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Vitamin C, also known as ascorbic acid, is vital for life, yet humans are among the few mammals that are unable to make their own supplies. Goats, for example, normally produce up to 13g of vitamin C every day, with synthesis increasing further during times of stress. Quite why we and some other primates lost or never acquired the ability to make vitamin C is one of the great mysteries of human biochemistry.
It is thought to have resulted from a genetic mutation 60 million years ago which, at the time, did not matter as our ancestors obtained enough supplies from their vegetarian diet, including berries and leaves such as purslane.
Vitamin C is essential for making collagen – the main structural protein in the body. It helps to maintain youthful skin, healthy bones and teeth, strengthens joint cartilage and contributes to immunity and energy production.
Dietary sources of vitamin C include most fruit and vegetables, especially lemon, limes, oranges and other citrus fruit, berries, blackcurrants, capsicum peppers, kiwi fruit and green leafy vegetables – an excellent reason to make sure you get your 5 a day.
A mild lack of vitamin C is associated with non-specific symptoms such as frequent colds and other infections, lack of energy, weakness and muscle and joint pain. This is sometimes referred to as pre-scurvy syndrome.
A more severe deficiency is associated with the potentially fatal disease of scurvy (hypoascorbaemia), which is associated with easy bruising, rough scaly skin, bleeding gums and poor wound healing due to impaired collagen production.
Vitamin C helps to maintain youthful skin, healthy bones and teeth, strengthens joint cartilage and contributes to immunity
A minimum daily intake of 10mg vitamin C is needed to prevent scurvy, and 20mg per day is needed for normal wound healing. The EU nutrient reference value (NRV) for vitamin C is 80mg, but this is widely considered to be too low.
When 7 healthy volunteers followed a diet supplying less than 5mg vitamin C per day for up to 6 months, the amounts subsequently needed to saturate their tissues suggested that the recommended daily intake of vitamin C should be increased to 200mg per day for optimal health.
The safe upper level for long-term use from supplements is 1 gram (1000mg) per day, although higher amounts can be taken in the short term (such as when treating a common cold).
Vitamin C is available in a variety of forms, from tablets, capsules, sustained-release versions and effervescent tablets and gummies (for those who dislike swallowing tablets). What's more, the type of vitamin C within these products can also vary.
In its basic form, vitamin C is acidic – hence its chemical name of ascorbic acid – so that high doses above 1 gram of vitamin C can cause indigestion in some people. When these high doses enter the alkaline environment of the lower digestive tract, an interaction known as Acid Rejection Syndrome can also trigger flatulence, diarrhoea and discomfort, as well as reduced vitamin C absorption.
These indigestion and laxative side effects are largely due to the acidity of vitamin C itself and are not a sign of toxicity.
If you are sensitive to the acidity of vitamin C, this can usually be overcome by taking a so-called Gentle Vitamin C supplement, in which the acidic vitamin is buffered by a mineral such as calcium to chemically neutralise the acid and form calcium ascorbate.
Another way to reduce potential side effects and to maximise absorption is to take a Sustained Release Vitamin C supplement, which delivers the dose slowly rather than all in one go.
If you don't like swallowing tablets, vitamin C supplements are available in chewable gummy form or as effervescent drinks.
For those who are not sensitive to acidity and who do not have difficulty in swallowing, non-chewable tablets supplying 1000mg of vitamin C are usually excellent value.
There are also premium supplements designed to make sure you absorb as much vitamin C as possible from your supplement. These combine vitamin C with plant-sourced fatty acids and bioflavonoids.
These added components act as carriers to enhance intestinal absorption, with a 233% increased uptake into cells compared with other forms of vitamin C, greater retention inside cells and a greater antioxidant capacity; all while remaining stomach-friendly. Healthspan's optimal-absorption vitamin C product is called Opti-C.
Dr Sarah Brewer is Healthspan's Medical Director and holds degrees in Natural Sciences, Surgery and Medicine from the University of Cambridge. Having worked as a GP and hospital doctor, Dr Sarah now holds an MSc in Nutritional Medicine from the University of Surrey and specialises in nutrition. She is also an award-winning writer and author.