Nutrition is a critical determinant of immune responses and
malnutrition the most common cause of immunodeficiency worldwide.
Protein energy malnutrition is associated with a significant
impairment of: CMI phagocyte function complement system secretory
IgA concentration cytokine production. Of the micronutrients
:zn,slenium,iron,cu,vit.A,C,E,B6 and folic acid have important
influences on immune responses. Overnutrition and obesity also
reduce immunity. Nutrition
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Malnutrition Undernourished a)consuming too few essential
nutrients b) using or excreting them more rapidly than they can be
replaced c)Loss of appetite d)chronic diseases especially disease
of the intestinal tract, kidneys, and liver e)drug or alcohol
dependencies Overnourished(dietary imbalances )
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Nutrient deficiencies The 5 aspects of immunity affected by
malnutrition are: a)CMI b)Phagocyte function c)Complement system d)
Secretory antibody e)Cytokine production
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Micronutrients Micronutrient deficiencies and infectious
diseases often coexist micronutrients are significant
immunomodulators and thus are critical in determining the outcome
of host microbe interactions Infections, in turn, aggravate
micronutrient deficiencies by a)reducing nutrient intake
b)increasing losses c)and interfering with utilization by altering
the metabolic pathways
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Antioxidant Micronutrient Deficiency Micronutrients such as
beta-carotene, vitamin C, selenium,copper, and riboflavin are
powerful antioxidants and are found to significantly influence
infection-related morbidity in humans. Beck and Levander in their
recent critical review describe the possibility of serious effects
of antioxidant-deficient status on viral infections.
Micro-nutrients like iron, copper, zinc, folic acid, and vitamins
A, C, E and B-6 all have important influences on immune
response
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Vitamin A As early as 1928, Green and Mellanby named vitamin A
as an anti-infective vitamin Apart from its effects on vision, the
role of vitamin A in maintaining the structural and functional
integrity of mucosal epithelial cells through its actions on gene
expression vitamin A controls cellular proliferation and
*differentiation
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The effect of vitamin A deficiency reduced number of
lymphocytes low immunoglobulin (Ig) concentrations Decreased
antibody responses to viral and bacterial antigens impaired T-cell
responses in vivo and in vitro Abnormal cytokine production Thus,
vitamin A deficiency leads to a suppression of many of the effector
functions of the immune system and consequently to a state of
immunodeficiency Hydrogen peroxide generation by neutrophils and
IL-1 production and cytotoxic functions in macrophages and
leukocyte lysozyme content of phagocytic cells was found to be low
in vitamin A deficient children.
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Keratinizing metaplasia with decreased mucus production caused
by disappearance of goblet cells is the most important change
observed on epithelial linings in vitamin A deficient children.
Such a change has been shown to increase bacterial adherence, thus
promoting colonization and subsequent invasion by pathogenic
microbes. Vitamin A also helps to maintain the mucous membrane and
skin, thus improving defense to infection
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Immune Adjuvant Effects of Vitamin A Administration of 100,000
to 200,000 IU of vitamin A as a single dose has been found to
enhance phagocytic functions in macrophages. Enhancement of
seroconversion rates to measles vaccine when coadministered with
vitamin A (84%) The immunopotentiating effects of large dose
administrations of vitamin A have led to their routine use in
reducing the severity and complications of infectious diseases like
measles and diarrhea. Supplementation of beta-carotene or vitamin A
in HIV-positive pregnant women was also found to reduce
verticaltransmission of the virus. The effects of vitamin A
administration in reducing the load of malarial parasitemia in
countries having endemic malaria is of clinical relevance
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Iron Besides being a hemopoietic factor, iron is essential for:
a) cell proliferation b)oxidative metabolism of various tissues c)
alter cell-mediated immune functions in children as well as in
pregnant women d) Circulating T-cell numbers were found to be
significantly impaired in children having iron deficiency and
anemia. e) Increased susceptibility to predominantly intracellular
microbial infections and also raise concerns about the success of
immunization programs among children living in communities having
widely prevalent iron deficiency
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Zinc is a biologically essential trace element: critical for
cell growth cell development and differentiation It is required for
DNA synthesis RNA transcription cell division cell activation
Zinc
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Zinc deficiency affects multiple aspects of innate and adaptive
immunity : lymphopenia increased infection prolonged healing time
both of which are indicators of compromised immunity lymphoid
atrophy decreased delayed cutaneous hypersensitivity responses and
lower thymic hormone activity. Zinc
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Zinc deficiency : decreases production of the Th1 cell
cytokines, IFN-[gamma], IL-2, and tumor necrosis factor
(TNF)-[alpha], which play major roles in tumor suppression. These
in turn inhibit the functional capacity of these cells Zinc
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Several investigators reported a significant association
between low plasma zinc levels and respiratory tract infections in
children Zinc-deficient individuals have been observed to exhibit
decreased thymulin levels and impaired cell- mediated immune
functions.
