Impact of Diet on Asthma: Q & A

It is well known that diet and nutrition are modifiable risk factors that can have a significant impact on chronic metabolic conditions such as type 2 diabetes. Evidence is accumulating that suggests food choices and dietary supplementation may also have an impact on the progression and management of respiratory disease, including asthma and chronic obstructive pulmonary disease. Have you been following the literature? Try these 6 questions to see what you know about asthma and hamburgers, among other interesting findings.

1. Which of the following diets may have protective effects against allergic respiratory diseases, according to epidemiologic studies?

A. Mediterranean

B. Ornish

C. Vegan

E. DASH

Answer, discussion and new question on next page.

Answer. A. Mediterranean

Several studies have suggested that the Mediterranean diet has protective effects against allergic respiratory disease.¹ A cross-sectional questionnaire study of 700 Greek children aged 10 to 12 years found that children with greater adherence to the Mediterranean diet were less likely to have wheeze or be diagnosed with asthma.² Other studies have linked adherence to the Mediterranean diet with better asthma control in adults,³ and have indicated a protective effect against wheeze and allergy in children born to women who followed the Mediterranean diet during pregnancy.⁴ The core of the Mediterranean diet is high intake of minimally processed foods, particularly olive oil, fruits, vegetables, breads, cereals, beans, nuts and seeds, low to moderate consumption of dairy, fish, poultry, and wine, and low intake of red meat. 

2. Carotenoids are plant pigments that may help decrease inflammation found in asthma. Which of the following is not a carotenoid?

A. Lycopene

B. α- and β-carotene

C. Lutein

D. β-cryptoxanthin

E. All of the above are carotenoids

Answer, discussion and new question on next page.

Answer. E. All of the above are cartenoids 

Carotenoids are fat-soluble antioxidants that can scavenge reactive oxygen species, reducing oxidative stress and potentially improving respiratory health.⁵ Lycopene is found mostly in tomatoes. α- and β-carotene are most highly concentrated in orange-colored fruits and vegetables, such as carrots, sweet potatoes, pumpkin, and cantaloupe. Lutein is found in green, leafy vegetables, such as kale, spinach, collard greens, and dandelion. β-Cryptoxanthin is found in tangerines, red peppers, pumpkin, butternut squash, paprika, and related fruits and vegetables.

3. Supplementation with vitamin C has been linked to reduced risk of asthma.

A. True

B. False

Answer, discussion and new question on next page.

Answer: B. False

While observational studies have suggested that vitamin C may be beneficial for respiratory health, interventional studies have failed to bear this out. One reason could be that supplementing with an isolated nutrient may not be enough to compensate for the variety of nutrients found in a well-rounded diet. Eating vitamin C–rich foods, such as fruits and vegetables, may be more effective than supplementing with vitamin C.¹

4. What mechanisms could explain the possible protective effect for vitamin D in asthma?

A. Vitamin D may decrease susceptibility and severity of respiratory infections

B. Vitamin D may decrease airway remodeling

C. Vitamin D may improve responsiveness to corticosteroids

D. A and B only

E. All of the above

Answer, discussion and new question on next page.

Answer: E. All of the above

Although vitamin D can be obtained from the diet, the main source of vitamin D is exposure to sunlight. Activated vitamin D may alter the production of antimicrobial compounds such as cathelicidins and defensins,⁶ as well as decrease the expression of rhinovirus receptors on endothelial and immune cells.⁷ In addition, in vitro studies have suggested that vitamin D may inhibit the proliferation of airway smooth muscle cells.⁸ Observational studies have suggested that vitamin D may improve responsiveness to corticosteroids,⁹ and reduce the incidence of asthma exacerbations.¹⁰ There is too little evidence from interventional trials, however, to  recommend widespread supplementation with vitamin D.¹      

5. All of the following statements about omega-3 polyunsaturated fatty acids (PUFAs) are true except:

A. Laboratory studies have shown that long-chain omega-3 PUFAs decrease the production of proinflammatory prostaglandins and leukotrienes

B. Laboratory studies have shown that long-chain omega-3 PUFAs down-regulate production of proinflammatory cytokines

C. Conflicting information exists about the role of omega-3 PUFAs in asthma

D. Because studies have suggested that long-chain omega-3 PUFAs have a positive effect on asthma, supplementation with omega-3 PUFAs is generally recommended

Answer, discussion and new question on next page.

