3.1 Vitamins

Vitamins are essential micronutrients that play crucial roles in our bodies. They act as coenzymes, regulate gene expression, and maintain tissue integrity. From supporting metabolism to protecting against oxidative stress, vitamins are vital for overall health and well-being.

Understanding vitamin functions helps prevent deficiencies and related diseases. Adequate intake through diet or supplements is key for different life stages and health conditions. By knowing vitamin roles, we can make informed choices to support our nutritional needs and prevent health issues.

Essential Roles and Functions of Vitamins

Roles of vitamins in nutrition

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• Vitamins are organic compounds required in small amounts for normal growth, development, and metabolic processes
  • Classified as either water-soluble (B-complex vitamins and vitamin C) or fat-soluble (vitamins A, D, E, and K)
  • Vitamins are considered micronutrients due to the small quantities required by the body
• Act as coenzymes or cofactors in enzymatic reactions enabling crucial metabolic processes
  • Thiamin (vitamin B1) serves as a cofactor for enzymes involved in carbohydrate metabolism (glucose oxidation)
  • Riboflavin (vitamin B2) is a precursor for FAD and FMN, which are involved in electron transport and energy production (cellular respiration)
  • Niacin (vitamin B3) is a component of NAD and NADP, which are involved in redox reactions (catabolism of carbohydrates, fats, and proteins)
  • Pyridoxine (vitamin B6) acts as a cofactor for enzymes involved in amino acid metabolism (transamination and decarboxylation)
  • Cobalamin (vitamin B12) functions as a cofactor for enzymes involved in DNA synthesis and fatty acid metabolism (myelin formation)
  • Vitamin C is a cofactor for enzymes involved in collagen synthesis and neurotransmitter production (dopamine and serotonin synthesis)
  • Vitamin A is a component of visual pigments (rhodopsin) and is involved in gene expression (cell differentiation and growth)
  • Vitamin D is involved in calcium and phosphorus homeostasis and bone metabolism (mineralization and remodeling)
  • Vitamin E is an antioxidant that protects cell membranes from oxidative damage (prevents lipid peroxidation)
  • Vitamin K serves as a cofactor for enzymes involved in blood clotting (activation of clotting factors) and bone metabolism (osteocalcin activation)
• Regulate gene expression and cell differentiation facilitating proper development and maintenance of tissues
  • Vitamin A and D receptors act as transcription factors to regulate gene expression (retinoic acid and vitamin D response elements)
• Maintain integrity of tissues and organs ensuring proper structure and function
  • Vitamin C is essential for collagen synthesis, which is important for connective tissue, skin, and blood vessels (prevents scurvy)
  • Vitamin A is necessary for maintaining the integrity of epithelial tissues (prevents xerophthalmia and night blindness)
• Support immune function protecting against infections and diseases
  • Vitamins A, C, and E have antioxidant properties that protect immune cells from oxidative damage (enhance phagocytosis and antibody production)
  • Vitamin D modulates immune response by regulating T-cell activation and cytokine production (enhances innate immunity and reduces autoimmunity)

Vitamins for disease prevention

• Antioxidant vitamins (A, C, and E) protect against oxidative stress and inflammation reducing the risk of chronic diseases
  • Cardiovascular disease (atherosclerosis and myocardial infarction)
  • Cancer (breast, prostate, and colon cancer)
  • Neurodegenerative disorders (Alzheimer's and Parkinson's disease)
• Vitamin D deficiency is associated with increased risk of bone disorders
  • Osteoporosis (reduced bone mineral density and increased fracture risk)
  • Rickets (softening and weakening of bones in children)
  • Adequate vitamin D intake and sun exposure can help prevent these conditions
• B-vitamins (folate, B6, and B12) are essential for homocysteine metabolism reducing the risk of cardiovascular disease and neural tube defects
  • Elevated homocysteine levels are associated with increased risk of atherosclerosis and thrombosis
  • Adequate intake of these vitamins can help reduce homocysteine levels and prevent associated conditions (spina bifida and anencephaly)
• Vitamin A is important for maintaining healthy vision and preventing eye disorders
  • Night blindness (impaired dark adaptation)
  • Xerophthalmia (dry eyes and corneal ulceration)
• Vitamin K is essential for blood clotting and bone health preventing hemorrhagic diseases and osteoporosis
  • Deficiency can lead to hemorrhagic disease of the newborn (prolonged bleeding and intracranial hemorrhage)
  • Adequate vitamin K intake can reduce the risk of osteoporosis in adults
• Vitamin C promotes wound healing and supports the immune system preventing infections and scurvy
  • Deficiency can lead to scurvy, characterized by impaired collagen synthesis and connective tissue weakness (bleeding gums and joint pain)

Vitamin deficiency risks and strategies

• Populations at higher risk for vitamin deficiencies include
  • Pregnant and lactating women due to increased nutrient demands for fetal development and milk production
  • Infants and children due to rapid growth and development requiring adequate vitamin intake
  • Elderly due to reduced absorption, decreased dietary intake, and increased medication use impacting vitamin status
  • Vegans and vegetarians may have limited intake of certain vitamins (B12 and D)
  • Individuals with malabsorption disorders (celiac disease and inflammatory bowel disease) have impaired vitamin absorption
  • Individuals with alcohol use disorder have impaired absorption and increased nutrient excretion
• Strategies to improve vitamin intake and status
  1. Encourage a balanced diet with a variety of nutrient-dense foods
     • Fruits, vegetables, whole grains, lean proteins, and fortified dairy products provide a wide range of vitamins
  2. Recommend vitamin supplements for at-risk populations or those with identified deficiencies
     • Prenatal vitamins for pregnant women to ensure adequate fetal development
     • Vitamin D supplements for breastfed infants and individuals with limited sun exposure to prevent deficiency
     • Vitamin B12 supplements for vegans and vegetarians to compensate for lack of dietary sources
  3. Fortify staple foods with essential vitamins to increase population-wide intake
     • Iodized salt to prevent iodine deficiency disorders
     • Vitamin D-fortified milk to improve bone health
     • Folic acid-fortified grains to reduce neural tube defects
  4. Implement nutrition education programs to promote awareness of vitamin-rich foods and the importance of a balanced diet
  5. Screen high-risk populations for vitamin deficiencies and provide targeted interventions
     • Vitamin A supplementation for children in developing countries to prevent xerophthalmia and reduce mortality

Vitamin Intake and Safety

• Recommended Dietary Allowance (RDA) provides guidance for adequate vitamin intake to meet the needs of most healthy individuals
• Bioavailability of vitamins can vary depending on factors such as food processing, cooking methods, and individual digestive health
• Tolerable Upper Intake Level (UL) establishes the maximum daily intake unlikely to cause adverse health effects
• Deficiency diseases can occur when vitamin intake is consistently below recommended levels, leading to specific health problems
  • Scurvy (vitamin C deficiency)
  • Beriberi (thiamin deficiency)
  • Pellagra (niacin deficiency)