Bread is packed full of carbohydrates, which then get processed as glucose in the body. This means that bread can raise your blood sugar quickly (it is high glycemic).
Eating a diet with a higher glycemic index is associated with a higher risk of chronic diseases such as diabetes. Bread also contains a lot of gluten. People can react to gluten in negative ways such as autoimmune problems like celiac disease.
Also, bread from the grocery store typically contains ingredients and additives that should be avoided, such as high-fructose corn syrup, azodicarbonamide, and phytic acid.
To learn more on whether bread is good or bad for your health, check out the infographic below.