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Lecture 2 : Macronutrients

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1: Carbohydrates

2: Fibers

3: Glycemic Index & Load

4: Protein and Amino Acids

5: Fats

6: Assential Fatty Acids








Carbohydrates:


  • Definition: Carbohydrates are macronutrients composed of carbon, hydrogen, and oxygen atoms, and they serve as the primary source of energy for the body. They are classified into simple carbohydrates (sugars) and complex carbohydrates (starches and fibers).

  • Basic: Simple carbohydrates include monosaccharides (e.g., glucose, fructose, and galactose) and disaccharides (e.g., sucrose, lactose, and maltose), which are quickly digested and absorbed, leading to rapid spikes in blood sugar levels. Complex carbohydrates, found in foods such as grains, legumes, and vegetables, consist of long chains of glucose molecules and provide sustained energy due to their slower digestion.

  • Intermediate: Carbohydrates are stored in the body as glycogen in the liver and muscles, serving as a readily available energy reserve during times of increased energy demand, such as exercise. Carbohydrate intake should be tailored to individual energy needs, with an emphasis on consuming whole, unprocessed sources to provide essential nutrients and dietary fiber.

  • Advanced: The glycemic index (GI) ranks carbohydrate-containing foods based on their effect on blood glucose levels compared to a reference food (usually glucose or white bread). High-GI foods cause rapid spikes in blood sugar levels, while low-GI foods result in slower, more gradual increases. Glycemic load (GL) considers both the quality and quantity of carbohydrates in a food, providing a more accurate measure of its impact on blood glucose levels. Balancing carbohydrate intake with other macronutrients and timing consumption around exercise can optimize performance, recovery, and metabolic health.




Fiber:


  • Definition: Dietary fibers are indigestible carbohydrates found in plant-based foods, including fruits, vegetables, whole grains, legumes, nuts, and seeds. They are essential for digestive health, regular bowel movements, and maintaining optimal blood sugar and cholesterol levels.

  • Basic: Fiber comes in two main forms: soluble and insoluble. Soluble fiber dissolves in water to form a gel-like substance, which helps slow digestion, stabilize blood sugar levels, and lower cholesterol levels. Insoluble fiber adds bulk to stool, promotes bowel regularity, and prevents constipation by speeding up the passage of food through the digestive tract.

  • Intermediate: Adequate fiber intake is associated with a reduced risk of various chronic diseases, including heart disease, type 2 diabetes, and certain cancers. The recommended daily intake of fiber varies by age and gender but generally ranges from 25 to 38 grams for adults. Increasing fiber intake gradually, staying hydrated, and consuming a diverse array of fiber-rich foods can support gastrointestinal health and overall well-being.

  • Advanced: Fiber fermentation by gut bacteria produces short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, which have anti-inflammatory and immune-modulating effects and contribute to gut barrier function. Prebiotic fibers, such as inulin, oligofructose, and resistant starch, selectively stimulate the growth and activity of beneficial gut bacteria, promoting a healthy gut microbiota composition. Incorporating a variety of fiber sources into the diet and focusing on whole, minimally processed foods can optimize gut health and support athletic performance and recovery.



Glycemic Index & Load:


  • Definition: The glycemic index (GI) and glycemic load (GL) are measures of how quickly carbohydrate-containing foods raise blood glucose levels and their overall impact on blood sugar, respectively.

  • Basic: The glycemic index ranks carbohydrate-containing foods on a scale from 0 to 100 based on their effect on blood glucose levels compared to a reference food (usually glucose or white bread). Foods with a high GI (≥70) cause rapid spikes in blood sugar levels, while those with a low GI (≤55) result in slower, more gradual increases.

  • Intermediate: Glycemic load considers both the quality and quantity of carbohydrates in a serving of food, providing a more accurate measure of its impact on blood glucose levels than the GI alone. It is calculated by multiplying the GI of a food by its carbohydrate content per serving and dividing by 100. Foods with a high GL (>20) may still have a significant impact on blood sugar levels despite having a low GI if consumed in large quantities.

  • Advanced: Understanding the glycemic index and load can help athletes make informed choices about carbohydrate sources to optimize energy levels, performance, and recovery. Consuming low to moderate GI/GL foods before exercise provides a steady release of energy, while high-GI/GL foods may be beneficial for rapidly replenishing glycogen stores post-exercise. However, individual responses to carbohydrates vary based on factors such as insulin sensitivity, activity level, and metabolic rate, highlighting the importance of personalized nutrition strategies.


