Content uploaded by Silvia Maggini
Author content
All content in this area was uploaded by Silvia Maggini on Jan 06, 2016
Content may be subject to copyright.
1
st
International Immunonutrition Workshop, Valencia, 3–5 October 2007, Valencia, Spain
Immune-enhancing role of vitamin C and zinc and effect on
clinical conditions
S. Beveridge
1
, E. S. Wintergerst
2
, S. Maggini
1
and D. Hornig
3
1
Bayer Consumer Care, Basel,
2
Bayer Diabetes Care, Basel, Switzerland and
3
Bayer Diabetes Care, Reinach, Switzerland
The present paper is intended to give an overview on the roles of vitamin C and Zn in immune functions. Vitamin C concentrations in the
plasma and leucocytes rapidly decline during infections and stress. Supplementation of vitamin C improves components of the human
immune system such as antimicrobial and natural killer (NK) cell activities, lymphocyte proliferation, chemotaxis and delayed-type
hypersensitivity. Vitamin C contributes to maintaining the redox integrity of cells and thereby protects them against reactive oxygen
species generated during the respiratory burst and in the inflammatory response. Similarly, Zn deficiency impairs cellular mediators of
innate immunity such as phagocytosis, NK cell activity, and the generation of oxidative burst. Thus, both nutrients play important and
complementary roles in immune function and the modulation of host resistance to infectious agents, reducing the risk, severity and
duration of infectious diseases. A deficiency in one of these essential nutrients weakens immunity since vitamin C is crucial for cellular
immunity and Zn for the production of antibodies.A large number of randomized controlled intervention trials with intakes of £1g
vitamin C and £30 mg Zn are available. These trials show that adequate intakes of vitamin C and Zn ameliorate symptoms and shorten the
duration of respiratory tract infections including the common cold. Natural defences can only provide full protection when the body has
sufficient Zn, as well as high levels of vitamin C.The physiological effects of vitamin C provide clear evidence and rationale for a number
of ways in which it might help to protect against infection. This evidence is termed mechanistic evidence because it stems from
knowledge of the chemical reactions and biochemical processes in which vitamin C is known to play an important role (Table). The
actions of Zn not only complement the actions of vitamin C to provide ‘double protection’ (Table), but may even have a synergistic effect.
Like vitamin C, in recent years research has proved that Zn is essential for effective immune defence at several different levels.
Table. Summary of the role of vitamin C and Zn in body defences
(1,2,3)
Defence Vitamin C Zn
Skin and mucosal barriers Collagen synthesis
Improved strength
Cellular proliferation
Maintains thickness
Neutrophils and macrophages Improved motility and chemotaxis
Enhanced killing
Overall improvement in phagocytosis
Lymphocytes Proliferation of stem cells
B- and T-cell differentiation
B- and T-cell interaction
B lymphocytes Antibody production
T lymphocytes Proliferation Proliferation and appropriate response
Destruction of infected tissue cells and tumours
Interferon Production enhanced
Adequate intakes of vitamin C and Zn are essential for health.This is of special importance in populations in which insufficient intake of
these nutrients is prevalent. The current belief is that regular prophylactic intakes of vitamin C at doses of ‡ 200 mg daily have no effect
on the incidence of the common cold, but may be beneficial in the reduction of the severity and duration of the symptoms, suggesting that
vitamin C plays some role in the respiratory defence mechanisms. However, the elderly, who have been shown to have a lowered vitamin
C status and may therefore be more prone to infections, individuals exposed to continuous oxidative stress, such as chronic smokers, and
individuals exposed to heavy physical exercise and/or cold environment may benefit from a moderate continuous vitamin C intake. Other
vulnerable population groups include children. As a result of the high prevalence of Zn deficiency, especially in children in developing
countries, and the impaired immune status, susceptibility to infectious diarrhoea, malaria and pneumonia is found to be substantially
increased. Large intervention trials with daily intakes of 10–30 mg Zn have shown that Zn supplementation could be an important
adjuvant therapy for treating these infectious diseases in children in developing countries. Given that both vitamin C and Zn have
an important and synergistic effect on immune function and the modulation of host resistance to infectious agents it is hence appropriate
and beneficial to combine the trace element Zn with a high dose of vitamin C in one supplement.
1. Wintergerst ES, Maggini S & Hornig DH (2006) Ann Nutr Met 50, 85–94.
2. Wintergerst ES, Maggini S & Hornig DH (2007) Ann Nutr Met 51, 301–323.
3. Maggini S, Wintergerst ES, Beveridge S & Hornig DH (2007) Br J Nutr 98, Suppl. 1, S29–S35.
Proceedings of the Nutrition Society (2008), 67 (OCE), E83 doi:10.1017/S0029665108006927