Vitamin C and experimental and field studies

1. By: Mohammad S. El-Lulu
Master of Clinical nutrition
Palestine - Gaza

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3. • Ascorbic acid, is a water-soluble micronutrient that is
easily excreted from the body when not needed.
• Person's age and health status can dramatically change
his or her need for vitamin C. (Levine M, 1986).
• Vitamin C is better absorbed in the presence of
flavonoids.
• The buffered forms should combine vit-C with minerals
like calcium, magnesium, or potassium. Buffered vit-C
may be helpful for individuals who have stomach
sensitivity (Worthington-Roberts B., Breskin M., 1984).
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4. • The protective role of vitamin C can help our skin and
gums from pinpoint hemorrhage (scurvy disease).
Cardiovascular diseases, cancers, and joint diseases are
all associated with vitamin C deficiency and can be partly
prevented by optimal intake of vitamin C (Kurl S et al,
2002).
• Vitamin C achieves much of its protective effect by
functioning as an antioxidant and preventing oxygen-
based damage to our cells. Structures that contain fat
(like the lipoprotein molecules that carry fat around our
body) are particularly dependent on vitamin C for
protection (Reaven PD, Witztum JL: 1996).
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5. • The vitamin C deficiency disease called scurvy (including
bleeding gums and skin discoloration due to ruptured
blood vessels).
• Poor wound healing.
• Weak immune function, including susceptibility to colds
and other infections.
• The lining of respiratory tract depend heavily on vitamin
C for protection, respiratory infection and other lung-
related conditions can also be symptomatic of vitamin C
deficiency (Englard S, Seifter S, 1986).
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6. • At high supplemental doses involving 5 or more grams of
vitamin C, diarrhea can result from the fluid in the
intestine becoming too concentrated ("osmotic diarrhea").
• Large supplemental doses of vitamin C can also increase
levels of uric acid in the urine, because vitamin C can be
broken down into uric acid. However, it is not clear that
increased uric acid in the urine can increase a person's
risk of forming uric acid kidney stones.
• Vitamin C can increase a person's absorption of iron from
plant foods (Levine M, Cantilena CC, Dhariwal KR,
1995).
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7. • Collagen is one type of fiber found within connective
tissue. Collagen fibers are made from protein, and they
are somewhat unusual in having large amounts of two
amino acids, called hydroxylysine and hydroxyproline.
These two amino acids seem to be important for
formation of all types of collagen and are needed to
provide the different collagen types with their appropriate
amount of strength and flexibility.
• Vitamin C is required to change proline into
hydroxyproline (the collagen form) and lysine into
hydroxylysine (once again, the collagen form) (Mirhadi SA
et al., 1990).
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8. • Poor intake of vitamin C-rich vegetables and fruits is a
common contributor to vitamin C deficiency.
• Smoking and exposure to second hand smoke also
increase the risk of vitamin C deficiency.
• The body's immune and detoxification systems make
special use of vitamin C, and overload in either of these
systems can increase risk of deficiency.
• The immune system protect the body from infection,
including white blood cells, complement proteins,
interferons; and vitamin C is especially important in the
function of these immune components (Groff JL, Gropper
SS, Hunt SM, 1995).
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9. • Most forms of cardiovascular disease, joint disease,
cancer, eye disease, thyroid disease, liver disease, and
lung disease require special emphasis on vitamin C
intake. The process of aging itself requires special
attention to vitamin C. In addition to these broader
categories, several specific health conditions also require
special emphasis on vitamin C. These specific health
conditions include (Subar A., Block G., 1990):
• Acne and Alcoholism, Alzheimer disease and asthma.
• Autism, depression and diabetes.
• Irritable bowel disease and Parkinsonism.
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10. According to National Academy of Sciences which established the
following (RDA) Recommended Dietary Allowances in 2000 for vitamin C:
Age in years Male Female
1-3 (adequate intake) 15 mg
4-8 (adequate intake) 25 mg
9-13 45 mg
14-18 75 mg 65 mg
19 and older 90 mg 75 mg
Pregnant females 80-85 mg
Lactating females 115-120 mg
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11. Food Sources
(adapted from world healthiest food; WHFood’s)
Food Serving size Calories Vit-C (mg)
Bell peppers, red, raw, slices 1 cup 24.8 174.8
Broccoli, steamed 1 cup 43.7 123.4
Strawberries 1 cup 43.2 81.70
Lemon juice, fresh ¼ cup 15.3 28.06
Grapefruit ½ each 36.9 46.86
Kiwifruit 1 each 46.4 57.00
Cantaloupe 1 cup 56.0 67.52
Oranges 1 each 61.6 69.70
Tomato, ripe 1 cup 37.8 34.38
Banana 1 each 108.1 10.75
Apples 1 each 81.4 7.87
Grapes 1 cup 61.6 3.68
Avocado, slices 1 cup 235 11.53
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13. • Every 500 mg increase in vitamin C intake, a man’s risk
of gout was cut by 17 percent. And for men with vitamin
C intakes of at least 1,500 mg/day, the risk of gout was
cut by 45 percent, said the findings of a prospective study
with 46,994 men.
