged from consuming alcohol during training or competition.

Each vitamin, be it water- or fat- soluble, has a unique role and, in some cases, works synergistically with other vitamins to contribute to health and well-being. Vitamins serve as promoters and regulators of many reaction in the body, including energy-producing reactions( thiamin,riboflavin,niacin,B6,B12, biotin, and panatothenic acid).  More specifically, the B vitamins, along with biotin and pantothenic acid, act as coenzymes that bind to enzymes to promote their activity and assure proper function in the metabolism of the macronutrients. Other important roles of vitamins include aiding in the visual processes ( vitamin A), blood clotting ( vitamin K), and protection of cell oxidative damage ( antioxidants; vitamins E and C).

B complex vitamins

The B complex vitamins include thiamin, riboflavin, niacin, B6,B12, pantotenic acid, and folate. These vitamins can be further classified as having roles in energy production, red blood cell production, and amino acid metabolism.

Energy production

Several B vitamins are essential to energy production by the body. these include. These thiamin, riboflavin, niacin, B6,biotin, and pantothenic  acid. Thiamin, riboflavin, and niacin in particular are associated with cofactors that are integral to energy- producing pathways for the macronutrients. Biotin , B6,B12, are coenzymes for various carboxylases involved in macronutrients metabolism.

Red blood cell production

Folate and B12 are involved in red blood cell production. Deficiencies of either nutrient can lead to anemia. Given the critical role that red blood cells serve in oxygen delivery throughout the body, inadequate intake of folate  or B12 is associated with fatigue and compromised athletic performance.

Amino acid metabolism

Vitamins B6 is required for amino acid metabolism. B6 is part of several enzyme system that are involved in nitrogen metabolism. Therefore, this nutrient is essential to reactions required for protein utilization as a fuel and synthesis of nitrogen- containing compounds in the body.

Vitamin c

Vitamin C supplementation is popular, given this nutrients roles in supporting the immune system and the healing process. Consumption of vitamin C (i.e., food source or supplement) can simultaneously facilitate iron absorption. Vitamin C is also a powerful antioxidant.

Fat soluble vitamins

The fat- soluble vitamins( A,D,E, and K) are stored in body lipids. As a result, these nutrients can be toxic if taken in excess. Only vitamin E has a role specific to exercise and human performance as an antioxidant.

Calcium is required for healthy bones and teeth, muscle contraction, nerve transmission, and blood clotting. The role of calcium in bone formation is well know. Low intake of dietary calcium results in calcium removal from the bone to maintain normal body processes. If low calcium intake persists, bone turnover is compromised and bone mass is reduced. Routine exercise, particularly weight-bearing exercise, enhances calcium utilization and maintenance of bone mass. Although it is important for men to consume adequate calcium, women appear to be at particular risk for poor calcium intakes that may ultimately increase risk of osteoporosis later in life.

Individual who restrict their total energy intake or consume a diet with limited dietary variety are at risk for insufficient vitamin and mineral intakes. These individuals would benefit from a multivitamin mineral supplement that provides the recommended amounts of these micronutrients.  Consumption of multiple vitamin or mineral supplements should be discouraged given the potential for toxicities or altered metabolism of other vitamins and minerals.