Model Answer
0 min readIntroduction
Vitamin C, also known as ascorbic acid, is an essential nutrient for humans. Unlike most mammals, humans cannot synthesize Vitamin C endogenously, making dietary intake crucial. It’s a water-soluble vitamin acting as a potent antioxidant and playing a vital role in various physiological processes. Its discovery and subsequent understanding revolutionized the prevention and treatment of scurvy, a historically devastating deficiency disease. This answer will detail the sources, RDA, biochemical significance, and clinical manifestations of Vitamin C deficiency, providing a comprehensive overview of this essential nutrient.
Sources of Vitamin C
Vitamin C is abundantly found in fruits and vegetables. Excellent sources include:
- Citrus fruits: Oranges, lemons, grapefruits, limes
- Berries: Strawberries, blueberries, raspberries, cranberries
- Vegetables: Bell peppers (especially red and yellow), broccoli, spinach, kale, tomatoes, potatoes
- Other sources: Acerola cherries, guava, papaya
The Vitamin C content in food can be affected by storage, cooking methods, and processing. Prolonged storage and high-temperature cooking can lead to significant losses.
Recommended Daily Allowance (RDA) of Vitamin C
The RDA for Vitamin C varies based on age, sex, and physiological status. According to the National Institutes of Health (NIH) (as of knowledge cutoff 2021):
| Age/Group | RDA (mg/day) |
|---|---|
| Infants (0-6 months) | 40 |
| Infants (7-12 months) | 50 |
| Children (1-3 years) | 15 |
| Children (4-8 years) | 25 |
| Children (9-13 years) | 45 |
| Adolescents (14-18 years) | 65-75 |
| Adults (19+ years) | 75 (women), 90 (men) |
| Pregnant women | 85 |
| Breastfeeding women | 120 |
| Smokers | +35 mg/day |
These recommendations are designed to ensure adequate intake for preventing deficiency and maintaining optimal health. Higher doses may be recommended in certain clinical situations.
Biochemical Significance of Vitamin C
Vitamin C plays a crucial role in several biochemical processes:
- Collagen Synthesis: It is an essential cofactor for the enzymes prolyl hydroxylase and lysyl hydroxylase, which are required for the hydroxylation of proline and lysine residues in collagen. This hydroxylation is critical for collagen stability and proper formation of connective tissues.
- Antioxidant Activity: Vitamin C is a potent water-soluble antioxidant, scavenging free radicals and protecting cells from oxidative damage. It regenerates vitamin E, another important antioxidant.
- Neurotransmitter Synthesis: It is involved in the synthesis of norepinephrine from dopamine.
- Carnitine Synthesis: Vitamin C is required for the synthesis of carnitine, which is essential for the transport of fatty acids into mitochondria for energy production.
- Immune Function: It enhances immune cell function, including neutrophil chemotaxis and phagocytosis.
- Iron Absorption: Vitamin C enhances the absorption of non-heme iron from plant-based foods.
Clinical Manifestations of Vitamin C Deficiency (Scurvy)
Prolonged deficiency of Vitamin C leads to scurvy, characterized by a range of symptoms:
- Early Symptoms: Weakness, fatigue, malaise, muscle aches.
- Gingivitis and Tooth Loss: Inflammation and bleeding of the gums, leading to tooth loosening and eventual loss.
- Petechiae and Ecchymoses: Small, pinpoint hemorrhages under the skin (petechiae) and larger bruises (ecchymoses) due to capillary fragility.
- Impaired Wound Healing: Delayed wound healing due to compromised collagen synthesis.
- Joint Pain and Swelling: Bleeding into joints can cause pain and swelling.
- Anemia: Impaired iron absorption can lead to iron-deficiency anemia.
- Severe Scurvy: Hemorrhage, edema, neuropathy, and ultimately, death if left untreated.
In infants, scurvy can present with irritability, pseudoparalysis (painful reluctance to move), and bone abnormalities.
Conclusion
Vitamin C is an indispensable nutrient vital for numerous physiological functions, ranging from collagen synthesis and antioxidant defense to immune competence and iron absorption. Maintaining adequate intake through a balanced diet rich in fruits and vegetables is crucial for preventing scurvy and ensuring optimal health. While severe deficiency is rare in developed countries, vulnerable populations, such as those with limited dietary access or certain medical conditions, remain at risk and require careful monitoring and intervention.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.