Micronutrients: Vitamin C

Micronutrients: Vitamin C

This week we will move on from fat-soluble to water-soluble vitamins, starting with vitamin C.

Most plant and animal tissues are able to synthesise vitamin C from glucose, however humans (along with other primates) are some of the few mammals unable to do this. This means that we must get our vitamin C from an external dietary source.

 Functions

Also known as ascorbic acid, vitamin C has several important functions in the body:

  • Like vitamin E, vitamin C is another powerful antioxidant, helping to protect cells and keep them healthy by scavenging free radicals.
  • It helps the body to absorb iron.
  • It is involved in the synthesis of collagen, which is necessary for the maintenance of healthy connective tissue, blood vessels and cartilage.
  • It also helps wound healing.

 

Sources:

  • Citrus fruits such as orangesVitamin C Sources
  • Orange juice
  • Red and green peppers
  • Strawberries
  • Blackcurrants
  • Broccoli
  • Brussels sprouts
  • Potatoes

Vegetables such as peppers, broccoli and sprouts etc. are good sources however major losses of the vitamin can occur during food storage, preparation and cooking.

 

Deficiency

Deficiency is rare but it can lead to the development of scurvy, a condition characterised by swollen gums, bleeding, joint and bone pain and reopening of previously healed wounds. Sub optimal vitamin C status can be associated with people who are just out of surgery, smokers and those individuals who have poor diets with little fresh food.

 

Requirements

The Food Safety Authority of Ireland recommends an intake of 60 mg/day for healthy adults. These RDAs are slightly higher than the EU and the UK recommended intakes of 40 mg/day. Vitamin C cannot be stored in the body so it must be included in the diet every day.

People often take high dose vitamin C supplements in the belief that it boosts immune function and helps prevent against cold. However research to date has found that although megadoses may benefit individuals exposed to brief periods of extreme physical stress (marathon runners for example), they are unlikely to reduce incidence of colds in the general population.

Regular supplementation in excess of 200mg per day may reduce the duration and severity of cold Vitamin C Supplementsymptoms to some extent but it probably of little clinical benefit. It has been suggested that in these higher doses, vitamin C may work as a weak antihistamine, reducing histamine levels in the blood. The effects of histamine include sneezing, blocked or runny nose, blocked sinuses etc. This would help explain why some people find improvements in their symptoms when increasing vitamin C intake. However there is also the very real possibility that this all may be down to the placebo effect. There is no shortage of evidence supporting the therapeutic effect of faith in treatment.

 

To minimise nutrient losses:

  • Wash fruits and vegetables before cutting or peeling
  • Steam over a small amount of water or quickly stir-fry veg to preserve heat-sensitive vitamins and to prevent vitamin loss in cooking water.
  • Recapture dissolved vitamins by using cooking water for soups, stews, or gravies.
  • In general, avoid high temperatures and long cooking times.

 

More Information

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Liam Leech, BSc (Hons) Sport and Exercise Science, MSc. ANutr.

Liam Leech

BSc (Hons) Sport and Exercise Science, MSc. ANutr.

 

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