Introduction to Human Nutrition Science

Fundamentals and Definitions of Nutrition Science

• Nutrition: The science of food, the nutrients and the substances therein, their action, interaction, and balance in relation to health and disease, as well as the process by which an organism ingests, digests, absorbs, transports, utilizes, and excretes food substances. It is also defined as the scientific study of food and its relation to health, specifically dealing with processes by which the body utilizes food for growth and maintenance.

• Food: Anything edible—whether solid, semisolid, or liquid—which when swallowed, digested, and assimilated in the body, proves useful to it. Food keeps a person alive, supplies energy for growth and development, regulates body processes, and protects against disease.

• Functional Food: Food that provides health benefits beyond its basic nutrient contribution.

• Convenient Food: Food, typically a complete meal, pre-prepared commercially to require minimum further preparation by the consumer.

• Food Science: The branch of science dealing with the study of chemical and physical properties of foods and changes occurring during processing, storage, and handling.

• Nutrients: Chemical compounds or components in food used by the body to function properly, supply nourishment, and maintain health.

• Health: Defined by the World Health Organization (WHO) of the United Nations as "a state of complete physical, mental and social well being and not merely the absence of disease and infirmity."

• Meal: Food served and eaten especially at one of the customary, regular occasions for taking food during the day, such as breakfast, lunch, or supper.

• Diet: Refers to food in terms of amount, proportion, composition, and its overall effect on health.

• Balanced Diet: A diet containing all nutrients in appropriate amounts and proportions to assure an individual of obtaining the minimum requirements of all nutrients.

• Dietetics: The application of the principles of nutrition science to the diet regarding health and disease.

• Therapeutics: The branch of medicine concerned with the treatment of disease and the action of remedial agents through a dietary approach.

Nutritional Status and Assessment

• Definition: Nutritional status is the condition of the human body as it relates to the consumption and utilization of food.

• Signs of Good Nutritional Status:

  • Shiny hair

  • Smooth skin

  • Clear eyes

  • Alert expression

  • Firm flesh on a well-developed structure

  • Correct weight in relation to height

  • Good stamina

  • Resistance to diseases

  • Regular sleep and elimination habits

• Signs of Poor Nutritional Status:

  • Poor physique

  • Very little stamina

  • Dull, lifeless hair

  • Dull eyes

  • Slumped posture

  • Fatigue

  • Overweight or underweight condition

  • Irregular diet, sleep, and elimination habits

  • Clinical symptoms of nutritional deficiency

Functions of Food

• Physiological Functions:

  • To provide energy for bodily activities

  • To repair damaged body tissues

  • To build new cells and tissues

  • To regulate metabolic and body processes

  • To protect the body against diseases

• Psychological Functions:

  • Food satisfies emotional needs.

  • It is used as a medium to express feelings such as special attention, friendship, recognition, or punishment.

• Social Functions:

  • Humans are social beings, and food serves as an essential medium for socialization.

  • It plays a central role during special social occasions, including marriages and birthday celebrations.

Categories and Chemical Properties of Nutrients

• Classification by Quantity or Mass:

  • Macronutrients: Carbohydrates, Proteins, and Fats (required in larger amounts).

  • Micronutrients: Vitamins and Minerals (required in small or trace amounts).

• Proteins:

  • Essential for growth in children and maintenance of body weight in adults.

  • Provide energy to a minor extent.

  • Constitute approximately $20\,\%$ of total body weight.

  • Synthesized from dietary proteins to make up for continuous internal protein loss.

  • Composed of basic building blocks called amino acids.

• Carbohydrates:

  • Primary and cheapest source of energy for performing physical work.

  • Account for $50\,\%$ to $70\,\%$ of total energy (Calorie) value in an average diet.

  • Common forms in food include starch, cane sugar (sucrose), glucose, fruit sugar (fructose), and milk sugar (lactose).

• Fats:

  • Serve predominantly as concentrated sources of energy.

  • Provide essential fatty acids necessary for maintaining optimal health.

  • Severe deficiency or absence of dietary fat leads to a specific skin deficiency disease known as phrynoderma.

• Vitamins:

  • Essential organic chemical compounds needed in minute quantities for normal physical functioning.

  • Inadequate intake leads to deficiency disorders.

  • Fat-soluble vitamins: Vitamin A, Vitamin D, Vitamin E, and Vitamin K.

  • Water-soluble vitamins: Vitamin B complex and Vitamin C.

• Minerals:

  • The human body contains approximately $24$ minerals, all obtained through diet.

  • Major Minerals: Calcium, Phosphorus, Sodium, Potassium.

