|Year : 2007 | Volume
| Issue : 3 | Page : 105-114
Nutrition and Asthma
KB Gupta, Manish Verma
Department of Tuberculosis and Respiratory Medicine, Pt. B.D. Sharma, PGIMS, Rohtak., India
K B Gupta
Department of Tuberculosis and Respiratory Medicine, Pt. B.D. Sharma, PGIMS, Rohtak.
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Increase in the asthma prevalence in many countries over the recent decades, highlights the need for a greater understanding of the risk factors for asthma. Because asthma is the result of interaction between genetic and environmental factors, increasing prevalence is certainly the result of changes in environmental factors because of process of wesernization. That is the reason for higher prevalence in countries where a traditional to a westernized lifestyle occurred earlier. This increasing prevalence has affected both rural and urban communities, suggesting that local environmental factors such as exposure to allergens or industrial air pollutions are not the sole cause. In the last few years, nutrition has represented an important conditioning factor of many cardiovascular, gastrointestinal and chronic pulmonary diseases. So it has been hypothesized that dietary constituents influence the immune system and thus, may also be actively involved in the onset of asthma and other allergic diseases. Dietary constituents can play beneficial as well as detrimental role in asthma. The possible role of diet in the development of asthma can be described as follows: first, a food allergen can cause asthma. Second, there is role of breast-feeding for prevention of asthma later in life. Third, a low intake of antioxidative dietary constituents might be a risk factor for asthma. Moreover, role of cations such as sodium, potassium and magnesium has been described in development of asthma. Finally, intake of fatty acids specially the role of omega-3 and omega-6 fatty acids play important role in cause of asthma.
|How to cite this article:|
Gupta K B, Verma M. Nutrition and Asthma. Lung India 2007;24:105-14
| Introduction|| |
Asthma is a condition of the lungs that results in inflammation of the air-passages. Asthma is a common source of morbidity and a significant cause of preventable mortality. Increase in the asthma prevalence in many countries over the recent decades, highlights the need for a greater understanding of the risk factors for asthma  . The prevalence of asthma is higher in countries where a traditional to a westernized lifestyle occurred earlier suggesting that a given population experiences a progressive increase in asthma cases during the process of westernization. Asthma is itself defined as a multifactorial disease with a large series of causative, inducing, triggering and aggravating factors, each of which help shape 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 interaction between genetic and environmental factors  , increasing prevalence is certainly the result of changes in environmental factors. The hypothesis made to explain the epidemic trend fall into two main groups: one that points to increasing exposure to aggressive factors, and the other that implicates decreasing exposure to protective factors. The most cited aggressive factors are airborne indoor or outdoor pollutants, high salt intake, indoor allergens, drugs (e.g. contraceptive pills) and vaccines. The principal proposed protective factors are antioxidants, microbial burden and physical exercise. This increasing prevalence has affected both rural and urban communities, suggesting that local environmental factors such as exposure to allergens or industrial airpollutions are not the sole cause  . In the last few years, nutrition has represented an important conditioning factor of many cardiovascular, gastro-intestinal and chronic pulmonary diseases. So it has been hypothesized that dietary constituents influence the immune system and thus, may also be actively involved in the onset of asthma and other allergic diseases  . The possible role of diet in the development of asthma can be described as follows: first, a food allergen can cause asthma. Second, there is role of breast-feeding for prevention of asthma later in life , . Third, a low intake of antioxidative dietary constituents might be a risk factor for asthma  . Moreover, role of cations such as sodium, potassium and magnesium has been described in development of asthma. Finally, intake of fatty acids specially the role of omega-3 and omega-6 fatty acids play a beneficial and detrimental role respectively in cause of asthma.
Although some researchers would argue that an allergic component contributes to more than 80% of young asthmatics and approximately 40% of adult asthmatics who experience  the association between diet and nonfood allergies are widely 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 very important cause of asthma but is often overlooked, as usual skin tests are often negative and history is often not helpful. In most 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 certain foods or drinks , . Children are more sensitive to foods than adults  .
