Vitamin C: What it is and why it’s important to athletes
Vitamin C is well-known for its role in keeping your immune system healthy, but its importance doesn't end there says sports nutritionist Stephen Smith. Here he explains all you need to know about this important vitamin
What is Vitamin C?
Vitamin C, along with the B vitamins, is one of the water-soluble vitamins. This means they dissolve well in either fats or water. As body water turns over relatively quickly, water-soluble vitamins aren’t stored in large amounts within the body, so it’s important that we regularly acquire them through our diets. We typically excrete water-soluble vitamins through the urine, which is why some multi-vitamins can leave our urine looking some bright shades of yellow.
What does Vitamin C do?
Vitamin C, or ascorbic acid, has a number of functions within the human body but is well known as an antioxidant, meaning it can help prevent cell damage. Vitamin C also plays an important role in the immune system, and helps with iron absorption and collagen development too. As such, you often see vitamin C being combined zinc, iron or collagen supplements, to aid with immune, blood and joint health.
Why is vitamin C important for athletes?
Vitamin C is important for immune health, so it’s imperative that triathletes get enough vitamin C as it may help prevent or reduce the length of colds and respiratory tract infections, meaning less training time lost to illness. Being deficient in vitamin C can lead to a range of symptoms, such as gum problems, dry hair and skin, and wounds taking longer to heal.
Also, importantly for the triathlete, vitamin C deficiency can be linked with anaemia, i.e. low levels of red blood cells or haemoglobin, which are essential for transporting oxygen around the body to hard-working muscles.
How much vitamin C do athletes need?
The typical recommendations for daily intake of vitamin C range from 30-75mg, depending on country, but I’d say to take this as a minimum. It’s not difficult to meet this amount if you’re eating a wide range of fruits and vegetables, for example, a typical 250ml glass of pure orange juice will contain about 125mg of vitamin C.
What foods are rich in vitamin C?
I’m sure we’re all aware of the story about sailors being given citrus fruits like oranges and lemons to eat to help prevent scurvy. This is because citrus fruits are particularly high in vitamin C, but other food sources rich in this important vitamin include: broccoli, kiwi, strawberries, bell peppers, tomatoes, white and sweet potatoes, and berries such as blackberries, raspberries or blueberries.
Should you take a vitamin C supplement?
Most athletes I speak to are already taking a multi-vitamin, which will more than meet the RDA. However, I’d recommend trying to meet the requirement from food rather than a supplement. Generally, there’s no need for daily supplementation with vitamin C if you’re eating a wide range of the fruits and vegetables mentioned above. There are times though where I will recommend vitamin C supplementation, such as at the onset of a cold, during international travel or when an athlete is recovering from a soft-tissue injury.
It’s important to note, though, that research has shown excessive amounts of vitamin C blunt the adaptions we’re trying to achieve from training. Chronic daily supplementation with 1,000mg of vitamin C has been shown to interfere with the cellular signals, which lead to positive training adaptions.
Paulsen et al (2014). Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial.J Physiol. 2014 Apr 15; 592(Pt 8): 1887–1901.
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Stephen Smith
Performance nutritionist 
