Nutritional Interventions to Improve Asthma-Related Outcomes through Immunomodulation: A Systematic Review

Abstract

Asthma is a chronic inflammatory disease of the airways, characterized by T-helper (Th) 2 inflammation. Current lifestyle recommendations for asthma patients are to consume a diet high in fruits and vegetables and to maintain a healthy weight. This raises the question of whether other nutritional interventions may also improve asthma-related outcomes and whether these changes occur via immunomodulation. Therefore, we systematically reviewed studies that reported both asthma-related outcomes as well as immunological parameters and searched for relations between these two domains. A systematic search identified 808 studies, of which 28 studies met the inclusion criteria. These studies were divided over six nutritional clusters: herbs, herbal mixtures and extracts (N = 6); supplements (N = 4); weight loss (N = 3); vitamin D3 (N = 5); omega-3 long-chain polyunsaturated fatty acids (LCPUFAs) (N = 5); and whole-food approaches (N = 5). Fifteen studies reported improvements in either asthma-related outcomes or immunological parameters, of which eight studies reported simultaneous improvements in both domains. Two studies reported worsening in either asthma-related outcomes or immunological parameters, of which one study reported a worsening in both domains. Promising interventions used herbs, herbal mixtures or extracts, and omega-3 LCPUFAs, although limited interventions resulted in clinically relevant results. Future studies should focus on further optimizing the beneficial effects of nutritional interventions in asthma patients, e.g., by considering the phenotypes and endotypes of asthma.

The Relationship Between Vitamin D and Asthma Exacerbation

“…Also, van Brakel et al performed a systematic review involving 30 articles describing 28 individual studies clustered based on six nutritional interventions -herbs, herbal mixtures and extracts, supplements, weightloss, vitamin D, and Omega-3 LCPUFAs. They found no improvement in lung function in four out of five studies from the vitamin D3 supplementation cluster while none of the studies recorded an improvement in asthma control or quality of life with vitamin D supplements [2]. In the metanalysis involving seven randomized controlled trials by Luo et al where four studies were in adults, the researchers found no improvement in asthma exacerbation following supplementation with vitamin D; the study findings were, however, based on a statistical analysis of the data from all the seven studies reviewed [5].…”

“…The lethality associated with asthma exacerbations highlights the importance of studying asthma and conditions limiting its flare-up [5]. Chronic inflammation from asthma modulated by immune cells, T-helper (Th) cells, leads to activation of mast cell and immunoglobulin E (IgE) and contribute to further inflammation of the airways, creating wheezing, chest tightness, and cough symptoms [2].…”

“…At the same time, low vitamin D also increases the risk of progressive lung diseases, and supplementing vitamin D is beneficial in both conditions [6,[8][9][10]. Several studies have also associated low vitamin D with asthma flare-ups, poor lung functions, and ineffectiveness of asthma medications [2,7].…”

“…Asthma is a chronic airway inflammatory condition that has several triggers, including viral infections, obesity, psychosocial stress, air pollutants, stress, tobacco smoke, indoor and outdoor allergy sources, as shown in Figure 1, as well as the poor use of asthma maintenance medications; and it affects people of all ages [1,2]. Severe asthma that is unresponsive to daily maintenance medications is called asthma exacerbation.…”

Nutrition in Asthma

“…The most recent systematic review, by van Brakel et al 94 found five studies, of which none reported positive associations with lung function or asthma control. 94 The studies using New Zealand green-lipped mussel extracts were most effective-were able to reduce FeNO 95 and exhaled H 2 O 2c . 96 Interestingly, the studies with the lowest doses seemed more effective.…”