The Daily Mail have featured an article on 'gut bacteria' and how scientists discovered that it can be the cause of Obesity. 
Gut bacteria doesn't only impact on Obesity, it can also be a co-creator of diseases like Crohns and stomach cancer. Bacteria was also a co-creator of the leg ulcer of ESME so it is also involved in disease of the veins. The human body was created to process food, not to eat processed foods.
In 2007, I spoke to an Austrian nurse about stomach cancers and she said that they were seeing a high increase in intestinal cancers. I asked her if she thought that wheat was a contributory factor. She admitted that it was, the human body was not created to eat so much wheat, yeast and cereals. Hence, the importance of the unleavened bread. When I was a child we had an egg for breakfast, with one slice of bread, on other days we would have Scott's porridge oats. Especially in the winter time when children have to be warmed up before going out into the cold.
By the time I had my son, it was cereals and due to TV advertising he would only eat cereal. He liked cereal and he would eat it for breakfast, dinner and tea if I allowed him to do so. He would take bowls of it, and eat it instead of sweets. He did go through a time when he was overweight in his teens, then the weight fell off of him and he gained his natural weight for his height. When he refused to eat good home cooked food, that is when he put on weight.
Do eating cereals make them more susceptible to the colds and virus's? I would say yes. My son was more vulnerable to colds than I have been in my life, he is also prone to migraines. However, I also eat a lot of garlic and that certainly keeps the colds away as well.
Cereal advertising should be banned, so that children do not see it.