• Mechanism: Vitamin C may reduce levels of uric acid in
the blood, thereby preventing the formation of the urate
crystal. This may be achieved by vitamin C having an
effect on the reabsorption of uric acid by the kidneys.
This would increase the speed at which the kidneys work
or protect against inflammation, all of which may reduce
gout risk, they added (Choi H.K., Gao X., Curhan G.,
2009).
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14. • Block and her co-workers recruited 242 women aged between
18 and 21. Two-thirds of the women were African-American,
while the other third was Caucasian. The blood levels of
vitamin C of the women ranged from 0.22 to 3.13 mg/dL.
• During follow-up over a ten year period, the researchers noted
that blood vitamin C levels were inversely associated with both
systolic and diastolic blood pressure.
• Mechanism: due to potential role for vitamin C via an
antioxidant mechanism, there is also possibility other
functions. These include a role in the function of smooth
muscle function, or prevention of nitric oxide which is a
vasodilator or compound that opens up the blood vessels
(Block G et al., 2008).
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15. • Vitamin C deficiency in the first weeks and months of life may
impair the development of neurones in the brain, and
decrease spatial memory, says an animal study from
Denmark.
• The Danish researchers took 30 new born guinea pigs and
randomly assigned them to one of two groups: One group was
fed a vitamin C-sufficient diet, while the other group was fed
the same diet but low in vitamin C. Levels of vitamin produced
deficiency, but were not extreme enough to cause scurvy.
• After two months, the animals were tested in a water maze,
and hippocampal neuron numbers were measured. Prof
Lykkesfeldt and his co-workers report that the vitamin C
deficient animals had a lower number of neurons in the
hippocampus, and also performed worse in the maze tests
(Lykkesfeldt J. et al., 2009).

16. • Increased intakes of vitamin C may increase the risk of
developing cataracts in some elderly people, according to a
new study.
• Findings from 24,593 Swedish women aged between 49 and
83 indicated that vitamin C use was associated with a 25
percent increase in the incidence of cataracts.
• Among the older women – over the age of 68 – vitamin C
supplements were associated with a 38 percent increase in
the risk of cataracts, report the researchers in the American
Journal of Clinical Nutrition.
• The findings were further complicated in women on hormone
replacement therapy, where the supplements were associated
with a 56 percent increase in cataracts (Rautiainen S. et al.,
2009).
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17. • Higher levels of vitamin C from the diet may reduce the
loss of bone mineral density in elderly men.
Protective mechanism:
• Sahni and co-workers state protective effects of vitamin
C for bone health could be expected since the vitamin
could counter the effects of oxidative stress, which plays
a role in weakening of the bone by resorption.
• Furthermore, vitamin C plays an important role in the
formation of collagen, which constitutes 90 percent of the
bone matrix (Sahni S. et al., 2008).
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18. • Vitamin C may reduce the effectiveness of chemotherapy
by protecting the cancer cells.
• Using lymphoma and leukemia cell lines with and without
pre-exposure to dehydroascorbic acid (DHA), Heaney
and his co-workers investigated the effects of the anti-
cancer drugs doxorubicin, cisplatin, vincristine,
methotrexate, and imatinib.
• They found that the efficacy of the chemotherapy drugs
tested was greatly reduced if the cells were pre-treated
with vitamin C, compared to untreated cancer cells.
Indeed, the reduction ranged from 30 to 70 percent,
report the researchers (Heany et al., 2008).
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19. • Administration of a physiological dose of [6S]-5-MTHF
• [6S]-5-methyl-tetra-hydro-folate with L-ascorbic acid
significantly improved the measured serum folate
response in folate saturated healthy men.
• When [6S]-5-MTHF was concurrently administered with
289.4 or 973.8 mg [vitamin C], the total serum folate
response was significantly improved (46.54.0 and
53.04.0 versus 34.33.8 h nmol/l) (Verlinde P.H.C.J et al.,
2007).
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20. • Increased blood levels of vitamin C may reduce the risk
of developing diabetes by 62 percent, says a study from
Cambridge.
• “Fruit and vegetable consumption may be protective for
diabetes risk, at least partially, through its effect on
obesity.”
• Oxidative stress, the situation in which an imbalance
between the levels of reactive oxygen species and
antioxidants exists, can lead to disturbed glucose
metabolism and hyperglycaemia (Harding A. et al).
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21. • Increased blood levels of vitamin C may reduce the risk of
stroke by 42 percent, suggests a large European-based study.
