Treating Asthma with Fruits and Vegetables

Image Credit: Pacific Northwest Agricultural Safety and Health Center / Flickr. This image has been modified.

How Fruits and Vegetables Can Treat Asthma

In my video Preventing Asthma With Fruits and Vegetables, I highlighted an international study of asthma and allergies involving more than a million kids. The study found a consistent inverse relationship between prevalence rates of asthma, allergies, and eczema and the intake of plants, starch, grains, and vegetables. Researchers speculated “over a decade ago that if these findings could be generalized, and if the average daily consumption of these foods increased, an important decrease in symptom prevalence could be achieved.” No need to speculate any more, though, because plants were finally put to the test.

Researchers have proposed that “by eating fewer fruits and vegetables, the susceptibility to potentially harmful inhaled substances of the population as a whole may be increased because of the reduction in antioxidant defenses of the lungs.” The thin lining of fluid that forms the interface between our respiratory tract and the external environment is our first line of defense against oxidative damage. Oxidative damage is important in asthma, contributing to airway contraction, excessive mucous production, and hypersensitivity. Antioxidants protect against oxidative stress, so our lung lining contains a range of antioxidants our body makes itself, as well as those obtained from our diet, particularly from fruits and vegetables.

We can even quantify the level of oxidative stress in people by measuring the level of oxidation products in their exhaled breath, which drops as we start eating more fruits and vegetables, and drops further as we combine more plants with fewer animal foods.

Do those with asthma really have lower levels of antioxidants than people without asthma? Compared to healthy controls, subjects with asthma had lower whole blood levels of total carotenoids and lower levels of each of the individual phytonutrients they measured: cryptoxanthin, lycopene, lutein, alpha-carotene and beta-carotene compared to healthy controls.

Therefore, they posit, “the accumulating evidence does suggest that diet has an influence in modulating the response of the lung to inhaled allergens and irritants. However, it is possible that the reduced carotenoid levels in asthma are a result of increased utilization in the presence of excess free radicals.” So it’s like a chicken-or-the-egg phenomenon.

We know antioxidant-rich diets have been associated with reduced asthma prevalence. However, direct evidence that altering intake of antioxidant-rich foods actually affects asthma was lacking, until now.

There are two ways to test the effects of fruits and vegetables on asthma. Add fruits and vegetables to people’s diets and see if their asthma improves, or take asthmatics and remove fruits and vegetables from their diets and see if they get worse.

The first such study of its kind, highlighted in my video, Treating Asthma With Fruits and Vegetables, placed subjects with asthma on a low antioxidant diet. After just a matter of days, there was a significant worsening of lung function and asthma control. The researchers conclude that, “This finding is highly significant for subjects with asthma, as it indicates that omitting antioxidant-rich foods from the diet, for even a short time frame, will have a detrimental effect on asthma symptoms.”

Ironically, the low antioxidant diet consumed by subjects, where they were restricted to one serving of fruit and up to two servings of vegetables per day, is typical of Western diets. In other words, the low antioxidant diet they used to worsen people’s asthma, crippling their lung function, was just like the standard American diet.

As about “half the population usually consumes a diet with an intake of fruit and vegetables equivalent to that in the study diet or less, it appears likely that this dietary pattern, which must be considered suboptimal for lung health, may have a significant impact on asthma management, indicating the potential for typical Western dietary patterns to contribute to a worsening of lung function and asthma control.”

Within just days, cutting down fruit and vegetable intake can impair lung function, but does adding fruits and vegetables help with asthma? That was the second phase of the study.

Asthmatics on the standard American diet had about a 40% chance of relapsing into an asthma exacerbation within three months. However, put them on seven servings of fruits and vegetables a day instead of three, and we cut their exacerbation rate in half, down to 20%. Imagine if there were a drug that could work as powerfully as a few fruits and vegetables.

If manipulating antioxidant intake by increasing fruit and vegetable intake can so powerfully reduce asthma exacerbation rates, why not just take antioxidant pills instead? I cover that in my video Treating Asthma With Plants vs. Supplements?

And if a few extra servings of fruits and vegetables can make that kind of difference, what about a whole diet composed of plants? Check out Treating Asthma and Eczema With Plant-Based Diets.

What else might antioxidant-rich diets help with? See:

How many antioxidants should we shoot for? See:

Where are antioxidants found the most?

-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.


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 Treat Asthma

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  1. I’m not surprised, but since I have had a Melanoma, what do you think of that association of citrus with Melanoma? I don’t think growing up in Australia and getting a widespread deep partial thickness sunburn that caused me to miss 6 weeks of school helped much. I also wonder if kids near citrus eat more and if it is really the sun exposure?

    1. Hi Robert. A few site users were discussing this in an earlier blog. See our comments and links, here. From one study mentioned it seems citrus juice and grapefruit was the potential culprits, but the authors conclude more research is needed before any strict claims against citrus is confirmed.

      1. A psoralen video highlighting the foods that contain it would be timely by Dr. Greger. Figs, citrus, celery, and much more. These foods can increase sunburn potential, for some in a real bad way. I get fried after eating celery and figs. Badly. Lips burn real bad after figs and getting some sunshine. Very few aware of this phenomenon.

