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Registered in England No. 2530437

Issue 70

A - Z Nutrients - Vitamin C

Vitamin C (ascorbic acid) is a ubiquitous
compound, present in the physiologies of almost all plants and animals. Humans,
other high primates, fruit bats and guinea pigs cannot produce their own bodily
supply of vitamin C, and consequently require a regular dietary intake.

Vitamin C is an unstable water-soluble vitamin that is sensitive to heat, air,
water (by leaching) and alkali (e.g. bicarbonate of soda). Certain metals,
e.g. copper also speed the oxidative destruction of vitamin C.

What does it do?

Vitamin C has very many functions in the
body - some still not completely understood. Below are listed some of the processes
in which it is involved:

Formation of collagen - the bodys intracellular

Growth, tissue repair and wound healing

Formation of antibodies and stimulation
of the white blood cell

Formation of corticosteroid hormones in
the adrenal gland

Absorption of iron and its necessary accumulation
in the bone marrow, spleen and liver

As an antioxidant nutrient, it protects
water-soluble substances from oxidation by allowing itself to be oxidised.

As an anti-histamine, vitamin C reduces
the effect of histamine produced by the immune system. Histamine is responsible
for many of the symptoms of allergies such as hay fever.

Carnitine formation in vegetarians, together with lysine.

What are the deficiency signs?

The classic vitamin C deficiency disease is scurvy,
early symptoms of which are usually bleeding of the gums and loosening of the
teeth, together with lassitude, weakness, irritability and muscle ache.

A prolonged marginal deficiency of vitamin C may not
lead to clinical symptoms, but may predispose towards heart disease and lowered

Is it toxic?

Vitamin C is on the whole extremely safe, with no toxic
effects even at dosages of grams per day. Transient diarrhoea is the usual side-effect
that is noted when excess levels are taken .

The only other possibility of danger from high vitamin
C intake occurs in people who have a family history of kidney stones, as oxalate
can combine with calcium to form the stones. However, people who are not at
high risk of kidney stones do not need to avoid vitamin C.

Taking very high doses of vitamin C - 5000 mg a day
and up - and then suddenly stopping the supplementation has been thought to
possibly cause "rebound scurvy". However a recent review has shown
there is no real basis for this belief. Nevertheless it is perhaps advisable
to come off high level vitamin C slowly.

Who should supplement?

The daily requirement of vitamin C should be obtained
through diet if current dietary guidelines are followed. However, those who
are wishing to boost the immune system during the winter months may benefit
from an extra vitamin C supplement.

Intake levels: milligrams (mg)

Upper safe level for daily supplementation = 2000mg

Recommended Daily Allowance = 60mg

(Smokers requirements are increased by 80mg)

Which foods?

Food (mg/100g)

Blackcurrants 200

Pepper, green 100

Brussels sprouts 90

Mango 80

Cauliflower 60

Cabbage 55

Oranges 50

Grapefruit 40

Sweet Potato 25

Tomatoes 20

Potatoes: new 16; Oct-Dec 19; Jan-Feb 9; Mar-May 8

Lettuce 15

Bananas 10

The main sources of vitamin C in the diet are potatoes,
fruit juices, citrus fruit and green vegetables. The vitamin C content of foods
varies very widely depending upon season, variety and freshness.


Vitamins are essential to maintain normal metabolic processes
and balance within the body, and the role of vitamin C is probably the most
varied of all vitamins making it the most versatile. The amount of a specific
vitamin required by an individual varies considerably and it is influenced by
such factors as body size, growth rate, physical activity, and pregnancy. Most
vitamins are stored minimally in human cells and vitamin C is no exception.

Vitamin C is a water-soluble vitamin, which means it
is easily excreted by the body if it is not used quickly. It is for this reason
that timed-release vitamins are useful for prolonging tissue saturation and
preventing wastage of the water-soluble vitamins. However, the fat-soluble vitamins
are stored in liver cells to a greater extent. Vitamins A and D, for example,
may be stored in sufficient amounts to maintain an individual without any intake
for 5 to 10 months and 2 to 4 months, respectively.

However, a deficiency of vitamin B compounds (except
vitamin B12) may be noted within days, and the lack of vitamin C will manifest
within weeks and may result in death in 5 to 6 months. The current recommended
dietary allowance (RDA) of vitamin C is 60 mg, which is based on the vitamins
role as an antioxidant as well as protection from deficiency.

