The relationship between respiratory health and nutrition is rarely discussed. As far as lung health is concerned, smoking, pollution, microbial infections, common cold and occupational exposure to dust particles are major concerns. For healthy respiratory systems, we require a diet high in powerful nutrients. In fact, recent evidence shows that a nutritious diet has a major say in mitigating risk factors associated with the onset and progression of critical lung illnesses such as Chronic Obstructive Pulmonary Disease, or COPD, and asthma. Statistics from the World Health Organization show that COPD caused 3.23 million casualties in 2019, making it the third leading cause of death globally.
Undernutrition, obesity, nutrients, active compounds of plant origin and specific food groups affect the development and progression of respiratory illnesses. We discuss nutrition’s role in lung health by citing and analysing cross-sectional, epidemiological and animal model studies.
Undernutrition and lung illnesses
Undernutrition begins in the womb. A poor respiratory system in a foetus is often a result of maternal malnourishment. Patients with COPD are frequently undernourished, and clinical nutrition management is a key component of disease management. Advanced COPD is associated with weight loss, muscle wasting and micronutrient deficiency, which collectively increase mortality risk. In a 2013 review, nutritional supplements and high-calorie intake were associated with improved muscular function in malnourished COPD patients. There is not much evidence available to link asthma and undernutrition. A Japanese observational study found that undernourished individuals had poor asthma control compared to normal participants. Supplementation with branched-chain amino acids addressed protein malnutrition in COPD and produced positive results such as the growth of fat-free muscle mass.
Obesity is linked to asthma
In the United States, 250,000 new asthma cases are caused annually by obesity. In adults with healthy weight, asthma prevalence is 7.1 per cent, while in obese adults, it is 11.1 per cent. What is even more shocking is the association between obese women and asthma—14.6 per cent of obese women were diagnosed with asthma, whereas only 7.9 per cent of lean women suffered from it.
There is a strong link between obesity and multiple chronic illnesses, including asthma. However, the mechanism explaining this link is yet to be investigated. According to a 2013 study, obesity alters the mechanical functions of the respiratory system, which could be linked to asthma. However, extra body weight and associated complications such as gastroesophageal reflux, difficulty in breathing during sleep, and low lung volume can worsen asthmatic conditions. A questionnaire-based cross-sectional study involving 1,113 active asthma patients found that individuals with high Body Mass Index (BMI) reported poor asthma-specific quality of life and asthma management as well as increased asthma-associated hospitalisation than patients with normal BMI (<25 kg/m2). One study explains how chronic inflammation associated with obesity affects the immune system and causes diseases such as dementia, atherosclerosis, sleep apnea, type 2 diabetes, asthma, arthritis, gout, fatty liver and septicemia.
Offspring of obese mothers are more likely to develop asthma. In a study involving 1 lakh pregnant women, it was found that maternal weight gain is associated with a 15-30 per cent increased risk of asthma in babies. Infant and childhood obesity have also been linked to wheezing and asthma, which means there is no doubt that obesity and asthma are related. Thus, maintaining a healthy weight at all stages of life is essential for keeping your lungs in optimal condition.
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Dietary habits and respiratory health
Dietary patterns have a significant impact on respiratory health. According to a 2013 review, ensuring a diet rich in antioxidants and omega-3 fatty acids during pregnancy and childhood may protect against allergic diseases. Known as the world’s most nutritious, the Mediterranean diet has been found to protect against allergic respiratory diseases.
Mediterranean cuisine consists of plant foods such as fruits, colourful vegetables, roots, tubers, nuts, beans, seeds, complex carbs and whole grains.
In the Mediterranean diet, olive oil is the primary cooking and dressing medium, which is loaded with healthy unsaturated fats— especially omega 3. A moderate amount of yoghurt, low-fat dairy, fish, and poultry is consumed. Wine and red meat are rare in Mediterranean culture. In terms of nutrition, this diet is very powerful since it’s rich in phytonutrients, antioxidants, omega-3, fibre, protein, vitamins, and minerals. Among 700 school-aged children, a 2011 study examined the relationship between Mediterranean diet days and childhood asthma. Interestingly, these diet days were found to be inversely related to incidents of asthma. Two more studies from 2008 and 2009 produced similar results. Consuming Mediterranean food during pregnancy is known to protect against wheezing and allergies in children aged 6 and a half years.
Conversely, the ‘Western diet’, which is typically loaded with refined white sugar, vegetable oils, salt, processed meat, trans-fats, and artificial preservatives, is found to increase the risk of wheezing and asthma in children. An analysis involving around 54,000 women found those who consumed a sugary, fat-laden Western diet had more frequent asthma attacks than those who ate more fruits and vegetables. This dietary pattern has also been linked to an elevated risk of COPD.
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Lung-protective food groups and nutrients
Fruits and vegetables are always considered the best protective food group. They contain phytonutrients, vitamins, minerals, and antioxidants that guard respiratory health. Evidence shows that eating fruit and cooked green vegetables may reduce incidents of wheezing among children aged 8-12. In a 2000 prospective cohort study from the United Kingdom, adults who consumed more fruits and vegetables for 3 months had a lower risk of asthma exacerbation. Consuming antioxidants such as vitamin C, vitamin E, flavonoids and carotenoids are beneficial to a growing foetus and adults with COPD. Rachel E Foong and Graeme R. Zosky’s study from 2013 explains how vitamin D deficiency is related to respiratory diseases, even though the mechanism is unclear. Vitamin D is imperative for optimal immune function.
The role of nutrition in protecting and promoting lung health cannot be overstated. There are, however, hardly any randomised control trials examining the association between dietary patterns, food groups, metabolic conditions and respiratory health. Most references are either epidemiological or cross-sectional. To that end, it is important to remember that a balanced diet contributes to overall physical well-being, including respiratory health.
Subhasree Ray is Doctoral Scholar (Ketogenic Diet), certified diabetes educator, and a clinical and public health nutritionist. She tweets @DrSubhasree. Views are personal.
(Edited by Zoya Bhatti)