Treating Asthma with Fruits and Vegetables

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In the international study of asthma and allergies in childhood of over a million kids, “[a] consistent inverse relationship [meaning protective relationship] was seen between prevalence rates of [asthma, allergies, and eczema] and the intake of [plants,] starch, [grains,] and vegetables. If these findings could be generalised, and if the average daily consumption of these foods increased,” researchers speculated over a decade ago that “an important decrease in symptom prevalence may be achieved.” No need to speculate any more, though; plants were finally put to the test.

Researchers had proposed that by eating less and less fruits and vegetables, this had “increased the susceptibility of the population as a whole to potentially harmful inhaled substances by reducing the antioxidant defences” within our lungs.

That makes sense; the thin lining of fluid that forms the “interface” between our lung lining and the “external environment” is our “first line of defence against oxidative damage,” which plays an important role in asthma…, “contributing to airway…contraction…, mucus,” and hypersensitivity. “Antioxidants protect against oxidative stress,” though, 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.”

In fact, 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 they start eating more fruits and vegetables, then drops further when they combine more plants with less animal foods.

So, 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 each of the individual phytonutrients they measured: “…cryptoxanthin, lycopene, lutein, alpha-carotene and beta-carotene compared to healthy controls.”

So, “[t]he accumulating evidence [does suggest] that diet [has] an influence [on] modulating the response of the lung to inhaled allergens and irritants.” But, wait a second; “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. Or, in cholesterol-free vernacular, which came first—the pea, or the pod?

We know “[a]ntioxidant-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’s 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, like they did here, take asthmatics and remove fruits and vegetables from their diets, and see if they get worse.

This was the first research group to see if “altering the intake of antioxidant-rich foods directly affects asthma outcomes. Placing subjects with asthma on a low antioxidant diet for [just a matter of] days led to a significant worsening of lung function and asthma control…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.”

“Interestingly, [ironically,] the low antioxidant diet consumed by subjects,” where they were restricted to one serving of fruit and only 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, to cripple their lung function, was just like the Standard American Diet.

“[As about half] the population usually consume[s] a diet with an intake of fruit and vegetables equivalent to the study diet or less, it appears likely that this dietary pattern, which must be considered suboptimal for lung health, may be having a significant impact on asthma management, indicating the potential for typical Western dietary patterns to contribute to [the] 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 actually help with asthma? That was the second phase of the study.

Asthmatics on the Standard American Diet in this study had about a 40% chance of relapsing into an asthma exacerbation in about three months. But, put them on seven servings of fruits and vegetables, instead of three, and you can cut their exacerbation rate in half—down to 20%, just with a few fruits and vegetables.

Please consider volunteering to help out on the site.

• L G Wood, M L Garg, R J Blake, S Garcia-Caraballo, P G Gibson. Airway and circulating levels of carotenoids in asthma and healthy controls. J Am Coll Nutr. 2005 24(6):448 – 455.
• L G Wood, M L Garg, H Powell, P G Gibson. Lycopene-rich treatments modify noneosinophilic airway inflammation in asthma: Proof of concept. Free Radic Res. 2008 42(1):94 – 102.
• E R Miller 3rd, L J Appel, T H Risby. Effect of dietary patterns on measures of lipid peroxidation: Results from a randomized clinical trial. Circulation. 1998 98(22):2390 – 2395.
• P Ellwood, M I Asher, B Björkstén, M Burr, N Pearce, C F Robertson. Diet and asthma, allergic rhinoconjunctivitis and atopic eczema symptom prevalence: An ecological analysis of the International Study of Asthma and Allergies in Childhood (ISAAC) data. ISAAC Phase One Study Group. Eur Respir J. 2001 17(3):436 – 443.
• A Seaton, D J Godden, K Brown. Increase in asthma: A more toxic environment or a more susceptible population? Thorax. 1994 49(2):171- 174.
• A Soutar, A Seaton, K Brown. Bronchial reactivity and dietary antioxidants. Thorax. 1997 52(2):166 – 170.
• L G Wood, M L Garg, J M Smart, H A Scott, D Barker, P G Gibson. Manipulating antioxidant intake in asthma: A randomized controlled trial. Am J Clin Nutr. 2012 96(3):534 – 543.

Image thanks to Baylor Health Care System via flickr

• air pollution
• allergies
• animal products
• antioxidants
• asthma
• beta carotene
• chicken
• cholesterol
• eczema
• eggs
• fruit
• grains
• lung health
• lutein
• lycopene
• oxidative stress
• peas
• phytonutrients
• Plant-Based Diets
• standard American diet
• vegans
• vegetables
• vegetarians