    2. It is worth reading the study if you have a history of melanoma. They carefully controlled for sun exposure and a bunch of other things. It is the second time this association has been found (albeit the first time was with one of the two cohorts in the study). It is diet in adults they looked at, not kids. The researchers suspect it is to do with the psoralens in citrus; note that psoralens are also high in a large family of veges that includes carrots, celery, parsnip, parsely, coriander, cumin, dill and others. For those of us with past severe sunburn and melanoma history the DNA damage is already done, but it may pay to consider the amount of psoralens in your diet so as not to encourage progression of other melanomas – eg, not to consume a lot of carrot and orange/celery juice.

      1. Thank you very much. I am an MD, like Dr Greger, who thinks that diet and other lifestyle interventions are the most important interventions. I will take your advice Kate and follow the study. I am so glad Dr Greger added Joseph Gonzales RD as he is prompt and thoughtful.

  2. I’ve been grappling with the issues of plant based diet now for over a year now, and wish there were more about how to ensure we get it right. My blood sugar went up, my teeth are suffering, the carbs are high on this diet compared to my old meaty, fattier one. But I got rid of acid reflux and lost weight on the plant based diet. I intend to win at it, but it’s not as easy as changing one’s food preferences. Dr. Greger sometimes gives us glimpses of his diet and that is very helpful. The blueberry amla soymilk smoothie I’m going to try out. I know his would not necessarily be for everyone, but it would help to have his menu and supplement choices as a sample of workable plan that has the research behind it, not that it’s medical advice, just common sense gained from observing research. When I mention the whole food plant-based diet to people, they are often sold already, but have heard horror stories or tried it themselves without a good plan and failed. They were not happy they had to abandon it, since they like the good effects. It’s sort of sad.

    1. bobluhrs: I’m glad you are having some partial success. I agree that the devil is in the details and it would be better to have full success. I also agree that seeing some meal plans that are backed by the best science is very helpful. I have some ideas for you:

      1) Check out the book, “Becoming Vegan – Express Edition” by Brenda Davis and Vesanto Melina. Dr. Greger has spoken highly of these authors and even had them as a guest blogger on this site. The book is excellent, extremely well researched, and includes some sample meal plans for varying levels of calorie needs. I consider it more of a reference book than a read-cover-to-cover book. So, it’s not a big investment in time to check out the book.

      2) 21 Days of Free Meal Plans – if you participate in the free PCRM (Physician’s Committee for Responsible Medicine) 21 Day Kickstart program, you will get 21 day’s worth of meal plans developed by top nutritionists. I believe that Dr. Greger has spoken support for this program and in addition to meal plans: They will hold your hand for 21 days, including recipes, videos, inspirational messages, and a forum where you can ask questions. The forum is monitored by a very respected RD.
      (Click the green “Register Now” button.)

      3) Here are Dr. Greger’s overall nutrition recommendations. It’s not quite the meal plans you are looking for, but it gives some great general advice that you will want to keep in mind, including B12:

      Hope that helps.

      1. I second Thea’s recommendation of Davis and Melina. I have the Expanded Edition. It’s permanently on my nightstand and I refer to it all the time. Everything in it is based on science, not on hunches or feelings. Just the data in tables and charts are worth the price.

    2. I agree so much!!! I got a great glimpse when Dr. G. said he had yams/sweet potatoes with dried cranberries, etc., sprinkled with cinnamon for breakfast one day. I tried something similar and had kabocha squash with frozen blueberries mixed in and sprinkled with cinnamon. It was delicious, and I never would have thought of it without having seen Dr. G’s breakfast comment one day.

  3. I´m vegan for many years, but there is no improvement in my asthma. I need an inhaler for most of the year. Seven servings of fruit and vegetables are a lot. I dont eat this every day. But I will try this in the next weeks. Best regards from Germany, Ruben

  4. Vitamin D3, or rather the hormone like substance D3, can treat and reduce the incidence of asthma attacks.
    Vitamin D3 is recommended on this site for all people. Sunlight would probably be better. Modern windows are UV opaque and probably let less D3 be made when people sit next to the them than ever before. I am interested in the D content of foods. I think cooking destroys it. Plants use Vitamin D and it may be present in fruits.

  5. My asthma resolved shortly after I eliminated all dairy products from my diet, around 25 years ago. I used to need to carry my inhaler with me at all times just in case I experienced a flare up. Haven’t touched one in over two decades now and feel great! Should have made the move from veggie to vegan sooner…

  6. I’m confused about reaching 9-13 servings of fruits and vegetables, as the USDA uses cups now instead. When you refer to a serving of fruit, is that the previously used USDA serving size of about 1/2 cup for most and 1 cup for leafy greens? Or is each serving now 1 cup for most and 2 cups for leafy greens? I find references to both measurements as a serving online. I don’t think I’m the only one confused! :) Thank you so much!

  7. asthma is a chronic disease but has good and successfully treatment with home cure in this site good procedure but if you want more then join now me may be i help someone.

  8. After discovering this site three weeks ago and reading several articles, I commenced a vegetarian diet (2 weeks ago). The asthma seemed to improve. However, in the second week I was tired, couldn’t sleep, had headaches and felt lethargic. I went back onto meat (only once per day) and feel better. Unsure how this has affected the asthma.

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