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HUMAN NUTRITION

I. Essential Nutrients: Vitamins and Minerals

1. Vitamin A (Retinol)

  • Description: Essential, fat-soluble vitamin stored in the liver.

  • Sources: Liver, milk, butter, cheese, yogurt, egg yolk, oily fish, fish liver oils, green leafy vegetables. Beta-carotene (from green leafy, red, orange, yellow fruits) is converted to Vitamin A by the liver.

  • Deficiency Causes: Low-fat diet, lack of dairy/liver/dark green vegetables, rice-based diets (no carotene), excessive alcohol consumption.

  • Deficiency Effects: Night blindness (due to lack of rhodopsin), poor complexion, dry skin, weakened immune system.

2. Vitamin C (Ascorbic Acid)

  • Description: Water-soluble, not stored in the body; excess is flushed daily (requires daily intake).

  • Sources: Mainly fruits and vegetables (e.g., tomatoes, citrus fruits).

  • Deficiency Causes: Diet lacking Vitamin C-rich foods.

  • Deficiency Effects: Slow wound healing, weakened immune system, easy bruising, bone fractures, scurvy, bleeding gums.

3. Vitamin D (Sunshine Vitamin)

  • Description: Fat-soluble, produced by sun exposure, stored in the liver and fatty tissue.

  • Sources: Fortified foods, salmon, sardines, fish liver oil, liver, raw milk, butter, cheese, margarine, eggs, daily sun exposure.

  • Deficiency Causes: Strict vegetarian diet, limited sun exposure (homebound, religious reasons, occupation), dark skin (reduces Vitamin D synthesis).

  • Deficiency Effects: Rickets in children; osteomalacia and osteoporosis (weak bones that break easily) in adults.

4. Iodine (Mineral Salt)

  • Description: Essential for proper thyroid function.

  • Sources: Seafood (fish, lobster, shellfish), table salt, vegetables grown in iodine-rich soils.

  • Deficiency Causes: Diet lacking iodine-rich foods, mountainous regions with iodine-poor soil.

  • Deficiency Effects: Goiter (enlarged thyroid gland), lethargy, fatigue, slow metabolism, weight gain.

5. Iron (Mineral)

  • Description: Present in every body cell.

  • Sources: Red meat, pork liver, kidneys, eggs, dark green leafy vegetables (spinach, cabbage, broccoli, lettuce), dried fruits (raisins, apricots), iron-fortified cereals and bread.

  • Deficiency Causes: Significant blood loss (menstruation, trauma, surgery).

  • Deficiency Effects: Anemia (reduced red blood cells).

II. Balanced Diet and Varying Nutritional Needs

1. Definition of a Balanced Diet

  • A diet containing all seven essential food nutrients in the correct quantities for growth, body repair, and maintaining overall health.

2. Dietary Needs by Group

  • Children:

    • Breast milk provides antibodies and essential nutrients (ideal for newborns up to 6 months).

    • Vitamin D aids calcium absorption for strong bones.

    • Protein promotes rapid growth.

    • Carbohydrates and fats provide energy.

    • Need extra calcium and Vitamin D for bone and teeth development.

  • Adults/Workers:

    • Balanced diet helps maintain healthy weight and strong immune system.

    • Men generally require more energy due to faster metabolism and greater muscle mass.

    • Minerals like calcium maintain bone strength.

    • High energy intake with low activity leads to weight gain.

  • Pregnant and Nursing Mothers:

    • Increased protein for fetal growth.

    • More iron for fetal hemoglobin formation and to prevent maternal anemia.

    • Fiber prevents constipation.

    • Breastfeeding mothers need additional calcium for milk production.

    • Vitamin C aids iron absorption and collagen formation.

    • Vitamin A is important for embryonic growth (heart, lungs, kidneys, retina).

    • Vitamin D assists calcium absorption for bone and teeth formation.

    • Reduced sugar intake is advised due to lower activity and weight gain risk.

