Vitamin C, also called ascorbic acid, exists as either ascorbic acid or ascorbate[1]. It is a water-soluble vitamin and found in many fresh fruits and vegetables[1]. It is also found in many dietary supplements[2]. Vitamin C is vital for various physiologic functions, such as synthesizing collagen and catecholamines and carnitine and peptide synthesis [1]. It is not manufactured in the human body, and deficiency can cause scurvy[1].
Oral vitamin C is an antioxidant supplement for immune protection against colds, flu, wound healing, cardiovascular health, and cancer prevention[1]. High-dose intravenous vitamin C is being studied
for treating cancer[1]. Food sources of vitamin C include- Kakadu plums, Acerola
cherries, Lemons, Brussel sprouts, Kale, Rosehips, Chilli peppers,
Guava, Sweet Yellow pepper, Thyme, Blackcurrant, Parsley,
Spinach, Kiwis, Litchis, Papaya, Strawberries, Oranges etc.[3]
Health Benefits
Common Cold
The advantages of vitamin C in fighting the common cold are
more assumed than evidenced by research[4]. According to a
2007 review of many studies, including 11,306 participants,
vitamin C supplements did not decrease the rate of colds in
participants compared to the general population[4].
But the authors noted that vitamin C could benefit performance
athletes or people living in icy climates[2].
A review study of 2013 from Finland shows that vitamin C cannot
prevent colds but may reduce their course by up to about 8% in
adults and 14% in children with a daily dosage ranging from
1,000- to 2,000-milligram dose[2].
Vision Loss
There is partial evidence that vitamin C supplements may slow
macular degeneration, an ageing-related eye disorder identified
by vision loss[2].
A 2001 study in Archives of Ophthalmology stated that people at
high risk of the disease who consumed 500 milligrams of vitamin
C per day and beta-carotene, vitamin E, and zinc delayed the
development of macular degeneration by 25% and the loss of
visual acuity by 15%.6[2].
A review from Tufts University concluded that taking 135
milligrams of vitamin C per day can stop some types of cataracts
and that doses of at least 363 milligrams could decrease the risk
of developing cataracts by not less than 57%.[2].
High Blood Pressure
The advantages of vitamin C in treating high blood pressure have
long been lauded, although the actual effects are not nearly as
solid as once believed[2].
In a study of 2012 from Johns Hopkins University, it was
demonstrated that high doses of vitamin C of around 500
milligrams daily produced only slight declines in systolic blood
pressure but had an insignificant effect on diastolic blood
pressure[5].
While scientists have yet to discover why this is, it is assumed
that strong doses of vitamin C have a slight diuretic effect that
supports removing excess fluid from the body and may help to
subside the pressure within your blood vessels[2].
Heart Disease and Cancer
Vitamin C is often erroneously complimented for its ability to
fight heart disease and cancer[2]. Much of the misperception
has been kindled by vitamin C’s antioxidant properties[2].
While antioxidants appear to decrease the oxidative stress
linked with these diseases, there is little to no proof that vitamin
C supplements can directly influence the risk[2].
Amongst the clinical findings:
● A 10-year study including 14,641 men above the age of 50
showed that a 500-mg dose of vitamin C did not change
heart attacks or stroke rates compared to a placebo[2].
● A 5-year study comprising 77,721 older women and men also
showed no correlation between vitamin C consumption and
the risk of lung cancer[2]
● A nine-year study including 8,171 older women explained
that 500 milligrams of vitamin C have no influence on
cancer rates compared to the general population[2].
Other benefits include:- treating vitamin C deficiency, cold,
bronchitis, wound healing, glaucoma, arthritis etc.[2].
MECHANISM OF ACTION
Ascorbic acid works as an antioxidant to protect against
oxidative damage from free radicals[1]. It inactivates nitric oxide,
enhances endothelium-dependent vasodilation, and acts by
different mechanisms depending on its plasma concentration[1].