A severe deficiency of vitamin C will result in a state called scurvy, and it
is thought that only 10mg of vitamin C is needed per day to prevent this. Early
symptoms of scurvy include excessive bleeding of the gums, and it is the ability
of vitamin C to strengthen collagen fibres that causes this. Collagen is one
of the most abundant proteins in the human body and is incorporated into connective
tissues, which include tendons, ligaments and blood vessels.

All proteins are made up of amino acids and collagen
is built using a repeating sequence of three amino acids called glycine, proline
and hydroxyproline. Hydroxyproline is produced by the addition of oxygen to
the proline amino acid once incorporated into the collagen structure, and this
is achieved by vitamin C. If vitamin C is absent, this conversion will not take
place and the collagen fibre will break down causing weakened connective tissue
and weakened arteries. This is primarily the reason why death can result if
no vitamin C is consumed for 5-6 months.

High intakes of the vitamin are generally well tolerated,
and it is generally accepted that tolerance levels of vitamin C will vary among
individuals. Where some could easily consume 5g of vitamin C a day without experiencing
any adverse effects, others may only be able to tolerate 500mg. Several populations
warrant special attention with respect to vitamin C requirements. These include
patients with periodontal disease, smokers, pregnant and lactating women, and
the elderly.


Scientific studies have determined the effects of chronic
vitamin C intake on the immune systems antioxidant defences during the immune
response induced by intense exercise. Blood samples were taken from 16 voluntary
athletes in normal conditions, both immediately after and 1 h after a duathlon
competition. Sportsmens nutrient intakes were determined before the competition.
After determining the normal blood vitamin C levels, the results were analysed
taking into account the vitamin C intake and their blood levels.

Two groups were constituted; the vitamin C supplemented
group and the control group, with the dietary vitamin C intake as the only statistical
difference between groups. The intense exercise induced a significant increase
in the production and distribution of white blood cells involved in the immune
response, which was higher in the supplemented group. The results showed that
high vitamin C intake influenced the response of the immune systems antioxidant
defences to oxidative stress induced by exercise. Therefore it can be concluded
that high vitamin C intakes before intense exercise results in an increased
immune response by white blood cells.

Free Radic Res. 2003 Sep;37(9):931-8


The antioxidant properties of vitamin C in the carotid
body (tissue that monitors the levels of oxygen) make it a likely nutrient for
detecting low blood oxygen levels. This study aimed to determine the effect
of vitamin C on breathing rate in a population of elderly women, in whom blood
oxygen and vitamin C levels may be deficient. The study used 18 healthy females
aged 60-80 years, and were given 1g of vitamin C twice daily. They found that
vitamin C improved the detection of low blood oxygen levels by an average of
44%. It was concluded that supplementation of vitamin C could improve the bodys
reaction to low blood oxygen levels.

J Int Med Res. 2003 Sep-Oct;31(5):448-57

Passive Smoking

Exposure to environmental tobacco smoke (ETS) has been
linked to increased risk of lung cancer and heart diseases in non-smokers. Current
research suggests that some of these diseases are associated with increased
damage to cells. A study investigated the effect of antioxidant (AO) intervention
on damage in the blood of non-smokers exposed to ETS (passive smokers). They
measured cell damage in the blood of 67 passive smokers, at the beginning and
after 2 months of daily intervention with AOs or placebo. The study subjects
were randomised into one of three treatment groups: vitamin C, "mixture"
(vitamin C, vitamin E, and a-lipoic-acid), and placebo. Oxidative stress in
subjects in the vitamin C and mixture groups decreased significantly when compared
with the placebo group. Daily AO supplementation (especially with vitamin C)
decreases damage to blood system cells in passive smokers. This finding might
be of importance for the prevention of ETS-associated adverse health effects
in non-smokers.

Nutr Cancer. 2003;45(2):176-84

The Heart

The aim of this study was to examine the relation between
vitamin C intake and risk of heart disease in women. Results from other investigations
on relation between vitamin C intake and risk of heart disease have been inconsistent.
In 1980, 85,118 female nurses completed a detailed food-frequency questionnaire
that assessed their consumption of vitamin C and other nutrients. Nurses were
followed up for 16 years for the development of incident heart disease. During
16 years of follow-up (1,240,566 person-years), they identified 1,356 incident
cases of heart disease. After adjustment for age, smoking, and a variety of
other coronary risk factors, they observed a modest significant inverse association
between total intake of vitamin C and risk of heart disease. Among women who
did not use vitamin C supplements or multivitamins, the association between
intake of vitamin C from diet alone and incidence of heart disease was weak
and not significant. In multivariate models adjusting for age, smoking, and
a variety of other coronary risk factors, vitamin C supplement use was associated
with a significantly lower risk of heart disease. Users of vitamin C supplements
appear to be at lower risk for heart disease.

