Expert Nutrition

Vitamin C
(Ascorbic Acid)

Vitamin C (ascorbic acid), is a water soluble vitamin that promotes the healing of wounds and is necessary to make and maintain collagen, the connective tissue that holds the body together. Vitamin C is arguably the body’s most important antioxidant and forms the front line defence against oxidative damage caused by free radicals. Because of its powerful antioxidant properties vitamin C has been associated with lowering the risk of heart disease, certain cancers and many health concerns that are generally associated with aging. Vitamin C also plays a very important role in the absorption of iron, helps in the release of energy from fatty acids and in the formation and breakdown of neurotransmitters found within the brain and nervous system.

In 1937 Albert Szent-Gyorgyi won a noble prize for his discovery of a chemical that protected fruits against discolouration and infection when bruised, that chemical substance we now know as vitamin C. Reports of deficiencies in vitamin C date back as early as the 1500's where the disease scurvy affected long sea voyageurs who lacked basic nutrition.

Vitamin C is essential for synthesis of collagen, the most abundant protein in the body. Collagen is a structural protein important for strengthening muscles, teeth, bones, skin, and blood vessels. Without adequate vitamin c, there is inadequate collagen and the integrity of these structures is compromised.

The antioxidant functions of Vitamin C includes scavenging oxygen free radicals (which can cause cellular damage) and in the regeneration of vitamin E. High intakes of vitamin C have been linked with a reduction in certain cancers (especially gastric) and cataracts, however excessive amounts may actually have a negative oxidation effect and damage our DNA.

Some texts, and most nutritional supplement companies believe that the recommended dietary intakes set for vitamin C and other antioxidants may be less than adequate to promote optimal health. It has been suggested that vitamin C intakes 2-3 times higher than the recommended daily intake are a useful objective to protection against some chronic degenerative diseases.

Vitamin C is a water soluble vitamin and therefore needs to be consumed on a regular basis. Good sources of vitamin C include most fruits and vegetables in particular blackcurrants, kiwi fruit, cauliflower, broccoli, honeydew melon, oranges, strawberries and spinach.Vitamin C is also found in beef, liver and kidney but at smaller doses. During the preparation and cooking of fruits and vegetables there can be a considerable loss of the vitamin C content and therefore fresh fruits and vegetables are best.

A popular treatment for the common cold, most studies suggest that it probably won’t prevent your cold, however it may lessen the severity and shorten the duration.

Additional Possible Benefits of Vitamin C3

  • May help reduce the risk of some cancers and heart disease
  • Retards macular degeneration in the eyes of the elderly

Recommended Dietary Intake for Vitamin C

A recent re-evaluation of dietary requirements for all vitamins and minerals was published by the National Health and Medical Research Council for Australia and New Zealand. The dietary recommendations for Vitamin C from this publication are summarised below.

Please refer to the following definitions when interpreting these recommendations:

RDI-Recommended Daily Intake
The average daily intake level that is sufficient to meet the nutritional requirements of nearly all (97-98%) health individuals in a particular life stage and gender group.

AI-Adequate Intake (used when an RDI cannot be determined)
The average daily nutrient intake level based on observed or experimentally-determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate.

UL-Upper Limit of Intake
The highest average daily nutrient intake level likely to pose no adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects increases.

RECOMMENDATIONS BY LIFE STAGE AND GENDER - Vitamin C

InfantsAI
0-6 months25 mg/day
7-12 months 30 mg/day

Children and AdolescentsRDI
All
1-3 years 35 mg/day
4-8 years 35 mg/day

Boys
9-13 years 40 mg/day
14-18 years 40 mg/day

Girls
9-13 years 40 mg/day
14-18 years 40 mg/day

AdultsRDI
Men
19-30 years 45 mg/day
31-50 years 45 mg/day
51-70 years 45 mg/day
>70 years 45 mg/day

Women
19-30 years 45 mg/day
31-50 years 45 mg/day
51-70 years 45 mg/day
>70 years 45 mg/day

Pregnancy
14-18 years 55 mg/day
19-30 years 60 mg/day
31-50 years 60 mg/day

Lactation
14-18 years 80 mg/day
19-30 years 85 mg/day
31-50 years 85 mg/day

It is not possible to establish a Upper Limit for vitamin C, but 1,000 mg/day is a prudent limit.

Source: National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand. Department of Health and Ageing, Canberra 2006, copyright Commonwealth of Australia reproduced by permission.

Vitamin C back to Vitamins


References:
1. Stanton R. Foods that harm, foods that heal: An A-Z guide to safe and healthy eating. Readers Digest; 2006, pp378-382.
2. MacWilliam, L.D. Comparative Guide to Nutritional Supplements. Northern Dimensions Publishing; 2005.
3. Wahlqvist, M.L., et al. Australia and New Zealand: Food and Nutrition. 2nd Ed. Allen and Unwin, Sydney; 2002, pp 259-262.
4. Mann, J., Truswell, S. Essentials of Human Nutrition. Oxford Medical Publications, New York 2000.
5. National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand. Department of Health and Ageing, Canberra 2006, copyright Commonwealth of Australia reproduced by permission.

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