Vitamin C and zinc are known to support innate and adaptive immunity through various mechanisms of action.^1-3 They also provide antioxidant activity which is crucial in offsetting the induction of oxidative stress caused by allergens or deficiencies in key antioxidants, and which is known to play an important role in allergic sensitisation.⁴ Supporting both immune and antioxidant functions are important first steps in preventive clinical care and provide the foundation for a more targeted approach to specific types of allergies.

Dosage Recommendations

Based on research findings, practitioners may consider the following dosing recommendations as outlined below:

 Vitamin C

• Clinically effective dose: Between 100-200 mg of vitamin C are suggested for prophylaxis, while significantly higher doses are needed for treatment,¹ e.g. up to 2g to provide a histamine-lowering effect.⁵
• Duration: While there is no specific data on the duration of use of vitamin C for allergies, 250 to 2000 mg taken for several weeks may provide a histamine-lowering effect.⁵
• Form: Buffered forms of vitamin C (i.e. calcium-, zinc- and sodium ascorbate) do not cause dental enamel erosion,⁶ and are thought to be less irritating to the stomach than ascorbic acid.⁵
• Drug interactions: Vitamin C has significant interactions with a variety of medications, some of which are beneficial, while others are not when co-administered.⁷
  • Methotrexate – contraindicated
  • Aluminium-based antacids - separate doses by at least 2 hours
  • Warfarin, oestrogens, statins, protease inhibitors (i.e. Indinavir) – prescribe with caution
  • Alkylating agents (i.e. Cyclophosphamide), antitumor antibiotics, pentobarbital – theoretical caution only
  • Amoxicillin, L-Dopa – beneficial interaction; coadministration recommended
• Safe dosing: Vitamin C is safe to take long-term as it is water-soluble, with any access being excreted in the urine. A tolerable upper intake level of 2 g of vitamin C has been recommended.⁸ Vitamin C has an extremely low potential for toxicity, with multi-gram supplements reported as causing only mild and transient gastrointestinal effects such as irritation, bloating, and diarrhoea.⁶

 

Zinc

• Clinically effective dose: There is no available clinical data to support specific doses of zinc for allergy prevention or treatment, however, the recommended therapeutic dose to treat deficiency is 25-50 mg elemental zinc for adults⁵ taken daily with meals, followed by 10-20 mg/day to prevent zinc deficiency in adults with low dietary zinc intake.⁹
• Form: Ideal forms of zinc include zinc amino acid chelate, zinc ascorbate, zinc citrate and zinc gluconate.
• Drug interactions: Zinc forms complexes with the following medications which results in reduced absorption and potential reduction in efficacy of both substances:
  • NSAIDs, tetracycline, quinolone - separate doses by at least 2 hours⁵
• Safe dosing: The recommended upper limit of elemental zinc is 40 mg/day from all sources.^8,10

 

Children dosages may be calculated based on adult doses using Young’s Rule or Clarke’s Rule. i.e.:

• Young’s Rule: [Age / (Age + 12)] x Recommended Adult Dose = Paediatric Dose.¹¹
• Clarke’s Rule: (Bodyweight in pounds divided by 150) x Adult Dose = Paediatric Dosage.¹²

 

Clinical Research Update

A review conducted in 2020 investigated the role of intracellular zinc in molecular and cellular functions associated with allergic inflammatory disease. It identified two interconnected processes that exacerbate each other: a) decreased zinc levels that enhance inflammatory activation typically seen in many Th2-driven allergic inflammatory diseases, and b) inflammatory processes that further lower intracellular zinc levels, causing a vicious cycle of zinc deficiency and inflammation. Zinc deficiency was therefore highlighted as a clear feature and treatment priority of allergic disease such as atopic dermatitis, bronchial asthma and chronic rhinosinusitis.¹³

Further supporting the need for zinc, but also vitamin C supplementation, are the findings of a recent cross-sectional study in asthmatic children (n=76) of whom 100% had zinc deficiency, and nearly 40% vitamin C deficiency. The study demonstrated that plasma zinc concentrations were positively correlated with forced expiratory volume (FEV1) (r = 0.27) and FEV1/ forced vital capacity (FVC) ratio (r = 0.65). In addition, vitamin C deficiency was found to be associated with severe asthma and airway obstruction.¹⁴

 

Clinical Take-Away

Allergic diseases are among the fastest growing chronic conditions worldwide. In Australia and New Zealand, one in five people develop an allergy at some time during their life, of which the most common ones are food allergies, atopic dermatitis (eczema), asthma and allergic rhinitis (hay fever).¹⁵ Supplementation with vitamin C and zinc offers an ideal foundation for the clinical care of allergy sufferers, as both support innate and adaptive immunity, as well as essential antioxidant support.

 

 

References

• Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. 2017 Nov 3;9(11):1211.
• Maywald M, Wessels I, Rink L. Zinc Signals and Immunity. Int J Mol Sci. 2017 Oct 24;18(10):2222.
• Wessels I, Maywald M, Rink L. Zinc as a Gatekeeper of Immune Function. Nutrients. 2017 Nov 25;9(12):1286.
• van Rijt LS, Utsch L, Lutter R, van Ree R. Oxidative Stress: Promoter of Allergic Sensitization to Protease Allergens? Int J Mol Sci. 2017 May 23;18(6):1112.
• Braun L. and Cohen M. Herbs and Natural Supplements, 4th Edition, Volume 2, Churchill Livingstone, Sydney, 2015.
• Hathcock, JN. Vitamin and Mineral Safety. 3rd Washington DC: Council for Responsible Nutrition. 2014.
• Herb Drug Nutrient. Nutrient information: Vitamin C. Available from: https://www.herbdrugnutrient.com/vitamin-c.
• Gropper SS & Smith JL. Advanced Nutrition and Human Metabolism. 7th Australia: Wadsworth CENGAGE Learning; 2018.
• Gaby, A., Nutritional Medicine. 2nd Concord, NH: Fritz Perlberg Publishing. 2017.
• National Health and Medical Research Council (NHMRC) Nutrient Reference Values for Australia and New Zealand. 2006.
• Wade CI, Martinez T. Young's Rule.. In: StatPearls. Treasure Island (FL): StatPearls, 2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554603/
• Delgado BJ, Safadi AO, Bajaj T. Clark's Rule.. In: StatPearls. Treasure Island (FL): StatPearls. 2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK541104/
• Suzuki M, Suzuki T, Watanabe M, Hatakeyama S, Kimura S, Nakazono A, et al. Role of intracellular zinc in molecular and cellular function in allergic inflammatory diseases. Allergol Int. 2020 Oct 27:S1323-8930(20)30133-7.
• Siripornpanich S, Chongviriyaphan N, Manuyakorn W, Matangkasombut P. Zinc and vitamin C deficiencies associate with poor pulmonary function in children with persistent asthma. Asian Pac J Allergy Immunol. 2020 Dec 2.
• Australasian Society of Clinical Immunology and Allergy (ASCIA). Common Myths About Allergy and Asthma. 2019 Available form: https://www.allergy.org.au/images/pcc/ASCIA_PCC_Common_myths_2019.pdf