J Am Coll Cardiol. 2003 Jul 16;42(2):246-52

Although dietary intake and blood levels of vitamin
C have been inversely associated with heart disease, the mechanism through which
it may exert its effect has not been fully explained. Since the clotting of
blood plays an important role in the onset of heart disease, we investigated
the effect of vitamin C on measures of certain markers that have been associated
with the risk of heart disease. 2 g daily of vitamin C supplementation was given
and cholesterol levels were 10% lower when subjects were receiving vitamin C
compared to placebo. Therefore vitamin C supplementation may be useful for the
reduction of blood cholesterol levels which in turn will reduce the risk of
heart disease.

Thromb Res. 2000 Oct 1;100(1):35-41


Experimental evidence suggests that administration of
high-dose vitamin C has beneficial vascular effects in type 2 diabetes. Thirty
patients, 45 to 70 years of age, with type 2 diabetes, were randomly assigned
to receive 500 mg vitamin C daily by mouth or placebo. The results showed that
after 1 month, oral vitamin C lowered blood pressure and improved arterial stiffness
in patients with type 2 diabetes. As strict control of blood pressure reduces
heart disease risk in diabetes, vitamin C supplementation may potentially be
a useful and inexpensive therapy.

Hypertension. 2002 Dec;40(6):804-9

Cell Protection

The human organism is incapable of producing vitamin
C on its own. We are therefore totally dependent on the presence of this vitamin
in our diet. Vitamin C is capable of essentially influencing the course of many
metabolic processes, and it is therefore used in the treatment and guard against
many diseases, including those that are a consequence of the activity of the
so-called reactive forms of oxygen. The presence of vitamin C in the anti-oxidant
protective system is believed to be very important, since it can react with
the free radicals of oxygen and other oxidants, and "sweep" them away.
Therefore, attention is more and more frequently focused on the possibility
of using vitamin C in the treatment of those circulatory diseases that are believed
to be associated with the action of free radicals. Routine administration of
vitamin C should be therefore recommended in the treatment of patients with
heart disease, treatment of patients after heart attack or in the treatment
of blood pressure.

Pol Merkuriusz Lek. 2001 Feb;10(56):122-5

The Bones

Vitamin C is known to enhance collagen synthesis, and
stimulate bone cell formation. Studies of dietary vitamin C intake and the relation
with bone mineral density (BMD) have been conflicting. The purpose of this study
was to evaluate the independent relation of daily vitamin C supplement use with
BMD in postmenopausal women. Subjects were 994 women of whom 277 women were
regular vitamin C supplement users. Daily vitamin C supplement intake ranged
from 100 to 5,000 mg and it was discovered that women taking both estrogen and
vitamin C had significantly higher BMD levels at all sites. Vitamin C supplement
use appears to have a beneficial effect on levels of BMD, especially among postmenopausal
women also using estrogen therapy and calcium supplements.

J Bone Miner Res. 2001 Jan;16(1):135-40

Cigarette Smoke

Recent results indicate that cigarette smoke induces
the damage of human blood proteins which is almost completely prevented by vitamin
C. Cigarette smoke-induced damage of proteins and blood fats are accompanied
by a decrease in the tissue vitamin C levels. Also, the cigarette smoke-induced
damage of proteins and lipid is reversed after discontinuation of cigarette
smoke exposure accompanied by vitamin C therapy. The results indicate that comparatively
large doses of vitamin C may protect the smokers from cigarette smoke-induced
damage and associated degenediseases such as heart disease.

Free Radic Biol Med. 2000 Jul 15;29(2):115-24


Vitamin and Mineral Safety, Council for Responsible
Nutrition: 1997

Health Essentials, Vitamin Guide: 1994

Manual of Nutrition (MAFF): 1989

The Vitamin Bible, Earl Mindell: 1988

Heart Disease

Scientific studies have shown that regular intakes of saturated fat is directly
associated with an increased risk of heart disease.

This study estimated that a 22% to 37% lower risk of heart disease could be
achieved by replacing saturated fat with healthier fats including polyunsaturated
and monounsaturated fatty acids. This could be achieved by supplementation or
increasing oily fish intake.

