Preventing Asthma with Fruits and Vegetables

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How Fruits and Vegetables Can Prevent Asthma

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 disease. “One might ask,” a group of researchers posited “whether this is because our politicians and senior administrators feel themselves to be more likely to suffer from the latter, and thus ignore allergic diseases as they mostly impact children and young adults” – who don’t vote.

An enormous study about asthma and allergies in childhood, highlighted in my video, Preventing Asthma with Fruits and Vegetables, was published that includes more than a million children in nearly a hundred countries, making it the most comprehensive survey of asthma and allergies ever undertaken. The researchers found striking worldwide variations in the prevalence and severity of asthma, allergies, and eczema—a 20 to 60-fold difference in prevalence of symptoms of asthma, allergic runny nose, and atopic eczema around the world. The large variability suggests a crucial role of local characteristics that are determining the differences in prevalence between one place and another.

What kind of environmental factors? Why does the prevalence of itchy eyes and runny noses range anywhere from 1% in India, for example, and 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 with increases in per capita consumption of plant foods. The more their calories and protein came from plant sources, the less allergies they tended to have.

In general, there seems to be an association between an increase in asthma prevalence and a decrease in consumption of fresh fruits, green vegetables, and other dietary sources of antioxidants, helping to explain why the prevalence of asthma and respiratory symptoms is lower in populations with high intake of foods of plant origin. High intakes of fat and sodium, and low intakes of fiber and carbohydrates, are linked with asthma, while traditional and vegetarian diets are associated with lower rates. For example, if we look closer within India, in a study of more than 100,000 people, “those who consumed meat (daily or occasionally) were more likely to report asthma than those who were strictly vegetarian.” This also meant avoiding eggs.

Eggs have been associated (along with soft drink consumption) with increased risk of respiratory symptoms and asthma in schoolchildren. On the other hand, consumptions of soy foods and fruits were associated with reduced risk of respiratory symptoms. In fact, removing eggs and dairy from the diet may improve lung function in asthmatic children in as little as eight weeks. Therefore, it may be a combination of eating fewer animal foods and more plants.

High vegetable intake, for example, has been found protective in children, potentially cutting the odds of allergic asthma in half. And fruit has also shown a consistent protective association for current and severe wheeze and runny nose in adolescents, and for current and severe asthma, allergies, and eczema in children.

Why is this? I’ve talked about the endocrine-disrupting industrial pollutants (see Dietary Sources of Alkylphenol Endocrine Disruptors) building up in the meat supply that may increase the risk of allergic disease, but the increase in asthma may be a combination of both a more toxic environment and a more susceptible population. One review notes that, “The dietary changes which have occurred over recent years may have led to a reduction in these natural antioxidant defenses, 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 those with the lowest intake of saturated fats may have a 10-fold protection, presumably because of saturated fat’s role in triggering inflammation.

The protective effect of plant-based food may also be mediated through effects on intestinal microflora. It turns out that differences 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 naturally on many fruits and vegetables. 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 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 been given antibiotics, so we can’t really tell if it’s the diet until we put it to the test (See Treating Asthma with Fruits and Vegetables).

More on preventing allergic diseases can be found in my videos 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 probiotics can affect immune function? Check out my video Preventing the Common Cold with Probiotics? And if you think that is wild, wait until you see Gut Feelings: Probiotics and 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? There are endocrine-disrupting industrial pollutants that build up in the food chain that may be playing a role. See my video Alkylphenol Endocrine Disruptors and Allergies. 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: Throw Household Products Off the Scent.

 I compare the efficacy of plants to pills (Treating Asthma With Plants vs. Supplements?) and explore the role an entire diet filled with plants might play in Treating Asthma and Eczema With Plant-Based Diets.

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, From Table to Able, and Food as Medicine.

Discuss

Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.


17 responses to “How Fruits and Vegetables Can Prevent Asthma

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  1. WOW!! All the more reason to eat loads of fruits and veggies!! But seeing this makes me wonder about that new study about citrus fruits. It doesn’t make sense that eating an orange or grapefruit each day could cause melanoma!! Do you see this as an accurate study? Or, is it an example of “more is not always better”?

      1. Yes, it was in the news yesterday. I think it might have some validity. Consider that lemon and lime juice on top of the skin makes someone very photosensitive. Maybe there are folks with leaky guts or some sort of indigestion/bad digestion of food (or unhealthy macrobiome) that allows ingested citrus to travel towards the skin, sweating it out, who knows. These science on this that came out really seems relevant and thorough, and has raised red flags.

