Asthma is a condition of the lungs that consequences in Inflammation of the air-passages. Asthma is a regular source of morbidity and a considerable cause of preventable mortality. Increase in the asthma occurrence in many countries over the recent decades, highlights the need for a better understanding of the risk factors for asthma. The occurrence of asthma is higher in countries where a traditional to a westernized routine occurred earlier suggesting that a given population experiences a progressive raise in asthma cases during the process of westernization. Asthma is itself explained as a multi-factorial disease with a large series of
causative, inducing, triggering and aggravating factors, each of which help figure the disease
phenotype in the single patient by interacting with the expression of his/her unique genetic background at a given age. Because asthma is the result of communication between genetic and environmental factors, increasing incidence is certainly the result of changes in environmental factors. The hypothesis made to explain the epidemic trend fall into two major groups: one that points to rising exposure to aggressive factors, and the other that implicates decreasing exposure to defensive factors. The mainly cited aggressive factors are airborne indoor or outdoor pollutants, high salt consumption, indoor allergens, drugs (e.g. contraceptive pills) and vaccines. The major proposed protective factors are antioxidants, microbial burden and physical exercise. This increasing occurrence has affected both rural and urban communities, suggesting that restricted environmental factors such as exposure to allergens or industrial air pollutions are not the only cause. In the last few years,
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nutrition has represented a significant conditioning factor of many cardiovascular, gastro-intestinal and chronic pulmonary diseases. So it has been hypothesized that dietary constituents effect the immune system and thus, may also be efficiently involved in the onset of asthma and other allergic diseases. The possible function of diet in the development of asthma can be described as follows: 1.A food allergen can cause asthma. 2. There is role of breast-feeding for avoidance of asthma later in life. 3. A low consumption of antioxidative dietary constituents might be a risk factor for asthma. Moreover, function of cations such as sodium, potassium and magnesium has been explained in development of asthma. Consumption of fatty acids specially the function of omega-3 and omega-6 fatty acids play a beneficial and harmful role respectively in cause of asthma.
Although some researchers would dispute that an allergic component contributes to more than 80% of young asthmatics and approximately 40% of adult asthmatics who experience the connection between diet and nonfood allergies are broadly ignored. It is reported in the United
States that about 6-8% of infants and about 1.5% of adults are allergic to food. Food is significant cause of asthma but is frequently overlooked, as usual skin tests are often negative and history is frequently not helpful. In the majority of the patients, symptoms appear gradually hours or days after ingestion of the food. It has been estimated that less than 10% of asthmatics may notice that their symptoms are provoked by definite foods or drinks. Children are more responsive to foods than adults.
Deaths in people who ingested foods to which they were extremely allergic have been reported. These deaths are frequently caused by a "hidden" ingredients in the food to which the person is allergic. The most of these deaths are due to severe allergy to peanut and nuts, and asthma appears to be a significant risk factor for this form of allergy. Sensitivity can happen by ingestion of minute quantities of food allergens and even by inhalation of food allergens carried in air or in cooking stinks.
A food allergic reaction is presumed to be the result of unusual immunological responses, consisting both of immunoglobin E (IgE) mediated and non-Ig-E-mediated response after ingestion of a pertinent food. Meats containing antibiotics fed to animals or tenderized with enzymes are recognized as rare causes. Sensitization occurs as a result of pinocytosis of antigenic protein molecules by intestine mucosal cells (perhaps in the Peyer's Patches) and
induction of an Ig-E antibody response. Subsequent entry of antigen into the blood-stream provokes an Ig-E-mediated reaction. The representative symptoms of food allergy are "oral allergy syndrome" with oral and perioral itching and rash, gastrointestinal symptoms such as nausea, vomiting and diarrhea, and dermatological manifestations such as urticaria and eczema. However, some patients show more severe symptoms, namely systemic anaphylaxis. Food induced anaphylaxis is often not easy to diagnose due to lack of skin manifestations, an indicator of early diagnosis of anaphylaxis, is found in about 50% of such patients. Peanuts, extensively used in a large number of prepared foods, are the most commonly to blame. Food allergy can cause both immediate and delayed patterns of asthma. Influence of foods on asthma can be mediated through raise in synthesis of prostaglandin- E2 (PG-E2 ). This can sequentially promote the formation of Ig-E and consequently allergic sensitization. Immediate food reaction (Type-I allergy mediated by Ig-E), can cause prompt, dramatic and life threatening asthma, is one consequence of anaphylactic reaction to food. Delayed patterns of food allergy (Non-Ig-E-mediated) can cause further persistent inflammatory form of chronic asthma. This is among the most neglected reasons of intrinsic asthma. Skin tests do not show delayed pattern of food allergy.
