Diet and asthma: some food for thought

Today in the western world, it’s impossible to walk down a city street without running into a fast food restaurant. When we’re surrounded by so many unhealthy food options it can be difficult to make healthy decisions, which can have a whole host of consequences for our health.

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We all know that eating fast food more than a few times a week is probably going to take a toll on our heart, weight, blood pressure, and cholesterol levels.1 But have we thought about the impact it can have on our respiratory health as well?

High intake of refined grains, red and processed meats, desserts, and fried foods (along with low intake of fruit and vegetables) is thought to promote a proinflammatory environment due to factors such as a lack of antioxidants. This can increase vulnerability to oxidative stress, leading to an excess of saturated fatty acids and potentially cause innate immune activation involving receptors such as toll-like receptor 4, which promotes the NF-κB inflammatory cascade. As we know, asthma is characterized by chronic inflammation of the airways, so could a modification in diet help to reduce the risk of the disease?2

While some may be skeptical about the anti-asthmatic effects of antioxidants, some studies have showed promising results.3–5 For example, a randomized controlled trial published in The American Journal of Clinical Nutrition investigated the effects of a low-antioxidant diet (≤2 servings of vegetables and 1 serving of fruit daily, with or without lycopene supplementation) compared with a high-antioxidant diet (5 servings of vegetables and 2 servings of fruit daily) in adults with asthma. The study showed that after two weeks, those on the low-antioxidant diet had a lower percentage predicted forced expiratory volume in one second (FEV1) and percentage predicted forced vital capacity (FVC), than those in the high-antioxidant diet group. In addition, at the end of the study, the high-antioxidant diet group was found to have greater time to exacerbation, with the low-antioxidant group 2.26 times (95% CI:1.04, 4.91; P=0.039) more likely to have an exacerbation.3
 

Results such as these suggest that increasing intake of antioxidant-rich foods can be more effective at improving asthma outcomes than using a nutrition supplement (which may explain the discrepancy in antioxidant supplementation study results). This indicates that it may be beneficial to consume antioxidants in their natural matrix (i.e. as part of a diet high in fruit and vegetables), as opposed to the isolated nutrients—but the level of evidence in this area in still low.3
As understanding of antioxidant enzymes increases, so will our understanding of the relationship between diet, oxidative stress, and asthma. But for now, results such as these indicate that eating plenty of fruit and vegetables probably won’t do asthmatics much harm and may even help with asthma control.3,6

References

  1. Eating Fast Food. Available at: http://www.heart.org/HEARTORG/HealthyLiving/HealthyEating/DiningOut/Eating-Fast-Food_UCM_301473_Article.jsp#.W2xuOtJKiUk. Accessed: August 2018.
  2. Guilleminault L et al. Nutrients 2017; 9(11): 1227.
  3. Wood LG et al. Am J Clin Nutr 2012; 96(3): 534–543.
  4. Wood LG et al. Free Radic Res 2008; 42(1): 94–102.
  5. Romieu I et al. Respir Res 2009; 10: 122.
  6. Hubbard R and Fogarty A. Thorax 2004; 59: 3–4.

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