<p>Only isolated in 1928 as ‘antiscorbutic factor’, vitamin C is an essential water soluble nutrient. Humans are one of the few species that cannot synthesise it themselves as we lack the enzyme L-guluconolactone oxidase which is required for the conversion of glucose into vitamin C.</p><h2>Practice points</h2><ul><li>As vitamin C is not extensively stored in the body, daily dietary consumption is required</li><li>Vitamin C content of food is affected by cooking techniques and storage - vitamin C is sensitive to light, heat and oxygen</li><li>Vitamin C supplements may be more effective when taken in divided doses</li><li>If taking a chewable form of Vitamin C, rinse the mouth afterwards with water or milk as ascorbic acid may damage tooth enamel over time</li><li>High doses (over 2000 mg/day) may cause loose bowel movements</li><li>High dietary intakes are associated with lower risk of cardiovascular disease, age-related macular degeneration and cataracts</li></ul><h2>Key functions &amp; indications</h2><p><strong>Immune system function: </strong>Modulates T-cell gene expression, stimulates production of interferons (proteins that protect cells against viral attack) and stimulates synthesis of antibodies (IgG, IgM).</p><p><strong>Enhances iron absorption:</strong> Forms soluble complexes, enhances absorption of non-haeme iron. Supplement alongside iron for iron-deficiency anaemia.</p><p><strong>Antioxidant :</strong> At physiological concentrations, vitamin C is the most effective aqueous antioxidant in plasma and tissues.</p><p><strong>Collagen synthesis:</strong> Assists wound healing and skin integrity.</p><p><strong>Neurotransmitter synthesis:</strong> Cofactor for biosynthesis of noradrenaline and serotonin, modulates catecholamine transmission and is neuroprotective.</p><p><strong>Anti-histamine:</strong> Via inhibition of release and enhanced degradation of histamine.</p><h2>Risk factors for deficiency/insufficiency</h2><ul><li>Fussy eaters with a limited food variety</li><li>Cigarette smoking, high alcohol consumption, pregnancy and lactation, thyrotoxicosis, chronic inflammatory disease, after major surgery and burns, infections and diabetes</li><li>Decreased absorption may occur with achlorhydria</li><li>Increased excretion may occur with chronic diarrhoea</li><li>Diabetics who significantly reduce their intake of fresh fruit and vegetables</li></ul><p>  
</p><img src="https://images.contentstack.io/v3/assets/blt948bd74310fc0ad0/blt339b983c4ba222a9/69f34450c7c3ba50efd05e08/vitamin_c_wheel.png" alt="vitamin_c_wheel.png" class="embedded-asset" /><p><em>*Scurvy occurs with frank deficiency. Frank deficiency is uncommon in Western countries; marginal deficiency states are not uncommon.</em></p><h2>Is scurvy an issue any more?</h2><p>A number of diabetic patients suffering from wounds that refused to heal led to research uncovering a surprising discovery of scurvy amongst Australians. A retrospective cohort study found around two thirds of patients whose wounds were not healing had extremely low levels of vitamin C. After supplementing with vitamin C, the wounds healed. They also received dietary advice. </p><h2>How to prevent scurvy</h2><ul><li>Eat fresh fruit and fresh vegetables</li><li>Good sources of vitamin C are capsicum, tomatoes, broccoli and citrus fruit</li><li>Don’t overcook vegetables</li></ul><h2>Sources</h2><p>Sources include fruit and vegetables particularly citrus fruits, strawberries, rockmelon, chilli, cabbage, cauliflower, broccoli and tomatoes.</p><p><strong>Kiwifruit (gold):</strong> 100 g contains 110 mg of ascorbic acid</p><p><strong>Mandarin (imperial):</strong> 100 g contains 58 mg of ascorbic acid </p><p><strong>Capsicum (red, raw):</strong><strong> </strong>100 g contains 152 mg of ascorbic acid</p><p><strong>Orange: (navel):</strong> 100 g contains 53 mg of ascorbic acid</p><p><a href="http://www.foodstandards.gov.au/science/monitoringnutrients/nutrientables/nuttab/Pages/default.aspx " target="_blank">Search for nutrient content of foods here</a></p><p> </p><h2>Vitamin C and zinc are commonly combined for immune health</h2><p> </p><p> </p>

