Carbohydrates are widely available in the form of sugars, fibers and starches. They can be found in healthy foods and also in unhealthy foods. Examples of foods containing carbohydrates are: bread, potatoes, rice, pasta, cereal, apples, bananas, dairy products and legumes. (Mozaffarian et al, 2011) Carbohydrates are the first source of energy for the muscles while exercising. (Madden et al, 2018) Adequate muscle glycogen levels are essential for athletic performance, however excessive carbohydrates are stored in the body as fat and can lead to weight gain, risk of developing diabetes and heart disease. Carbohydrates have the form of monosaccharides, disaccharides, or polysaccharides. All forms of carbohydrates after ingestion are converted to glucose within one and a half hour. Glucose is important to maintain the energy in the cells, tissues and organs. (Madden et al, 2018) Carbohydrates are grouped into simple and complex and they are also classified based on their ability to raise blood glucose, which is measured by the glycemic index (GI). There is evidence that diets rich in low GI carbohydrates decrease the risk of cardiovascular disease and diabetes type 2. (Barclay et al, 2008) According to Li et al (2015) higher intake of carbohydrates from whole grains was linked to a lower risk of cardiovascular disease by 9%. The American College of Sports Medicine, the Academy of Nutrition and Dietetics and the Dietitians of Canada support the daily intake of carbohydrates as they offer a greater ATP amount per oxygen volume and athletic performance during long high intensity exercises is enhanced by adequate carbohydrates availability. (2009)
Protein intake promotes a healthy appetite regulation, increases muscle growth and improves metabolism. It also ensures faster recovery period and tissue regeneration. Excessive protein intake can lead to weight gain, reduced amounts of fibers and carbohydrates and high risk of cardiac disorders if the main source of protein is red meat and full fat dairy products. High protein consumption can also increase the risk of kidney disease. Excellent sources of protein are lean pork and beef, poultry, fish, eggs, beans, tofu, and low-fat dairy products. (Weigle et al, 2005) Proteins are made of amino acids. There are 20 amino acids, and the human body can produce only 11 of them. The rest are called essential amino acids and the only way to produce them is through digestion from a protein rich diet. It is found that non vegetarian adolescents in the US consume higher amounts of protein as compared to vegetarian adolescents. (Segovia-Siapco et al, 2019) According to the International Society of Sports Nutrition (ISSN) athletic population should aim for 1.4-2.0 g protein/kg body weight/day. (Jager et al, 2017) Post exercise, Poortmans et al (2012) suggest a protein intake of 15-20 g (either from low fat milk or protein shake) and carbohydrates intake of 30 g in the form of a maltodextrine shake within the first one hour, in order to promote muscle protein formation and collagen regeneration of the tendons.
Fats are divided into three categories: saturated fats, trans fats and unsaturated fats, which are further divided into monounsaturated and polyunsaturated (omega 3 and omega 6). Fats are essential for the absorption of fat-soluble vitamins A,D, E and K. The ingestion of fats starts at the mouth, with two chemical components, the lingual lipase and phospholipids, which break fats into small particles. Next, in the stomach gastric lipase further breaks down fats into diglycerides and fatty acids within 2–4 hours after a meal. Next, in the intestines, bile and pancreatic lipase creates monoglycerides and fatty acids. According to Liu et al (2017) saturated fats intake should be less than 10% of total energy intake. Trans fats significantly increase cardiovascular disease risk as they promote endothelial malfunction, increased LDL and triglycerides and low HDL. (Liu et al, 2017) Their consumption should be as limited as possible. With regards to cis-monounsaturated fatty acids (MUFA) they are created in the liver, so there’s no need for dietary intake. On the contrary, cis-polyunsaturated fatty acids (PUFA) contain essential fatty acids and they’re considered healthy. (Liu et al, 2017) Foods rich in PUFA are lean protein foods, nuts, seeds, nut butter, fatty fish (salmon, sardines), fish-oil supplements, flaxseed oil, canola oil, sunflower oil, corn oil, avocados, and egg yolks.