Eating fast food and consuming sugary drinks renders the most common asthma inhaler ineffective, a study warns.
The findings are worrying because asthmatics tend to eat a diet high in saturated fat and sugar, the Australian researchers found.
Therefore, those who eat unhealthy food are putting themselves further at risk as their diet is likely to interfere with the relaxation of the airways.
Australian researchers examined the Dietary Inflammatory Index (DII) to assess the inflammatory potential of individual diets.
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They then compared the DII among asthmatics to that of healthy people to find a connection between asthma and diet.
The study, headed by Professor Lisa Wood, Head of the Nutrition programme at the Centre for Asthma and Respiratory Diseases at the University of Newcastle, New South Wales, found that the DII score was higher among asthmatics.
This indicates that the diets of those with asthma were more pro-inflammatory than the diets of controls.
For every 1 unit increase in DII score, the odds of having asthma increased by 62 per cent.
The team also found that lung function was reduced by around a tenth in the third of patients with the highest DII score versus the third of patients with the lowest.
Professor Wood said: "The usual diet consumed by asthmatics in this study was pro-inflammatory relative to the diet consumed by the healthy controls, as assessed using the DII score.
"The DII score was associated with lower lung function and increased systemic inflammation. Hence, consumption of pro-inflammatory foods in the diet may contribute to worse asthma status."
In another study, Dr Mehra Haghi studied the effects of dietary fat on the effectiveness of ventolin, the most common inhaler-based treatment for asthma, also known as salbutamol.
Eating junk food can be incredibly bad for those with asthma. Photo / Thinkstock
The researchers analysed the effect of exposure to fatty acids on the transport of the treatment through bronchial epithelial cells.
Dr Haghi said: "We found that the amount of salbutamol transported through cell membrane was significantly higher in the presence of polyunsaturated fatty acids compared with saturated fatty acids or no fats at all.
"Incubation with polyunsaturated fatty acids appeared to reduce the stiffness of the cell membrane.
"Our findings suggest that the presence of polyunsaturated fatty acids is essential for membrane fluidity.
"Our findings also demonstrate that if saturated fatty acids are present, then this effect is lost and drug transport is inhibited.
"The study provides the first evidence that the transport of salbutamol can be modified by varying dietary fat consumption.
"While polyunsaturated fatty acids enhance drug transport, the presence of saturated fat inhibits drug transport, which is likely to interfere with relaxation of the airways."
Dr Samantha Walker, Deputy Chief Executive of Asthma UK, says: "Asthma is a very complex condition which is why continued research is so crucial.
"These studies provide the first evidence that 'bad' saturated fats, such as those found in butter, can adversely affect the way in which the active ingredients in salbutamol inhalers work. Interestingly this study has also demonstrated that 'good' fats, such as those found in oily fish, may enable salbutamol to work more effectively.
"In light of this it is even more important that people with asthma ensure they eat a balanced diet with plenty of fruit and vegetables and maintain a healthy weight.
The new research was presented at this year's meeting of the Thoracic Society of Australia and New Zealand.
As a general rule, if a product contains flour or sugar, it is considered 'pro-inflammatory'.
Pro-inflammatory foods include:
• White rice
• Soft drink
• Hard cheese
• Fruit juice
• Baked goods