C10

Fundamentals of Nutrition and Dietetics

  • Nutrition is defined as the science that interprets the interaction of nutrients and other substances in food concerning the maintenance, growth, reproduction, health, and disease of an organism. It encompasses several biological processes, including:

    • Food intake

    • Absorption

    • Assimilation

    • Biosynthesis

    • Catabolism

    • Excretion

  • The diet of an organism consists of the foods it consumes, which are primarily determined by the availability and palatability of those foods.

  • For humans, a healthy diet involves specific preparation and storage methods designed to:

    • Preserve nutrients from oxidation, heat, or leaching.

    • Reduce the risk of foodborne illnesses.

  • An unhealthy diet in humans can lead to various conditions:

    • Deficiency-related diseases: Blindness, anemia, scurvy, preterm birth, stillbirth, and cretinism.

    • Nutrient excess conditions: Obesity and metabolic syndrome.

    • Chronic systemic diseases: Cardiovascular disease, diabetes, and osteoporosis.

    • Malnutrition outcomes: Wasting in acute cases and the stunting of marasmus in chronic cases.

Classification of Essential Nutrients

  • Essential nutrients are categorized into two groups based on the daily quantity required for consumption:

  • Macronutrients: Nutrients needed regularly and in fairly large amounts. They supply energy and building blocks for growth, metabolism, and other body functions. These include:

    • Carbohydrates

    • Proteins

    • Fats

    • Fiber

    • Water

  • Micronutrients: Substances required in the diet in only small amounts, including minerals and vitamins. While foods are often mixtures of nutrients, they are grouped by the nutrient they contain in abundance:

    • Body-building/Growing foods: Rich in protein.

    • Energy-giving foods: Rich in fats or carbohydrates.

    • Protective foods: Rich in vitamins and minerals.

  • Energy values of macronutrients:

    • Carbohydrates provide 4 calories/g4\,\text{calories/g}.

    • Proteins provide 4 calories/g4\,\text{calories/g}.

    • Fats provide 9 calories/g9\,\text{calories/g}.

Detailed Breakdown of Macronutrients

  • Carbohydrates: These include fiber, starch, and sugar. Dietary guidelines often recommend that they comprise 45−65%45-65\% of total daily calories.

    • Sources: Bread, wheat, all types of potatoes, maize, rice, cassava, pasta, macaroni, bananas, sweets, sugar cane, sweet fruits, and honey. (Vegetables, beans, nuts, and seeds contain lesser amounts).

    • Classification based on sugar units:

      • Monosaccharides and Disaccharides: Simple sugars or simple carbohydrates easily utilized by the body. Patients with diabetes mellitus should limit these to avoid glucose regulation issues. Examples include honey, sugar, and sweet fruits.

      • Polysaccharides: Complex carbohydrates that must be broken down into simple sugars. These include starch and cellulose and can generally be consumed by diabetic patients without restriction.

  • Proteins: Essential for building muscle mass, making hormones and enzymes, tissue repair, and preserving lean muscle mass. They serve as an energy source when carbohydrates are unavailable.

    • Sources: Meats, chicken, eggs, fish, breastmilk, beans, nuts, lentils, cheese, milk, and legumes.

  • Fats and Oils: Concentrated energy sources important for young children. They improve food palatability.

    • Saturated Fats: Usually solid at cool temperatures. Excessive intake is linked to heart and blood vessel problems. Animal sources typically contain more saturated fats.

    • Unsaturated Fats: Usually liquid at room temperature and considered healthy fats. Sources include fish, oil seeds (sesame, sunflower), maize oil, groundnut oil, and breastmilk.

  • Water: Essential for life; an adult requires approximately 2−3 liters2-3\,liters per day. Humans can survive only a few days without it. Functions include:

    • Creation of cells and fluids (tears, digestive juices, breastmilk).

    • Sweat production for cooling.

    • Facilitating essential body processes that occur in aqueous environments.

    • Maintaining moisture in the lining of the mouth, intestines, eyelids, and lungs.

    • Urine production to carry waste from the body.

  • Fiber: A mixture of carbohydrates not digested like other nutrients, passing through the gut nearly unchanged.

    • Sources: Vegetables (cabbage, carrots, cassava), fruits (banana, avocado), peas, beans, whole-grain wheat flour, and refined maize or sorghum.

    • Benefits:

      • Increases food bulk, aiding in weight management.

      • Softens and bulks feces to prevent constipation.

      • Slows nutrient absorption, helping nutrients enter the bloodstream gradually (crucial for diabetes mellitus).

Detailed Breakdown of Micronutrients

  • Vitamins (Protective Foods): Vital factors necessary for normal body function.

    • Fat-soluble (A, D, E, K): Soluble in fats and fat solvents; insoluble in water. Utilized only if sufficient body fat is present.

