Vitamin C is also known as ascorbic acid and was first isolated in 1932 from lemons. Vitamin C is an essential water-soluble vitamin which is not synthesized in the human body. As it is water-soluble vitamin the body cannot store for long durations and a daily dietary intake from food is necessary to replenish this nutrient. Some animals can produce vitamin C in high amounts by the liver from glucose. High amounts of ascorbate, a mineral salt of ascorbic acid is found in various tissues including the eyes, adrenal gland and the pituitary gland.
The name Ascorbic is derived from medieval Latin ‘scorbutus’ which means scurvy and ‘a’ referring to being without. Scurvy is one of the deficiency symptom of vitamin C and manifests with gum problems and a host of other symptoms.
Vitamin C is involved in the formation of collagen which helps maintaining healthy connective tissues and has antioxidant properties. Vitamin C acts as a cofactor for protocollagen hydroxylase needed to convert tropocollagen to collagen. 
Collagen is essential for skin, bone, teeth, cartilage and tendons. Collagen consists of elastin fiber produced by fibroblasts which requires vitamin C.
Maintains healthy skin, hair and nails
Vitamin C is needed for the formation of collagen which helps maintain healthy skin, hair and nails. Collagen consists of various amino acids which help with hair growth. In addition these amino acids contribute to healthy appearance of the skin and nails. Collagen supports the connective tissues found in the skin.
Improves bone and joint health
The role vitamin C plays in collagen formation is essential for the connective tissues found in bones, joints, vertebral discs, ligaments, tendons and cartilage. Collagen contains protein building blocks needed to maintain healthy and strong tendons, bones, cartilage and teeth. Collagen can help heal fractures and by repairing the tissues needed for healing.
Can help with anemia (iron deficiency)
Vitamin C can help with anemia caused by iron deficiency as it aids with iron absorption and also protects iron from oxidation with its antioxidant activity. Vitamin C helps with iron absorption and can help alleviate symptoms of anemia associated with iron-deficiency anemia.
Helps heal wounds
Vitamin C has an important function in the healing process of wounds with its antioxidant activity and helps maintain and protect the health of cells. It protects cells from oxidation and free radicals. It works synergistically with vitamin E in its role of reducing free radicals in the body and both are key nutrients for antioxidant activity.
Prevents and reduces viral infections
Sufficient supply of vitamin C is important for the development of white blood cells which helps defend against infections. Abosorbic acid is involved in the immune function of cells which can help combat bacterial, viral and fungal diseases.
Certain viral conditions such as pneumonia have shown reduced levels of vitamin C. Many studies on animals have shown a deficiency associated with infections and illness due to bacteria, viruses and protozoa. It has shown to help alleviate symptoms of the common cold.
Vitamin C has been used for reducing symptoms of shingles (herpes zoster) which manifests with a painful rash on the skin. Shingles occurs due to the presence of the zoster virus which is also associated with chickenpox. In addition to vitamin C other key nutrients have also shown some benfits which includes vitamin E and vitamin B12.    
Reduces allergy symptoms
Hayfever is a common type of allergy which increases the production of histamine. Vitamin C can help reduce histamine levels which has a positive effect in reducing symptoms of sneezing and a stuffy nose associated with allergies which has been shown in doses of up to 2 g.
Supports cardiac and vascular health
Vitamin C which helps with forming collagen is needed for the connective tissues found in the capillary walls that help maintain blood vessels. It also has the benefit of helping to prevent bruises.
The reduced calcification can help reduce risk of certain conditions such as arteriosclerosis and atherosclerosis.
These particular functions of vitamin C can help protect against heart disease and cardiovascular vascular disease. Vitamin C also helps by reducing bad cholesterol (LDL) levels and triglycerides.
Protects against cancer
Research on vitamin C is showing the potential of this nutrient helping to protect against some forms of cancer. Vitamin C is involved in reducing free radicals. It also helps neutralize preservatives found in processed foods such as nitrites. Nitrites and other preservatives are showing to potentially increase the risk of cancer. Many individuals afflicted by cancer also tend to have a deficiency of vitamin C.
Helps with thyroid function
Vitamin C aids in the production of thyroid hormones. It helps in copper metabolism which has a role in thyroidal function. Although vitamin C can help activate certain copper dependent enzyme activity high amounts of the nutrient can have an adverse effect of depleting copper. Very low copper levels can lead to hyperthyroidism or other thyroid disorders.
