The consumption of alcohol is linked to the risk for breast cancer. Drinking alcoholic beverages increases the risk of breast cancer, even at relatively low (one to three drinks per week) and moderate levels. The risk is highest among heavy drinkers. Dietary factors that may increase risk include a high-fat diet and obesity-related high cholesterol levels. Dietary iodine deficiency may also play a role. Evidence for fiber is unclear. A 2015 review found that studies trying to link fiber intake with breast cancer produced mixed results. In 2016 a tentative association between low fiber intake during adolescence and breast cancer was observed.