CSD - Nutrition Science Overview

Guidance on Energy and Macronutrients across the Life Span

• Poor nutrition is a major risk factor for chronic diseases, contributing to 1 in 5 deaths globally.
• Food is medicine interventions are increasingly studied to prevent and treat chronic diseases.
• Dietary intake is complex, with a wide variety of food ingredients and functions throughout life.
• Energy and macronutrients are central to contemporary nutritional concepts.

Historical Development of Nutrition Science

• Ancient Greek philosophers recognized food as crucial for replacing body tissue and maintaining body heat.
• Antoine Lavoisier's work defined metabolism as an oxygen-requiring combustion process.
• 19th century researchers identified proteins (Mulder/Berzelius), lipids (Chevreul), and carbohydrates (starches/sugars).
• Early 20th century research recognized micronutrients (vitamins/minerals) beyond macronutrients for optimal health.
• The Great Depression and World War II highlighted nutritional needs, and the US established the "Recommended Daily Allowances" (RDAs).
• RDAs evolved into Dietary Reference Intakes (DRIs), a broader set of nutrient reference intakes including RDAs, Tolerable Upper Intake Levels, and Acceptable Macronutrient Distribution Ranges (AMDR).
• DRIs address the relationship between nutrients and chronic disease risk.

Energy

• Atwater measured the metabolizable energy from carbohydrates, fats, and proteins (4, 9, and 4 kcal/gram respectively).

• Dietary Reference Intakes (DRIs) for energy use the doubly labeled water method for indirect calorimetry to quantify total energy expenditure over several weeks.

• The Estimated Energy Requirement (EER) is the predicted average energy intake needed to maintain energy balance.

• Wearable sensors and mobile apps are useful for assessing individual and population-level food intake and activity.

Protein

• Proteins are major structural and functional components of the body, composed of 20 amino acids.
• Nine amino acids are essential (indispensable) and must be obtained from the diet.
• Six additional amino acids are conditionally essential.
• The remaining amino acids are dispensable (nonessential).
• Individuals who consume only plant-based foods need to ensure adequate intake of all essential amino acids.

Fat

• Fats are primarily triglycerides (glycerol backbone with fatty acids).

• Saturated fats have no double bonds and are solid at room temperature, found in animal products.

• Unsaturated fats have one or more double bonds (either cis or trans) and are liquid at room temperature, sourced mainly from plant-derived oils and fatty fish.

• Essential fatty acids: Linoleic acid (omega-6) and Alpha-linolenic acid (omega-3) are crucial precursors for various bioactive lipids.

• Trans fats are produced industrially and are associated with increased risk of cardiovascular disease.

Carbohydrates

• Sugars and starches are digested to provide cellular energy.
• Sugars are naturally present in fruits, and lactose in dairy.
• Starches are plant-derived polysaccharides, found in potatoes, rice, and wheat.
• Added sugars are added during food processing (e.g., sugar, dextrose, high fructose corn syrup).

Dietary Recommendations

• Dietary guidelines aim to minimize chronic disease risks while providing essential nutrients at each stage of life.
• Establishing calorie requirements and choosing healthy food patterns are crucial.