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Egg: Egg is a most allergenic food, and little amounts of egg can result in asthma symptoms within minutes, including anaphylaxis. This is also seen after contact with egg through non-oral passages. Reactions may happen first time in a child who is given egg
Milk: Patients with very sensitive milk allergy can react to a very minute quantity of milk protein, including small contamination, and even inhalation of milk powder and exhibit with asthma.
Soy: Because of the approximately unlimited uses of soy, it is an insidious hidden allergen. As with other allergens, soy protein may give rise to asthma symptoms and anaphylaxis.
Wheat: Wheat is the extreme allergenic of all cereals. Ig E antibodies have been demonstrated to many constituents of wheat. Wheat is most fertile in gluten, with the other grains containing a lesser combination of gluten and gliadin. For the wheat hypersensitive individual, products made from oats, rice, rye, barley or corn may be used. However, cross reactions, although abnormal, may occur between wheat and these cereals.
Peanuts: Peanut allergy is one of the most widespread food allergies. It can cause asthma and anaphylaxis leading to death in a lot of cases
Fish: Though fish oils have beneficial part in asthma, fish is one of the common reasons of food allergy. It is normally recommended that patients allergic to fish should evade all fish species. Sulfites and sulfating agents such as sulfur dioxide, sodium bisulfite, potassium bisulfite, potassium metasulfite, sodium sulfite - both occurring naturally or used in food processing, have been found to trigger asthma. Common food origins are dried fruits and vegetables, potatoes (some packaged and prepared), wine, bottled lemon or lime juice, strimp (fresh, frozen or prepared) and pickled foods. All food allergens commonly affect the children under the age of six years. Some preservatives and additives may induce asthma. Red wine contains a number of congeners that give them their distinctive flavours, but these may also induce attack of asthma, perhaps by a direct effect on mast cells causing release of mediators. In general, however, alcohol is a mild bronchodilator. It has been postulated that asthma associated with chewing betel-nuts is chemically mediated by cholinergic stimulation. Children responsive to food have higher rates of hospitalization due to asthma. In addition, children responsive to food require more steroid medications to control their asthma symptoms. Presence of food sensitization may be a useful marker for identifying children more severe asthmatic children.
The epithelial lining of the respiratory system, by virtue of its big surface area and its function in gas exchange and host defence, is vulnerable to oxidant injure. The toxicity of oxidants which are straight inhaled such as cigarette smoke and air-pollution or created through inflammatory process such as in response to allergen and viral infection, is usually balanced by the defensive activity of an array of endogenous antioxidant defense system which may be functionally dependent on sufficient supply of nutritional antioxidants. Reactive oxygen types, released from eosinophills, alveolar macrophages, and neutrophills, seem to play a main role in asthma. They may contract airway smooth muscles, stimulate histamine liberate from mast cells and mucus secretion. Therefore asthma is also associated with oxidative-antioxidative imbalance. Antioxidants such as vitamin-A/Î²carotene, vitamin-C, vitamin-E and selenium are important dietary components which may prevent oxidative damage. Therefore, they may decrease inflammation caused by allergen exposure
Vitamin-C: Vitamin-C is the most widely investigated among antioxidants and has been demonstrated to be associated with a reduced risk of asthma. Minor plasma and leukocyte concentration of vitamin-C has been associated with a high occurrence of asthma in adults
and in children, increased respiratory symptoms, decreased pulmonary functions and increased airway responsiveness. Supplementation with vitamin-C has been demonstrated to reduce asthma severity and frequency, exercise provoked bronchospasm and airway responsiveness to methacholine. Vitamin-C is a free radical scavenger occur in intracellular and extracellular lung fluids and defends against endogenous as well as exogenous oxidants. It subscribe to the regeneration of membrane bound oxidized vitamin-E to function again. Vitamin-C is known to have a general antihistamine influence. It also prevents the prostaglandins production. Moreover, vitamin-C decreases the duration of episodes and the severity of symptoms of the common cold. Vitamin-E: Vitamin-E effects have been learned and there is evidence of beneficial influences of vitamin-E on asthma. There is evidence of an inverse connection between vitamin-E intake and both allergen skin sensitization and whole serum Ig-E levels in adults. High vitamin-E intake is associated with decreased asthma incidence. Vitamin-E is occurring in extracellular lung fluid and lipid membrane, where it commutes oxygen radicals and lipid proxy radicals to less reactive types. Thus vitamin- E is a membrane stabilizer and principle defence against oxidant provoked membrane injury by unmaking the lipid peroxidation chain reaction.
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Vitamin-A and B-carotene have defensive effect in asthma. Vitamin-A derivatives of retinol influences the development, maintainance, differentiation, and regeneration of lung epithelial cells and may play a medium role in the development of airway disease. Vitamin-A/Î²-carotene helps to avoid membrane lipid oxidation.
