Vitamin C is one of the most well studied vitamins due to its obvious impacts on human health. In 1932, the relationship between vitamin C and scurvy was discovered, and in 1975, we learned about the role of vitamin C as an antioxidant. As an antioxidant, vitamin C removes reactive oxygen species from the body and protects it from being damage. These “redox” reactions help to reduce inflammation, thus reducing our risk of illness and disease (with inflammation being at the core of most disease states). Vitamin C is also used to produce the master antioxidant and detoxifier of the body, glutathione. Glutathione is known to boost energy levels, strengthen the immune system to prevent illness and infection, fight inflammation and clear toxins (e.g., sugar, alcohol, heavy metals, chemicals, pollution, etc.), improve recovery after exercise, repair damaged cells and slow down the aging process. Basically, more glutathione equals better health and vitality!
Vitamin C has a dual responsibility in decelerating the ageing process to keep us looking and feeling young (…or younger!) via its antioxidant properties and by providing a co-substrate for the synthesis of collagen – a protein that forms connective tissue and gives plumpness to the skin and cushioning to the joints. Look at any “anti-wrinkle” face cream and you will sure see “collagen” spread across the front label. Imagine your skin is an inflated balloon. Over time, a balloon will deflate and become floppy and wrinkly (sound familiar, anyone?). Collagen is like the helium air that re-inflates the balloon to fill out those wrinkles and keep it as plump as possible!
Signs & Symptoms of Deficiency
A deficiency in vitamin C results in the failure to form connective tissue (from collagen). An extreme deficiency, known as scurvy, is characterised by bleeding gums, pain in the extremities, oedema, fatigue, ulceration and death. A marginal deficiency in vitamin C leads to non-specific symptoms such as; loss of appetite, weakness, tiredness, wrinkled skin, poor wound healing and low immunity (e.g., frequent coughs and colds). A deficiency in vitamin C may also lead to or worsen a deficiency in iron (i.e., an essential mineral) due to its “helper” properties for iron absorption. When vitamin C and iron are consumed together (e.g., lemon juice squeezed over an egg omelette), vitamin C grabs a tight hold of iron to help the body absorb more of it. So, if there isn’t enough vitamin C coming in, then iron may not be getting well absorbed. This is a particularly important point for vegetarians and vegans who consume less bio-available sources of iron and are at an increased risk of becoming iron deficient (i.e., non-haem iron in plant foods).
Recommended Daily Intake
Clinical scurvy is known to occur at vitamin C intake levels of 7 to 8 mg or less per day. The recommended daily intake is set at amounts well-beyond those needed to prevent scurvy. However, vitamin C is not only needed to prevent scurvy – it supports many essential functions in the human body (…did I mention its anti-ageing properties!?). Adults require 45 mg of vitamin C each day, while pregnant women require 60 mg daily to cater for the incredible development of a new human. Lactating women need 85 mg daily. Babies are not born with the best immune systems so they require relatively high amounts of vitamin C for antioxidant support. Vitamin C also helps synthesise the additional collagen that is required for rapid growth during infancy.
Population data shows that Australian adults generally consume adequate amounts of vitamin C, with men consuming an average of 103 milligrams per day and women consuming an average of 85 milligrams per day. Vitamin C itself is not toxic. However, for people affected by haemochromatosis (i.e., iron storage disease), their condition will worsen with increased vitamin C intake. This is because vitamin C increases the absorption of iron, and haemochromatosis is a problem of iron excess in the body (leading to chronic iron toxicity if left unmanaged).
Supplementation of vitamin C may be indicated for people exposed to periods of severe physical stress. For example, hospitalised patients who are recovering from illness, infection and/or surgery may require up to 250 mg per day (under medical supervision). Research investigating the use of high-dose vitamin C as an adjunct to cancer treatment is also promising, but more high-quality scientific trials are needed. People who undertake regular strenuous exercise may also require higher amounts of vitamin C (i.e., more than 45 mg per day) as it is involved in energy production, tissue regeneration and repair. Regular smoking may also increase one’s risk of becoming vitamin C deficient, alongside the tremendous list of other negative health outcomes.
Dietary Sources of Vitamin C
Many foods contain good amounts of vitamin C. However, it should be recognised that by the time certain foods reach your mouth, their vitamin C content may have declined significantly. Vitamin C content declines with time (e.g., length of storage) and temperature (e.g., cooking of raw vegetables, thawing of frozen vegetables). Fresh fruit and vegetables that are consumed raw or lightly stir-fried are the best sources of vitamin C. Choosing local produce that hasn’t endured excessive travel and storage is another great way to get the most vitamin C out of your fruit and veggies. Even better, grow your own!
The well-known recommendation to consume two servings of fruit and five servings of vegetables everyday is heavily influenced by our requirement for vitamin C. Although it is a myth that only fruit and vegetables contain vitamin C. It is possible for someone following a “Carnivore”-type diet or a therapeutic low-fibre diet (i.e., meat only, little or no vegetables) to achieve an adequate vitamin C intake considering vitamin C is found in meat and animal products (Table 2), though in lesser amounts.
To account for the loss of vitamin C with time and temperature, aim for a vitamin C intake that is double your recommended daily intake (RDI). For example, if you are a non-pregnant or lactating adult, you should aim to include 90 mg of vitamin C in your diet each day. Across a whole day, you could reach this by consuming 100 g cooked cauliflower (45 mg), 50 g cooked peas (25 mg), 10 g sundried tomato (10 mg), 30 g pistachio nuts (2 mg), and 200 g cooked salmon (8 mg).
Table 1. Vitamin C Content in Plant Foods
Table 2. Vitamin C Content in Animal Foods
Take-Home Points
Vitamin C is essential for collagen production and tissue repair.
Vitamin C is one of the three vitamins that are also classed as antioxidants (i.e., vitamins A, C and E). Antioxidants protect against inflammation and disease.
Glutathione, produced from vitamin C, is a powerful antioxidant and detoxifier.
A severe deficiency in vitamin C causes scurvy. A mild deficiency in vitamin C can cause wrinkled skin, weakness, poor wound healing and low immunity.
Pregnancy, lactation, and periods of high stress (including work-related stress, exercise, illness and injury) require and increased intake of vitamin C.
Fruit and vegetables are the richest sources of vitamin C, though heating and storage practices significantly reduce their vitamin C content. When it comes to fruit and veggies, choose local produce and lightly stir-fry.
Meat and animal products contain vitamin C and it is possible to achieve an adequate vitamin C intake without fruit and vegetables, if necessary.
By Jessica Turton
Accredited Practising Dietitian
This article provides general information from the current scientific evidence base and clinical judgement of the author. It is designed for educational purposes only and should not be substituted for medical advice. The author recommends you seek personally tailored support from a qualified healthcare practitioner before undertaking any major lifestyle change.
References
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United States Department of Agriculture. USDA Food and Nutrient Database – Vitamin C. Cited 25 June 2018. Available from https://ndb.nal.usda.gov/ndb/nutrients
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