    • Water-soluble (B-complex, C, Folic Acid): Soluble in water and cannot be stored in the body.

  • Functions and Sources of Vitamins:

    • Vitamin A: For healthy teeth, skin, and eyes. Found in eggs, meat, milk, cheese, dark green leafy vegetables, squash, and carrots.

    • Vitamin B: Helps use food energy, digest proteins, and supports the central nervous system, digestion, and metabolism. Found in lean meats, eggs, fish, dairy, soybeans, yeast, broccoli, beef, cabbage, and whole grains.

    • Vitamin C: Supports the immune system, wound healing, and iron absorption. Found in citrus fruits, green peppers, strawberries, tomatoes, broccoli, potatoes, and cantaloupe.

    • Vitamin D (‘Sunshine Vitamin’): Helps calcium absorption for healthy bones and teeth. Found in dairy, fish, oysters, and through sunshine exposure.

    • Vitamin E: Protects against free radical damage and helps form red blood cells. Found in wheat germ, corn, nuts, seeds, olives, spinach, and vegetable oils.

    • Vitamin K: Essential for blood clotting and strong bones. Found in cabbage, cauliflower, spinach, and soybeans.

  • Minerals: Substances required for health and the function of soft tissues, fluids, and bones.

    • Calcium: For bones, teeth, blood clotting, and nerve/muscle function. Sources: Dairy, dark green vegetables, legumes.

    • Phosphorus: For bones, teeth, and ATP production. Sources: Dairy, meats, grains.

    • Potassium: For water balance and nerve/muscle function. Sources: Meats, dairy, fruits, vegetables, grains.

    • Iodine: Found in certain hormones. Sources: Seafood, dairy, iodized salt.

    • Iron: Component of hemoglobin. Sources: Meats, eggs, legumes, grains, leafy vegetables.

    • Zinc: Found in certain digestive enzymes. Sources: Meats, seafood, grains.

    • Sulfur: Aids protein and cartilage production. Sources: Proteins from various foods.

Principles of a Balanced Diet and the Food Guide Pyramid

  • A balanced diet involves choosing a wide variety of foods and drinks from all food groups to maintain recommended nutrient levels while restricting intake of saturated fat, cholesterol, simple sugar, salt, and alcohol.

  • The Food Guide Pyramid Levels:

    • Peak (Use Sparingly): Fats, oils, and sweets (added sugars and naturally occurring fats).

    • Middle Upper (2-3 Servings): Milk, Yogurt, and Cheese group; Meat, Poultry, Fish, Dry Beans, Eggs, and Nuts group.

    • Middle Lower: Vegetable group (3−5 servings3-5\,servings) and Fruit group (2−4 servings2-4\,servings).

    • Base (6-11 Servings): Grains including bread, rice, and chapati.

Malnutrition and Undernutrition

  • Malnutrition encompasses deficiencies, excesses, or imbalances in energy and nutrient intake. It is split into two broad groups:

    • Undernutrition: Includes stunting (low height for age), wasting (low weight for height), underweight (low weight for age), and micronutrient deficiencies.

    • Overnutrition: Includes overweight, obesity, and diet-related noncommunicable diseases such as heart disease, stroke, diabetes, and cancer.

  • General Signs and Symptoms of Undernutrition:

    • Reduced appetite and lack of interest in food/drink.

    • Constant fatigue and weakness.

    • Frequent illness and slow recovery.

    • Slow-healing wounds and poor concentration.

    • Feeling cold and increased risk of surgical complications.

    • Depression, reduced sex drive, and fertility problems.

  • Severe Undernutrition Indicators:

    • Difficulty breathing.

    • Thin, dry, inelastic, pale, and cold skin.

    • Hollow cheeks and sunken eyes due to facial fat loss.

    • Dry, sparse hair that falls out easily.

  • Contributing Factors and Causes:

    • Low food intake or lack of breastfeeding.

    • Mental health problems and digestive/stomach disorders.

    • Social and mobility issues.

    • Alcoholism.

Questions and Discussion

  • Question: These illnesses are considered as a burden on public health and contribute significantly to the cost of health care.

    • Answer: All of the choices (Malnutrition, Foodborne illnesses, Vitamin deficiency).

    • Rationale: All these conditions negatively affect public health and healthcare expenses.

  • Question: Deficiency of this vitamin can cause anemia and problems with the nerves.

    • Answer: Vitamin B12.

    • Rationale: Vitamin B12 deficiency specifically leads to anemia and neurological issues.

  • Question: What are the best sources of micronutrients in our diets?

    • Answer: Fruits and vegetables.

    • Rationale: These food groups are naturally rich in vitamins and minerals.

  • Question: Which nutrients are needed in our diets for growth (especially for children, teens, and pregnant women) and to improve the immune system?

    • Answer: Proteins.

    • Rationale: Proteins are fundamental ‘body-building’ nutrients required for growth and tissue repair.