Vitamin C is also involved in the adrenal function which helps in combatting stress. Chronic stress can deplete vitamin C and impair adrenal functions which can impair thyroid health.
Vitamin C is showing to help in fertility of both men and women. In women vitamin C can be found concentrated in ovaries. It helps to aid in the synthesis and regulation of hormones essential for fertility. Some studies are showing that vitamin C has an important role in ovulation and may help stimulate ovulation. Vitamin C can help with synthesis of progesterone a hormone that peaks during ovulation. Vitamin C can be helpful for women who have low levels of progesterone or luteal phase defect.
Vitamin C is also associated with the menstrual cycle where healthy cycles are linked with improved fertility.
It also has potential benefits for male fertility.
Helps with insulin production
Vitamin C deficiency has been linked to diabetes and studies are showing benefits of vitamin C supplementation in those with diabetes mellitus (type 2). The effect of vitamin C has shown to reduce blood glucose levels in those with type 2 diabetes.  
Vitamins: A, B3, B5, B6, B9, B12, E
Minerals: Ca, Co, Cu, Fe, Mg, Mn, Na, Se, Zn
Other: Glutathione, bioflavonoids (hesperidin, rutin)
Vitamin C regulates uptake and metabolism of iron and has been used for iron deficiency anemia. 
Vitamin C helps activate certain copper dependent enzymes. 
Vitamin C has a role in copper metabolism with scurvy-like symptoms observed in a copper deficiency state. 
Vitamin C, vitamin E and selenium are antioxidants that work synergistically for maintaining health and deficiency or imbalance of each can directly impact use of each nutrient in the body 
Vitamin C and E work synergistically and function as antioxidants however high dose of vitamin C may increase requirement for vitamin E. High doses of vitamin E can also increase the requirement of vitamin C.  
Vitamin C helps protect vitamin E by helping to recycle it into the active form of E.
Bioflavonoids such as hesperidin and rutin work synergistically with vitamin C. 
Vitamin C is involved in regulating copper metabolism. 
Vitamin C helps with folic acid metabolism.
Minerals: Cu, Fe, Zn
Metals: Al, Hg, Pb, Cd
Other: Pectin, high intracellular glucose, high amounts of ascorbate, alcohol, Aspirin smoking, medications (sulfa antibiotics, cortisone), environmental toxins and pollution, oral contraceptives, viral infections (pneumonia, flu, common cold), stress.    
High doses of vitamin C may deplete copper by inhibiting absorption or impairing metabolism. If copper stores are not restored this can cause symptoms of copper deficiency. Iron which is increased by vitamin C competes with copper for absorption and high levels can lead to a copper deficiency.   
Vitamin C deficiency can increase serum copper due to improper copper metabolism. 
High copper reduces vitamin C.
Vitamin C reduces zinc levels.
High vitamin C can cause iron toxicity by reducing copper levels which is needed to utilize iron. 
Vitamin C can be found in a variety of vegetable and fruit sources. Vegetable sources of vitamin C include green vegetables, broccoli, brussel sprouts, cabbage, asparagus, cauliflower, kale, spinach, tomatoes, peppers, potatoes and sweet potatoes. Fruit sources of vitamin C include strawberries, berries, apples, melons, kiwi, lemons, limes, grapefruits and oranges.
Some foods and drinks may be fortified with vitamin C. Rosehips contain a high amount of vitamin C with up to 20 times more vitamin C than found in oranges. Meat and fish are a poor source of vitamin C with only some raw fish containing a small amount of vitamin C.
Raw fruits and vegetables preferably of organic source are the best source of vitamin C as heat and cooking destroys the nutrient.
The amounts recommended for vitamins and minerals are different for each country which can be found on the government website of host country. The nutritional data for each country are based on scientific research which are presented by the scientific academies in each country to help advise governmental departments for food and human nutrition.
Below is a list of some of the countries and the EU for which nutritional guidelines are available found on corresponding official government website (including the national academy of science website for the USA).
