Vitamin A reduce sebum production

Sebum plays the biggest role in formation of acne. If there were no sebum, there would be no acne. Vitamin A may help to reduce sebum production. However, high doses of vitamin A can carry a risk of decreased bone density, birth defects, headache, and muscle and joint pain. Vitamin A supplementation may not be necessary if there is adequate intake of beta-carotene, vitamin E, and zinc, all necessary for vitamin A formation. Decreasing unhealthy fats such as margarine, hydrogenated oils, processed foods, and other sources of transfats can also improve absorption. The top ten vitamin A-rich foods are: liver, sweet potatos, carrots, mangoes, spinach, cantaloupe, dried apricots, milk, egg yolks, mozzarella cheese. Take note that alcohol, coffee, or excessive iron can all deplete your body's supply of this essential vitamin.
Sources: 1, 2, 3

Caffeine cause acne

According to some experts, caffeine-containing foods and beverages can cause or worsen acne. This may be more of an inference by association, however, as the link between the aggravation of rosacea (sometimes called adult acne), a type of skin inflammation in adults not related to acne, can be traced to food sensitivities or allergies associated with caffeine-containing foods. It is also possible that the processed sugar in caffeinated soft drinks aggravates acne. Others claim that acne and rosacea are not worsened by the caffeine contained in certain foods but by the flushing effect of ingesting hot beverages, which can make the conditions look worse. Phyllis A Balch, Prescription For Dietary WellnessPenguin Books, 2003Page 228

Mini fast to treat acne

24 hours a day the body attempts to eliminate waste products, but is often hampered by the piling in of harmful foods. When you eat you actually stop the body cleansing process. This is because it now has to work on digesting new food. This is why fasting is good - it basically let your body cleanse itself. Every good thing has to be taken in moderation. Though fasting has its benefits, you need food to survive! What some people suggest is to have a mini fast. Try to have mini fast for your breakfast. Have one type of fruit for breakfast. This will slow down the cleansing process but still allow it to continue to a degree. Oranges are best. Have only one type of fruit. Not apples and oranges, not grapefruit and orange juice. Just one type of food for this breakfast mini fast. What I have learned from this mini fast acne treatment technique is that don't eat too much unnecessary food, as it affect our body cleansing process. It make sense why Muslim say they fast to cleanse their body.
Sources: 1, 2