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Copper A medical publication in 1867 reported that, during the
cholera epidemics in Paris of 1832, 1849 and 1852, copper workers
did not develop cholera. Another observation was that persons with
Menke's disease died from frequent and severe infections due to an
inadequate immune response. Menke's is an inherited disease causing
defective copper absorption and severe copper deficiency1.1
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Copper Some of the recent research showed that interleukin 2 is
reduced in copper deficiency and is likely the mechanism by which T
cell proliferation is reduced. The number of neutrophils in human
peripheral blood is reduced in cases of severe copper deficiency.
Not only are they reduced in number, but their ability to generate
superoxide anion and kill ingested microorganisms is also reduced
in both overt and marginal copper deficiency
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-Carotene and other carotenoids may enhance immune function by
quenching singlet oxygen and other reactive oxygen species,
including free radicals. -Carotene
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PMN reactive oxygene and free radicals killing of bacteria
human PMN incubated with -carotene and bacteria, the bacteria were
killed efficiently and the PMN were not damaged or destroyed by the
free radicals. -Carotene
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*T helper cell numbers were significantly increased in
individuals given -carotene supplementation. *A large body of
epidemiological evidence has shown that diets rich in carotenoids
have been associated with lower risk of developing many types of
cancer *it was shown that human natural killer cells killed
significantly more tumor cells when incubated with - carotene than
human cells not exposed to -caroten -Carotene
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Carotenoids may increase the tumoricidal activity of the
cytotoxic T cells, macrophages and/or natural killer cells by any
of these mechanisms of action. T and B lymphocyte proliferation
induction of specific effector cells capable of killing tumor cells
and the secretion of factors required for the communication between
immunologically competent cells. -Carotene
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Vitamin C (ascorbic acid) is a powerful antioxidant and immune
booster, an antiviral and anticancer nutrient. The white blood
cells utilize vitamin C to fight microbes, infections and
inflammation; during which levels of vitamin C are depleted.
Animals; except for guinea pigs have the necessary enzyme to
synthesize vitamin C in their liver. But humans lack this vitamin C
synthesizing enzyme. During high stress situations, our requirement
for vitamin C increases. Vitamin C is a good example of a nutrient
where experimental deficiencies have shown consistently increased
susceptibility to infections Vitamin C
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Human milk
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Advantages of human milk Human milk provides the newborn with:
a) nutrients b)growth factors c)anti-infectious substances
Breastfeeding to account for the decrease in number and severity of
infants intestinal and respiratory infections,as well as of
septicemia and meningitis the enhancement of maternal-infant
bonding and avoidance of allergic diseases
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The protective activity of breastfeeding against infections is
explained by antimicrobial factors such as the: immunoglobulins
Leucocytes Lysozyme Lactoferrin and bifidus factor
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Human milk contains IgA antibodies Human milk also directly
affects the neonates immune system, because it contains a factor
that stimulates IgA synthesis in the infant cell-mediated immunity
is transferred from mother to infant through human milk
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First,Human milk shows antimicrobial activity.A lower incidence
of infections may in turn reduce risk for sensitisation
Secondly,breastfeeding has been proposed to affect the
gastrointestinal flora in a direction that may be favourable in
terms of prevention of sensitisation, since introduction of cows
milk promotes the growth of gram-negative endotoxin producing
bacteria with adjuvant properties that enhance sensitisation
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Thirdly, certain hormones, identified in human milk, such as
cortisol, growth factors such as epidermal growth
factor,insulin-like growth factor,milk growth factor,and
transforming growth factor (TGF), may support the anatomic
integrity of the mucosal barrier in the infant.
