Improving Respiratory Health With Strawberries

Introduction

The importance of our respiratory health cannot be minimised. In 2019, in England and Wales, 72,440 people died from respiratory-related diseases alone.¹ Although this has decreased over the years as a result of increasing awareness and support with smoking cessation, the number of mortalities is still far too high. In addition to this rather extreme reason to improve respiratory health, many different factors must be considered. For example, improved respiratory health will make it exponentially easier to maintain an active lifestyle, and enhancing both physical and mental health in the long-term.

There are many ways we can improve our respiratory health. These include maintaining an active lifestyle, diet modifications and removing respiratory pollutants such as smoking.² This article will mainly address diet modifications, specifically the importance of strawberries for improving our respiratory health, t, how they are important and provide different ways we can incorporate strawberries into our diet whilst ensuring a holistic approach to our respiratory health.

Nutritional components of strawberries

Vitamin C

Strawberries are consumed worldwide and are important sources of nutritional components such as Vitamim C, folate and polyphenols among many others. A Japanese-based study examined the effect of strawberries on serum Vitamin C content among healthy individuals. They found a significant increase in Vitamin C content following strawberry consumption compared to the control group.³ Consequently, it is clear that strawberries may play an important role in providing humans with Vitamin C and therefore improving our health.

Importance of Vitamin C for immune system support

Vitamin C appears to have multiple effects on the cellular functions of both the innate and adaptive immune systems. Although the exact mechanisms are unclear, it is likely its action as a cofactor for numerous biosynthetic and gene-regulatory enzymes plays a large role in its immune-modulating effects. Specifically, Vitamin C stimulates neutrophil migration to the site of infection, enhances phagocytosis and oxidant generation, and microbial killing. At the same time, it protects host tissue from excessive damage by enhancing neutrophil apoptosis and clearance by macrophages and decreasing neutrophil necrosis. Furthermore, Vitamin C can prevent and treat respiratory and systemic infections by enhancing various immune cell functions.⁴

Antioxidant properties

As an antioxidant, Vitamin C protects against oxidative stress-induced cellular damage. This bioactivity bears relevance to many inflammatory disorders such as Asthma and affects arterial elasticity and blood pressure regulation.⁵

Anthocyanins and flavonoids

Anthocyanins are flavonoid derivatives in many fruits and plants, most commonly known for their natural colouring abilities. They are present in strawberries, giving it its bright red colour. However, Anthocyanins are also hugely beneficial to our health in many ways.

Antioxidant properties

Several studies have shown that Anthocyanins inhibit COX activity, reduce PGE2 production, and reduce inflammation by inhibiting NF-κB and PI3K Akt signalling pathways. The overall effect is a significant anti-inflammatory response that Anthocyanins exert.⁶

Potential impact on respiratory conditions

Through similar mechanisms, Anthocyanins have been shown to affect respiratory conditions positively. Growing evidence supports this hypothesis that dietary flavonoids, such as those found in strawberries and other fruit, positively impact lung function and other respiratory conditions. The mechanisms of this are thought to be through attenuation of airway hyperresponsiveness, inflammation and remodelling, all producing a synergistically beneficial effect on the respiratory system ⁷

Research and studies

Numerous studies have been conducted investigating the link between strawberries and respiratory health. Some, such as Alvarez-Suarez et al examined the effect of strawberries on oxidative stress markers and cardiovascular risk. Others, such as Mehta et al focussed on lung function specifically. Although there are a variety of studies in this area, the conclusions we can draw from them remain similar.

Reduction in oxidative stress

A strong correlation has been found between strawberry intake and a reduction in oxidative stress. Sandoval-Salazer et al investigated this correlation when coupled with a high-fat diet. The study examined the effect of strawberry extract on oxidative stress levels in obese rats. The results concluded that there is a significant reduction in oxidative stress when strawberries are consumed.⁸

Improvement in lung function

Mehta et al⁷ highlights this impact very clearly. The study investigated the effect of different dietary flavonoids on lung function in elderly males. Lung function decreases with age, so elderly males were used specifially highlight the effects of these flavonoids. Strong inverse associations were found between anthocyanin intake and age-related decline in lung function. Significantly slower rates of FEV1 and FVC decline in subjects consuming regular anthocyanin were observed.

These studies further support the hypothesis that strawberries may have a significant impact on improving respiratory health.

Strawberries and asthma 

Relationship between asthma and oxidative stress

Oxidative stress plays a role in the development of many major diseases such as cancer, cardiovascular disease and immunological diseases. Oxidative stress may also play a role in the pathogenesis of asthma, a chronic inflammatory airway disease. Despite an inconclusive debate surrounding whether oxidative stress observed in asthma patients is due to the inflammation of the airways or if it is a causative factor in the pathogenesis of asthma, many recent clinical studies have supported the role of oxidative stress in the development of chronic immunological diseases such as asthma. Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) transfer stimulating signals as a critical intracellular second messenger, resulting in the modulation of immune responses such as the chronic airway inflammation seen in Asthma.⁹

Role of strawberries in reducing asthma symptoms

As mentioned earlier in the report, strawberries contain many antioxidants such as Vitamin C and anthocyanin. These possess strong anti-inflammatory properties. Asthma is a chronic inflammatory disease of the airways, therefore substances exerting an anti-inflammatory effect such as strawberries help to alleviate the inflammation seen in the pathogenesis of asthma and consequently aid in its control. As aforementioned, strawberry consumption allows the body to deal with oxidative stress relatively effectively. Oxidative stress in asthma is the source of many triggers, such as coughing/wheezing and inflammation. Providing the body with this increased antioxidant effect mitigates these triggers somewhat and has been shown to significantly impact asthma patients long-term.¹⁰

Incorporating strawberries Into the diet

Dietary recommendations for asthma

Evidence suggests diets that include plant-based foods may improve asthma symptoms through their effect on system inflammation, oxidation and microbial composition. Similarly, increased fruit and vegetable intake, reduced animal product consumption, and weight management might mediate cytokine release, free radical damage, and immune responses involved in the development and course of asthma. However, it is important to note that further clinical trials are still necessary to investigate this.¹¹

Methods to incorporate strawberries into the diet

As discussed throughout this report, strawberries potentially significantly impact respiratory health, but how does one creatively incorporate this into a diet? Below are just a few ways

• Fruit smoothies
• Fruit salads 
• Breakfast Bowls
• Snacks

Other lifestyle factors

Exercise

Although it is clear strawberries have a positive impact on respiratory health, the importance of taking a holistic approach to respiratory health must be considered. Regular exercise is vital in this regard to mitigate triggers of conditions such as asthma and strengthen the immune system, somewhat mitigating the risk of contracting infections and reducing the likelihood of the onset of respiratory diseases.

Avoidance of Irritants

Smoking

Smoking is the leading cause of lung cancer and can greatly damage the respiratory system. This may lead to increased infections, increased symptoms such as wheezing/coughing and an impaired immune system. Therefore, avoidance or stopping smoking is vital to improving and maintaining respiratory health.

Summary

• There are various steps we can take to improve our respiratory health, these include dietary modifications, exercise and smoking cessation
• Strawberries are a rich source of Vitamin C, which positively impacts immune system support and provides antioxidant properties
• Strawberries are a rich source of anthocyanin, a flavonoid derivative which possesses strong antioxidant properties, reducing oxidative stress and therefore mitigating triggers and the onset of respiratory conditions
• Oxidative stress is thought to play a role in the development of asthma, therefore the antioxidant effect of strawberries helps mitigate this risk
• Strawberries should be used synergistically with other diet modifications, regular exercise and avoidance of pollutants to use a holistic approach to respiratory health