Acne is caused by overproduction of sebum--an oily substance--by sebaceous glands that lie under the skin, other irritants and bacteria. Excess amounts of sebum or other irritants accumulate and block hair pores of the skin. Bacteria then infect the cells and tissues that block the pore. Foods or substances that cause irritation or inflammation, increase bacteria or boost production of sebum can trigger acne. While research results are mixed, there are many clinical reports and well-designed studies that support the contention that food can trigger acne. While it does not seem that acne is a food-related problem, oily and sugary foods may exacerbate the symptoms. Foods such as shellfish, iodized salt, and milk, which are high in iodine, may also exacerbate acne and should be avoided. In general, if you are concerned about acne, foods to be aware of, eat less or avoid include dairy products, processed foods, fatty and fried foods, meat and sugar.
Foods high on the glycemic index (GI) list can trigger acne include processed grains such as white bread, biscuits and cake; simple carbohydrates such as sugar, fructose, corn syrup and other sweeteners; and processed breads, cereals and carbohydrates. Many sweets, junk and snack foods, contain sugars that are quickly metabolized into blood sugar.
Acne can be caused by food allergies. The immune system detects the allergen—the food you are allergic to—and attacks it as if it were an invading organism. This misguided protective response by the body results in various reactions including, for some people, acne. Dairy products to be avoided include milk, butter, cheese, chocolate, cream, eggs, and margarine.
The types of fats we consume on a daily basis have a big impact on the health of our skin. Foods that contain trans-fatty acids are thought to contribute to subcutaneous oil, and to stimulate fatty acids and other irritants under the skin's oil glands and hair follicles. Foods to avoid include fatty foods such as milk, milk products such as cheese, sour cream, and ice cream, fried foods, margarine, shortening, synthetically hydrogenated vegetable oils (industrially processed liquid oils, such as soy, corn, safflower, cottonseed and canola) and fried foods.
Iodine is reported to exacerbate acne. Processed foods contain high levels of iodine (from the salt), and should be avoided. Other foods that contain iodine include fast foods, iodized salt, dairy products, egg yolks, chocolate, seafood, kelp, dried fruit, commercial bakery products and onions.
Other foods and substances such as alcohol, coffee, soda, cocoa, meat, poultry and soft drinks are also thought to trigger or exacerbate acne.
For example, it is thought that meat contains hormone or hormone-like substances that trigger hormonal responses including testosterone, which then increases sebum production.
Likewise, foods that contain caffeine or other stimulants such as coffee, chocolate, cocoa or caffeinated soda are thought to stimulate hormonal responses that trigger the release of sebum. Alcohol, as well as chocolate, fried food and refined sugar are thought to contribute to an acidic internal environment that may foster acne.