vitamin is an essential nutrient that plays an important role in many
biological processes. It belongs to the group of water-soluble vitamins, which include Vitamin B 12 and ascorbic acid along with its derivatives. Vitamin C was discovered by an Hungarian
biochemist Albert Szent-Gyorgyi. In 1928, he isolated a chemical substance called "hexuronic acid"
from plant juices and animal adrenal glands and suspected it to be the "antiscorbutic" factor. Later
in 1932, British chemist Walter Haworth renamed 'hexuronic acid as 'ascorbic acid' (commonly known
as vitamin C) and also determined its molecular structure. Szent-Gyorgyi was awarded the Nobel
prize in the year 1937 in recognition of his accomplishment with vitamin C.
Ascorbic acid is a six carbon water-soluble weak sugar acid and it's chemical molecular formula is
C,H,O. The derivatives of ascorbic acid are L-ascorbic acid (functional form of vitamin C, AA),
dehydro-L-ascorbic acid (oxidised form, DHA) and monodehydro-Lascorbic acid (free radical form).
Humans and many other animal species are unable to synthesise ascorbic acid from glucose and
thus must be acquired from external sources. As it is water-soluble and the body does not store
it, an adequate daily intake of this vitamin is required for maintaining good health.
Functions of Vitamin C
Vitamin C has a wide variety of functions in the human body, right from maintaining healthy
skin to that of protecting from infections. Following are the benefits of vitamin C
Collagen synthesis: Vitamin C plays an important role in biosynthesis of
collagen, a protein which is the major component of connective tissues that binds the cells
together. It provides structural integrity and supportive framework to tissues in the organs
and skin. It acts as a matrix or cementing substance in maintaining bone health and promotes
faster healing of wounds.
Antioxidant: Like vitamin, vitamin C also acts as an excellent antioxidant. Individual can get
exposed to free radicals in the environment from cigarette smoking, ultraviolet light from sun
and air pollution. It aids in protecting cells from the damage caused by free radicals and reactive
oxygen species (ROS). Antioxidant properties of vitamin C contribute in elimination or toxins,
delaying skin's ageing process and prevents or delays development of certain cancers (for e.g:
stomach, prostate, lung and colon), cardiovascular diseases and other conditions in which
oxidative stress is a causative factor
Common cold: Vitamin C has been shown to have a strong effect on
preventing or shortening the duration of common cold.
Allergy and asthma relief: Vitamin C is present in the airways of lungs and inadequate vitamin
C levels have been associated with reduced or impaired lung function. Vitamin C acts as a natural
anti-histaminic agent and helps in reducing asthmatic symptoms.
Immunity: Vitamin C increases production of white blood cells and is
important for normal immune function. It helps in preventing viral infections. To protect immune
system in HIV-positive individuals, vitamin C is frequently prescribed as a supplement
Age-related
muscular degeneration (AMD) and cataract: These two eye problems are the leading
cause of vision loss in older individuals. Taking vitamin C supplements along with adequate
supply of other essential nutrients slow the progression of AMD and reduce the risk of developing
cataract.
Iron absorption: Vitamin C helps in absorption of non-heme iron from
plant-based foods.
Cardiac diseases: Vitamin C control high blood pressure and LDL-bad cholesterol
levels thus reducing the risk of coronary heart diseases or cardiovascular diseases.
Amino acids synthesis: Vitamin C is required in synthesis of Amino acids
that aid in regulation of regular metabolic functions of the body, for e.g. in
the synthesis of Thyroid Stimulating Hormone (TSH) hormones.
Vitamin C is also used in synthesis of certain neurotransmitters and helps in normal production
of adrenal hormones.
Deficiency of Vitamin C
Generations ago vitamin C deficiency was common.
In the 1600s and 1700s, a lot of British sailors on long voyages across the oceans suffered and
died from *Scurvy caused due to insufficient vitamin C intake. Sir James Lind through his
experiment discovered that consuming citrus fruits or juices could cure scurvy. British navy
made sure that all the sailors had lemon juice as a part of their ration when they were on long
voyages. Later on, lemon juice was substituted by lime juice due to its more ascorbic acid
content which would protect the sailors from developing scurvy and the sailors were later
nicknamed as "Limeys".
Inadequate amount of vitamin C in the body can cause its deficiency which affects many bodily
functions. Vitamin C deficiency can lead to a diseased condition known as 'Frank Scurvy'.
Individual who gets little or no vitamin C for many weeks can get scurvy. Generally, symptoms
of scurvy develop after a few months of vitamin C depletion. Initial symptoms of scurvy include
weakness, malaise, fatigue and gum inflammation. As vitamin C deficiency progresses, it affects
the formation of collagen which weakens and causes breakdown of connective tissues causing
'petechiae, purpura' (small red or purple spots on the skin), corkscrew hairs, hyperkeratosis, joint
pain and poor wound healing. Depression, swollen and bleeding gums as well as teeth loss are
additional symptoms of deficiency.
Individual with vitamin C deficiency may develop iron deficiency
anemia due to increased bleeding and inability to absorb non-heme iron. Prolonged vitamin C
deficiency can lead to bone diseases in children, nervous system related problems, edema and
shortness of breath. Although its deficiency is rare in developed countries, but can still occur in
individual with limited food variety. If not treated, scurvy can be fatal. It can be treated with
oral supplementation of vitamin C
Vitamin C deficiency risk factors
Today, in modern societies occurrence of scurvy is rare due to easy access to fresh fruits and
vegetables rich in vitamin C. However, several groups of individuals are more likely than
others to suffer due to inadequate amounts of vitamin C.
smokers or passive smokers:
Smokers require increased amount of vitamin C in the body to repair the damage caused by
oxidative stress. Also, individuals exposed to second hand smoke have decreased levels of
vitamin C.
