The findings published in the journal Thorax, part of the BMJ group, and reported in the Guardian suggest that a link between fast food and asthma and allergies is biologically plausible. It could be "related to higher saturated fatty acids, trans fatty acids, sodium, carbohydrates and sugar levels of fast food and possibly preservatives". Fast foods have high levels of industrially hydrogenated vegetable fats such as margarine, which can be a source of trans fatty acids – "and there is some evidence that dietary intake of trans fatty acids is associated with asthma and allergy".
Children in their early teens who ate fast food three or more times a week saw a 39% increased risk of asthma, while six and seven years olds had a 27% increased risk. The good news? Eating three or more pieces of fruit a week cuts the chances of asthma and allergies by 11-14%.