Deaths in children, adolescents, and adults who ingested foods to which they were highly allergic have been reported , . These deaths are often caused by a "hidden" ingredients in the food to which the individual is allergic ,, . The majority of these deaths are due to severe allergy to peanut and nuts, and asthma appears to be an important risk factor for this form of allergy  . Sensitivity can occur by ingestion of minute quantities of food allergens , and even by inhalation of food allergens carried in air or in cooking fumes ,,, .
A food allergic reaction is presumed to be the result of abnormal immunological responses, consisting both of immunoglobin E (IgE) mediated and non-Ig-E-mediated response after ingestion of a relevant food. Meats containing antibiotics fed to animals or tenderized with enzymes are recognized as occasional 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 exhibit more severe symptoms, namely systemic anaphylaxis. Food induced anaphylaxis is often difficult to diagnose due to lack of skin manifestations, an indicator of early diagnosis of anaphylaxis, is found in about 50% of such patients. Peanuts, widely 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. Effect of foods on asthma can be mediated through increase in synthesis of prostaglandinE2 (PG-E2 )  . This can in turn promote the formation of Ig-E and consequently allergic sensitization. Immediate food reaction (Type-I allergy mediated by Ig-E), can cause sudden, dramatic and life threatening asthma, is one consequence of anaphylactic reaction to food. Delayed patterns of food allergy (Non-Ig-E-mediated) can cause more persistent inflammatory form of chronic asthma. This is among the most neglected causes of intrinsic asthma. Skin tests do not show delayed pattern of food allergy.
Common foods causing asthma are milk, eggs, fish, peanuts, soy, yeast, cheese, wheat, rice and chocolates ,, .
Egg : Egg is one of the most allergenic of all foods, and minute amounts of egg can result in asthma symptoms within minutes, including anaphylaxis. This is also seen after contact with egg through non-oral routes , .Reactions may occur first time in a child who is given egg  . Although ovalbumin, ovomucoid, and ovotransferrin have been identified as the major allergens in egg white, 10 other unnamed allergens of lesser importance have been identified. These allergens are also present in egg yolk but in lesser quantities  .
Milk : Patients with very sensitive milk allergy can react to a very small quantity of milk protein, including minor contamination  , and even inhalation of milk powder and present with asthma  .
Soy : Because of the almost unlimited uses of soy, it is a insidious hidden allergen. As with other allergens, soy protein may cause asthma symptoms and anaphylaxis , .
Wheat : Wheat is the most allergenic of all cereals. Ig E antibodies have been demonstrated to many components of wheat. Wheat is most rich in gluten, with the other grains containing a lesser mixture 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 unsual, may occur between wheat and these cereals ,, .
Peanuts : Peanuts are one of the most allergenic foods and peanut allergy is one of the most common food allergies ,,, . It can cause asthma and anaphylaxis leading to death in many cases.
Fish : Though fish oils have beneficial role in asthma, fish is one of the common causes of food allergy  . It is generally recommended that patients allergic to fish should avoid all fish species  .
Sulfites and sulfating agents such as sulfur dioxide, sodium bisulfite, potassium bisulfite, sodium metasulfite, potassium metasulfite, sodium sulfite - both occurring naturally or used in food processing, have been found to trigger asthma  . Common food sources are dried fruits and vegetables, potatoes (some packaged and prepared), wine, beer, 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 provoke asthma. Examples of such provoking compounds are - preservaties e.g. sulfur dioxide and sodium benzoate, colourants (natural or synthetic) e.g. tartrazine, flavour enhancers e.g. monosodium glutamate and salicylates e.g. aspirin like substances found in many foods. Red wine contains a number of congeners that give them their dinstictive flavours, but these may also provoke attack of asthma, perhaps by a direct effect on mast cells causing liberation of mediators , . In general, however, alcohol, itself is a mild bronchodilator , .
It has been postulated that asthma associated with chewing betel-nuts is chemically mediated by cholinergic stimulation  .
Children sensitive to food have higher rates of hospitalization due to asthma. In addition, children sensitive to food require more steroid medications to manage their asthma symptoms. Presence of food sensitization may be a useful marker for identifying children with more severe asthma. In an Indian study, it was found that deterioration in asthma can be prevented by specific food avoidance in many patients  .
