Nutrition strategies for managing asthma

June 3, 2002 in Healthy Eating, Nutrition for Children and Teenagers

Nutrition strategies for managing asthma

Asthma is one of the most commonly diagnosed illnesses in North America, affecting 13% of all Canadian students aged 5 to 19. It is a chronic lung condition that causes breathing difficulties, such as wheezing, coughing and shortness of breath. There is no cure for asthma, although it can be effectively controlled with medication and other management strategies.

People with asthma have very sensitive airways that become swollen and inflamed when exposed to irritants. During an asthma attack, the airways or bronchial tubes tighten, making it difficult for the lungs to force air in and out. This tightening and narrowing of the airways is known as bronchoconstriction and can be caused by contraction of the small muscles surrounding the bronchial tubes, swelling of airway linings, or the production of excess mucus.

Triggers or stimuli that irritate the airways often provoke asthma attacks. These triggers usually vary from person to person and can include:

  • Cold air or changes in weather or temperature
  • Exercising, crying, laughing
  • Food allergies
  • Stress or emotional upset
  • Cigarette smoke
  • Strong odours, strong fumes or other inhaled irritants

The most common causes of airway inflammation are allergens -- pollen, especially from grasses, weeds and trees; animal dander and secretions; moulds; and dust mites. Some allergens provoke an immediate asthmatic reaction by irritating the overly sensitive airways. However, in most cases exposure to allergens is also accompanied by inflammation, which tends to develop over a longer period of time. This delay can make it very difficult to identify the factors that are causing the asthma. Asthmatic symptoms may not appear until 4 to 8 hours after initial contact with the allergen or may re-appear several hours after the initial asthma attack has been successfully treated.



  • Wheezing
  • Coughing
  • Shortness of breath or laboured breathing
  • Chest tightness


Who's at risk?

The following people are more susceptible to developing the condition:

  • Individuals with a family history of asthma
  • Children - asthma affects up to 10% of children
  • Young boys -- during childhood, asthma affects twice as many boys as girls
  • Teenage girls - during adolescence, more girls than boys develop asthma
  • Babies born to women who smoke during pregnancy


Dietary Approaches

Eat a healthy diet. Be sure to eat at least 5 to 10 servings of fruits and vegetables each day and include at least one citrus fruit in your daily diet. Evidence is mounting for the protective effects of fruits and vegetables on lung function. One survey of over 46,000 people aged 15 and older determined that those with the highest intake of fruits and vegetables had a 30 percent lower risk of asthma compared to those who ate the least. It appears that vitamin C-rich fruits are especially helpful in reducing wheezing in children with asthma. A study of 12-year old asthma sufferers revealed that following a vegetarian diet for one year provided a significant decrease in asthma symptoms and allowed medication to be drastically reduced or discontinued.

Eating plenty of fruits and vegetables may prevent asthma in a few different ways. These foods offer important vitamins, minerals and antioxidants that are needed for healthy lung function. But people that eat more produce also tend to eat more fibre and less fat, two habits that can help maintain a healthy body weight. Studies conducted among women find that weight gain in early adulthood significantly increases the risk of developing adult onset asthma. What's more, researchers have learned that when obese individuals with asthma lose weight, their asthma symptoms improve.

Eating oily fish may also help prevent asthma and improve symptoms if you have the condition. Fish contains an omega-3 fatty acid called DHA (docosahexaenoic acid), which is used by the body to produce anti-inflammatory compounds. Studies show that populations that consume more fish have improved lung function and lower rates of asthma. Aim to eat fish three times a week. Better choices include salmon, trout, herring, mackerel, sardines and fresh tuna.

A low salt diet may also help provide symptom relief since many asthmatics, especially males, appear to be salt-sensitive. Evidence suggests that a high intake of salt may trigger spasm of the bronchial smooth muscle and that a low salt diet may even reduce the need for asthma medications. Consume no more than 2400 milligrams of sodium each day. As often as possible, avoid eating processed foods and adding salt to foods.