Other Vitamins: Asthmatics are typically lacking in vitamin-B complex (especially vitamin-B6 and B12) and folic acid and supplementing these subjects with multivitamins can help to decrease asthma symptoms. A lack of vitamin-B6 has been found in many asthma patients. This may be due to the circumstance that the medications in many asthma inhalers resist with the absorption of vitamin-B6 by the body. In mild to average situations, the addition of vitamin-B6 supplement to the aliment appears to lessen the incidence of asthma attacks. It has been discovered in a study that vitamin-B12 taken in huge doses can decrease likelihood that asthmatics react to foods with sulfites
Flavones and Flavanoids
Flavones and flavanoids are naturally occurring antioxidants which may account for defensive effect. These stabilize mast cells.
Fruits and Vegetables
Few studies have demonstrated a decreased risk of asthma in relation to a high fruit consumption. High intake of fruits is combined with a reduced risk of depression in FEV1, over a time. Eating vegetables and fruits are defensive for asthma/wheeze. Fruits and vegetables are better. Daily intake of fruits and vegetables in infancy reduce the risk of asthma.
Intake of fast foods is associated with increased risk of asthma in children. Frequent intake of hamburger showed a dose dependent association with asthma symptoms. Intake fast foods and meat raises the risk of asthma/wheeze among children.
Selenium: Selenium has been most strongly combined with asthma. Studies have demonstrated reduced selenium intake and reduce serum levels in patients with asthma. Selenium deficiency may greatly raise the risk of asthma. Selenium acts as a cofactor for the antioxidant enzyme glutathione peroxidase, which decrease the synthesis and liberation of leukotriene B4. Along with vitamin-C, reduce the activation of nuclear factor kappa-Î², a transcription factor that upregulates inflammatory cytokines related with the asthmatic immune response.
Magnesium: Magnesium has different biological effects of potential relevance to asthma, including bronchodilatation when given intravenously in cruel severe asthma. There is also strong evidence of guard by dietary magnesium against asthma. Reduced magnesium consumption was found to be combined with brittle asthma. These influences of magnesium are mediated by its qualities of smooth muscle relaxation and mast cell stabilization.
Sodium: It has been demonstrated that bronchial reactivity to histamine is related to 24 hours urinary sodium excretion. Bronchial reactivity appears to increase with greater salt consumption. Research proposes that the effects of sodium are limited to persons with asthma. Dietary sodium may raise airway reactivity and cause bronchoconstriction through potentiation of the electrogenic sodium pump in the membrane of the airway smooth muscles. Trace Minerals: There are evidences adjoining copper,zinc and manganese with asthma. Copper and zinc have a function in antioxidant defense as cofactor in superoxide dismutase. Zinc is a very important trace mineral for most immune mechanisms in the body to act, including lymphocyte (T-cell) function. Zinc deficiency may also cause to an enhanced Th2 immune response. Manganese has been found lacking in bronchial biopsies of asthmatic patients, indicating manganese replacement could help in treatment of asthma.
Role of Fatty Acids
Dietary fatty acids have important function in asthma. Ingestion of omega-3 fatty acids is potentially beneficial and of omega-6 fatty acids is baneful to asthma. Decreased omega-3 fatty acid/omega-6 fatty acid ratio causes to high chances of asthma. Well studied beneficial influence of fish in asthma is attributed to the existence of omega-3 fatty acids in fish oil. Fish oil consists eicosapentaenoic acid (EPA) and docasahexaenoic acid (DHA) which are competitive substrates for arachidonic acid for producing of inflammatory mediators. In humans, the main substrate for eicosanoid production is arachidonic acid, an unsaturated fatty acid which contains a 20-carbon molecule with four double carbon bounds, the first of which is at the sixth carbon atom from the methyl end of the molecule (omega-6 fatty acid). The production of eicosanoids by inflammatory cells starts with the liberation of arachidonic acid from membrane phospholipid by phospholipase enzymes, and subsequent metabolism by
cycloxygenase or lipoxygenase, enzymes, and subsequent prostaglandin or leukotrience productions. The derivatives of arachidonic acid are leukotriene B4 (LTB4), a potent neutrophil chemoattractant and a pro-inflammatory mediator and cysteinyl series of LT (LTC4, D4, E4) which cause potent smooth muscle contraction and bronchoconstriction. In contrast, EPA and DHA (omega-3 fatty acids), as well as inhibiting arachidonic acid metabolism, is a substrate for the less active prostanoids (e.g. thromoxane A3) and LT (LTB5) and so has the potential to decrease airway inflammation, severe bronchoconstriction and airway hyper responsiveness. On the other hand, omega-6 fatty acids such as linoleic acid, may effect the development of allergic sensitization by increasing the making of prostaglandin E2 (PGE2), thus raising Th2 lymphocyte response and Ig-E generation. Fish oil may therefore relieve certain inflammatory respiratory diseases, preserve usual airway resistance, and modulate allergic sensitization. Unsaturated fatty acids in trans-configuration, happening in ruminant fat, dairy products and industrially hydrogenated fats, have been found to show inhibiting effect on desaturation and chain elongation of very important fatty acids in precursors of inflammatory mediators and on the activity of cycloxigenase. Full fat cream and butter (rich in saturated fats) is associated with a decreased risk of asthma in young children
Among amino acids, of special interest are the amino acids: cystine, methionine, glycine and glutamic acid, which collectively subscribe to glutathione metabolism which is an significant antioxidant that may influence susceptibility to asthma. Cystine, is of particular
interest, as it may be changed to reduced form of cysteine by macrophages, which thus increases intracellular glutatione. Arginine, the precursor for nitric oxide, which has been demonstrated to be elevated in asthma and glutamine, which has powerful antibacterial qualities in vivo are also of interest. In addition, phenylalanine is potentially significant since uncontrolled phenylketonuria is related with increased plasma Ig-E and atopic dermatitis. Studies have drawn attention to tryptophan, where the metabolic pathways may shift in asthmatic persons as compared to control subjects, as shown by elevated urinary kynurenic acid and xantharenic acid excretion in children with asthma. In a study, there was strong inverse connection between fasting plasma glycine level and asthma risk. It is therefore, possible that diferences in the pattern of amino acids consumption arising from an overall.
