Vitamin C, also known as Ascorbic Acid, is a water-soluble vitamin. Vitamin C foods exist abundantly in nature as various coloured fruits and vegetables. Vitamin C cannot be generated by humans, hence we depend on the plant-based or animal-based Vitamin C foods to provide us with the required intake.

Vitamin C is a powerful antioxidant and it supports vital body functions and organs. It usually exists in reduced and oxidized forms as Ascorbate and Dehydroascorbic acid respectively. These two forms are easily inter-convertible and biologically active.

Vitamin C is easily destroyed by oxygen, alkali, and high temperature. Hence, one needs to carefully handle Vitamin C foods to avoid damage to Vitamin C by:

• Not over-heating the foods
• Not over-cooking
• Avoiding prolonged exposure to air of juiced, mashed, and cut vitamin C foods. In short, eat them fresh!

Vitamin C Absorption and Critical Factors

When taken through diet or supplements, Vitamin C concentration in blood is balanced through: absorption from small intestine and reabsorption or excretion through kidneys. At low doses (20 mg), absorption can reach nearly 100%, whereas at higher doses (12 g), only 16% is absorbed.

When excreted, a part of Vitamin C is excreted in form of oxalic acid. So, it is advisable for patients with oxalate stones to limit daily intake of Vitamin C to 500 mg.

Vitamin C functions in our body

Our body requires Vitamin C for normal physiological and psychological functions.

• It helps in the synthesis and metabolism of required nutrients as tyrosine, folic acid, and tryptophan, hydroxylation of glycine, proline, lysine, carnitine and catecholamine.
• It also increases the absorption of iron in the gut by reducing ferric to ferrous state.
• As an antioxidant, it protects the body from free radicals, pollutants, and toxins.

Vitamin C Benefits

Collagen synthesis for Flawless Skin

Collagen constitutes the principal protein of skin, bones, teeth, cartilage, tendons, blood vessels, heart valves, inter vertebral discs, cornea, eye lens. Vitamin C is important in the synthesis and maintenance of collagen especially type III and IV. Also, studies show that Ascorbic Acid is beneficial in wound healing either pre-operative or post-operative.

Supports Energy Metabolism in Muscles

Vitamin C is an important cofactor in synthesis of muscle carnitine. Carnitine is required for the transport and transfer of long chain fatty acids into mitochondria for energy production. 

Boosts Immune System

Vitamin C along with Vitamins: E, B6, B12, Folate and minerals as: Selenium, Zinc, Copper and Iron can stimulate our immune system for body defense. Also, Vitamin C is found to prevent over immune system stimulation which can cause tissue damage. Also, it has an anti-bacterial action.

Common Cold and Rhinitis

Studies suggest that high dose of Vitamin C (1-3g) can reduce duration and symptoms of common cold. Also, studies suggest that administration of Ascorbic Acid in rhinitis stimulates our immune system to synthesize immunoglobulins to attack infections.

Neurodegenerative disorders

Ascorbic Acid has shown to be effective in reducing cognitive functions decline which occurs in Alzheimer disease.

Also, some studies show that administration of Ascorbic Acid with anti-pscychotic drugs is beneficial in reducing free radicles which cause brain damage leading to schizophrenia.

Reproductive organs

Studies show that low Ascorbic Acid can cause high free radicles concentrations. These free radicles can damage reproductive organs in male. However, high doses of Ascorbic Acid show to cause reproduction failure. Also, supplementation of Vitamin C can increase the progesterone level in infertile women.

Coronary Artery Disease and Atherosclerosis

Studies show that Ascorbic Acid facilitates the conversion of cholesterol into bile acids and hence lowers blood cholesterol levels. Also, studies show that Ascorbic acid prevents LDL oxidation through its antioxidant effect. Also, it decreases LDL, cholesterol and triglycereids, and enhances HDL levels. Thus it reduces risk of atherosclerosis and stroke.

Also, Ascorbic Acid was found to strengthen arteries by stimulating collagen synthesis in artery walls and prevent adhesion of white blood cells to damaged arteries. It also helps to preserve Vitamin E – alpha-tocopherol inside the cells.