Identify food allergies. Studies on food allergies reveal that reactions to food can cause asthma symptoms, especially in children. To determine if food allergies trigger your child's asthma, try an elimination/challenge diet as outlined below. You may want to seek the help of a registered dietitian ( to help determine food allergies.

  1. Elimination phase. For a period of two weeks, eliminate common food allergens - dairy products, soy foods, citrus fruits, nuts, wheat, shellfish, fish, eggs, corn and sulfite food additives.
  2. Challenge phase. After two weeks, start introducing one food every three days. Keep a food and symptom diary. Record everything you eat, amounts eaten and what time you ate the food or meal. Document any symptoms, the time of day you started to feel the symptom, and the duration of time you felt the symptom.


Vitamins and Minerals

Vitamin B6. This vitamin may help to lessen asthma symptoms in children. One study found that a B6 supplement provided significant improvement after the second month of treatment. Children were able to reduce their dosage of asthma medication. Studies in adults have not found such benefits.

The best food sources of B6 include meat, poultry, fish, liver, legumes, nuts, seeds, whole grains, green leafy vegetables, bananas, and avocados. A multivitamin and mineral supplement will provide extra B6. If you take a separate B6 pill do not exceed the daily upper limit of 100 milligrams. Taking high doses of vitamin B6 for an extended period of time has toxic effects can cause irreversible nerve damage.

Vitamin C.  A number of studies point to the protective effects of vitamin C in asthma. This antioxidant vitamin is concentrated in the fluid that surrounds the lungs where it acts to protect the lungs from free radical damage. Studies show that people with asthma tend to have lower levels of vitamin C in their lung fluid. One study found that 2 grams of supplemental vitamin C reduced exercise-induced asthma in children and young adults.

The best food sources of vitamin C include citrus fruit, strawberries, kiwi fruit, cantaloupe, broccoli, bell peppers, Brussels sprouts, cabbage, tomatoes, and potatoes. To supplement, take 1000 milligrams of time-released vitamin C twice daily.

Magnesium.  This mineral plays an important role in lung function by influencing the contraction/relaxation state of bronchial smooth muscle. Studies show that low dietary intakes of magnesium is linked with impaired lung function, spasms of the bronchial passageway and wheezing. In one study, 40 percent of patients with asthma were deficient in magnesium. In another study have found that supplementing the diet with magnesium can help reduce asthma symptoms in people who are magnesium deficient.

To prevent a magnesium deficiency, include the following foods in your diet: nuts, seeds, legumes, prunes, whole grain cereals, leafy green vegetables, Brewer's yeast, and dairy products. Keep in mind that much magnesium is lost in refining foods, so a diet high in refined or processed food will be lacking magnesium.

To supplement, take 150-200 milligrams of magnesium citrate, aspartate, succinate or fumarte once or twice daily. Taking more than this can cause diarrhea.

Herbal Remedies

Boswellia (Boswellia serrata). This herbal product is derived from the resin of the Indian Boswellia tree. Although very few studies have been conducted, one double-blind trial did find that the herb reduced the frequency of asthma attacks and improved breathing capacity in adults with mild asthma when taken for six weeks. Seventy percent of people taking the herb experienced improvement. Boswellia is thought to work by reducing inflammation.

The effective dosage was 300 milligrams three times daily. Buy a product standardized to contain 37.5% boswellic acids. It may take up to 8 weeks to notice improvement in asthma symptoms. Boswellia has not been evaluated for safety in children or pregnant or breastfeeding women. The herb is not recommended at these times.

Recommended Websites

The Lung Association of Canada

The Asthma Society of Canada

American Lung Association


The above excerpt is from "Leslie Beck's Nutrition Encyclopedia" (Penguin Canada, 2001/2003), available at bookstores across the country. The following is copyrighted and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or means - electronic, mechanical, photocopying, or likewise.

All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.