Using data from NHANES database, we examined the frequency of dining out, the risk of having gastrointestinal illnesses among different groups of people and the association between them. Although the results showed no significant association between the two things, we made some analysis on it and drew some conclusions.
As the world economy growing rapidly, food industry also develops faster and thus people’s alternatives to dining increase . People today not only have meals at restaurants or food stands, but also order food online, which gives them more alternatives when considering something to eat or drink. Since it brings too much convenience for those who are unwilling or unable to prepare meals by themselves, people would rather just stay at home and have their food delivered to their hands easily .
Using Fig. 2, we tried to demonstrate the association between having meals not prepared at home and gastric diseases. People have food passed through their mouth and esophagus into the stomach. The mechanical activity of the gastrointestinal tract helps to store and digest food . There are three explanations about the association. First, most fast food is rich in energy so people who frequently eat it will get too much fat intake, which does harm to their health. Second, when we prepare meals at home, we may pay more attention to the amount of salt added into the food. However, we cannot control the salt content when eating out in some restaurants or food stands. We learned from a former study that high salt intake could be associated with an increased risk of atrophic gastritis with intestinal metaplasia . Third, a study showed that among people’s sodium dietary intake, sodium added to food outside the home accounted for about 70%. Too much sodium intake is associated with gastric cancer [20, 21]. In a word, since nutrient intake and absorption are necessary for the survival of living organisms and has evolved into the specific task of the gastrointestinal system, we should pay more attention to the nutrient contents when choosing places to eat and sources of food .
By adding other single factors, we found some differences among people with different genders, ages, races and family incomes. According to Table 1, we can conclude that males showed more tendency on having meals out than females, which may due to males’ greater preference for fatty food and females’ paying more attention to their weight and figure [23, 24, 25]. When taking ages into consideration, it is obvious that younger persons show greater preference for food that are not home prepared than the older ones [26, 27]. That is mainly because young people’ s lifestyle has changed a lot due to the rapid development of society . When taking races into consideration, Non-Hispanic Black and White show more preference for eating out. In single factor analysis, we can also learn that the Non-Hispanic Black are more likely to have stomach or intestinal illness than other races. This may be related to different eating habits of people from different areas around the world. For example, in some areas the prices of beef are lower than that of vegetables. For this reason, people with lower income tend to have beef rather than vegetables that can prevent people from stomach cancer . Additionally, people who prefer eating beef that is not fully cooked may be more likely to develop gastric diseases. A former study told us that Salmonella may be transmitted from cattle to human through raw or undercooked beef . Finally, we can conclude that people with more family income tend to eat out compared with the lower ones, which is defined by the amount of $20,000. But people with higher income are less likely to have gastric diseases mainly because they pay more attention to food quality and nutrient balance. It reflects that people’ s dining-out behaviors can be influenced by economic level .
Different individuals do not have the same definition of stomach or intestinal illness, which we mention here includes some small symptoms of diarrhea and vomiting. This may be the reason why our research did not come out as a positive outcome. People sometimes neglect the symptom of a chronic illness and do not take it seriously, which may limit the number of people who suffer from such kind of disease during the survey. However, a previous study based on Chinese population found that stomach and gastric distension were related to the eating behaviors of eating out in restaurants . This result was the hypothesis we raised, but found totally not the same situation in the USA. This might be the difference of food safety and the huge gap of cooking habits between the east and the west. Another study showed that carbohydrate digestibility could influence people’ gastric health . Dietary carbohydrate is one of the most important sources of nutrition, whose digestion and absorption rely on a complex process. It begins with starch hydrolysis by pancreatic amylase in small intestinal lumen. Further digestion occurs on the surface of the intestinal cell . Thus, having food with poor digestibility when dining out can affect people’ s stomach and intestinal health, even cause gastric diseases. Furthermore, a previous study showed that there was association between poverty and gastric cancer, so we can predict that people with lower income tend to have higher risk of developing gastric diseases .
Some previous studies focused on the impact of dining out on body weight, BMI, metabolic syndrome  and cumulative phthalates inside human body  and obtained positive outcomes. Eating too much food that is not prepared at home is harmful to human body to some extent. The studies showed us that unbalanced nutrients, too much fat or salt intake and irregular dining times are the mainly problems people must be concerned about when choosing something to eat. Also, it is said that food away from home tends to higher in energy density but lower in fruits and vegetables [38, 39, 40, 41]. Additionally, the problem we study today is related to food safety. As delivery food becomes more and more popular especially among young people, it is hard not to worry about the food quality. Since it is difficult for food consumers to tell whether the food is safe and healthy to eat, people may gradually develop some chronic diseases if frequently eating out and harmful substances accumulating in their bodies. Most studies highlighted the dietary factors of patients suffering from gastric cancer [42, 43]. Since our research shows that there is no significant association between dining out and gastric illness, we can assume that people today are more concerned about food safety and trying to develop a new lifestyle with healthy eating behaviors. Besides, more restaurants in America are attempting to provide a balanced diet and high-quality food for consumers. In this case, people gain enough energy from food and keep healthy at the same time, no matter they have meals that are prepared at home or not.
There are some advantages of our research. First, we get to learn the prevalence of having meals out and the risk of having gastric illness among American adults. It can be a good reference for those who want to observe the eating behaviors among adults in America. Second, it can raise people’s awareness of food safety and nutrition intake in daily life. It is said that frequency of eating out may be related to high BMI, insulin resistance, triglycerides and low HDL-cholesterol concentrations . It may be difficult for someone to have meals prepared at home all the time, but no matter how the food is prepared, the most essential point is to guarantee the food quality and keep nutrition balanced. There are also some limitations of our research. For instance, the data we collected measuring the frequency of having meals out are limited to just one week. Whereas, having stomach or intestinal illness is a long cumulative process. Thus, there may be a mismatch between the exposure variable and the outcome variable. Another drawback is that we did not give a clear definition of the stomach or intestinal illness, which vary from chronic to acute. This may limit our data showing the number of persons who suffer from such kind of disease.
In parallel with the rapid development of society and technology, we should always broaden our scope of knowledge and try to accept new concepts in daily life. As restaurant industry growing faster, we should pay more attention to our eating behaviors and healthy lifestyles. The government and educational institute also have the responsibility to advocate and educate some knowledge about healthy diet and life to people, especially to younger children . And future research should be done on exploring the best way or frequency to eating out, considering people with different genders, ages, health conditions and so on.