Increase in the proportion of protein from animal origins may have subscribed to the rise in asthma occurrence that has occurred in a lot of developed countries.
The use of intravenous cure with multiple nutrients, including magnesium, for acute and chronic asthma may be of significant benefit. Pulmonary actions improve progressively, the longer patients take treatment.
The plasticity of the immune system in early life recommends that it will be dietary effects at this stage that will have the greatest influence. Really, early exposure to cow's milk protein has been related to the development of atopy and asthma. Studies indicate that protracted and
exclusive breast feeding significantly reduces the risk of asthma and other allergic diseases among children. Children with positive family history are more likely to develop asthma or eczema when fed solids previous. Guidelines prescribe that exclusive breast feeding for
the first 4-6 months with introduction of solids thereafter, egg, milk, and fish being added to the diet finaly. Even introduction of milk other than breast milk before the age of 4 months
of age has been found a important risk factor for all asthma and atopy related outcomes in children aged 6 years. Cow's milk has been chosen the food allergen most commonly affecting children. It has been prescribed that if breast feeding is not possible, consider supplementing infants with omega-3 fatty acids, lactobacillus probiotics and protein hydrolyzed formula. Fatty acid contents of colostrum were connected to atopic sensitization in children and data demonstrated links between the two can be observed as early as during the first few days of lactation. Breast feeding was found to be defensive for asthma
.Role of Maternal Diet
A meta-analysis of maternal dietary avoidance during pregnancy to inhibit atopic diseases in infants at high risk concluded that such prevention is unlikely to substantially decrease the risk of atopy in the child. Moreover, such a diet may have a deleterious effect on maternal and/or fetal nutrition. So it is prescribed to cease strict elimination diets during pregnancy. Maternal vitamin-E intake during pregnancy has the potential to affect postnatal susceptibility to asthma and atopic diseases by modulating fetal and neonatal Th-cell response during first encounter with allergensl. Similarly, maternal oily fish consumption
during pregnancy may guard off-springs from asthm.
Intestinal Flora and Probiotics
Evidence that the gut micro-flora may be combined with the development of atopy comes from studies comparing Estonian infants with Swedish infants. Estonian infants have a low occurrence of atopy and show greater gut colonization with lactobacillus and Eubacteria,
whereas Swedish infants, who have a higher occurrence of atopy, show greater levels of Clostridium difficile. Furthermore, iso-caproic acid, a complex related with C. difficile, has been exposed almost exclusively in allergic infants, and the levels of other composites associated with Lactobacillus flora were higher in non-atopic infants . Thus it has been recommended that promotion of Lactobacillus and other potentially helpful gut micro-organisms may defend against the development of atopic disease. Breast feeding upgrades gut colonization with bifidobacterium, and thus decreases chances of atopy and/or asthma.
Dietary supplementation with probiotics has demonstrated emboldening results in asthma. In a doublepo blind, randomized, placebo controlled trial, lactobacillus (given prenatally to mothers and then postnatally for 6 months to their infants) resulted in 50% reduction in the
celerity of atopic eczema at the age of two years. Thus, the function of probiotics can be considered to avoid asthma. A key factor with probiotic intervention is that it does not make any harm. The probiotics may supply a natural means of beneficially modulating the immune system. However, the mechanism lasts unclear and more data wants to be available before conclusion can be made on their ability to impact on the increase of the other allergic disease including asthma.