It has been said that we should pay much more attention to food allergens as the possible and the hidden cause of asthma, even in adult allergic subjects. One should carefully consider medical history and all asthmatics should be asked whether they have noticed any association with particular food. One should perform various laboratory studies including skin prick testing, Ig-E CAP RAST and related examinations, basophil histamine release etc  . At present, there is no definite and reliable tests to diagnose food allergy. The final mainstay of diagnosis is the demonstration of the relief of symptoms on removal of a given food item and recurrence of symptoms on its reintroduction (eliminate challenge testing).
The only proven treatment for food allergy is strict elimination of the relevant offending allergen (s). It should be noted here, however that elimination diet may lead to unwanted side effects such as malnutrition and eating disorders. But if successful, the food induced symptoms will certainly disappear. The diet revision should be complete and comprehensive to resolve them. It can be presumed that symptomatic reactivity is lost over time. Approximately, one third of children and adults lose their clinical reactivity after 1-2 years of allergen avoidance  .
The epithelial lining of the respiratory system, by virtue of its large surface area and its role in gas exchange and host defence, is vulnerable to oxidant damage  . The toxicity of oxidants which are directly inhaled such as cigarette smoke and air-pollution or generated through inflammatory process such as in response to allergen and viral infection, is normally balanced by the protective activity of an array of endogenous antioxidant defense system which may be functionally dependent on adequate supply of nutritional antioxidants.
Reactive oxygen species, released from eosinophills, alveolar macrophages, and neutrophills, seem to play a key role in asthma. They may directly contract airway smooth muscles, stimulate histamine release from mast cells and mucus secretion  . Asthma is, therefore, also associated with oxidative-antioxidative imbalance. Antioxidant status may affect asthma risk by influencing the development of the asthmatic immune phenotype, the asthmatic response to antigen provocation, or the inflammatory response during and after an asthma attach. Antioxidants such as vitamin-A/βcarotene, vitamin-C, vitamin-E and selenium are important dietary constituents which may prevent oxidative injury. Therefore, they may reduce inflammation caused by allergen exposure  .
Vitamin-C: Vitamin-C is the most extensively investigated among antioxidants and has been shown to be associated with a reduced risk of asthma ,,,,,, . Lower plasma and leukocyte concentration of vitamin-C has been associated with a high prevalence of asthma in adults  and in children  , increased respiratory symptoms  ,reduced pulmonary functions ,, and increased airway responsiveness ,, . Supplementation with vitamin-C has been shown to decrease asthma severity and frequency  , exercise induced bronchospasm and airway responsiveness to methacholine  . A 100 mg increase in vitamin-C intake per day is associated with an approximately 10-50 ml increase in forced expiratory volume in one second (FEV1)  .
Vitamin-C is a free radical scavenger present in intracellular and extracellular lung fluids and protects against endogenous as well as exogenous oxidants  . It is the most abundant antioxidant substance present in the extracellular fluid in the lung and contribute to the regeneration of membrane bound oxidized vitamin-E to function again  . Vitamin-C is known to have a general antihistamine effect  . It also inhibits the prostaglandins production  .
Most of the exacerbations of asthma in children have been associated with upper respiratory viral infections, especially rhinovirus  . There are suggestions that vitamin-C supplementation may affect the susceptibility to common cold in subjects with low intake of vitamin-C  . Moreover, vitamin-C reduces the duration of episodes and the severity of symptoms of the common cold  .
Natural sources of vitamin-C are citrus fruits and red and yellow pepper.
Vitamin-E: Vitamin-E effects have been studied and there is evidence of beneficial effects of vitamin-E on asthma ,,, . There is evidence of an inverse association between vitamin-E intake and both allergen skin sensitization and total serum Ig-E levels in adults  . High vitamin-E intake is associated with reduced asthma incidence  .
Vitamin-E is present in extracellular lung fluid and lipid membrane, where it converts oxygen radicals and lipid proxy radicals to less reactive forms. Thus vitaminE is a membrane stabilizer and principle defence against oxidant induced membrane injury by breaking the lipid peroxidation chain reaction  .
Vitamin-E seems to suppress neutrophil migration  and inhibits Ig-E production  . It may be immunomodulatory and also able to influence T-helper cell development in direction of Th1, subtype  .
