Vitamin C is a water-soluble vitamin that is found primarily in vegetables and fruit. Many mammals can make vitamin C in their own bodies from glucose, but humans and a few other animals cannot, and have to get it from their diet. Vitamin C is best known for supporting a healthy immune system. It also has a vital role in the production of collagen in the body – a protein that is important for the structure of our skin, bones, blood vessels, cartilage and more. Vitamin C is one of the most unstable vitamins in foods – that is, it is easily lost during cooking and even with general exposure to light, air and heat (i.e. in storage).
Primary functions of Vitamin C
- Vitamin C is essential for the production of collagen. Collagen is the most abundant type of protein in the body. It gives shape and support to all our connective tissues, which includes the skin, bones, blood vessels, gums and teeth, the cartilage in our joints, and our ligaments and tendons that hold our bones and muscles together. This means that vitamin C is also vital for healing and repair of these tissues.
- Vitamin C is important for immune function. It may have several roles here, including supporting the body’s primary barrier against invasion by microbes – our skin and the internal linings of our body. It may also have a role in increasing the activity of our immune cells such as neutrophils and lymphocytes, and increasing production of antibodies and other immune chemicals.
- Vitamin C is an important antioxidant. It protects our cells against oxidative damage (free radical damage) and more specifically, protects water-soluble molecules in the body – including DNA. Vitamin C also helps to recycle vitamin E, a primary fat-soluble antioxidant.
- Vitamin C supports energy metabolism in the body. This means it contributes to our body’s ability to create energy from the food that we eat.
- Vitamin C supports iron metabolism. It can increase the absorption of ‘non-heme’ iron that is found in plant foods such as spinach. Vitamin C may also have a wider role in iron metabolism, including supporting the production of ferritin – the storage form of iron in the body, and decreasing loss of iron from the body’s cells.
- Vitamin C is involved in production of vital brain chemicals such as noradrenaline and serotonin. Noradrenaline is involved with the body’s ‘fight or flight’ response to stress, while serotonin is the brain chemical most associated with mood and wellbeing.
How much do we need?
The EU nutrient reference value for vitamin C for adults is 80mg. Nutrient reference values refer to the amount needed to ensure that the needs of nearly all the population (97.5%) are being met.
However, it’s thought that the optimal amount of vitamin C may be much greater than this. Animals make several thousand milligrams (mg) a day in their bodies – and may produce up to tens of thousands of milligrams in some cases. The Linus Pauling Institute advises that 400mg of vitamin C a day is nearer to an optimal and safe level for adult men and women. More than this may be indicated at times of greater need – see Dosages below for more information.
The best food sources of vitamin C include:
- Fruits: citrus fruits (especially the peel), kiwi fruits, blackcurrants, papaya, strawberries, pineapple and persimmons (‘sharon fruit’).
- Vegetables: broccoli, peppers, kale, Brussels sprouts, herbs such as chives and parsley, sugar snap peas, and raw red cabbage.
As an indication, a kiwi fruit may contain around 80mg of vitamin C, a cup of broccoli (when raw) about 80mg, and half a cup of blackcurrants around 100mg. However, actual levels can be very dependent on how they have been grown and how long – or under what conditions – they have been stored and transported.
Deficiency signs and symptoms*
Symptoms of vitamin C deficiency may include:
- Bleeding gums, easy bruising and poor wound healing (related to poor collagen production)
- Poor resistance to infection
- Mood changes or depression
- Rough skin
When severe, vitamin C deficiency is known as scurvy, and this can cause more severe versions of the symptoms above, as well as diarrhoea, shortness of breath, severe pains in the limbs and the joints, swollen gums and anaemia.
*If you experience any of these symptoms, please consult your doctor or health practitioner.
Forms and bioavailability
There are many different forms of supplemental vitamin C on the market. These include:
- L-ascorbic acid – the ‘pure’ vitamin C molecule. This is often the cheapest form.
- Mineral ascorbates, such as calcium ascorbate and magnesium ascorbate. These forms are ‘buffered’, meaning they are less acidic than pure L-ascorbic acid. This means that they can be gentler on the digestive system. These forms can also provide useful amounts of the minerals they are attached to (i.e. calcium, or magnesium). However, the vitamin C itself is not thought to be any better absorbed in this form than pure L-ascorbic acid.
