Biological Functions of Vitamin C
Collagen Synthesis:
One of the most important biological functions of vitamin C is its role in collagen synthesis. Collagen is a protein that provides structure and support to the body’s tissues, including the skin, bones, and cartilage. Vitamin C is required for the hydroxylation of proline and lysine residues in collagen, which is necessary for the formation of stable triple helices. Without sufficient vitamin C, collagen synthesis is impaired, which can lead to scurvy, a disease characterized by weakness, bleeding gums, and impaired wound healing.
Antioxidant:
Vitamin C is also a powerful antioxidant that helps to protect the body against oxidative stress. Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS) and the body’s antioxidant defences. ROS can damage DNA, proteins, and lipids, which can lead to chronic diseases such as cancer, cardiovascular disease, and neurodegenerative diseases. Vitamin C helps to neutralize ROS by donating an electron to the free radical, which stabilizes it and prevents further damage.
Immune System:
Vitamin C is also important for a healthy immune system. It helps to stimulate the production and function of white blood cells, which are involved in fighting off infections and diseases. Vitamin C also enhances the production of antibodies and cytokines, which are molecules that help to regulate the immune response. Studies have shown that vitamin C can reduce the severity and duration of respiratory tract infections, such as the common cold and pneumonia.
Iron Absorption:
Another important function of vitamin C is its role in enhancing iron absorption. Iron is an essential mineral that is required for the formation of haemoglobin, the protein that carries oxygen in the blood. However, iron absorption can be impaired by certain compounds, such as phytates and tannins, which are found in plant foods. Vitamin C can help to overcome this by reducing the ferric form of iron to the more soluble ferrous form, which is better absorbed by the body.
Recommended Intake of Vitamin C
The recommended intake of vitamin C varies depending on age, sex, and other factors. The National Institutes of Health (NIH) recommends the following daily intake of vitamin C:
- Infants (0-6 months): 40 mg/day
- Infants (7-12 months): 50 mg/day
- Children (1-3 years): 15 mg/day
- Children (4-8 years): 25 mg/day
- Children (9-13 years): 45 mg/day
- Adolescents (14-18 years): 75 mg/day for males, 65 mg/day for females
- Adults (19 years and older): 90 mg/day for males, 75 mg/day for females
- Pregnant women: 85 mg/day
- Breastfeeding women: 120 mg/day
It is important to note that smokers require higher amounts of vitamin C due to increased oxidative stress. The NIH recommends that smokers consume an additional 35 mg/day of vitamin C.
Dietary Sources of Vitamin C
Vitamin C is found in a variety of fruits and vegetables, particularly citrus fruits, berries, kiwi, mango, papaya, pineapple, and watermelon. Other good sources of vitamin C include bell peppers, broccoli, Brussels sprouts, cabbage, cauliflower, kale, spinach, and tomatoes. Some fortified foods, such as breakfast cereals and juices, may also contain added vitamin C.
It is important to note that vitamin C is sensitive to heat and light, and can be destroyed during food preparation and storage. To maximize the amount of vitamin C in your diet, it is recommended to eat fresh fruits and vegetables and to cook them as little as possible.
Potential Health Benefits of Vitamin C
In addition to its essential biological functions, vitamin C has been studied for its potential health benefits. Here are some of the areas where vitamin C may play a role:
Cancer Prevention:
Vitamin C has been shown to have anti-cancer properties, particularly in the prevention of oxidative DNA damage and inflammation. Some studies have also suggested that a high intake of vitamin C may be associated with a reduced risk of certain cancers, such as lung, breast, and colon cancer. However, more research is needed to confirm these findings.
Cardiovascular Health:
Vitamin C may also have benefits for cardiovascular health. It has been shown to lower blood pressure and reduces the risk of heart disease and stroke. Vitamin C may also help to improve endothelial function, which is the ability of blood vessels to dilate and contract.
Skin Health:
Vitamin C is essential for the synthesis of collagen, which is important for healthy skin. Some studies have suggested that vitamin C may also have anti-ageing effects, such as reducing the appearance of fine lines and wrinkles.
Brain Function:
Vitamin C may also have benefits for brain function. It has been shown to enhance cognitive performance in some studies, particularly in older adults. Vitamin C may also help to reduce the risk of cognitive decline and dementia.
Warnings and Precautions
While vitamin C is generally safe and well-tolerated, there are some potential risks and side effects to be aware of:
Kidney Stones:
High doses of vitamin C may increase the risk of kidney stones in some people, particularly those with a history of kidney stones. This is because vitamin C can be converted to oxalate, which can accumulate in the kidneys and form stones.
Gastrointestinal Distress:
Some people may experience gastrointestinal distress, such as diarrhoea, nausea, or abdominal cramps when taking high doses of vitamin C. This is because vitamin C can have a laxative effect at high doses.
Interactions with Medications:
Vitamin C may interact with certain medications, such as warfarin, aspirin, and some chemotherapy drugs. If you are taking any medications, it is important to talk to your doctor before taking high doses of vitamin C.
Inaccuracies and Misconceptions
There are some common misconceptions and inaccuracies about vitamin C that are important to address:
Mega-Dosing:
Some people believe that taking very high doses of vitamin C, such as several grams per day, can cure or prevent diseases such as cancer. However, there is little evidence to support these claims, and high doses of vitamin C can have potential risks and side effects.
Natural vs. Synthetic:
Some people believe that natural sources of vitamin C, such as fruits and vegetables, are superior to synthetic sources, such as supplements. However, vitamin C is chemically identical whether it comes from natural or synthetic sources, and both can be effective in meeting daily requirements.
Conclusion
Vitamin C is an essential nutrient that plays many important biological roles in the body. It is involved in collagen synthesis, antioxidant defence, immune function, and iron absorption, among other functions. Vitamin C can be found in a variety of fruits and vegetables, and can also be taken as a supplement. While vitamin C is generally safe and well-tolerated, it is important to follow recommended intake guidelines and be aware of potential risks