Australia and New Zealand
Vitamin C supplements are available as capsules, tablets, effervescent tablets and liquid form. There are various types of vitamin C supplements. L ascorbic acid is the common type but may cause ‘acid stomach’ in some people. Ascorbate is the mineral salt of ascorbic acid and can be found in mineral bound ascorbates such as calcium abscorbate and sodium ascorbate. Sodium ascorbate is the buffered form of vitamin C and more tolerable than ascorbic acid by some people. Ascorbic acid is acidic and ascorbate is alkaline, therefore it is preferable to take sodium ascorbate away from meals to avoid interacting with stomach acid needed for digestion. Liposomol vitamin C is thought to be better absorbed however studies are limited and most people are likely to absorb vitamin C.
Some vitamin have added bioflavonoids which may enhance the antioxidant activity of vitamin C such as rutin and hesperidin.
It is best to take vitamin C in divided doses if taking high amounts as a majority of the amount taken will be excreted.
Some health professionals recommend the "Bowel Tolerance Test" to determine amount of vitamin C taken. The test involves titrating doses of vitamin C until it causes diarrhea. This is done to determine best doses in terms of the therapeutic uses of vitamin C. However this is mostly applicable to very sick patients and cannot determine the levels of vitamin C in an individual. 
Vitamin C is stable in an acidic environment. Vitamin C can be destroyed by heat, light, oxidation, and alkaline solutions.
The following are signs and symptoms of a vitamin C deficiency:
- Muscle weakness
- Joint and muscle aches
- Shortness of breath
- Frequent infections
- Gastrointestinal problems
- Impaired collagen synthesis
- Vascular degeneration
- Loss of appetite
- Growth cessation
- Tooth decay
- Swollen gums
- Bleeding gums
- Loose teeth
- Loss of teeth
- Red spots on skin (corkscrew hair)
- Rashes (dermatitis)
- Poor wound healing
- Easy bruising
- Swollen ankles and wrists
- Anemia (microcytic anemia)
- Pale skin
- Decreased insulin production
- Male infertility
- Impaired hormonal production
- Sunken eyes
- Cracked lips
A severe deficiency of vitamin C can lead to a condition known as scurvy which is no very common, however it is a very severe disease. Scurvy was first discovered in 1747 by a Scottish doctor James Lind who found the condition manifesting in sailors. Scurvy was a common cause of death in sailors. The condition was halted in some sailors and symptoms of scurvy improved by consumption of citrus fruits such as lime by those afflicted.
A minimum of about 10 mg of Vitamin C is sufficient to prevent scurvy. 
The causes of vitamin C deficiency include:
- Reduced dietary intake of fruits and vegetables
- Poor diet and malnutrition
- Excessive alcohol intake
- Chronic kidney disease
- Oral contraceptives
- Medications (antibiotics, aspiring and barbiturates)
Vitamin C is measured through blood serum and is determined if vitamin C plasma levels drop below 0.2mg/dL.
Vitamin C toxicity is likely to occur from chronically excessive and high dosed supplemental intake usually over the amount of 2,000 mg per day of vitamin C.
Signs and symptoms of vitamin C toxicity include:
- Stomach pain / cramps
- High stomach acid (acid stomach)*
- Joint pains
- High or toxic levels of iron
- Copper deficiency
- Low estrogen
- Low progesterone
- Low prolactin
- Premenstrual Syndrome (PMS)
- Impaired insulin response
- Opposite effect to anti-clotting medications
- Increased urination
- Increased uric acid
- Kidney stones (common in people with kidney disease or gout)
- Excreting oxalic acid (excess can lead to kidney stone formations)
- Rebound scurvy
Rebound scurvy can manifest when a person after taking excessively high doses of vitamin C stops intake too quickly.
Vitamin C is a water-soluble vitamin and high amounts will simply be excreted out of the body through urination.
Acid stomach where the stomach has high levels of acid can be caused by L ascorbic acid, this can be counteracted by taking a buffered form of vitamin C such as sodium ascorbate.
Patients needing dialysis due to kidney disease or renal failure taking chronic high vitamin C may cause death although this is considered to be rare. 
Low amounts of ascorbate are recommended for chronic kidney disease and hemodialysis patients. 
Vitamin C can also reduce the effect of anticoagulation medications such as warfarin (Coumadin) making treatment with the drug ineffective.
Vitamin C may interact with certain medications. It is important to seek medical guidance from a health physician before supplementing with vitamin C.