Healthnotes Newswire People who eat more apples are less likely to develop asthma than are those who eat few, according to new research published in the American Journal of Respiratory and Critical Care Medicine.1 The study also found that high intake of foods rich in the mineral selenium reduce asthma risk. Among those who already have asthma, consumption of 1 to 2 glasses of red wine per day was associated with reduced severity of the disease.
This is the first study to report a protective effect of high apple intake on asthma, and the first to report a protective effect of high red wine intake on asthma severity. Previous research has consistently found reduced levels of selenium in the blood of adults with asthma,2 so the protective effects of a selenium-rich diet were somewhat anticipated.
Asthma is an inflammatory condition of the airways, where breathing becomes restricted due to constriction of small air passages in the lungs, called bronchi. Allergies and stress are common triggers of asthma attacks.
What do red wine, apples, and selenium-rich foods (e.g., seafood, meat, eggs, whole grains, legumes, Brazil nuts) have in common? The answer is that they are all rich in antioxidants. Apples and red wine are both high in flavonoids, which have powerful antioxidant properties. However, there are hundreds of different flavonoids in the human diet, and many in apples and red wine. Which ones are responsible for the effects observed in this study? It is not possible to say with certainty. The authors of the study suggest that the blue-black pigments (anthocyanins) found in grapes, berries, and many other plants may be key, since they are present in both apples and red wine. Anthocyanins are powerful antioxidants and free radical scavengers. These flavonoids could reduce asthma inflammation through a variety of known mechanisms.
Selenium may also be capable of suppressing the inflammation of asthma. Selenium, itself an antioxidant, is required to activate one of the most important antioxidants found in the body, called glutathione. Glutathione is thought to protect against oxidative stress in the air passages and could thus mitigate the signs and symptoms of asthma. Interestingly, glutathione and anthocyanins have shown uniquely synergistic properties in test tube research, in which they recycle one another back to their active forms and may increase each others efficacy.3
For reasons beyond those suggested by the current research, it appears prudent to eat apples 2 to 4 times per week, drink a glass of red wine in the evening, and eat plenty of whole grains. Do the results of the new study mean that people with asthma should take selenium or flavonoid supplements? Unfortunately, the research does not go far enough to make such a conclusion possible. Population-based studies such as this one are only able to establish associations, not cause-and-effect relationships. Selenium, for example, may only be a marker for some other component of the diet that protects against asthma. Population-based studies can suggest a direction for future research, but controlled clinical trials of individual nutrients would be required to state with confidence that any particular supplement could help people with asthma.
Controlled clinical trials have been conducted for several nutritional and herbal supplements. In fact, one small clinical trial has even been conducted on selenium, in which supplementation with 100 mcg of sodium selenite (a form of selenium) per day for 14 weeks resulted in clinical improvement in six of eleven people with asthma, compared with only one of ten in the placebo group.4
People with asthma, in addition to following the dietary advice suggested by the new study, may also want to consider other supplements, such as fish oil (rich in eicosapentaenoic acid, or EPA),5 lycopene,6 magnesium,7 8 vitamin B6,9 10 and vitamin C.11 Research on all of these nutrients is fairly preliminary and, in some cases (such as vitamin C and fish oil), contradictory. Herbs that have demonstrated some efficacy against asthma in preliminary studies include boswellia,12 coleus,13 ephedra,14 ivy leaf, picrorhiza,15 16 and tylophora.17 18 As with the nutrient supplements discussed above, research on these herbal preparations is of a preliminary nature, and contradictory evidence also exists for some of them.
Asthma is a potentially serious medical condition and should always be treated under the care and supervision of a qualified healthcare practitioner.References