UNLOCKING THE POWER OF VITAMIN C: A COMPREHENSIVE GUIDE

Food Sources of Vitamin C

Vitamin C, also known as L-ascorbic acid, is an essential nutrient that our bodies require to function properly. It is classified as a water-soluble vitamin, which means that it dissolves in water and does not remain in the body for long periods. As such, it needs to be replenished regularly through our diet. This essential vitamin plays several important roles in the body. Firstly, it functions as a potent antioxidant, protecting cells from damage caused by harmful molecules known as free radicals. Furthermore, vitamin C is required for the production of collagen, a protein that gives structure to many tissues in the body, including bones, cartilage, muscles, and blood vessels. 

Unlike some other animals, humans are unable to produce vitamin C internally, so we must obtain it from external sources, primarily through the consumption of fruits and vegetables. Moreover, beyond its antioxidant and collagen-forming functions, vitamin C plays a vital role in supporting the immune system, helping to defend the body against infections and illnesses. It also aids in the absorption of non-heme iron, the type of iron found in plant-based foods, thereby contributing to overall iron levels in the body. 

DIETARY SOURCES

Vitamin C can be found in various foods, including fruits and vegetables. Here are some examples:

• Fruits: Guava, longan, papaya, lime, tangerine, berries, mango, banana

• Vegetables: Green leafy vegetables like kale, mustard leaves (sawi), bok choy, and spinach

• Other vegetables: Bell pepper, bitter gourd, carrot, cabbage, cauliflower, lettuce, tomato, and okra

VITAMIN C WITH HEALTH BENEFITS

Eye Health

Age-related macular degeneration (AMD) and cataracts are two of the most common causes of vision loss in older individuals. Oxidative stress may contribute to the aetiology of both conditions. Hence, researchers have proposed that vitamin C and other antioxidants play a role in the development and/or treatment of these diseases. 

The Common Cold

In the 1970s, Linus Pauling proposed that vitamin C can effectively treat and prevent the common cold. However, subsequent controlled studies have produced inconsistent results, leading to confusion and controversy, despite the fact that public interest in the subject remains high. In the general population, taking prophylactic vitamin C reduced cold duration by 8% in adults and 14% in children. When taken after the onset of cold symptoms, vitamin C had no effect on cold duration or symptom severity. Vitamin C supplements may shorten the duration of a common cold and reduce symptom severity in the general population, possibly due to the antihistamine effect of high-dose vitamin C. 

Cardiovascular Disease (CVD)

Various epidemiological studies have found that eating a lot of fruits and vegetables reduces the risk of developing CVD. This association could be attributed in part to the antioxidant content of these foods, as oxidative modification of low-density lipoproteins, is a leading cause of CVD. In addition to its antioxidant properties, vitamin C has been shown to reduce monocyte adherence to the endothelium, improve endothelium-dependent nitric oxide production and vasodilation, and reduce vascular smooth-muscle-cell apoptosis, thereby preventing plaque instability in atherosclerosis. A study discovered that individuals in the top quartile of baseline plasma vitamin C concentrations had a  42% lower risk of stroke than those in the bottom quartile. 

Cancer Prevention

Epidemiologic evidence suggests that eating more fruits and vegetables reduces the risk of most cancers. Possibly due to their high vitamin C content. Vitamin C can inhibit the formation of carcinogens, such as nitrosamines, modulate the immune response, and, through its antioxidant function, possibly reduce oxidative damage that can lead to cancer. Additionally, various studies have discovered an inverse relationship between dietary vitamin C intake and cancers of the lung, breast, colon or rectum, stomach, oral cavity, larynx or pharynx, and oesophagus. Vitamin C plasma concentrations are also lower in cancer patients than in healthy controls. 

DOSAGE,  TOXICITY AND TOLERABLE UPPER INTAKE LEVELS (UL)

According to the Recommended Nutrient Intakes (RNI) of 2017, the typical daily vitamin C intake for healthy adults is 70 milligrams. For pregnant and lactating women, the recommended doses are slightly higher, at 80 and 95 milligrams per day, respectively. 

However, excessive vitamin C consumption may have negative consequences. These may include diarrhoea and other stomach issues, increased oxalate excretion, which may contribute to kidney stone formation, higher levels of uric acid in the urine, pro-oxidant effects, a condition known as “rebound scurvy”, enhanced iron absorption, which may result in iron overload, decreased levels of vitamin B12 and copper, increased oxygen demand in the body, and erosion of dental enamel. 

To reduce these risks, health officials have set a tolerable upper intake level for vitamin C at 2,000 milligrams per day in adults. Going beyond this limit may increase the likelihood of experiencing negative side effects, particularly for individuals who are more sensitive or have underlying health conditions. 

PRECAUTIONS!

Vitamin C supplements may not be suitable for individuals with certain medical conditions. For example, it is not recommended for those with blood disorders such as thalassemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, sickle cell disease, or hemochromatosis. If you’ve had angioplasty, you should avoid taking vitamin C supplements right before or after the procedure. Diabetics should exercise caution when taking vitamin C supplements because they have the potential to raise blood sugar levels. 

In addition, individuals who have oxalate nephropathy or nephrolithiasis should use vitamin C supplements with caution.  Ascorbic acid’s acidifying effect increases the risk of cysteine, urate, and oxalate stones forming. 

CONCLUSION

Understanding the significance of vitamin C in our daily lives reveals a variety of health benefits, ranging from immune system support to protection against chronic diseases such as CVD and certain cancers. However, it is critical to stick to the recommended daily dosages and be aware of the potential negative effects of excessive consumption. By incorporating a balanced diet rich in fruits and vegetables, we can harness the power of vitamin C while minimising the risks. Remembering to consult with healthcare professionals, especially for those with specific medical conditions, ensures the safe and effective use of this essential nutrient. 

FUN FACT

Did you know that vitamin C is sensitive to both heat and light? When foods high in vitamin C are exposed to high temperatures or extended cooking times, the vitamin can degrade and lose its potency. Since vitamin C dissolves in water, it can also escape into cooking liquids and be lost if not consumed. To preserve vitamin C content, use quick cooking methods such as stir-frying or blanching, and limit the amount of water used when cooking. Furthermore, eating fruits and vegetables raw when they are at peak ripeness ensures that you get the most vitamin C. 

REFERENCES

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Carr, A. C., & Frei, B. (1999). Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. The American Journal of Clinical Nutrition, 69(6), 1086–1107. https://doi.org/10.1093/ajcn/69.6.1086

Harvard School of Public Health. (2023, March). Vitamin C. The Nutrition Source; Harvard. https://www.hsph.harvard.edu/nutritionsource/vitamin-c/

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National Coordinating Committee on Food and Nutrition. (2017). Recommended nutrient intakes for Malaysia.

National Institutes of Health. (2021, March 26). Office of Dietary Supplements - Vitamin C. National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/

Villagran, M., Ferreira, J., Martorell, M., & Mardones, L. (2021). The Role of Vitamin C in Cancer Prevention and Therapy: A Literature Review. Antioxidants, 10(12), 1894. https://doi.org/10.3390/antiox10121894