<h2>Contraindications/cautions</h2><ul><li>In patients who are sensitive to iron overload, vitamin C supplementation may exacerbate iron toxicity by mobilising iron reserves. Supplement with caution in people with erythrocyte glucose-6-phosphate dehydrogenase deficiency, haemochromatosis, thalassaemia major or sideroblastic anaemia</li></ul>

Cautions

<h2>Possible interactions</h2><ul><li><strong>Aluminium-containing antacids: </strong>increases drug side effects. Vitamin C chelates aluminium and increases aluminium absorption. To avoid interaction separate dose of medication by at least 2 hours </li><li><strong>Antihypertensive drugs:</strong> may have an opposing effect to drug a clinical trial 6 weeks in duration with a treatment of both vitamin C 500 mg and grape seed extract 1000 mg increased blood pressure in hypertensive patients. Interaction is possible. Avoid combination of vitamin C and grape seed extract with hypertensive patients </li><li><strong>Desferrioxamine: </strong>opposing drug effect. Vitamin C may cause transient deterioration of cardiac function with desferrioxamine, avoid concomitant use </li><li><strong>Estrogen:</strong> may increase blood levels of the drug. Possible interaction. Use with caution under the supervision of a healthcare professional</li><li><strong>Paracetamol: </strong>high doses of vitamin C (&gt;3g) may decrease the elimination rate of paracetamol. Possible interaction. Use with caution </li></ul><p>For more information visit: <a href="~/link.aspx?_id=4471DACF65C148EA8FD82B23FD6712D4&_z=z">https://www.blackmoresinstitute.org/interactions</a> </p>

Interactions

<h2>Dosage range</h2><ul><li>Adult RDI 45 mg/d</li><li>Optimal intake may be ≥200 mg/d</li><li>Typical supplementary doses range from 500-3000 mg/d</li><li><strong>Treating deficiency in adults:</strong> 100mg taken 3-5 times daily until 4000 mg has been administered followed by a maintenance dose of 100 mg/day</li><li><strong>Respiratory infections:</strong> ≥2 g/day</li><li><strong>Nutrient Reference Values:</strong> <a href="https://www.nrv.gov.au/nutrients/vitamin-c" target="_blank">https://www.nrv.gov.au/nutrients/vitamin-c</a></li></ul>

Dosage

<h2>Supplements</h2><ul><li>Vitamin C is found in low doses in multivitamins and higher doses in stand-alone products up to 1000 mg per dose</li><li>May contain cofactors such as bioflavonoids</li><li>Available forms are ascorbic acid (primary dietary form); mineral ascorbates (calcium and sodium ascorbate) which are buffered to be gentle on the stomach; and ascorbyl palmitate - a fat soluble form used in topical creams and serums</li><li>Chewable and non-chewable tablets and powdered forms are commonly available</li></ul>

Supplements

<p><strong>1. </strong>Braun L, Cohen M. Herbs and Natural supplements. 4th edition. Chatswood: Elsevier 2015 </p><p><strong>2. </strong>Natural Medicines 2016 Professional Monographs https://naturalmedicines.therapeuticresearch.com/databases/food,-herbs-supplements.aspx </p><p><strong>3.</strong> Oregon State University; Linus Pauling Institute; Micronutrient Information Centre 2016 http://lpi.oregonstate.edu/mic </p><p><strong>4. </strong>Australian Government, National health and Medical Research Council and Ministry of Health New Zealand. Nutrient Reference Values for Australia and New Zealand https://www.nrv.gov.au/nutrients </p>

Vitamin C (ascorbic acid)

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