Reduces risk of Diabetes and Complications

Studies have found that Hyperglycemia in both type I and II Diabetes is associated with increase in reactive oxygen species (ROS) and decrease in Vitamin C. The increase in ROS is responsible for nephropathy and retinopathy.

Administration of both Vitamins C and E show to decrease ROS levels.

Prevents Heavy Metals Toxicity

Studies show that Vitamin C is effective in treatment of lead toxicity in humans. Animal studies show that administration of Vitamins C, E and Zinc reduce the brain damage occurred by arsenic.

Lowers Cancer Risk

There is an evidence that a high intake of Vitamin C is linked with a low risk for cancer of oesophagus, oral cavity, stomach, pancreas, cervix, rectum and breast and also non-hormonal cancers.  

The suggested mechanisms for Vitamin C in the treatment and prevention of cancer are: enhancing the immune system, stimulating the formation of collagen, preventing metastasis (spreading), preventing viruses that can cause cancer, wound healing in cancer patients after surgery, enhancing the effectiveness of chemotherapy, reducing the toxicity of chemotherapy, preventing free radical damages and neutralizing some carcinogens.

Also, in-vitro studies show high intravenous doses of Vitamin C have preferable targeting effect to tumor cells rather than normal cells. 

Vitamin C Recommended Dietary Allowance (RDA)

Age Group	RDA mg/day	Upper Limit
0-6 months	40
7-12 months	50
1-3 years	15	400
4-8 years	25	650
9-13 years	45	1200
14-18 years (Male)	75	1800
14-18 years (Female)	65	1800
more than 18 years (Male)	90	2000
more than 18 years (Female)	75	2000
Pregnancy	80 – 90
Breastfeeding	115 – 125

Vitamin C Foods

Plant sources are important because of high content of vitamin C up to 5,000 mg/100 g. Vitamin C is found in citrus fruits, green peppers, red peppers, strawberries, tomatoes, broccoli, brussels sprouts, turnip, Indian gooseberry and other leafy vegetables. Top sources of Vitamin C include:

• Citrus fruits – Orange, Lime, Grapefruit, Mandarins, and Pomelo
• Berries – Raspberry, Blackberry, Cranberry
• Guava
• Herbs such as curry leaves and Moringa
• Indian Gooseberry or Amla is the richest plant-based sources of Vitamin C.
• Kiwi

Dietary Tip: one piece of Amla, or a Kiwi, or an Orange is enough to cover your daily Vitamin C.

Vitamin C Deficiency:

Causes of Vitamin C Deficiency

Low fruits and vegetables intake (often associated with poor diet choices or imposed restrictive diet plans).

Also, evidence has shown that certain drugs like nifedipine and aspirin decrease concentration of Vitamin C.

High risk groups for Vitamin C Deficiency

Cigarette smokers exhibit decreased plasma Vitamin C concentrations despite adequate dietary intakes

Individuals with chronic hyperglycemia due to: diabetes, sepsis, or stress.

Adult males consistently exhibit lower plasma vitamin C concentrations across the life cycle than do their female counterparts.

Symptoms of Vitamin C Deficiency

Scurvy occurs upon Vitamin C deficiency. Common physical symptoms of scurvy include:

• swelling of the lower extremities
• bleeding gums
• malaise or fatigue
• bruising
• petechiae
• corkscrew hairs
• dry skin
• hemorrhaging
• depression
• hysteria
• social introversion.

On intervention of Vitamin C from foods and supplements, these psychological disorders relief firstly.

Toxicity due to high intake of Vitamin C

Single doses >1000 mg/day can cause gastrointestinal distress, nausea, and osmotic diarrhea, as the body attempts to rid itself of the high concentration of vitamin C.

The tolerable upper intake level (UL) for vitamin C is 2000 mg daily.

The side effects are generally not serious and can be easily reversed by reducing the intake of Vitamin C. Furthermore, there is no consistent and compelling data on serious health effects of vitamin C in humans.

References

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3783921/

https://journals.sagepub.com/doi/pdf/10.1177/1533210110392951

https://lpi.oregonstate.edu/mic/vitamins/vitamin-C