• Strokes occur when blood clots or an artery bursts in the brain
and interrupts the blood supply to a part of the brain.
• Myint and co-workers followed the subjects for 9.5 years and
documented 448 strokes during this time. The subjects
completed a health and lifestyle questionnaire at the start of
the study, and blood samples were taken to measure vitamin
C levels.
• The highest average blood levels of vitamin C (greater than 66
micromoles/litre) were associated with a 42 percent lower risk
of stroke, compared to the lowest average blood levels (less
than 41 micromoles/litre) (Myint P.K.et al, 2008).
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22. References:
• Block G, Jensen C.D., Norkus E.P., Hudes M., Crawford P.B., (2008). Vitamin C in plasma is
inversely related to blood pressure and change in blood pressure during the previous year in young
Black and White women. Nutrition Journal. 7:35 doi:10.1186/1475-2891-7-35.
• Choi H.K, Gao X., Curhan G., (2009). Vitamin C Intake and the Risk of Gout in Men: A Prospective
Study. Archives of internal medicine. 169 (5): 502-507.
• Englard S, Seifter S (1986). The biological functions of ascorbic acid. Ann Rev Nutr 1986;6:365-
406.
• Groff JL, Gropper SS, Hunt SM (1995). Advanced Nutrition and Human Metabolism. West
Publishing Company, New York, 1995.
• Harding A.-H, Wareham N.J., Bingham S.A., Khaw K., Luben R., Welch A., Forouhi N.G. Plasma
Vitamin C Level, Fruit and Vegetable Consumption, and the Risk of New-Onset Type 2 Diabetes
Mellitus - The European Prospective Investigation of Cancer - Norfolk Prospective Study. Archives
of Internal Medicine. 168 (14): 1493-1499.
• Heaney M.L., Gardner J.R., Karasavvas N., Golde D.W., Scheinberg D.A., Smith E.A., O’Connor
O.A, (2008). Vitamin C Antagonizes the Cytotoxic Effects of Antineoplastic Drugs. Cancer
Research. Volume 68: 8031-8038. doi: 10.1158/0008-5472.CAN-08-1490.
• Kurl S, Tuomainen TP, Laukkanen JA et al (2002). Plasma vitamin C modifies the association
between hypertension and risk of stroke. Stroke 2002 Jun;33(6):1568-73.
• Levine M (1986). New concepts in biology and biochemistry of ascorbic acid. N Engl J Med
1986;314:892-902.
• Levine M, Cantilena CC, Dhariwal KR (1995). Determination of optimal vitamin C requirements in
humans. Am J Clin Nutr 1995;62(suppl):1347S-1356S.
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23. References:
• Lykkesfeldt J., Tveden-Nyborg P., Johansen L.K., Raida Z., Villumsen C.K., Larsen J.O., (2009).
Vitamin C deficiency in early postnatal life impairs spatial memory and reduces the number of
hippocampal neurons in guinea pigs. American Journal of Clinical Nutrition. doi:
10.3945/ajcn.2009.27954.
• Mirhadi SA, Singh S, Gupta PP (1990). Effect of Garlic Supplementation to Atherogenic Diet on
Collagen Biosynthesis in Various Tissues of Rabbits. Indian Heart J.;42(2):99-104.
• Myint P.K., Luben R.N., Welch A.A., Bingham S.A., Wareham N.J., Khaw K.-T, (2008). Fruit and
vegetables: think variety, go ahead, eat!. American Journal of Clinical Nutrition. Volume 87: 5-7.
• Rautiainen S., Ejdervik Lindblad B., Morgenstern R., Wolk A., (2009). Vitamin C supplements and
the risk of age-related cataract: a population-based prospective cohort study in women.
doi:10.3945/ajcn.2009.28528.
• Reaven PD, Witztum JL (1996). Oxidized low density lipoproteins in atherogenesis: role of dietary
modification. Ann Rev Nutr 1996;16:51-71.
• Sahni S., Hannan M.T., Gagnon D., Blumberg J., Cupples L.A., Kiel D.P., Tucker K.L., (2008). High
vitamin C intake is associated with lower 4-year bone loss in elderly men. Journal of Nutrition.
Volume 138: 1931-1938.
• Subar A, Block G (1990). Use of vitamin and mineral supplements. Am J Epidem 1990;132:1901-
1011.
• Worthington-Roberts B, Breskin M (1984). Supplementation patterns of Washington State
dietitians. J Am Diet Assoc 1984;84(7):795-800.
• Verlinde P.H.C.J., Oey I., Hendrickx A.M., Van Loey A.M., Temme E.H.M., (2007). L-ascorbic acid
improves the serum folate response to an oral dose of [6S]-5-methyltetrahydrofolic acid in healthy
men. European Journal of Clinical Nutrition. doi: 10.1038/sj.ejcn.1602840.
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