FORGET about chocolate and greasy foods. Eating too much refined bread and cereal may be the true culprit behind the pimples that plague many a youngster.
That's the theory of a team led by Loren Cordain, an evolutionary biologist at Colorado State University in Fort Collins. Highly processed breads and cereals are easily digested. The resulting flood of sugars makes the body produce high levels of insulin and insulin-like growth factor (IGF-1).
This in turn leads to an excess of male hormones. These encourage pores in the skin to ooze large amounts of sebum, the greasy goop that acne-promoting bacteria love. IGF-1 also encourages skin cells called keratinocytes to multiply, a hallmark of acne, the team say in a paper that will appear in the December issue of Archives of Dermatology.
An Australian team will soon test the theory by putting 60 teenage boys with acne on a low-carbohydrate diet for three months to see if it makes a difference. "There's lots of anecdotal evidence," says Neil Mann, the nutrition researcher at RMIT University in Melbourne who will oversee the study. "Dermatologists will tell you they have put patients on low-carbohydrate diets and seen improvements. This will be the first controlled study."
Up to 60 per cent of 12-year-olds and 95 per cent of 18-year-olds in modern societies suffer from acne, and for a few the zits persist into middle age. Yet acne is almost unknown in subsistence societies such as the Kitava islanders in Papua New Guinea and the Ache of the Amazon.
"The only foods available to these populations are minimally processed foods," Cordain points out. "They don't know refined sugars or refined grains." The Inuit people of Alaska also used to be acne-free, but pimples arrived along with a Western diet.
This could be because modern breads are made from more finely ground flour, and cereals are manufactured using high-pressure processes that disrupt the grains' protein structures with air bubbles, in either case giving digestive enzymes easy access to the starch. The pancreas responds to speedy digestion by gushing out truckloads of insulin.
Evidence suggests a link between insulin or IGF-1 and acne. Many women with acne overproduce insulin and IGF-1. When IGF-1 was used to treat people with a condition called Laron syndrome, they experienced a spike in male hormones, followed by acne. And the insulin-blunting drug metformin has been found to curb acne in women with polycystic ovary syndrome, a condition in which too much insulin is secreted.
Acne may not be the only problem caused by eating large quantities of highly refined starches. Such diets have also been blamed for causing short-sightedness (New Scientist, 6 April, p 9) and contributing to adult onset diabetes.
Author: Douglas Fox