When you breathe in, the air is drawn in through the nose and mouth and down the airway tubes (bronchi) of the lungs. When you breathe out, the reverse happens. In people with asthma, the bronchi become inflamed and this causes them to become narrower, so it is harder to force air in and out of the lungs (breathing in and out); this leads to breathing difficulties, coughing, and wheezing. According to the Mayo Clinic, asthma is a chronic (long-term) condition in which the bronchi narrow, swell and produce excess mucus, which then fills the airways and further reduces the amount of air that can pass through.
Asthma can be triggered by multiple things, including exposure to something you’re allergic to (e.g., an allergen like pollen) or an irritant, virus, exercise, emotional stress, and other factors such as sudden changes in temperature and some foods. An asthma attack occurs when the symptoms become severe. Attacks can begin suddenly and range from mild to life-threatening when the bronchi swell so much that oxygen cannot enter the lungs and therefore cannot reach the blood. In such cases, urgent medical attention is needed.
According to Medical News Today, there are several types of asthma:
- Childhood asthma. More common than adult asthma, affecting 9.7% of 5–14-year-olds.
- Adult-onset asthma. Less common than childhood asthma but symptoms are more likely to be persistent. Precipitating factors include respiratory illness, allergies and irritants, obesity and smoking.
- Occupational asthma. Results from exposure to an irritant or allergen in the workplace, e.g., flour dust in a bakery, oil fumes in a garage, animal fur in a pet shop or lab.
- Severe asthma. Around 5-10% of cases are severe asthma. Difficult to control with medication. Around 3-4% of asthma sufferers are refractory, meaning the medications don’t work to control asthma.
- Seasonal asthma. Caused by seasonal irritants like pollen in the summer or cold air in the winter.
How Nutrition Affects Asthma
Nutrition is known to affect the course of asthma in some individuals from very early in life, there is evidence that if the mother eats foods she is allergic to she might well affect the allergies the baby experiences after birth1 (Wyness 2014), which can lead to asthma in childhood.
About 40-50% of people with asthma generally don’t need to watch what they eat, beyond eating healthily (asthma.org.uk). However, 50-60% of asthma sufferers are allergic, intolerant, or sensitive to certain foods or food additives, and in this case, eating those foods could trigger an asthma attack. Some common food allergens are gluten (from wheat and cereal products), lactose in milk, tree nuts, sesame seeds, and soya. Some of these allergies, such as milk and eggs, are more common in children but can develop in adults too. A severe allergic reaction (anaphylaxis) may appear similar to an asthma attack and can be life-threatening. Sulphite food preservatives can cause sensitivity reactions, with similar effects on asthma. These include sodium bisulphite (E222), potassium bisulphite (E228), sodium metabisulfite (E223), potassium metabisulphite (E224), and sodium sulphite (E221), and are commonly used in food processing or preparation.
Tips on Nutrition and Asthma
Medical advice is to eat a healthy diet with plenty of fresh fruits and vegetables, which are rich in antioxidants, and to avoid processed food where possible as these might contain additives that can trigger a sensitivity reaction.
Foods you’re allergic or intolerant to should be avoided. The most common foods associated with allergies are:
- Cow's milk
- Shrimp and other shellfish
- Tree nuts
Like other allergens, food allergens cause the body to release histamine, which can cause an asthma attack or even anaphylaxis.
Sensitivity-causing sulphite preservatives can be found in many processed and fresh foods such as dried fruits or vegetables, packaged or prepared potatoes, bottled lime or lemon juice, fresh and frozen shrimp and pickled foods. Sugar may play a big part in diet-related asthma in children, according to WebMD, and large amounts of sugary food like sweets should probably be avoided.
There is an anti-inflammatory diet for asthma; fresh fruits, vegetables and whole grains appear to have anti-inflammatory properties, although this has been disputed. Conversely, high-fat foods can increase bronchial inflammation2 (Guilleminault et al 2017), children who regularly eat fast food are more likely to have asthma symptoms. Foods that are rich in vitamins D and E, and fish oil can also have an anti-inflammatory effect on the bronchi and the body as a whole. In addition, food rich in dietary fibre can have a protective effect on bronchial inflammation by influencing the number and type of bacteria in the body.
According to Everyday Health, scientific studies have identified some foods that have particularly good (but temporary) anti-asthma properties, including apples and oranges, spinach, pomegranates and tomato juice, which are rich in antioxidants; ginger and turmeric, related plants, which are rich in a substance called curcumin that has anti-inflammatory properties3 (Abidi et al 2014); salmon and beans. Medical News Today adds cucumber to this list.
There is evidence that certain drinks can temporarily lessen the symptoms of asthma, including caffeinated drinks like coffee and tea, drinks containing vitamin D, some herbal teas such as ginger, and water. Conversely, people with asthma should avoid alcohol and sugary drinks. Alcoholic drinks contain sulphites and histamine, which may both induce asthma symptoms, and sugar has been implicated in bronchial inflammation and immune response4 (Kierstein et al 2008).
There is a connection between nutrition and asthma, but in most people with asthma, this extends only to eating well as part of a healthy lifestyle. Avoidance of foods that precipitate allergic or sensitivity reactions is recommended, as is excess dietary fat and sugar. There is some evidence that certain foods have a beneficial effect beyond promoting general good health, but these effects are temporary at best and not universally accepted.
1. Wyness L. Nutrition in early life and the risk of asthma and allergic disease. British Journal of Community Nursing [Internet]. 2014;19(Sup7):S28-S32. Available from: https://www.magonlinelibrary.com/doi/abs/10.12968/bjcn.2014.19.Sup7.S28
2. Guilleminault L, Williams E, Scott H, Berthon B, Jensen M, Wood L. Diet and Asthma: Is It Time to Adapt Our Message?. Nutrients [Internet]. 2017;9(11):1227. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707699/
3. Abidi A, Gupta S, Agarwal M, Bhalla H, Saluja M. Evaluation of Efficacy of Curcumin as an Add-on therapy in Patients of Bronchial Asthma. JOURNAL OF CLINICAL AND DIAGNOSTIC RESEARCH [Internet]. 2014;8(8):HC19–HC24. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190737/
4. KIERSTEIN S, KRYTSKA K, KIERSTEIN G, HORTOBAGYI L, ZHU X, HACZKU A. Sugar Consumption Increases Susceptibility to Allergic Airway Inflammation and Activates the Innate Immune System in the Lung. Journal of Allergy and Clinical Immunology [Internet]. 2008;121(2):S196-S196. Available from: https://www.jacionline.org/article/S0091-6749(07)03158-2/fulltext