    • Folic Acid/Vitamin B9 supplements help prevent neural tube defects.

  • Athletes:

    • Require more energy-rich foods for physical activities.

    • Increased protein for muscle mass.

    • More carbohydrates for energy.

  • People with HIV/AIDS:

    • A healthy, balanced diet boosts the immune system.

    • Need plenty of fresh fruits and vegetables (especially Vitamin C) and more protein to gain weight or build muscle mass.

3. Factors Affecting Dietary Needs

  • Age:

    • Babies, Toddlers, Young Children (0-10 years): High energy, protein, calcium, and Vitamin D needs for rapid growth and development.

    • Puberty and Adolescence (11-19 years): Energy and protein requirements often higher than adults; females need more iron (menstruation), males more calcium (bone thickening).

    • Elderly Persons: Energy needs decline due to decreased physical activity and metabolic rate (less energy-dense food); muscle mass replaced by fat (burns fewer kilojoules); calcium and Vitamin D supplementation recommended (osteoporosis risk); Vitamin C supplements may be beneficial due to reduced fruit/vegetable intake.

  • Gender:

    • Males generally require more energy-giving foods and protein than females of the same age due to greater muscle mass and higher metabolic rates.

  • Activity Level:

    • Active individuals require more energy (carbohydrates, fats).

    • Highly active children need more nutrients.

    • Athletes need more protein for muscle building and carbohydrates for energy.

    • Workers doing heavy labor require more energy than those doing light work.

  • Pregnancy:

    • See "Pregnant and Nursing Mothers" above for specific needs.

III. Malnutrition and Associated Health Problems

1. Starvation

  • Cause: Severe lack of food or undernutrition, often due to poverty and famine.

  • Effects: Body consumes carbohydrates, then fat reserves, then protein (muscles), and finally organs, leading to death.

2. Constipation

  • Cause: Lack of fiber/roughage in the diet.

  • Effects: Infrequent and difficult defecation, increased risk of colon cancer.

3. Coronary Heart Disease (CHD)

  • Cause: Narrowing of coronary arteries (supplying heart muscles) due to excessive animal fats and cholesterol deposition.

  • Effects: Heart attack (if heart muscles lack glucose and oxygen), potentially leading to death.

4. Obesity

  • Cause: Overconsumption of sugar, refined foods, and fatty foods.

  • Effects: Can lead to diabetes and coronary heart disease.

5. Scurvy

  • Cause: Lack of Vitamin C or a diet deficient in fresh fruits and vegetables.

  • Effects: Weak blood vessels, easy bruising, bleeding gums, poor wound healing, anemia.

IV. Dietary Health Problems from Overconsumption (Namibia Context)

1. Overconsumption of Sugar

  • Effects: Weight gain/obesity (stored as fat), leading to coronary heart disease, high blood pressure, Type 2 diabetes. Also causes tooth decay.

2. Overconsumption of Fat

  • Effects: Weight gain and obesity. Animal fats (saturated fats) contain cholesterol, leading to hypertension, high blood pressure, and coronary heart disease (due to arterial blockage).

3. Overconsumption of Meat

  • Effects: Can cause constipation and weight gain/obesity. Red meat's saturated fats and cholesterol can lead to hypertension and coronary heart disease.

4. Overconsumption of Salt

  • Effects: Causes hypertension (high blood pressure), increasing the risk of strokes and coronary heart disease. Can lead to osteoporosis by causing calcium loss. Also increases the risk of stomach cancer and kidney disease.

V. Factors Contributing to Famine

1. Increasing Population

  • Leads to a decrease in available food resources and an inability to grow sufficient food.

2. Drought and Flooding

  • Lack of rain or unpredictable rainfall makes crop cultivation and animal rearing difficult.

3. Poverty

  • Unequal distribution of wealth means poor people cannot afford food, even if a country has enough to feed its population.

4. Unequal Food Distribution

  • Countries facing drought or wars may not receive sufficient food relief, exacerbating starvation and potential deaths.