Nutrition: The Science of Health and Disease Prevention

Definition and Importance

Nutrition is the science of optimal cellular metabolism and its impact on health and disease. It encompasses the processes by which food and nutrients affect growth and development, cellular function and repair, health promotion, and disease prevention.

• Nutrition is essential for development, hormonal regulation, thermoregulation, tissue integrity, immunity, glucose regulation, and is influenced by culture.

• Optimal nutrition supports all body systems and is a cornerstone of personal and public health.

Categories of Nutrients

Overview of Nutrients

Nutrients are substances in food that provide energy, form body structures, and regulate the body's biochemical reactions (metabolism). There are six general categories of nutrients:

• Carbohydrates

• Proteins

• Fats

• Vitamins

• Minerals

• Water

Each nutrient plays a unique role in maintaining health and supporting bodily functions.

Carbohydrates

Structure and Function

Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen. Through photosynthesis, plants combine carbon dioxide and water to form glucose, the most basic unit of carbohydrates.

• Carbohydrates are the body's preferred source of energy.

• Storage form: Glycogen (in liver and muscles).

• Energy yield: 1 gram = 4 kcal.

• Recommended intake: 55% of daily calories (6-10 g/kg body weight per day).

Types of Carbohydrates

• Simple Carbohydrates (Sugars): Monosaccharides (glucose, fructose, galactose) and disaccharides (lactose, maltose, sucrose).

• Complex Carbohydrates (Starches): Chains of glucose molecules found in foods like pasta, rice, breads, and potatoes.

• Fibre: Indigestible part of plant foods, important for digestive health.

• Insoluble Fibre: Wheat, rice, bran, whole grains.

• Soluble Fibre: Oats, beans, root vegetables, citrus fruits.

• Both Types: Apples, pears, bananas, prunes, cabbages.

Glycemic Index (GI)

The glycemic index measures how quickly carbohydrate-containing foods raise blood glucose levels. Foods with a high GI are rapidly digested and absorbed, causing a quick rise in blood sugar, while low GI foods are digested more slowly, resulting in a gradual increase.

• Low GI: Less than 55 (e.g., most fruits, legumes, whole grains).

• High GI: Greater than 70 (e.g., white bread, rice cakes, watermelon).

• Relevance: Important for diabetes management and overall metabolic health.

Proteins

Structure and Function

Proteins are made of amino acids and are essential for the structure and function of body tissues. They provide 4 kcal per gram and should make up 10-35% of daily caloric intake (0.8 g/kg body weight per day).

• High-Quality Proteins: Contain all essential amino acids (e.g., meat, fish, eggs, dairy, quinoa, soy).

• Low-Quality Proteins: Lack one or more essential amino acids (e.g., most plant sources).

Vegetarian Protein: Mutual supplementation (combining grains, legumes, seeds, and nuts) ensures all essential amino acids are consumed.

• Muscle Growth: Exercise, not excess protein intake, stimulates muscle growth. Excess protein can lead to increased metabolic waste and potential weight gain if caloric intake exceeds needs.

Fats

Types and Functions

Fats are a concentrated energy source (1 gram = 9 kcal) and are necessary for cell structure, hormone production, and absorption of fat-soluble vitamins (A, D, E, K). Recommended intake is less than 30% of daily calories.

• Unsaturated Fats ("Good Fats"): Mainly from plant sources, liquid at room temperature (e.g., olive oil, nuts, seeds, fish).

• Saturated Fats ("Bad Fats"): Mainly from animal sources, solid at room temperature (e.g., butter, fatty meats, cheese).

• Trans Fats ("Ugly Fats"): Produced by hydrogenation, found in processed foods (e.g., margarine, baked goods). Increase risk of cardiovascular disease.

Cholesterol: Essential for cell membranes and hormone synthesis, but high blood cholesterol increases cardiovascular risk. Genetics and diet both play roles in cholesterol levels.

Vitamins and Minerals

Vitamins

Vitamins are organic compounds that assist in digestion, absorption, metabolism, and excretion. They do not provide energy but are essential for health.

• Water-Soluble: B vitamins, vitamin C

• Fat-Soluble: Vitamins A, D, E, K

Minerals

Minerals are inorganic elements that serve structural and regulatory roles in the body. They are classified as major (macro) or trace (micro) minerals based on the amount required by the body.

• Major Minerals: Calcium, phosphorus, potassium, sodium, magnesium

• Trace Minerals: Iron, zinc, copper, iodine, selenium

Absorption of vitamins and minerals can be affected by medications, food interactions, and individual health status.

Water

Role in the Body

Water is a major component of all body tissues and is essential for survival. It transports nutrients, removes waste, and regulates body temperature.

• Humans can only survive a few days without water.

• Water is a constituent of blood and is vital for cellular function.

Food Labelling and Nutrition Recommendations

Understanding Food Labels

By law, most packaged foods must display a nutrition facts table, including serving size, calories, nutrients, percent daily values (% DV), and an ingredient list. This helps consumers make informed choices about their diet.

Canada's Food Guide

Canada's Food Guide provides evidence-based recommendations for healthy eating, emphasizing variety, balance, and moderation.

Nutrition Issues: Past and Present

Historical Deficiency Diseases

• Rickets: Vitamin D deficiency

• Scurvy: Vitamin C deficiency

• Beriberi: Thiamine (B1) deficiency

• Night Blindness: Vitamin A deficiency

Current Nutrition-Related Diseases

• Diabetes

• Hypertension

• Metabolic Syndrome

• Hypercholesterolemia

• Cancer

Nutrition in the Community: Local and National Strategies

Food Insecurity and Food Deserts

Food deserts are areas with limited access to affordable and nutritious food, often requiring residents to travel long distances or rely on convenience stores with limited healthy options.

• Solutions include community gardens, local markets, mobile markets, and support for neighborhood stores to offer healthier options.

Government and Community Initiatives

• Mother Baby Nutrition Supplement: Financial support for low-income expectant women and families with infants to promote healthy eating during pregnancy and early childhood.

• Provincial Healthy Eating Plans: Aim to ensure all residents have access to adequate, nutritious, and safe food supplies.

Self-Management and Nutrition

Concept of Self-Management

Self-management is the ability of individuals and caregivers to engage in daily tasks required to maintain health and well-being, or to manage chronic disease, based on knowledge and collaboration with healthcare teams.

• Includes patient education, person-centered care, health promotion, care coordination, collaboration, and addressing health disparities.

Summary Table: Major Nutrients and Their Functions

Key Equations

• Energy Provided by Macronutrients:

• Body Mass Index (BMI):

Conclusion

Understanding the fundamentals of nutrition is essential for personal health, disease prevention, and effective self-management. Applying evidence-based recommendations and being aware of local and national resources can help individuals and communities achieve optimal health outcomes.