Can what you eat affect asthma? Although research is far from definitive, there are some hints that this might be true.
"There's really no diet that will eliminate or cure your asthma but there are certain things you could be incorporating to help," says Robert Graham, MD, an internist with Lenox Hill Hospital in New York City.
Keep in mind that individual reactions to food vary a great deal, but here are some guidelines on what to eat to possibly help asthma, or at least not make it worse.
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Here's one more reason to put apples on your list of foods to eat everyday. A British study found that even after controlling for other factors, people who reported eating two to five apples a week had a 32% lower risk of asthma than people who ate less. Any amount less than that didn't seem to make a difference one way or the other.
The authors speculate that beneficial compounds known as flavonoids may be responsible. One flavonoid in particular, khellin, has been shown to open up airways.
Vitamin C is a potent antioxidant that may ward off lung damage by fighting free radicals. One in Japan found that those with the highest intake of vitamin C were less likely to suffer from asthma than those with lower intake.
Although vitamin C can be found in most fruits and vegetables, they are super-abundant in citrus fruits such as orange and grapefruit, kiwi fruit, broccoli, Brussels sprouts and tomatoes.
Carrots are famous for containing beta-carotene, another antioxidant. Preliminary studies suggest that beta-carotene, which is converted to vitamin A in the body, may reduce the incidence of exercise-induced asthma.
The pigment is also essential to keep your eyes and immune system in top shape and may even help with heart disease, cancer, and Alzheimer's disease.
Look for beta-carotene not only in carrots but other vibrantly colored fruits and vegetable such as apricots, green peppers and sweet potatoes.
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It seems that every week there's a new headline on how caffeine mightor might notaffect your health. With regards to asthma, at least, caffeine is emerging as a good guy.
One found that caffeinated coffee might modestly improve airway function for up to four hours after it is consumed, when compared with drinking decaf Joe.
"Caffeine is a bronchodilator that may improve airflow," says Dr. Graham. For the same reason, black tea might be beneficial as well.
Although skin reactions such as hives are the most common manifestation of an egg allergy, asthma is another possible reaction.
Egg allergies are most common in children and many outgrow them. If you or your child has such an allergy (your allergist can confirm with skin or blood tests), avoid eggs and egg productsso read labels carefully.
One woman in Spain who was allergic to eggs had an asthmatic reaction to a paste used to preserve ancient buildings, prompting a few experts to warn of allergic reactions in people who restore old buildings. The more likely exposure, though, is through food.
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Flax seeds are high in omega-3 fatty acids as well as magnesium. Some research suggests that omega-3s, abundant in salmon and other oily fish, have a beneficial effect on asthma, but that research is still preliminary.
Magnesium may be another helpful ingredient as it relaxes the muscles surrounding the bronchi, the airways, and so keeps them open, says Dr. Graham. Constriction of the bronchi is what triggers an asthma attack.
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According to Dr. Graham, garlic has anti-inflammatory properties. Certainly centuries of folklore has put garlic at the top of the list as a remedy for any number of ailments from hemorrhoids to viral infections.
But garlic does contain allicin, an exceptionally powerful antioxidant. A 2009 study revealed that as allicin decays in the body, it produces an acid that destroys free radicals. Does it help asthma? It might, says Dr. Graham.
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Best and worst
The data are mixed as to whether milk and other dairy products can exacerbate asthma. Still, some people do have a bona fide allergy to milk, which can result in wheezing, coughing, and other respiratory symptoms.
On the other hand, milk is one of the best sources of vitamin D, which may ease symptoms of asthma.
Whatever the final verdict on milk and other dairy products, experts are increasingly realizing that "one of most important aspects in asthma is understanding allergies," says Dr. Graham.
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Peanuts can provoke potentially fatal allergic reactions in some people and allergic asthma in others. But the harmful properties of this nut may go beyond that.
One study found children with asthma who also had a peanut allergy seemed to develop asthma earlier than kids without a peanut allergy and were also more likely to be hospitalized and more likely to need steroids.
Many asthmatic children with peanut allergies also have allergies to grass, weeds, cats, dust mites and tree pollen, all of which can trigger asthma attacks.
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The data on whether salt exacerbates asthma are mixed, but an association does make sense.
The hallmark feature of asthma is inflammation and tightening of the airways, and salt can contribute to inflammation by causing fluid retention.
"I always tell people to eat less sodium if they have asthmatic symptoms," says Dr. Graham. Reducing salt intake is good for lots of other reasons as well. And keep in mind that most salt intake comes from restaurant or processed foods, not the salt shaker on your kitchen table.
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Shellfish allergies are the third most common allergy in children (after peanuts and milk), but adults can develop these allergies as well.
If this is you, avoid crab, crayfish, lobster and shrimp dishes. (Although scallops, oysters, clams, and mussels cause fewer reactions, consult your allergist about whether these are safe for you to eat.)
Beware also of hidden shellfish in fish stock and other products and be wary of cross contamination. Unlike egg allergies, shellfish allergies usually stay with you your whole life.
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Best and worst
Several studies, along with anecdotal evidence, suggest that wine can trigger asthma attacks, possibly due to the presence of preservatives called sulfites (also found in dried fruit and shrimp).
Other studies suggest it might be the alcohol itself or another ingredient of the libation.
But still other studies found less asthma and less severe asthma in people who drank red wine. Given the mixed research, watch your intake and avoid it if it seems to be a problem.
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Avocados contain an important antioxidant called glutathione, says Dr. Graham. Experts in general hail the health-promoting qualities of antioxidants far and wide. Their role in the body is to protect cells against the damage inflicted by free radicals.
Avocadobe it in a salad or in guacamolealso are rich in monounsaturated fat, the kind of fat you actually want in your diet because it helps lower cholesterol.