Researchers led by Andy Smith of the School of Psychology at Cardiff University in Cardiff, Wales conducted two studies. In the first, 498 healthy individuals were asked to return to the clinic within six to 96 hours of the first signs of symptoms of an upper respiratory infection. A total of 188 people reported coming down with a cold.
When asked about their lifestyle, researchers found those who developed colds were much more likely to drink and smoke than those who did not. Those under a lot of stress also were more likely to become sick, researchers note.
In the second study, 100 participants were asked to keep a diary for 10 weeks to record any illness or any problems with memory or attention span. The study volunteers were divided into two groups: those who reported a single illness and those who reported more than one illness.
Study participants also were questioned about their lifestyles. The results showed those who reported more than one illness over the 10-week period were less likely to eat breakfast and more likely to consume alcohol. Individuals with multiple illnesses also reported having endured difficult life events in the preceding 12 months that contributed to feelings of stress, researchers reported.
The research was funded by the Economic and Social Research Council of the United Kingdom.
Smith, a professor of psychology, said these findings confirm previous research that showed stress and negative feelings can impair the immune system, leaving it vulnerable to infection. They indicate there are "clear interactions between the brain and the immune system," Smith told United Press International from Cardiff. "What one would hope is if you reverse those factors ... if you try to have positive mood, you may have the benefits."
However, there might be drawbacks to that too, Smith said. If people are in a better mood, they generally socialize more and more socializing could increase exposure to potential infections.
The results also uphold the popular axiom that breakfast is the most important meal of the day.
"There's certainly some evidence that breakfast, certainly breakfast cereal consumption, is a marker of a healthier lifestyle," Smith said. Many breakfast cereals on the market today are fortified with nutrients, he added, so there might be some nutritious benefit in the cereal.
Ruth Kava, director of nutrition at the American Council on Science and Health in New York, agreed a nutritious breakfast can help fuel a person throughout the day. Protein, found in eggs, cheese and yogurt, for example, is necessary to create antibodies, Kava explained. Antibodies are immune system molecules that fight off infection.
However, she said there is no data suggesting people who skip breakfast occasionally are going to get sick.
"There are plenty of people who fast for a day and who don't necessarily catch a cold every time," Kava told UPI.
The pastry and coffee-on-the-go breakfast is OK once in a while, she said, but not something to make a habit of.
"I think doing that once in a while isn't a big problem, but you should vary what you have."
(Reported by Katrina Woznicki in Washington.)