The study discovered that a higher intake of cholesterol
and saturated fat were related to increased heart disease risk among women with
type 2 diabetes. Among diabetic persons, replacement of saturated fat with monounsaturated
fat may be more effective in lowering heart disease risk than it is replacement
with carbohydrates.

Am J Clin Nutr 2004;79:999-1005

Fish oils

A study aimed to investigate whether British Indo-Asian
Sikhs have higher blood fat concentrations, and lower dietary intakes of long
chain omega-3 polyunsaturated fatty acids (PUFAs) than do age and weight matched
Europeans. Results showed that at the start, the Indo-Asians had significantly
higher blood fat, and omega-6 PUFA values and significantly lower long chain
omega-3 PUFAs (EPA and DHA) than did the Europeans. A significant decrease in
blood fat and a significant increase in EPA and DHA levels were observed after
fish oil supplementation.

Am J Clin Nutr 2004;79:974-82

Heart Disease

Both low vitamin B6 and elevated inflammatory markers
are related to higher risk of heart disease.

A study was carried out with 742 participants, 475 with
severe heart disease and 267 free from coronary atherosclerosis. Heart disease
risk factors such as homocysteine were measured. Results showed that the prevalence
of B6 concentrations in the lower half of the population was significantly higher
among heart disease patients than among heart disease-free subjects. Results
showed that low plasma B6 concentrations are inversely related to major markers
of inflammation and independently associated with increased risk of heart disease.

Am J Clin Nutr 2004;79:992-8

Body Fat

Healthy overweight men and women aged 18 to 65, received
capsules containing either 4.5 grams CLA-free fatty acid, 4.5 grams CLA-triglycerides
or 4.5 grams of olive oil (placebo). After six months, individuals taking either
form of CLA experienced a significant reduction in body fat mass, while those
in the placebo group saw no change. Both forms of CLA were equally effective
in body fat mass reduction and considered safe, when used for one year in healthy,
overweight adults.

Based on the findings of this one-year study the researchers
concluded that CLA taken either in the natural or free fatty acid form in healthy,
overweight adults for one year, results in a significant decrease of body fat.

American Journal of Clinical Nutrition, 2004; 79(6):1118-1125

Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) comprises
a range of behavioural problems including inattention, hyperactivity and impulsiveness.
Diagnosis and treatment of the disorder is made difficult due to its unknown
biological basis. Several studies have identified abnormalities in membrane
fatty acids in some subjects with ADHD, and some success has been reported using
lipid therapies. The data suggests that some patients with ADHD have higher
rates of oxidative breakdown of omega-3 polyunsaturated fatty acids. Such a
biochemical abnormality may underlie the previously observed fatty acid deficiencies,
as well as providing further rationale for the use of anti-oxidant and/or lipid
supplementation therapy in the treatment of ADHD.

Nutr Neurosci. 2003 Oct;6(5):277-81

Mental Development

Docosahexaenoic acid (DHA, an Omega-3 fatty acid) and
arachindonic acid (AA, an Omega-6 fatty acid) are long-chain polyunsaturated
fatty acids (LCPs) that are important for mental development. Research has shown
that LCPs are associated with improved visual and cognitive development: breast-fed
children had higher IQ scores compared with children who received an infant
formula that did not contain LCPs. Because breast milk contains LCPs and the
formulae in these studies did not, it is possible that LCPs may contribute to
improved cognitive development.

J Fam Health Care. 2002;12(6 Suppl):5

Cell Protection

CLA, a derivative of a fatty acid called linoleic acid
is unique because unlike most antioxidants which are components of plant products,
it is present in food from animal sources such as dairy foods and meats. CLA
concentrations in dairy products typically range from 2.9 to 8.92 mg/g fat.
Dietary CLA improves certain aspects of the immune defence. It is now thought
that CLA itself may not have anti-oxidant capabilities but may produce substances
which protect cells from the negative effects of harmful oxygen molecules.

J Am Coll Nutr 2000 Apr;19(2 Suppl):111S-118S

Evidence has shown that consumption of diets high in fruits and vegetables is
associated with reduced risk of cancers. A study aimed to determine whether
a decrease in DNA damage following exposure to harmful oxygen species could
be provoked in immune cells. The capacity for repair of different types of DNA
damage. Damage to DNA following exposure to harmful oxygen molecules decreased
more rapidly in immune cells from volunteers given the mixed carotene capsules
and DNA repair mechanisms in immune cells increased from volunteers given the
cooked carrots. These results suggest that carotenoids and carotenoid-rich foods
can influence DNA damage/repair by modulation of discrete stages in the DNA
repair mechanisms.