- Ester-C®. This is a combination of calcium ascorbate (one of the buffered, gentle forms of vitamin C, as above) with small amounts of a form called dehydroascorbic acid and calcium threonate, xylonate and lyxonate. This form has been reported in animal studies to be better absorbed than standard ascorbic acid, although there don’t seem to be any good quality human studies to back up this idea. Some small human studies have found it more useful for specific purposes, such as reducing urinary oxalate levels (which can lead to kidney stones). Like other buffered forms, it can be better tolerated than standard vitamin C.
- ‘Food-form’ / ‘wholefood’ vitamin C. Most vitamin C in supplements is isolated ascorbic acid, or ascorbic acid attached to minerals in buffered form. In contrast, ‘food-form’ or ‘wholefood’ vitamin C provides naturally occurring vitamin C in the form of fruit powders, such as cherry, amla fruit, camu camu or rosehips, or combinations of these. These are said to contain more naturally occurring phytonutrients such as bioflavonoids that are found with vitamin C in whole foods. They are said to be better retained and utilised in the body compared to isolated vitamin C. However, the doses of actual vitamin C found in these supplements tends to be quite a lot lower than other forms.
- Time-release vitamin C. This is a standard vitamin C – usually plain L-ascorbic acid – that is specially coated to ensure it is released more slowly in the digestive system. This may be a good way to get more out of high-dose (i.e. greater than 500mg) vitamin C products. However, it may not be advised for those who have a weak digestive system or poor absorption.
Adults: Standard dosages for adults can vary from about 200mg a day to several grams a day. The maximum dose recommended on supplements tends to be between 1,000mg and 3,000mg a day. Some practitioners recommend using vitamin C up to ‘bowel tolerance’ for certain situations or individuals. This means the maximum amount that does not cause digestive irritation for the individual – for some people this may be up to 10g (10,000mg) or more. For general, long-term use, we believe that 500mg a day is a good amount to use, in line with the recommendations of the Linus Pauling Institute. In ‘food-form’ vitamin C supplements, 200mg or less may be enough.
Children: Children’s vitamin C supplements tend to provide no more than about 500mg as a daily dose. Practitioners may advise more than this where required.
What to look out for when buying a supplement
As we saw above, there may not be a great deal of difference in absorption between the different forms of vitamin C.
- For those who are not affected by the acidity of vitamin C, then the standard L-ascorbic acid (often just labelled ‘Vitamin C’) may be sufficient.
- For those need a gentler form, the buffered forms such as calcium ascorbate, magnesium ascorbate, mixed ascorbates or Ester-C® can be better.
- For those who prefer to get their vitamin C from the most natural sources, the ‘food-form’/ ‘wholefood’ vitamin C supplements are a great choice.
- For those who want to take a high dose vitamin C (e.g. 1000mg) once a day rather than smaller amounts over the course of the day – and they have generally good digestion – then the time-release vitamin Cs can be a good option.
If you are taking any medications or have any medical condition, please consult your healthcare practitioner before taking vitamin C.
For those not taking medication, vitamin C is generally considered a safe supplement at low or high levels and for most people. ‘Too much’ tends to be very dependent on the individual – if you’ve taken too much (which for most people is somewhere between 2,000 and 10,000mg), then you will experience loose bowels or other digestive upset, and this is an indication that you should lower your dose.
- http://lpi.oregonstate.edu/mic/vitamins/vitamin-C [This link leads to a website provided by the Linus Pauling Institute at Oregon State University. Lifestyle Labs is not affiliated or endorsed by the Linus Pauling Institute or Oregon State University.]
- Bush MJ, Verlangieri AJ. An acute study on the relative gastro-intestinal absorption of a novel form of calcium ascorbate. Res Commun Chem Pathol Pharmacol. 1987 Jul;57(1):137-40.
- Moyad MA et al. Vitamin C with metabolites reduce oxalate levels compared to ascorbic acid: a preliminary and novel clinical urologic finding. Urol Nurs. 2009 Mar-Apr;29(2):95-102.
- Gruenwald J et al. Safety and tolerance of ester-C compared with regular ascorbic acid. Adv Ther. 2006 Jan-Feb;23(1):171-8.
- Haas, E. and Levin, B. (2006). Staying healthy with nutrition. Berkeley: Celestial Arts. P.142
- Lane DJ, Richardson DR. The active role of vitamin C in mammalian iron metabolism: much more than just enhanced iron absorption! Free Radic Biol Med. 2014 Oct;75:69-83.
- Haas, E. and Levin, B. (2006). Staying healthy with nutrition. Berkeley: Celestial Arts. P.141