Vitamin-A and b-Carotene: Vitamin-A and B-carotene have protective effect in asthma ,,, . Vitamin-A derivatives of retinol influence the development, maintainance, differentiation, and regeneration of lung epithelial cells and may play a central role in the development of airway disease , . Vitamin-A/βcarotene are lipid soluble and acts by their antioxidant action that helps to prevent membrane lipid oxidation  .
The joint effect of the intake of vitamin-C, vitamin-E and β-carotene was found to be smaller than the sum of their individual independent effect  . This may be caused by their presence in the same foods and by biological interaction of vitamin-C and E , .
Other Vitamins: Asthmatics are typically deficient in vitamin-B complex (especially vitamin-B 6 and B 12 ) and folic acid and supplementing these subjects with multivitamins can help to reduce asthma symptoms.
A deficiency of vitamin-B 6 has been found in many asthma patients  . This may be due to the fact that the medications in many asthma inhalers interfere with the absorption of vitamin-B 6 by the body  . In mild to average cases, the addition of vitamin-B 6 supplement to the diet appears to lessen the occurrence of asthma attacks  .
It has been found in a study that vitamin-B 12 taken in large doses can decrease likelihood that asthmatics react to foods with sulfites  .
Flavones and Flavanoids
Flavones and flavanoids are naturally occurring antioxidants found particularly in fruits and red wine, which may account for protective effect associated with these fruits ,,, . These are also mast cell stabilizer  .
Other dietary antioxidants
In a study, whole blood levels of antioxidantscarotenoids, lycopene, lutein, β-cryptoxanthin, a-carotene and β-carotene were measured and found to be significantly lower in asthma patients than in control  .
Fruits and Vegetables
Several studies have demonstrated a reduced risk of asthma in relation to a high fruit intake ,,,, . High intake of fruits is associated with a reduced risk of decline in FEV 1 , over a time ,, . The FEV1 in subjects with a high intake of fruits (once per week or more) is about 80-100 ml higher than in subjects with a low intake (less than once per week)  . In an Indian study, it was suggested that eating vegetables and fruits are protective for asthma/wheeze  .
Fruits and vegetables are better than vitamins pills. In a study it was found that daily intake of fruits and vegetables in infancy decrease the risk of asthma more than that by the intake of extra vitamins and cod liver oil supplements  .
It has also been found that fruits, rather than vegetables are more constantly related with increased level of lung functions. This may be explained by the fact that more fruits are high in vitamin-C, which may be more important dietary antioxidant , .
One of the most effective method of exploiting that effect to individual and population benefit is probably dietary manipulation to increase the intake of natural foods and particularly fresh fruits and vegetables.
It has been found that intake of fast foods is associated with increased risk of asthma in children. In a study, eating at fast food outlets was a significant risk factor for asthma as were the lowest intake of milk, vegetables and of fibers  . In another study, frequent consumption of hamburger showed a dose dependent association with asthma symptoms  .
In an Indian study, it was suggested that consumption of pasta, noodles and the like fast foods and meat increases the risk of asthma/wheeze among children  .
Selenium: Among minerals, selenium has been most strongly associated with asthma. Studies have demonstrated decreased selenium intake and decrease serum levels in patients with asthma ,,,, . Selenium deficiency may greatly increase the risk of asthma  .
Selenium functions as a cofactor for the antioxidant enzyme glutathione peroxidase, which is proposed to counter oxidation and to reduce the synthesis and release of leukotriene B 4 , an inflammatory mediator  . Selenium may also, along with vitamin-C, attenuate the activation of nuclear factor kappa-β, a transcription factor that upregulates inflammatory cytokines associated with the asthmatic immune response , .
Magnesium: Magnesium has several biological effects of potential relevance to asthma, including bronchodilatation when given intravenously in acute severe asthma  . There is also strong evidence of protection by dietary magnesium against asthma 1,, .
In a study, reduced magnesium intake was found to be associated with brittle asthma  . These effects of magnesium are mediated by its properties of smooth muscle relaxation and mast cell stabilization  . Milk and other dairy products, whole grains, nuts, legumes, leafy green vegetables are good sources of magnesium.
