Hormonal shifts that occur every month in women during reproductive years can cause physical symptoms and changes in mood, both prior to and during the menstrual (MEN-struhl) period. Premenstrual syndrome, or P-M-S, usually starts a week to 10 days before a woman's period. It can trigger increased appetite and food cravings, such as for salty or sugary foods, especially chocolate. It's believed that a craving for sweets may be linked to the body's desire to raise levels of the hormone serotonin (ser-uh-TONE-un), which drop prior to menstruation. However, the mood swings and depression that accompany P-M-S might be caused or aggravated when women increase their sugar intake. Research conductedat Texas A&M University shows that depression and fatigue which accompany P-M-S often vanish when sugar and caffeine are removed from the diet. Research at M-I-T noted that eating substances high in fats and sugars also triggered P-M-S symptoms. You may find that avoiding sugar and caffeine, while also eating a low-fat, high-complex carbohydrate diet may help. If you have severe cramps during your cycle, consider avoiding dairy products, meat, oils, and fried foods.