  • Trace Minerals: Iron, Iodine, Fluorine, Zinc, Copper, Cobalt, Magnesium, Chloride.

  • Calcium and Phosphorus: Structural formation of bones and teeth.

  • Sodium, Potassium, and Chloride: Maintenance of fluid and water balance in the body.

  • Iron and Copper: Synthesis and formation of hemoglobin.

  • Iodine: Normal functioning and regulation of the thyroid gland.

• Water:

  • Defined as an essential nutrient because daily requirements exceed the body's metabolic production capacity.

  • Serves as the primary solvent facilitating all internal biochemical reactions.

Multifactorial Determinants of Human Nutrition

• Human nutrition is influenced by a wide array of interconnected biological, socioeconomic, environmental, and cultural factors:

  • Education

  • Science

  • Technology

  • Agriculture

  • Health

  • Medicine

  • Genetics

  • Tradition

  • Community

  • Economic Status

  • Culture

  • Religion

  • Age

  • Family

  • Climate

Comprehensive Classification Schemes of Foods

• Classification Systems:

• By Chemical Nature: Carbohydrates, Proteins, Fats, Vitamins, Minerals, Dietary Fiber, Water.

• By Chemical Properties: Organic and Inorganic.

• By Mass: Macronutrients and Micronutrients.

• By Origin: Plant Foods and Animal Foods.

• By Function in the Body: Energy Giving, Body Building, Protective.

  • Functional Classification:

• Body Building Foods: Rich in protein; includes meat, milk, poultry, fish, eggs, pulses, etc.

• Energy Giving Foods: Rich in carbohydrates and fats; includes cereals, sugars, fats, oils, etc.

• Protective Foods: Rich in vitamins and minerals; includes vegetables, fruits, milk, etc.

  • Nutritional Broad Heads:

• Energy Yielding Foods: Rich in carbohydrates, fats, or pure fats and sugars (e.g., cereals, roots and tubers, dry fruits, sugars, fats). Cereals also provide significant protein, minerals, and vitamins for lower-income groups in developing countries.

• Body Building Foods: Rich in protein:

  • High Biological Value: Milk, eggs, meat, fish.

  • Medium Biological Value: Pulses, oilseeds, nuts, low-fat oilseed flours.

• Protective Foods:

  • Vitamins, minerals, and high biological value proteins: Milk, eggs, fish, liver.

  • Vitamins and minerals specifically: Green leafy vegetables, other vegetables, fruits.

  • Classification by Color ("Eat a Rainbow"):

• White

• Yellow

• Orange

• Red

• Blue-Purple

• Green

Structured Food Group Systems

• Basic 11-Food Group System:

1. Cereals and millets, and their products: Contributes Thiamine, Niacin, Riboflavin, Iron, Carbohydrates, and Cellulose.

2. Legumes and pulses (including dry beans, peas, and nuts): Contributes Proteins and B-Vitamins.

3. Meat, poultry, and fish: Contributes Proteins, Phosphorus, Iron, and B-Vitamins.

4. Eggs: Contributes Proteins, Fat, Vitamins, Iron, and Phosphorus.

5. Milk and milk products: Contributes Calcium, Phosphorus, Proteins, and Vitamins.

6. Roots and tubers: Contributes Carbohydrates and Ascorbic acid.

7. Green leafy vegetables: Contributes Pro-vitamin A (Carotene), Ascorbic acid, and Iron.

8. Other Vegetables: Contributes Ascorbic acid and Potassium.

9. Fruits: Contributes Ascorbic acid and Cellulose.

10. Fats and oils: Contributes Essential Fatty Acids and Vitamin E.

11. Sugar and Jaggery: Contributes Carbohydrates.

• The 7-Food Group System:

1. Green and yellow vegetables: Contributes Carotene (Pro-vitamin A), Ascorbic acid, and Iron.

2. Oranges, grapefruit, tomatoes, raw cabbage, or salad greens: Contributes Ascorbic acid.

3. Potatoes, other vegetables, and fruits: Contributes Vitamins, minerals in general, and Cellulose.

4. Milk and milk products: Contributes Calcium, Phosphorus, Proteins, and Vitamins.

5. Meat, poultry, fish, and eggs: Contributes Proteins, Phosphorus, Iron, and B-Vitamins.

6. Bread, flour, and cereal (whole grain, enriched, or restored): Contributes Thiamine, Niacin, Riboflavin, Iron, Carbohydrates, and Cellulose.

7. Butter and fortified margarine: Contributes Vitamin A and Fat.

• Five Food Group Plan (Nutrition Expert Group, ICMR):

1. Cereals, roots, and tubers (Rice, wheat, maize, ragi, sorghum, pearl millet, potato, tapioca, sweet potato, etc.): Rich sources of starch; fair to good sources of proteins and certain B-vitamins.

