Preventing Asthma with Fruits & Vegetables

Preventing Asthma with Fruits & Vegetables
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A study involving more than a million kids suggests the striking worldwide variation in childhood rates of allergies, asthma, and eczema is related to diet.

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

“Asthma is the most common chronic disease in children.” And, the prevalence is increasing around the world. Despite this, most research dollars are spent on adult chronic diseases. “One might ask whether this is because our politicians and senior administrators feel themselves to be more likely to suffer from the latter, and ignore [allergic] diseases because they have their major impact on children and young adults [who don’t vote]. [Imagine] how much more effort would be put into elucidating causes of a disorder that increased [at the same escalated rate] in the middle aged and elderly.”

Well, finally: an international study of asthma and allergies in childhood, studying more than a million children in nearly a hundred countries, making it “the most comprehensive survey of these diseases ever undertaken.” What did they find?

They found “a wide variability in the prevalence and severity of asthma, [allergies,] and eczema.” We’re talking “20-fold to 60-fold differences in prevalence of symptoms of asthma, allergic [runny nose], and atopic eczema” around the world. Striking worldwide variations in the prevalence of allergic symptoms. What does it all mean? Well, “[t]he large variability…suggests a crucial role of [some kind of] local…characteristics [determining] the differences in prevalence between one place and another.” What kind of environmental factors?

Like, why does the prevalence of itchy eyes and runny noses range anywhere from 1% in India, for example, up to 45% of kids elsewhere? There were some associations with regional air pollution and smoking rates, but the most significant associations were with diet. Adolescents “showed a consistent pattern of decreases in symptoms of wheeze (current and severe), allergic rhinoconjunctivitis and atopic eczema, associated with increased…consumption of [plants]. The more their calories and protein came from plant sources, the less allergies they seemed to have.

In general, there seems to be an “association between an increase in asthma prevalence and a decreased consumption of fresh fruits, green vegetables, and other dietary sources of antioxidants,” helping to explain why “the prevalence of asthma and respiratory symptoms are lower in populations with high intake of foods of plant origin.” “Intakes of high fat and sodium, and low fiber and carbohydrates are linked with…asthma, while traditional and vegetarian diets are associated with lower rates…”

For example, if you look closer within India, in a study of more than 100,000 people, “[t]hose who consumed [meat, for example], daily or even occasionally, were more likely to report asthma than those who were strictly vegetarian,”—which meant also avoiding eggs. Eggs have been associated, along with soda, with an “increased risk of respiratory symptoms and asthma [in schoolchildren] whereas consumptions of soy [foods] and fruits [were] associated with reduced risk of respiratory symptoms.” In fact, removing eggs from the diet, along with dairy, may improve lung function in asthmatic children in as little as eight weeks. So maybe it’s a combination of eating less animal foods and more plants.

“[H]igh vegetable intake,” for example, has been found “protective” in children, cutting the odds of allergic asthma in half. And, “[f]ruit showed a consistent protective association…for current and severe wheeze and [runny nose] in…adolescent[s]” and for current and severe asthma, allergies, and eczema in children.

But, why? I’ve talked about the endocrine-disrupting industrial pollutants building up in the meat supply that may increase the risk of allergic diseases, but the increase in asthma may be a combination of both “a more toxic environment [and] a more susceptible population.”

“The dietary changes which have occurred over recent years may have led to a reduction in these natural antioxidant defences, resulting in a shift of the antioxidant status of the whole population and leading to increased susceptibility to oxidant attack and airway inflammation.”

In adults, for example, the risk of airway “hyper-reactivity [may increase] seven-fold among those with the lowest intake of vitamin C [from plant foods], while the lowest intake of saturated fats gave a 10-fold protection,” presumably because of saturated fats have a role in triggering inflammation.

The “protective effect of plant[-based] food may [also] be mediated through effects on intestinal microflora.” It turns out that “[d]ifferences in the indigenous intestinal flora might affect the development and priming of the immune system in early childhood.”

Kids with allergies, for example, tend to be less likely to harbor lactobacilli, the good bacteria that’s found in fermented foods, and, also, just naturally on fruits and vegetables. And lactobacillus probiotics may actually help with childhood asthma, which may help explain why children raised on largely organic vegetarian diets may have a lower prevalence of allergic reactions. Infants raised in this way tend to have more good lactobacilli in their guts, compared to controls, though they were also more likely to have been born naturally, breastfed longer, and not given as many antibiotics.

So, you can’t really tell whether it’s the diet, until you put it to the test—which we’ll explore next.

Please consider volunteering to help out on the site.

Image thanks to Jakob Montrasio and dieselbug2007 via flickr

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

“Asthma is the most common chronic disease in children.” And, the prevalence is increasing around the world. Despite this, most research dollars are spent on adult chronic diseases. “One might ask whether this is because our politicians and senior administrators feel themselves to be more likely to suffer from the latter, and ignore [allergic] diseases because they have their major impact on children and young adults [who don’t vote]. [Imagine] how much more effort would be put into elucidating causes of a disorder that increased [at the same escalated rate] in the middle aged and elderly.”

Well, finally: an international study of asthma and allergies in childhood, studying more than a million children in nearly a hundred countries, making it “the most comprehensive survey of these diseases ever undertaken.” What did they find?