Sodium: It has been shown that bronchial reactivity to histamine is related to 24 hours urinary sodium excretion101.Bronchial reactivity appears to increase with greater salt intake ,,,,,,,, . Studies have linked increasing dietary salt intake with worsening asthma symptoms and increased bronchodilators use ,, .
Following sodium restriction in three double blind clinical trials, improvements were noted in airway responsiveness , , FEV1 , , and asthma symptoms , .Research suggests that the effects of sodium are limited to individuals with asthma. Dietary sodium may increase 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 linking copper, zinc and manganese with asthma ,,, . Copper and zinc have role in antioxidant defense as cofactor in superoxide dismutase  . Zinc is an essential trace mineral for most immune mechanisms in the body to function, including lymphocyte (T-cell) function  . Zinc deficiency may also lead to an enhanced Th 2 immune response  . Manganese has been found deficient in bronchial biopsies of asthmatic patients, indicating manganese replishment could help in treatment of asthma [l08] .
Role of Fatty Acids
Dietary fatty acids have important role in asthma. Intake of omega-3 fatty acids is potentially beneficial and of omega-6 fatty acids is detrimental to asthma ,,, .Reduced omega-3 fatty acid/omega-6 fatty acid ratio leads to high chances of asthma. Mechanisms of action proposed for dietary polyunsaturated omega-6 and omega-3 fatty acids include modification of gene expression, signal transduction pathways and production of eicasanoids, the prostagiandins and leukotrienes which are potent inflammatory mediators ,, . Well studied beneficial effect of fish in asthma is attributed to the presence of omega-3 fatty acids in fish oil  . Fish oil contains eicosapentaenoic acid (EPA) and docasahexaenoic acid (DHA)  which are competitive substrates for arachidonic acid for generation of inflammatory mediators.
In humans, the principal substrate for eicosanoid production is arachidonic acid, an unsaturated fatty acid which comprises 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 begins with the release of arachidonic acid from membrane phosphollpid by phospholipase enzymes, and subsequent metabolism by cycloxygenase or lipoxygenase, enzymes, and subsequent prostaglandin or leukotrience products  . The derivatives of arachidonic acid (an omega-6 fatty acid) are leukotriene B 4 (LTB 4 )  , a potent neutrophil chemoattractant and a pro-inflammatory mediator and cysteinyl series of LT (LTC 4 , D 4 , E 4 ) which produce 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 A 3 ) and LT (LTB 5 ) and so has the potential to reduce airway inflammation, severe bronchoconstriction and airway hyper responsiveness. EPA also reduces the production of cytokine- Tumar necrosis factor-a (T'NF-α)  which increases airway responsiveness  . On the other hand, omega-6 fatty acids such as linoleic acid, may influence the development of allergic sensitization by increasing the formation of prostaglandin E 2 (PGE 2 ), thus promoting Th2 lymphocyte response and Ig-E generation , . Fish oil may therefore alleviate certain inflammatory respiratory diseases , , preserve normal airway resistance  , and modulate allergic sensitization  .
There is also some evidence that the balance of the unsaturated fatty acids in diet may act directly to influence gene expression  . Sources of omega-3 fatty acids are fish oil, fish, shellfish and leafy vegetables. Sources of omega-6 fatty acids are vegetable fats such as margarine and processed foods.
Unsaturated fatty acids in trans-configuration, occurring in ruminant fat, dairy products and industrially hydrogenated fats, have been found to exhibit inhibiting effect on desaturation and chain elongation of essential 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 reduced risk of asthma in young children , .
Among amino acids, of particular interest are the amino acids: cystine, methionine, glycine and glutamic acid, which collectively contribute to glutathione metabolism  which is an important antioxidant that may influence susceptibility to asthma ,. Cystine, is of particular interest, as it may be converted to reduced form of cysteine by macrophages, which thus increases intracellular glutathione  . Arginine, the precursor for nitric oxide, which has been shown to be elevated in asthma  and glutamine, which has powerful antibacterial properties in vivo  are also of interest. In addition, phenylalanine is potentially important since uncontrolled phenylketonuria is associated with increased plasma Ig-E and atopic dermatitis  .Studies have drawn attention to tryptophan, where the metabolic pathways may differ in asthmatic subjects as compared to control subjects, as demonstrated by elevated urinary kynurenic acid and xantharenic acid excretion in children with asthma ,, . In a study, there was strong inverse relationship between fasting plasma glycine level and asthma risk  . It is therefore, possible that changes in the pattern of amino acids intake arising from an overall increase in the proportion of protein from animal sources  may have contributed to the rise in asthma prevalence that has occurred in the most developed countries  .
