Daily requirement of vitamin C
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Dr Sean Bulley from Plant & Food Research along with Carolyn Cairncross from the New Zealand Nutrition Foundation explain the importance of vitamin C in the diet. Examples of plant foods rich in vitamin C are given, and advice is offered about the efficacy of vitamin C supplementation.
Point of interest
Some nutritionists believe that the daily dose of vitamin C is best taken in by consuming a plant food, like kiwifruit, rather than in tablet form. What is the reason for this?
DR SEAN BULLEY
In the body, vitamin C plays two major roles. It is required for the proper functioning of many different enzymes and to make properly functional collagen. The other role that vitamin C plays is it acts as an antioxidant. It helps detoxify free radicals that occur just through daily life, and this is incredibly important for continued health and wellbeing.
Foods that supply vitamin C are our citrus foods, so things like oranges, mandarins, lemons, fruits such as kiwifruit, and also vegetables have vitamin C in them, and potatoes are a good source of vitamin C.
There is very limited evidence that vitamin C supplements have a positive health benefit. There are research studies that show that the incidence of colds isn’t reduced but the severity is, so your cold will only be shortened for half a day, so it’s not a major benefit of vitamin C supplements.
The recommended daily intake for adolescents is slightly higher than that for adults and that’s to take into account growth, but it’s only 45 milligrams per day. When you consider that vitamin C supplements are often 1,000 or 2,000 milligrams per day, you can see that you are taking far more than what is required in your daily diet.
With vitamin C, it’s water soluble, and so the excess will be excreted, but you can take too much of it, as it interferes with the action of other nutrients. It’s far better to get your vitamin C from some food, and an orange will provide your daily vitamin C requirements.