Br J Nutr. 2004 Jan;91(1):63-72

Prostate Health

In a study seventy-six prostate cancer patients between
ages 50 and 80 were supplemented with 60mg soy isoflavones or placebo for a
12 week period and changes in size of prostate and steroid hormones were analysed.
Serum testosterone was reduced or showed no change in 61% of subjects in the
isoflavone group compared to 33% in the placebo group. Prostate size decreased
or was unchanged in 69% of the subjects in the isoflavone treated group compared
to 55% in the placebo group. These data suggest that supplementing early stage
prostate cancer patients with soy isoflavones may alter prostate size and testosterone
levels in a larger number of subjects.

Prostate. 2004 May 1;59(2):141-7.

Baby Health

A study was undertaken to evaluate whether zinc supplementation
during pregnancy affects babys heartbeat. At 10 to 16 weeks gestation, women
received supplements containing 60 mg iron, 250 µg folic acid with or
without 25 mg zinc. Zinc supplementation was associated with lower heart rate,
greater number of accelerations, and greater heart rate variability. Supplementation
effects on heart rate and accelerations were more pronounced after 28 weeks
gestation. Prenatal supplementation of zinc-deficient mothers may be beneficial
to foetal nervous system development.

Am J Obstet Gynecol. 2004 Apr;190(4):1106-12.


A study was carried out to investigate the effect of
glucosamine sulphate on long-term symptoms in postmenopausal women with knee
osteoarthritis (OA).

After 3 years, postmenopausal participants in the glucosamine sulfate group
showed no joint space narrowing, whereas participants in the placebo group experienced
narrowing. Percent changes after 3 years showed an improvement in the glucosamine
sulfate group and a trend for worsening in the placebo group.

Menopause. 2004 Mar-Apr;11(2):138-43.

Bone Health

A study was conducted to determine whether one year
of supplemental calcium intake would increase bone mineral density in the hip,
spine and the femor (upper leg bone) in female distance runners. 23 women received
either 1000mg/d of supplemental calcium or placebo tablets for a year. Calcium
supplementation prevented loss in the femor. The study concluded that the addition
of 800mg/d of supplemental calcium to the diet of young adult female distance
runners with regular calcium intakes of approximately 1000mg/d, prevents bone
mineral loss and therefore will help keep bones stronger.

Int J Sport Nutr Exerc Metab. 2004 Feb;14(1):7-17.


The aim of this study was to clarify a potential therapeutic
role of coenzyme Q(10) (CoQ(10)) in infertile men with poor sperm movement.
CoQ(10) was administered orally and semen samples were collected at the start
and after 6 months of therapy. CoQ(10) levels increased significantly in sperm
cells after treatment and a significant increase was found in sperm cell motility.
Therefore administration of CoQ(10) may play a positive role in the treatment
of poor sperm movement. This is probably the result of its role as an energy
providing nutrient and its antioxidant properties.

Fertil Steril. 2004 Jan;81(1):93-8.

Nutrition during Pregnancy

Women can safely commence omega 3 intake in early pregnancy
to allow the full benefits to be incorporated into the body. Pregnant women
should consider the intake of omega-3 oils and evening primrose oil throughout
pregnancy in order to possibly prevent premature delivery, promote an easier
birth, assist the babys brain and eye health and create the perfect conditions
for the babys cell membranes which will promote optimum lifelong wellness.
Benefits to the mother may include prevention of postnatal depression and the
comfort of knowing that she is giving her baby a healthy start in life.

Midwifery Today Int Midwife 2004 Spring;(69):26-31

Circulatory Health

This research evaluated the effect of supplementation
of omega-3 and omega-6 fatty acids on blood vessel function in healthy men and
women aged 40 to 65. 173 healthy volunteers took one of six oil supplements
for 8 months. Supplements were placebo, oleic acid rich sunflower oil, evening
primrose oil, soya bean oil, tuna fish oil, and tuna/evening primrose oil mix.
As a conclusion, fish oil supplementation has a beneficial effect on blood vessel
function even in normal healthy subjects. Improvement of the diet by an increase
of 6% in eicosapentaenoic acid (EPA) and 27% in docosahexaenoic acid(DHA) (equivalent
to eating oily fish 2-3 times/week) might have significant beneficial effects
on circulatory function and health.

Cardiovasc Res.2003 Oct 1;59(4):955-62

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