Individuals consuming limited food variety: Individuals who consume restrictive
diets, elderly, alcoholics, men who live alone, children, people with mental illness or drug abuse are
vitamin C deficient. Though fruits and vegetables are the best sources, many of them have small
amounts of vitamin C content.
Infants who feed on evaporated or boiled milk: In developed countries,
infants are fed breastmilk or infant formula which have sufficient amount of vitamin C. Many
infants are fed evaporated or boiled cow's milk for many reasons. Little amount of vitamin
C is present in cow's milk, boiling the same destroys its content which can cause vitamin C
deficiency.
Individuals with certain medical conditions: Some medical conditions like
malabsorption disorders, Crohn's disease, some types of cancer, indigestion, kidney diseases
requiring hemodialysis, etc. can reduce absorption of vitamin C.
Toxicity of Vitamin C
Vitamin C is water-soluble, thus when consumed in excess does not get absorbed by the body,
and is rapidly excreted via urinary pH. Vitamin C has low toxicity and does not cause detrimental
effects to health, especially if the nutrients are obtained from food. In some healthy individuals,
ingestion of high doses of vitamin C might cause diarrhea and gastrointestinal disturbances,
nausea, vomiting, insomnia, fatigue, headache, hot flashes and skin rashes (in infants). The
chances of these side-effects increase with increased dosage. If a dose of vitamin C supplement
exceeds 2000 mg/day, it has been shown to cause rebound scurvy, exacerbate gout symptoms,
promote kidney stone formation in individuals with preexisting renal disorders and cause
hemolysis in glucose-6-phosphate dehydrogenase (G6PD) deficient patients. In patients with
thalassemia and hemochromatosis, consumption of high doses of vitamin C may lead to iron
overload resulting in tissue damage. Also, excessive consumption of chewable vitamin C might
cause erosion of dental enamel.
Symptoms caused due to high doses of vitamin C are usually resolved within one to two weeks
of discontinuation or reduction of supplementation dosage.
Sources of Vitamin C
Our body does not synthesise vitamin C, thus continuous replenishment is needed for
maintaining its levels in the body. Fruits and vegetables are the richest natural sources
of vitamin C.
Fruits: They are excellent sources of this vitamin; these include citrus
fruits like oranges, lemons, grapefruits, mandarin, tangerines and limes, and berries like
strawberries, raspberries, cranberries, blueberries. Other fruits like papaya, watermelon,
kiwi, mango, pineapple, blackcurrant, amla (Indian gooseberry), guavas and cantaloupe are
also rich sources of vitamin C.
Vegetables: Vegetables that are good sources of vitamin C include bell
peppers (of all colours), cauliflower, broccoli, cabbage, tomatoes, potatoes, Brussels sprouts,
peas, turnips, dark leafy vegetables, summer and winter squash, etc.
Animal sources: liver or kidneys tissues of animals have highest
ascorbic acid content, but in comparison with plant sources it is very low.
Other than the whole fruits and vegetables, canned and fresh citrus juices or juices fortified
with vitamin C can also be a good source of this vitamin. However, fresh juices contain more
active vitamin C. Vitamin C is not present in grains, thus it is added in some fortified breakfast
cereals.
Vitamin C is sensitive to heat, air and light and hence, the vitamin content of the foods may get
reduced by overcooking and prolonged storage. Stir-fried, steamed or microwaved food may reduce
the loss due to cooking. Consuming raw or lightly cooked food can provide most of the vitamin C
present in them.
Recommended Dietary Allowances (RDA) for Vitamin C
The RDA is based on the amount of vitamin C intake required to maintain near maximal
neutrophil ascorbate concentration, with minimal excretion of vitamin C through urine.
To provide sufficient antioxidant protection, the RDA for adult males is set at 90 mg/day
and for adult females, it is 75 mg/day. For children aged 1 to 8 years RDAs range from
15-25 mg/day and for boys and girls aged 9 to 18 years, it range from 45-75 mg/day and
45-65 mg/day, respectively. The recommended intake of vitamin C for smokers is additionally
increased by 35 mg/day as compared to non-smokers, in order to counteract the oxidative
stress or damage caused by nicotine consumption. The tolerable upper intake for vitamin C
is 2000 mg/day. A number of factors other than the age and gender that can potentially affect
the recommended amounts of vitamin C intake include smoking status, bioavailability and its
interactions with other nutrients.
Estimation of Vitamin C Levels
Assessment of vitamin C status in the body can include dietary history of an
individual and measurement of total ascorbic acid in serum, leukocytes and urine. A number
of techniques have been used for vitamin C estimation, of which high performance liquid
chromatography (hplc blood test) coupled with electrochemical detection (ECD) methods are the current
methods of choice. Also, total ascorbic acid analysis of isolated leukocytes is done using 2,4-
dinitrophenylhydrazine colorimetric method. Normal levels of vitamin C in the body ranges
from 0.6-2.0 mg/dL." A value less than normal indicates vitamin C deficiency.
