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(d) Zinc & Immunity

2007-02-10T09:57:00.000+08:00

Zinc is known to play a central role in the immune system. For zinc-deficient persons they are likely to experience increased susceptibility to a variety of pathogens.
Zinc has a primary role in the gene regulation within lymphocytes and is crucial for normal development and function of cells mediating non-specific immunity such as neutrophils and natural killer cells.

The macrophage, an essential cell in many immunologic functions, is adversely affected by zinc deficiency, which can dysregulate intracellular killing, cytokine production, and phagocytosis. Cytokines are important proteins secreted by many types of cells when the immune system is faced with inflammatory and infectious diseases. They have synergistic immune effects when bound with antibodies.

Zinc also functions as an antioxidant and can stabilize membranes. Therefore, free radicals can be picked up and brought away from cells and as a result cells do not get oxidised and lysed. Zinc deficiency also affects development of acquired immunity by preventing both the outgrowth and certain functions of T lymphocytes such as activation and Th1 cytokine production. Likewise, B lymphocyte development and antibody production, particularly immunoglobulin G, is compromised.

In addition, Zinc is also a cofactor in more than 300 enzymes influencing various organ functions, therby having a secondary effect on the immune system.

In general, all kinds of immune cells show decreased function after zinc depletion. In monocytes, all functions are impaired, whereas in natural killer cells, cytotoxicity is decreased, and in neutrophil granulocytes, phagocytosis is reduced.

BEWARE!

Excessive intake of zinc can impair immune responses too. From the Journal of the American Medical Asscoiation, a study was carried out on eleven healthy adult men. They were required to ingest 150 mg of elemental zinc twice a day for six weeks. It was then observed that the serum high-density lipoprotein concentration decreased significantly and low-density lipoprotein level increased slightly. This was associated with a reduction in lymphocyte stimulation response to phytohemagglutinin as well as chemotaxis and phagocytosis of bacteria by polymorphonuclear leukocytes. Thus, zinc supplementation on an excessive intake could have adverse effects in healthy persons.

Many thanks to:
The American Society for Clinical Nutrition,Inc
American Medical Association

Both sources are retrieved on 9 February 2007.

(c) Vitamin C & Immunity

2007-02-10T09:46:00.000+08:00

Being a natural anti-oxidant, vitamin C basically reduces the oxidative reactions in the body. These oxidative reactions are considered as harmful due to the free radicals produced which do oxidative damage to body tissues.

Research show that dietary vitamin C increases the levels of immunoglobulin and its complementary component. Since immunoglobulin is a crucial component in immune response and increase in these protective cells, vitamin C would indirectly boost the immune system (Dorling Kindersley Pty Limited, 2000).

To sum up, the powerful anti-oxidant vitamin C inhibits oxidative activities of pathogens while simultaneously strengthening immune response.

Many thanks to:
Journal of Dairy Science
Physiologic reviews

Both sources are retrieved on 9 February 2007.

(b) Carotenoids & Immunity

2007-02-10T09:38:00.000+08:00

Carotenoids are converted to Vitamin A in our body. Vitamin A can be obtained from dietary sources such as dark leaf vegetables, carrot, sweet potato, peach, orange, apple and other bright colour fruits.

Vitamin A is essential for good eyesight and night vision. It is also needed for bone growth, reproduction and cell division. They can prevent and fight against infections which help to regulate the immune system.

This is achievable by producing white blood cells that wipe out harmful bacteria and viruses. Vitamin A can help lymphocytes to fight against infections more efficiently. Vitamin A promotes healthy surface linings of the eyes and the respiratory, urinary and intestinal tracts which reduce the risks of bacteria infection especially when these linings break down.

This vitamin is also beneficial to the skin and mucuous membranes formation as they function as a barrier to bacteria and viruses (US National institute of health, 2006). The recommendation of vitamin A intake is 1000μg per day for adults (Aparna Oltikar, M.D, 2004).

Many thanks to:
Office of Dietary Supplements
U.S. National Library of Medicine

Both sources are retrived on retrieved on 9 February 2007.

(a) Omega 6 Fatty Acid & Immunity

2007-02-10T09:02:00.000+08:00

Omega-6 fatty acids are essential fatty acids (EFAs), which are not synthesized by the body but are essential to our body and obtained from dietary sources. Omega-6 fatty acids together with Omega-3 fatty acids play an important role in brain function, normal growth and development.

EFAs are polyunsaturated fatty acids (PUFAs), which are important for stimulating skin and hair growth, maintaining bone health, regulating metabolism and maintaining reproductive capability.

Most Omega-6 fatty acids are consumed in a form of Linoleic Acid (LA), which is converted to gamma-linolenic acid (GLA) then undergoes further breakdown to arachidonic acid (AA). LA and AA should not be taken in excess as they will promote inflammation, leading to several diseases.

On the other hand, GLA can reduce inflammation. Having sufficient amounts of nutrients like magnesium, zinc, Vitamin C, Vitamin B3 and Vitamin B6, aids in promoting GLA to be converted to dihomogamma-linolenic acid (DGLA) rather than AA. DGLA prevents negative inflammatory effects as it partially becomes a substance known as prostaglandins, which reduces inflammation (University of Maryland Medical Center (UMMC), 2004).

Prostaglandins makes platelets less sticky, lowers blood pressure by relaxing smooth muscles in the walls of the arteries, increases loss of sodium and water, decreases inflammation and enhances immunity. (Enerex Botanicals Ltd, 1997-2007)

Many Thanks to:
University of Maryland Medical Center (UMMC)
Enerex Botanicals Ltd.
Both sources are retrieved on 9 February 2007.

hello =D

2007-02-03T01:41:00.000+08:00

hello.

Our question is to explain how the following dietary factors play a role in immune system response:
a. Omega 6 fatty acids
b. Carotenoids
c. Vitamin C
d. Zinc

Stay tuned!