The Centers for Disease Control and Prevention on Friday issued a warning to consumers who eat chia powder, which is made from ground dried chia seeds and often added to smoothies and other foods for its health benefits. Some of the recalled brands are Organic Traditions, Green Smoothie Girl, Navitas Naturals and Williams-Sonoma. Twenty-one people in 12 states have been sickened with salmonella linked to the chia powder, the C.D.C. said. Two have been hospitalized. Regulators in Canada are investigating similar illnesses. Symptoms include diarrhea, fever and abdominal cramps 12 to 72 hours after infection. Illnesses were reported in Arizona, California, Colorado, Connecticut, Florida, Massachusetts, Michigan, New York, Ohio, Utah, Washington and Wisconsin.