The Three Macronutrients: Carbohydrate, Protein, and Fat, Their Roles and The Recommended Dietary Allowances for Each.

 
The Glycemic Index (GI) and Its Impacts the Digestion of Carbohydrates Within the Human Body.
The glycemic index is an index used to rate the rate of different carbohydrates increasing the sugar levels in the blood. The index uses glucose as a reference food, and it has a score of 100. Carbohydrates are broken fast and have a high glycemic index, such as baked potatoes, among others (Vega-Lopez et al., 2018). These carbohydrates release glucose in the blood quickly. On the other hand, carbohydrates that are broken slowly release glucose at a slower rate and, hence, a low glycemic index. Such carbohydrates increase the digestion time and help with the feeling of satiety. Foods that may lower the glycemic index include fructose, fibres, protein, fat, and lactose.

Macronutrients can be defined as nutrients required in large amounts by the body. There are three macronutrients: carbohydrates, proteins, and fats (Oliphant et al., 2019). Carbohydrates are chains of sugars and include sugars, starches, and fibres. Average carbohydrates contain four calories in one gram. Carbohydrates are the primary energy source in the body and are in two forms: complex and simple. The recommended calorie level from carbohydrates is around 45-46% of daily calories. Proteins are the building blocks and are responsible for growth and tissue restoration. When digested, proteins form polypeptides and amino acids for ease of absorption. The USDA recommended calorie level from proteins is 10-35% of daily calories.

On the other hand, Fats are the densest source of energy in the body. Fats help with the absorption of vitamins and the energy stored in the body. One gram of fat contains nine calories and only 25-35% of daily calories are recommended. Fats are further classified into saturated and unsaturated. Saturated fats are from animal sources, whereas unsaturated fats are from plants. In addition, there are trans fats from commercial manufacturing, which are very unhealthy since they increase the LDL cholesterols.