Nutritional Biochemistry for Registered Dietitians

1. Macronutrient Metabolism

Macronutrient metabolism involves the biochemical processes through which carbohydrates, fats, and proteins are broken down and utilized by the body. Each macronutrient has a unique metabolic pathway:

Carbohydrate Metabolism

Carbohydrates are primarily broken down into glucose, which is then used for energy. The glycolysis pathway in the cytoplasm converts glucose into pyruvate, which can enter the mitochondria for further oxidation in the Krebs cycle. Insufficient glucose can lead to the breakdown of glycogen (glycogenolysis) or the production of glucose from non-carbohydrate sources (gluconeogenesis).

Example: When you eat a slice of bread, the starch is broken down into glucose, which is then used by your muscles during exercise.

Fat Metabolism

Fats, primarily triglycerides, are broken down into fatty acids and glycerol. Fatty acids undergo beta-oxidation in the mitochondria, producing acetyl-CoA, which enters the Krebs cycle. Glycerol can be converted into glucose via gluconeogenesis. Fat metabolism is crucial for long-term energy storage and utilization.

Example: Consuming a high-fat meal results in the storage of excess energy as adipose tissue, which can be mobilized during prolonged fasting or exercise.

Protein Metabolism

Proteins are broken down into amino acids, which can be used for energy, synthesis of new proteins, or converted into glucose or fat. The urea cycle processes excess nitrogen from amino acids, producing urea for excretion. Protein metabolism is essential for tissue repair and growth.

Example: After intense physical activity, muscle proteins are broken down to provide amino acids for muscle repair and growth.

2. Micronutrient Functions

Micronutrients, including vitamins and minerals, play critical roles in various biochemical processes. They are often cofactors in enzymatic reactions, act as antioxidants, or are involved in structural roles.

Vitamin C

Vitamin C, or ascorbic acid, is a water-soluble vitamin that acts as an antioxidant, protecting cells from oxidative stress. It is also essential for collagen synthesis, which is crucial for skin, blood vessels, and connective tissues. Deficiency in vitamin C leads to scurvy, characterized by bleeding gums and poor wound healing.

Example: Citrus fruits like oranges are rich in vitamin C, which helps in the production of collagen, keeping your skin healthy and firm.

Calcium

Calcium is a mineral that is vital for bone health, muscle contraction, and nerve function. It is regulated by parathyroid hormone and calcitonin. Adequate calcium intake is crucial for preventing osteoporosis and maintaining cardiovascular health.

Example: Dairy products like milk and cheese are excellent sources of calcium, which is essential for building strong bones and teeth.

Iron

Iron is a component of hemoglobin, which carries oxygen in the blood. It is also a part of myoglobin, which stores oxygen in muscles. Iron deficiency can lead to anemia, characterized by fatigue and weakness. Dietary sources include red meat, lentils, and spinach.

Example: Eating a spinach salad can help increase your iron intake, which is crucial for maintaining healthy blood oxygen levels.

Understanding these key concepts of nutritional biochemistry is essential for Registered Dietitians to provide effective dietary advice and support optimal health.