The use of intravenous treatment with multiple nutrients, including magnesium, for acute and chronic asthma may be of considerable benefit. Pulmonary functions improve progressively, the longer patients receive treatment  .
The plasticity of the immune system in early life suggests that it will be dietary influences at this stage that will have the greatest impact. Indeed, early exposure to cow's milk protein has been linked to the development of atopy and asthma  . Studies indicate that prolonged and exclusive breast feeding significantly decreases 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 earlier. Guidelines recommend that exclusive breast feeding for the first 4-6 months with introduction of solids thereafter, egg, milk, and fish being added to the diet last ,,, . Recent WHO feeding guidelines propose the introduction of solids after the sixth months following exclusive breast feeding for the prevention of asthma and atopy  . Even introduction of milk other than breast milk before the age of 4 months of age has been found a significant risk factor for all asthma and atopy related outcomes in children aged 6 years  .Incidence of allergy to cow's milk has been estimated to be from 0.3% to 7% in general infants and from 14% to 30% in "Suspected allergic" infants. In general, cow's milk has been designated the food allergen most commonly affecting children. It has been recommended that if breast feeding is not possible, consider supplementing infants with omega-3 fatty acids, lactobacillus probiotics and protein hydrolyzed formula  .
In a study, fatty acid contents of colostrum were linked to atopic sensitization in children and data showed links between the two can be observed as early as during the first few days of lactation  . In an Indian study, breast feeding was found to be protective for asthma  . This protective effect may operate through several mechanisms. These include the exclusion of milk other than breast milk (and its potentially allergic components) from the infant's diet, and the provision of immunomodulatory, anti-inflammatory, nutritional, or other components in human milk.
Role of Maternal Diet
A meta-analysis of maternal dietary avoidance during pregnancy to prevent atopic diseases in infants at high risk concluded that such avoidance is unlikely to substantially reduce the risk of atopy in the child. Moreover, such a diet may have an adverse effect on maternal and/or fetal nutrition. So it is recommended to cease strict elimination diets during pregnancy  .
Several lines of evidence suggest that maternal dietary antioxidant intake during pregnancy may have relevant antenatal influence. Maternal vitamin-E intake during pregnancy has the potential to influence postnatal susceptibility to asthma and atopic diseases by modulating fetal and neonatal Th-cell response during initial encounter with allergens . Similarly, maternal oily fish intake during pregnancy may protect offsprings from asthma.
Intestinal Flora and Probiotics
Evidence that the gut microflora may be associated with the development of atopy comes from studies comparing Estonian infants with Swedish infants. Estonian infants have a low prevalence of atopy and display greater gut colonization with lactobacillus and Eubacteria, whereas Swedish infants, who have a higher prevalence of atopy, display greater levels of Clostridium difficile rthermore, iso-caproic acid, a compound associated with C. difficile, has been detected almost exclusively in allergic infants, and the levels of other compounds associated with Lactobacillus flora were higher in non-atopic infants. Thus it has been suggested that promotion of Lactobacillus and other potentially beneficial gut micro-organisms may protect against the development of atopic disease. Breast feeding promotes gut colonization with bifidobacterium, and thus reduces chances of atopy and/or asthma .
Another method with potential to enhance the numbers of potentially beneficial organisms in the gut is the use of probiotics. Dietary supplementation with probiotics has shown encouraging 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 rate of atopic eczema at the age of two years . Thus, the role of probiotics can be considered to prevent asthma. A key factor with probiotic intervention is that it does not cause any harm. Indeed, probiotics certainly result in a more friendly gut flora, witch may have other beneficial effect on health apart from reducing rates of atopic diseases
The probiotics may provide a natural means of beneficially modulating the immune system. However, the mechanism remains unclear and more data needs to be available before conclusion can be made on their ability to impact on the development of the other allergic disease including asthma .
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