        1. Thanks! Citrus has been identified as a “trigger” for pain in patients with migraine headaches and arthritis, but to my knowledge this is very rare.

        2. guest, you may be on to something about leaky gut and citrus.
          3 yrs ago I started drinking 1/2 a lemon in a glass of water. I have no history of ever being allergic to any food, even had the standard test done and nothing showed up. I guess it didn’t include lemon.

          Anyways I ended up with hives all over my body. Red bumps that also itched. After freaking out about that for a while I spent $100 to see a dermatologist and they prescribed me some prednisome.
          But before I took that it dawned on me to stop the lemon juice first, and very soon the hives left me.
          I guess as you get older something new might pop up. About the only citrus I eat now is maybe some orange on a salad.

    1. I haven’t heard or seen this, but if there is any validity at all, I am sure it is because of what gets done to it chemically in growth and processing, not the inherent fruit quality.

    2. Maybe people who eat more citrus also live in warm climates where citrus is grown and get more sun exposure. Could be a factor!

  2. I usually eat one type or another of citrus each day, so I may need to stop!
    Thanks for such prompt replies!!! I love the work that goes on here at Nutrition Facts!!!!!

    1. Well, if you are not experiencing any pain or discomfort I would suggest eating all the citrus you want! Just look at how healthful the stuff is! Here is a little ditty on citrus, if interested. Thanks, LAURALEAH! Of course, ultimately it’s up to you to decided what’s best to eat. Glad you are finding some helpful tips here at NutritionFacts. If you have not already, please consider keeping up with the new videos posted every weekday and subscribe to the daily video feed.

      Best,
      Joseph

      1. Just a thought to add here and that is consideration for people like me whose asthma is triggered by a salicylate sensitivity. I know I am not in the “average” group of those whose trigger is this, but I do know of at least two other persons in my area who have this too. We were all diagnosed with it by allergists. We must be careful how much fruit and veggies we eat and are equipped with our lists that tell us which fruit and veggies are “very high”, “high” etc for salicylate (which is nature’s preservative of the fruit or vegetable). PS I just love your site and it is helping me and so many others cheers, Ann

      1. Also, as I often say on this blog, don’t forget that the total diet is important. I have checked out these references and find that the poor citrus has been taken out of context. As Walt Willet, MD, of Harvard says, “Food is a package deal.” Nearly all of the health professionals in the cited studies were carnivores. Dr Campbell comments on this in his excellent book, The China Study. So, what we are really seeing in these studies is the possible effects of citrus within the context of a meaty diet. Does that apply to you? Anyone seen any studies of the frugivore vegans – do they have a higher incidence of malignant melanoma? Or what about the low fat, whole food vegans? It is my understanding that these last two groups are, in fact, widely known for their excellent skin quality and generally low cancer rates. Wasn’t there a study a few years ago that attributed cancer in general to low fruit consumption?

        1. Totally agree. It kind of seems to me that the increasingly bad animal and processed junk heavy diets, all the chemicals we are exposed to, and whatever else, are linked to the explosion of asthma, allergies, sensitivities, autoimmune issues, etc.. The whole gluten thing comes to mind. Why suddenly are there all these issues with gluten when bread has always been the “staff of life”? A dysfunctional gut and microbiome seem connected to all these issues that can manifest themselves differently in individuals, rather than being the direct fault of a food “trigger” that has been part of our diet for ages. I’m old and all this is new. In our whole school I didn’t know a single kid with asthma and only one with allergies severe enough to cause problems, and our school nurse dealt with mostly boo-boos and sniffles. Today she/he has to be a pharmacist. Crazy!

  3. Gateway to the Flavours of India
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  4. Very interesting case study which I’ve heard before and think is true but is only half the story.

    I was diagnosed with asthma as a child and it seemed as though I steadily grew out of it, but I later decided that it coincided with moving home as my bedroom was always very damp. We assumed that it was being caused by allergens in the air being produced by damp.

    Upon moving house again in the past year we found my childhood asthma had returned. What was the common factor between now and when I was a child? Both rooms that I slept in (in each house) I found small patches of mould under the bed and nestled in to the carpet. After much research, about a final solution, we purchased a PIV unit which you can learn about here to ensure I was breathing good quality air and that humidity levels weren’t a breeding ground for mould spores and allergens.

    The take away here is, of course the diet is important. But if the air you’re breathing is bad over a sustained period of time. It will impact your respiratory system and there are lots of stories to back this up.

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