Plasma concentrations of less than 0.1mM are accomplished
through oral consumption of dietary or supplemental forms[1].
At pharmacologic plasma concentrations ranging from 0.3 –
20mM through intravenous injection(IV), ascorbic acid is
oxidized to ascorbate radical[1]. This radical acts as a prodrug
for hydrogen peroxide generation inside interstitial fluids[1]. As a
result of which DNA damage and adenosine triphosphate (ATP)
depletion occur[1]. Also, it triggers ataxia telangiectasia mutated
adenosine monophosphate-activated protein kinase (AMPK) and
inhibits the mammalian target of rapamycin (mTOR) in cancer
cells[1].
Another study claimed that ascorbate could direct
hematopoietic stem cell function and leukemogenesis[6]. In
leukaemia, vitamin C compensated for Tet2 mutations to
recover normal function[1]. Pharmacological ascorbate
selectively stimulated these cells in non-small-cell lung cancer
(NSCLC) and glioblastoma (GBM) cells[1]. Ascorbate reduces
colon cancer cell proliferation by downregulating specificity
proteins[1]. It also lessens ATP levels and induces autophagy and
cell death in prostate cancer cells[1]. Preferred oxidative
cytotoxic effects on cancer cells may be due to the presence of
intracellular iron, copper, overexpression of sodium-dependent
vitamin C transporter 2 (SVCT-2), and an increase in p53
activity[1]. Furthermore, high-dose vitamin C was known to
inhibit metastasis of breast cancer cells by inhibiting epithelial-
mesenchymal transition[1].
The oxidized form of ascorbic acid, such as dehydroascorbic
acid, may have cytoprotective effects by maintaining
mitochondrial membrane potential[1].
HEALTH RISKS
Common side effects include nausea, vomiting, heartburn,
stomach cramps[1-2].
Case reports for Oral Consumption of Vitamin C.
Patients with a history of kidney stones have shown
nephrolithiasis, acute renal failure or renal insufficiency and
increased oxalate kidney stone formation[1].
Hemolytic anaemia: May happen at extreme doses in patients
with G6PDH deficiency[1].
Severe cyanide poisoning: With concomitant use of three grams
of amygdalin and 4800mg of vitamin C per day[1].
Dental caries or eroded dental tooth: With extreme usage of
chewable tablets[1].
Case reports for Intravenous administration of Vitamin C.
During infusion:-
The typical reaction includes increased urinary flow and
thirst[1].
Isolated incidences include nausea, vomiting, unpleasant
fluttering in the abdomen, chills, and headaches[1].
After infusion:-
Isolated incidences include confusion, increased leg edema
persisting for a few days[1].
DOSAGE and APPLICATION
Usually, Vitamin C is available as a dietary supplement in tablet,
capsule or powder form. For topical administration as a skin
cream and also Vitamin C can be administered intravenously.
Orally:-
● Children 0 – 6 months: 40milligrams per day
● Children 7 – 12 months: 50 milligrams per day
● Children 1 – 3 years: 15 milligrams per day
● Children 4 – 8 years: 25 milligrams per day
● Children 9 – 13 years: 45 milligrams per day
● Females 14 – 18 years: 65 milligrams per day
● Males 14 – 18 years: 75 milligrams per day
● Females of 19years and above: 75 milligrams per day
● Males of 19 years and above: 90 milligrams per day
● Pregnant females 14 -18: 80 milligrams per day
● Pregnant females 19 years and above: 85 milligrams per day
● Breastfeeding females 14 – 18: 115 milligrams per day
● Breastfeeding females 19 years and above: 120 milligrams
per day1
People who smoke should take an extra 35 milligrams per day[2].
Those diagnosed with vitamin C deficiency should take between
100 to 200 milligrams per day until blood levels are
normalized[2].
Dosage for topical administration:-
● For erythema: A formulation containing 10% vitamin C, 2%
zinc sulfate, and 0.5% tyrosine used daily for eight[7].