Answer: D. Because studies have suggested that long-chain omega-3 PUFAs have a positive effect on asthma, supplementation with omega-3 PUFAs is generally recommended (not true)

Laboratory studies have suggested that long-chain omega-3 PUFAs can decrease production of certain types of prostaglandins and leukotrienes, as well as decrease proinflammatory mediators such as NF-ĸB, interleukin-1β, and TNF-α. Although some observational studies in humans have suggested a beneficial effect of fish consumption in asthma, others have shown the opposite.¹ A 2010 Cochrane review found insufficient evidence to recommend supplementation with omega-3 PUFAs in persons with asthma.¹¹

6. Consumption of “fast food” has been linked to increased risk of asthma in children.

A. True

B. False 

Answer and discussion on next page.

Answer: A. True

The “western” dietary pattern, which includes refined grains, cured and red meats, fried foods, high-sugar beverages and desserts, and high-fat dairy products, has been linked to higher risk of asthma in children. In particular, take-away meals, such as hamburgers and high-salt foods, have been linked to asthma, wheezing, and airway hyperresponsiveness. One study, in particular, found that a dietary challenge with high-fat fast food resulted in increased airway inflammation and impaired bronchodilator recovery.¹¹      

References:

1. Bronwyn SB, Wood LG. Nutrition and respiratory health. Nutrients. 2015;7:1618-1643. doi:10.3390/nu7031618

2. Arvaniti F, Priftis KN, Papadimitriou A. Adherence to the Mediterranean type of diet is associated with lower prevalence of asthma symptoms, among 10-12 years old children: the PANACEA study. Pediatr Allergy Immunol. 2011;22:283-289. doi:10.1111/j.1399-3038.2010.01113.x.

3. Barros R, Moreira A, Fonseca J. Adherence to the Mediterranean diet and fresh fruit intake are associated with improved asthma control. Allergy. 2008;63:917-923. doi:10.1111/j.1398-9995.2008.01665.x.

4. Chatzi L, Torrent M, Romieu I. Mediterranean diet in pregnancy is protective for wheeze and atopy in childhood. Thorax. 2008;63:507-513. doi:10.1136/thx.2007.081745. Epub 2008 Jan 15.

5. Grieger JA, Wood LG, Clifton VL. Improving asthma during pregnancy with dietary antioxidants: the current evidence. Nutrients. 2013;5:3212-3234. doi:10.3390/nu5083212.

6. Hiemstra PS. The role of epithelial β-defensins and cathelicidins in host defense of the lung. Exp Lung Res. 2007;33:537–542.

7. Martinesi M, Bruni S, Stio M, Treves C. 1,25-Dihydroxyvitamin D3 inhibits tumor necrosis factor-α-induced adhesion molecule expression in endothelial cells. Cell Biol Int. 2006;30:365–375.

8. Song Y, Qi H, Wu C. Effect of 1,25-(OH)2D3 (a vitamin D analogue) on passively sensitized human airway smooth muscle cells. Respirology. 2007;12:486–494.

9. Searing DA, Zhang Y, Murphy JR, et al. Decreased serum vitamin D levels in children with asthma are associated with increased corticosteroid use. J Allergy Clin Immonol. 2010;125:995–1000.

10. Foong R, Zosky G. Vitamin D deficiency and the lung: disease initiator or disease modifier? Nutrients. 2013;5:2880–2900.

11. Thien FCK, Woods R, De Luca S, Abramson MJ. Dietary marine fatty acids (fish oil) for asthma in adults and children (Cochrane Review). In: The Cochrane Library. Chichester, UK: John Wiley & Sons, Ltd; 2002 (updated 2010).

12. Wood LG, Garg ML, Gibson PG. A high-fat challenge increases airway inflammation and impairs bronchodilator recovery in asthma. J Allergy Clin Immunol. 2011;127:1133–1140.