Bread CAN cause acne. 

More Info: A U.S. study recently confirmed an intriguing international delineation with regards to this question.  Because most teenagers in the United States eat refined, or white processed bread, they were indeed susceptible to acne because of this food staple.

Acne Vulgaris: A Disease of Western Civilization Archives of Dermatology

Refined breads are quickly digested within the human system, leading to a spike in insulin and related growth factor IGF-1. However, in many other parts of the world, the link between bread and acne is minimal or non-existent, because the bread consumed is unrefined. The IGF-1 growth factor triggers an increase in the level of male hormones in the body, which in turn causes the excretion of a larger amount of sebum.

Sebum Secretions

The sebaceous glands that produce sebum are concentrated most heavily in the forehead, chin, middle of the back, ear canals, and genital area. They funnel directly into hair follicles and secrete a solution that is a mixture of glycerides, free fatty acides, squalene, and several other so-called lipids.

There are also some sebaceous glands that output directly to the skin. The ones on the eyelids are called Meibomian glands, those on the male foreskin, Tysons glands, and the glands on the upper lip or genitals are known as Fordyce spots. In all cases, the insulin and IGF-1 triggered by refined bread can make their way to these various channels.

Low-Carb Diet

For a number of years, doctors had been gathering anecdotal evidence of a the positive link between a low-carb diet and the incidence of acne. But it wasn't until a group of Australian researchers in the early 2000s created a controlled study of 60 subjects that this was specifically put to the lab test.

Today's processed breads are made with a more finely ground flour. Another culprit in today's food chain is the high-pressure manufacturing process for breakfast cereals, which alters the protein construction of flour and adds in air bubbles. In either case, it translates to the pancreas being able to more readily get to the starch of the food and secrete increased amounts in insulin into the body system.