Most of us welcome the arrival of spring after a long cold winter. But warmer weather also marks the beginning of months of sneezing, wheezing and sinus congestion for many people. And if you're among the three million Canadians who have asthma, the release of countless pollens and moulds can prevent you from exercising, concentrating at work, even getting a good night's sleep.
It's estimated that 75 per cent of people with asthma also have seasonal allergies, reactions that can increase the frequency and severity of asthma attacks.
While medications are needed to help treat and prevent symptoms, a healthy diet is also an important part of an asthma treatment plan. It seems specific foods, vitamins, minerals can have a direct impact on asthma.
Asthma is a chronic inflammatory lung condition that causes chest tightness, wheezing, coughing and shortness of breath. Attacks can range from mild to severe and are usually provoked by triggers that irritate the airways such as seasonal allergies, food allergies, cold weather, exercise and cigarette smoke.
Although usually diagnosed in childhood, asthma can occur at any age. Risk factors include having a family member with asthma or allergies, being obese, exposure to high levels of allergens such as dust mites during infancy, and exposure to cigarette smoke or chemicals in the workplace.
Asthma rates have nearly doubled in North America over the past two decades and many researchers believe our changing diet may be partly to blame. Studies suggest that eating fewer fruits and vegetables and more processed foods is increasing asthma risk.
While diet can't cure asthma, studies suggest the following foods and nutrients can help manage - and possibly prevent - the condition.
Eat fruit and vegetables
Children and adults who have higher intakes of fruit and vegetables have lower rates of asthma. It seems the earlier their introduction into the diet, the better. In a study of 502 children, aged 6 to 16 years, those who ate fresh produce daily during infancy were 43 per cent less likely to develop asthma after one year of age. Asthma sufferers who eat plenty of fruits and vegetables also tend to have the condition under better control.
A Mediterranean diet rich in grapes, apples, tomatoes, nuts and olive oil may also protect from asthma. A 2007 study found that children who grew up eating this diet were 66 per cent less likely to have asthma-like symptoms compared to kids who ate fewer of these foods.
Fruit and vegetables provide vitamins, minerals and antioxidants needed for healthy lung function.
Aim to include at least seven servings of fruits and vegetables in your daily diet. Children aged 2 to 3 need at least 4 servings and four to eight-year olds need five. One serving is equivalent to one medium sized fruit, ¼ cup (50 ml) of dried fruit, ½ cup (125 ml) of vegetables and 1 cup (250 ml) of salad greens.
Get healthy fats
Studies suggest that eating oily fish may help prevent asthma and improve symptoms if you have the condition. Fish contains DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), omega-3 fatty acids used by the body to produce anti-inflammatory compounds. Aim to eat oily fish (also low in mercury) - salmon, trout, herring, mackerel, Arctic char and sardines - two times a week.
Avoid consuming large amounts of omega-6 fats found in corn, soybean and safflower oils, as well as many margarines and processed foods. There's some evidence these fats may promote inflammation and worsen asthma.
Boost vitamin E
People who consume more
vitamin E from foods - not supplements - have a lower risk of developing asthma. In addition to its antioxidant properties, vitamin E helps maintain the proper function of immune cells called mast cells. When mast cells react and accumulate in an uncontrolled manner, inflammatory compounds are released, which can contribute to asthma.
The best food sources of vitamin E include vegetable oils, almonds, peanuts, soybeans, whole grains, wheat germ, wheat germ oil, avocado and green leafy vegetables.
Low dietary intakes of magnesium have been linked with impaired lung function, airways spasms and wheezing. What's more, one study found that 40 per cent of asthma sufferers were deficient in magnesium. Magnesium is needed for the proper contraction and relaxation of the bronchi that carry air to the lungs.
Most Canadians do not meet their daily magnesium requirements. To increase your intake, include nuts, seeds, legumes, prunes, whole-grain cereals, leafy green vegetables and wheat germ in your diet.
A diet high in processed foods will be lacking magnesium since the mineral is lost in refining.
Manage food allergies
Food allergies confirmed to trigger asthma include milk, eggs, peanuts, tree nuts, soy, wheat, fish and shellfish. Food additives that can worsen asthma include sulfites added to foods such as dried fruit, wine, shrimp, bottled lemon juice and commercial potato products like frozen French fries and peeled, precut potatoes.
If you have food allergies, read ingredient lists on food labels to identify the presence of food allergens. If you suspect your child has a food allergy, discuss allergy testing with your pediatrician.
Being overweight or obese is thought to boost the risk of asthma by 50 per cent. Studies have also shown that when individuals with asthma lose excess weight, their symptoms improve. Increased weight might lead to inflammation in the respiratory tract or cause the airways to be hyper responsive, a hallmark of asthma.
Eat right when pregnant
Mounting evidence suggests that eating certain foods during pregnancy can influence the risk of children developing asthma. Studies have linked eating apples, fish and a Mediterranean diet during pregnancy with a lower risk of asthma in their children.
If you have a family history of allergies or asthma, consider avoiding nuts while pregnant. A 2008 study of nearly 4,000 expectant mothers found that those who ate nuts and nut butter daily - versus rarely or never - increased their children's risk of asthma by more than 50 per cent.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.