Just how bad is fast food for health? Cheng Wang and his team at the Sichuan University in Chengdu in western China and Lisa Wood from the University of Newcastle, Australia, are trying to answer this question.
They reviewed many different studies from other scientists according to specific criteria. They then summarised the results in an overview.
How did the team conduct the study?
The team searched for all the studies on fast food in relation to allergic diseases published in English up to February 2018 in the OVID full-text database.
The search turned up a total of 4,138 hits. All the articles were reviewed by Wang and his team in order to determine whether they contained analysable data on the subject, how good the data quality was, and whether any of them had been published more than once. Following this selection, 16 studies remained with a total of nearly 610,000 participants.
The researchers extracted information from the data sets about which fast food products were consumed and how often, and which allergy symptoms were recorded.
What were the findings of the study?
The consumption of hamburgers in particular was associated with severe asthma or acute shortness of breath. Those who ate hamburgers at least three times a week had a significantly higher risk than those who only had them once or twice a week.
It remains unclear which ingredient(s) in the fast food products could be responsible for the more frequent occurrence of allergic diseases. The researchers discuss the following mechanisms:
- Impact on the immune system: Due to the high saturated fat content in fast food products, the immune system produces more inflammatory cells, resulting in chronic inflammation, which can affect the airways.
- Poor nutrition: Fast food contains very few essential nutrients such as vitamins, minerals and antioxidants. A balanced diet should always include plenty of fresh fruits and vegetables.
How can the findings help?
Many people eat fast food every day. Ready meals can be found in nearly every food shop, in freezers and on shelves; snack stalls are a popular choice and highly frequented. Delivery services are springing up everywhere in big cities; a single phone call can get you more than enough to eat.
Ready-to-eat industrial food products not only cause weight gain, but also appear to promote allergic diseases.
Wang and his team are calling for further studies in order to confirm their findings and to find out which ingredients or mechanisms in fast food have an impact on allergy risk.