They found “a wide variability in the prevalence and severity of asthma, [allergies,] and eczema.” We’re talking “20-fold to 60-fold differences in prevalence of symptoms of asthma, allergic [runny nose], and atopic eczema” around the world. Striking worldwide variations in the prevalence of allergic symptoms. What does it all mean? Well, “[t]he large variability…suggests a crucial role of [some kind of] local…characteristics [determining] the differences in prevalence between one place and another.” What kind of environmental factors?

Like, why does the prevalence of itchy eyes and runny noses range anywhere from 1% in India, for example, up to 45% of kids elsewhere? There were some associations with regional air pollution and smoking rates, but the most significant associations were with diet. Adolescents “showed a consistent pattern of decreases in symptoms of wheeze (current and severe), allergic rhinoconjunctivitis and atopic eczema, associated with increased…consumption of [plants]. The more their calories and protein came from plant sources, the less allergies they seemed to have.

In general, there seems to be an “association between an increase in asthma prevalence and a decreased consumption of fresh fruits, green vegetables, and other dietary sources of antioxidants,” helping to explain why “the prevalence of asthma and respiratory symptoms are lower in populations with high intake of foods of plant origin.” “Intakes of high fat and sodium, and low fiber and carbohydrates are linked with…asthma, while traditional and vegetarian diets are associated with lower rates…”

For example, if you look closer within India, in a study of more than 100,000 people, “[t]hose who consumed [meat, for example], daily or even occasionally, were more likely to report asthma than those who were strictly vegetarian,”—which meant also avoiding eggs. Eggs have been associated, along with soda, with an “increased risk of respiratory symptoms and asthma [in schoolchildren] whereas consumptions of soy [foods] and fruits [were] associated with reduced risk of respiratory symptoms.” In fact, removing eggs from the diet, along with dairy, may improve lung function in asthmatic children in as little as eight weeks. So maybe it’s a combination of eating less animal foods and more plants.

“[H]igh vegetable intake,” for example, has been found “protective” in children, cutting the odds of allergic asthma in half. And, “[f]ruit showed a consistent protective association…for current and severe wheeze and [runny nose] in…adolescent[s]” and for current and severe asthma, allergies, and eczema in children.

But, why? I’ve talked about the endocrine-disrupting industrial pollutants building up in the meat supply that may increase the risk of allergic diseases, but the increase in asthma may be a combination of both “a more toxic environment [and] a more susceptible population.”

“The dietary changes which have occurred over recent years may have led to a reduction in these natural antioxidant defences, resulting in a shift of the antioxidant status of the whole population and leading to increased susceptibility to oxidant attack and airway inflammation.”

In adults, for example, the risk of airway “hyper-reactivity [may increase] seven-fold among those with the lowest intake of vitamin C [from plant foods], while the lowest intake of saturated fats gave a 10-fold protection,” presumably because of saturated fats have a role in triggering inflammation.

The “protective effect of plant[-based] food may [also] be mediated through effects on intestinal microflora.” It turns out that “[d]ifferences in the indigenous intestinal flora might affect the development and priming of the immune system in early childhood.”

Kids with allergies, for example, tend to be less likely to harbor lactobacilli, the good bacteria that’s found in fermented foods, and, also, just naturally on fruits and vegetables. And lactobacillus probiotics may actually help with childhood asthma, which may help explain why children raised on largely organic vegetarian diets may have a lower prevalence of allergic reactions. Infants raised in this way tend to have more good lactobacilli in their guts, compared to controls, though they were also more likely to have been born naturally, breastfed longer, and not given as many antibiotics.

So, you can’t really tell whether it’s the diet, until you put it to the test—which we’ll explore next.

Please consider volunteering to help out on the site.

Image thanks to Jakob Montrasio and dieselbug2007 via flickr

Doctor's Note

More on preventing allergic diseases can be found in Preventing Childhood Allergies and Preventing Allergies in Adulthood.

More on protecting lung function with fruits and vegetables can be found in Preventing COPD with Diet.

Surprised that probiotics can affect immune function? Check out Preventing the Common Cold with Probiotics? And, if you think that’s wild, wait until you see Gut Feelings: Probiotics & Mental Health.

What might be in plants that’s so beneficial? See Anti-inflammatory Antioxidants.

What might be in animal products that is harmful to lung function? Endocrine-disrupting industrial pollutants that build up in the food chain may be playing a role; see Alkylphenol Endocrine Disruptors & Allergies and Dietary Sources of Alkylphenol Endocrine Disruptors. Also, there’s an inflammatory omega-6 fatty acid, found predominantly in chicken and eggs, that may contribute to inflammation as well. See Inflammatory Remarks about Arachidonic Acid.

Choosing fragrance-free personal care products may also help reduce airway reactivity; see Throw Household Products off the Scent.

If fruit and vegetables are so powerful at preventing allergic diseases, what about treating allergies with plants? Coming right up! My next video is Treating Asthma with Fruits & Vegetables. Then, I compare the efficacy of plants to pills (see Treating Asthma with Plants vs. Supplements?), and I close out this video series by exploring the role an entire diet filled with plants might play in Treating Asthma & Eczema with Plant-Based Diets.

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