2. Milk group (Includes milk as well as other protein-rich foods like pulses, nuts, meat, fish, eggs, etc.): Rich sources of proteins, minerals, and vitamins.

3. Fruits and green leafy vegetables (Papaya, orange, mango, Indian gooseberry, guava, and all green leafy vegetables): Rich sources of certain vitamins and minerals.

4. Other Vegetables (Beans, brinjal, ladies finger, etc.): Fair sources of certain vitamins, minerals, and roughage.

5. Fats, oils, and pure carbohydrate foods (Vegetable oils, animal fats, sugar, jaggery, honey, sago, custard powder, starch, etc.): Rich sources of energy. Vegetable oils supply essential fatty acids and Vitamin E; butter supplies Vitamin A; animal fats are rich in cholesterol but poor in essential fatty acids and Vitamin E.

• Four Food Group Plan (Suggested by ICMR 2011):

1. Cereals, millets, and other cereal products (Whole grain, enriched, restored): Contributes Thiamine, Niacin, Riboflavin, Iron, Carbohydrates, and Cellulose.

2. Meat, fish, nuts, oilseeds, legumes, and pulses (Beef, veal, pork, lamb, poultry, fish, eggs, dry beans, peas, and nuts): Contributes Proteins, Phosphorus, Iron, and B-Vitamins.

3. Vegetables and Fruits: Contributes Vitamins, minerals, and Cellulose.

4. Milk and milk products (Milk, yoghurt, curd, cheese, and ice cream; cheese and ice cream can replace part of the milk): Contributes Calcium, Phosphorus, Proteins, and Vitamins.

Purposes and Applications of Food Classification Systems

• Tool for Nutritional Assessment and Screening: Discloses dietary nutrient inadequacies through brief history systems, providing early indicators of potential deficiency risk.

• Tool for Nutritional Counseling: Provides structured framework for healthcare teams to educate and counsel patients on balanced intake.

• Explaining Therapeutic Diets: Facilitates scientific menu planning and clear patient communication regarding medically tailored diets based on nutrient composition.

• Food Labeling and Surveillance: Provides standard categories used for national nutrition surveillance systems and food package labeling.

Food Pyramids and Dietary Models

• Traditional Food Guide Pyramid:

• Top Level (Apex): Fats, oils, and sweets — Use sparingly. (Symbols represent naturally occurring or added fats and added sugars).

• Second Level (Middle-Top):

  • Milk, yogurt, and cheese group: $2 \text{ to } 3$ servings daily.

  • Meat, poultry, fish, dry beans, eggs, and nuts group: $2 \text{ to } 3$ servings daily.

• Third Level (Middle-Bottom):

  • Vegetable group: $3 \text{ to } 5$ servings daily.

  • Fruit group: $2 \text{ to } 4$ servings daily.

• Base Level (Bottom):

  • Bread, cereal, rice, and pasta group: $6 \text{ to } 11$ servings daily.

  • MyPyramid Model:

• Features vertical color-coded bands representing Grains, Vegetables, Fruits, Fats, Milk, and Meat & Beans, alongside stairs with a person running to emphasize physical activity.

Dietary Guidelines to Improve Nutritional Status

• Physiological Adaptation: Tailor daily dietary intake to match specific physiological conditions and individual physical activity levels.

• Dietary Variety: Incorporate a wide variety of food groups and distinct food items in everyday meals.

• Nutritional Value Prioritization: Prioritize overall nutrient density and quality over taste alone.

• Local and Seasonal Consumption: Emphasize fresh, locally available, and seasonal foods.

• Leafy Green Integration: Frequently include green leafy vegetables to satisfy essential mineral requirements.

• Raw Food Preference: Prefer fresh raw fruits and vegetables over excessively cooked items to preserve dietary fiber and thermosensitive vitamins.

• Balanced Proportions: Use salt, sugar, and dietary oils in moderation and balanced proportions.

• Processing Techniques for Enhanced Value: Prepare low-cost, highly nutritious foods using traditional processing methods such as fermentation, malting, and sprouting.

• Culinary Preservation: Practice proper food handling, preparation, and cooking methods to minimize nutrient degradation and loss.

• Hydration: Drink adequate amounts of pure, clean water daily.

• Regular Meal Timing: Never skip meals under any circumstances.

• Frequent Snacky Meals: Opt for smaller, nutritious snack-style meals at regular intervals rather than a few heavy meals to shorten fasting durations and sustain energy levels.

• Public Awareness: Promote nutritional education across populations to empower healthy dietary choices.