● Skin wrinkles from sun damage: Usually, topical vitamin C
products are applied daily[7]. Studies have used creams
containing 3% to 30% vitamin C[7]. Do not use vitamin C
preparations to the eye or eyelids[7]. Also, please avoid
contact with clothes or hair as it can cause
discolouration[7].
Dosage for IV administration:-
● For atrial fibrillation: 2 grams of vitamin C once or twice in
the day before going for heart surgery followed by 1-2
grams for 4-5 days daily after heart surgery[7].
● For decreasing pain after surgery: 3 grams of vitamin C for
the first 30 minutes of surgery has been used[7].
PRECAUTIONS/WARNINGS
Be aware of consuming a large amount of Vitamin C as it can
cause:-
● Repeated kidney stone formation[1]
● Hemochromatosis[1]
● Observed G6PDH deficiency[1]
● Renal impairment or on chronic hemodialysis[1]
For Special group:-
Pregnant and Lactating: Vitamin C is LIKELY SAFE for pregnant
or breastfeeding women when consumed orally in a
concentration of 2000 mg/day for women above 19 years old
and 1800 mg daily for women 14 – 18 years old or when given
administered intravenously or intramuscularly[7]. Consuming
too much vitamin C during pregnancy can cause problems for
the newborn baby[7]. It is POSSIBLY UNSAFE when ingested
orally in excessive amounts[7].
Children and infants: Vitamin C is LIKELY SAFE when
consumed orally[7]. It is POSSIBLY UNSAFE when ingested
higher than 400 mg daily for children of age group 1 -3 years,
650 mg daily for children 4 to 8 years, 1200 mg daily for children
9 – 13 years, and 1800 mg daily for adolescents 14 to 18 years[7].
It is recommended that before taking Vitamin C, consult your
doctor.
INTERACTIONS
Iron: Ascorbic acid enhances iron absorption and modulates
storage and transport in the body[1]. Notable in patients with
hemochromatosis[1].
Chemotherapeutic drugs: Vitamin C may decrease the
effectiveness of some antineoplastic agents, including
vincristine, doxorubicin, methotrexate, etc.[1].
Bortezomib: Ascorbic acid consumption lessens the activity of
bortezomib[1]. In a clinical trial using these agents collectively,
the interaction is reduced by administering bortezomib and
ascorbic acid in the morning and evening, respectively[1].
Glutathione: Glutathione is an antioxidant that decreases the
pro-oxidant cytotoxic effects of ascorbic acid[1].
Beta-blockers: Ascorbic acid can improve the cardioprotective
effects of beta-blockers in post-bypass patients[1].
Paracetamol: When consumed simultaneously, vitamin C
increases the absorption of paracetamol in healthy volunteers
and may increase the risk of side effects[1].
KEYWORDS:- cancer, cancer, lung cancer, glioblastoma, colon
cancer, leukaemia, non-small cell lung cancer, prostate cancer,
breast cancer, metastasis, leukemogenesis
REFERENCES
[1]https://www.mskcc.org/cancer-care/integrative-
medicine/herbs/vitamin-c#references-1
[2]https://www.verywellhealth.com/the-benefits-of-vitamin-
c-supplements-89083
[3]https://www.healthline.com/nutrition/vitamin-c-
foods#TOC_TITLE_HDR_5
[4]Hemilä, Harri, and Elizabeth Chalker. “Vitamin C for
preventing and treating the common cold.” Cochrane database of
systematic reviews 1 (2013).
[5]Juraschek, Stephen P., et al. “Effects of vitamin C
supplementation on blood pressure: a meta-analysis of
randomized controlled trials.” The American journal of clinical
nutrition 95.5 (2012): 1079-1088.
[6]Agathocleous, Michalis, et al. “Ascorbate regulates
haematopoietic stem cell function and leukaemogenesis.” Nature
549.7673 (2017): 476-481.
[7]https://www.webmd.com/vitamins/ai/ingredientmono-
1001/vitamin-c-ascorbic-acid