Protein and Amino Acids:


  • Definition: Proteins are macronutrients composed of amino acids, which are essential for building and repairing tissues, synthesizing hormones and enzymes, and supporting immune function and muscle growth and repair.

  • Basic: Amino acids are the building blocks of proteins and are categorized as essential (must be obtained from the diet), nonessential (can be synthesized by the body), or conditionally essential (become essential under certain conditions, such as illness or intense exercise). Complete proteins contain all essential amino acids in adequate proportions and are found in animal-based foods such as meat, poultry, fish, eggs, and dairy products, while plant-based sources may require combining complementary proteins to ensure all essential amino acids are obtained.

  • Intermediate: Protein quality is determined by its amino acid composition, digestibility, and bioavailability. The protein digestibility-corrected amino acid score (PDCAAS) and the digestible indispensable amino acid score (DIAAS) are methods used to evaluate protein quality and its ability to meet human nutritional requirements. Athletes may have higher protein needs to support muscle protein synthesis, repair, and adaptation in response to training.

  • Advanced: Optimal protein intake for athletes depends on factors such as training intensity, duration, frequency, and individual goals. Recommendations typically range from 1.2 to 2.2 grams of protein per kilogram of body weight per day, with higher intakes often recommended during periods of intense training or calorie restriction. Timing protein consumption around exercise, combining protein sources to maximize amino acid availability, and focusing on high-quality, nutrient-dense sources can help athletes meet their protein needs and optimize performance, recovery, and body composition.



Fats:


  • Definition: Fats, also known as lipids, are macronutrients composed of fatty acids and glycerol and serve as a concentrated source of energy, insulation, and essential nutrients, including fat-soluble vitamins (A, D, E, and K).

  • Basic: Fatty acids are classified as saturated, monounsaturated, or polyunsaturated based on their chemical structure. Saturated fats are typically solid at room temperature and are found in animal-based foods such as meat, dairy, and tropical oils. Monounsaturated and polyunsaturated fats are liquid at room temperature and are found in plant-based oils, nuts, seeds, and fatty fish.

  • Intermediate: Essential fatty acids, including omega-3 and omega-6 fatty acids, cannot be synthesized by the body and must be obtained from the diet. Omega-3 fatty acids, found in fatty fish (e.g., salmon, mackerel, and sardines), flaxseeds, chia seeds, and walnuts, have anti-inflammatory properties and are important for heart and brain health. Omega-6 fatty acids are abundant in vegetable oils (e.g., soybean, corn, and sunflower oil) but should be consumed in moderation to maintain a balanced ratio with omega-3 fatty acids.

  • Advanced: Dietary fats play diverse roles in the body, including cell membrane structure, hormone synthesis, nerve function, and nutrient absorption. Despite their high energy density, fats should not be demonized, as they are essential for optimal health and performance. Athletes may benefit from incorporating a variety of healthy fats into their diet, including omega-3-rich sources, to support inflammation management, joint health, cognitive function, and endurance performance.



Essential Fatty Acids:


  • Definition: Essential fatty acids (EFAs) are polyunsaturated fatty acids that cannot be synthesized by the body and must be obtained from the diet. The two primary EFAs are alpha-linolenic acid (ALA), an omega-3 fatty acid, and linoleic acid (LA), an omega-6 fatty acid.

  • Basic: Omega-3 fatty acids are found in fatty fish (e.g., salmon, mackerel, and sardines), flaxseeds, chia seeds, hemp seeds, walnuts, and leafy green vegetables. They are important for cardiovascular health, brain function, and inflammation regulation. Omega-6 fatty acids are abundant in vegetable oils (e.g., soybean, corn, and sunflower oil) and are involved in immune function, skin health, and hormone production.

  • Intermediate: The conversion of ALA to the longer-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is limited in the body, making direct consumption of EPA and DHA-rich foods (e.g., fatty fish and algae-based supplements) or supplementation advisable for individuals with low fish intake or specific health concerns. Balancing the intake of omega-3 and omega-6 fatty acids is important, as an excessive ratio of omega-6 to omega-3 fatty acids may promote inflammation and contribute to chronic disease risk.

  • Advanced: Emerging research suggests that optimizing the ratio of omega-3 to omega-6 fatty acids in the diet may have implications for athletic performance, recovery, and injury prevention by modulating inflammation, oxidative stress, and immune function. Athletes may benefit from incorporating omega-3-rich foods or supplements into their diet to support cardiovascular health, cognitive function, joint integrity, and overall well-being.