Instruct: Classify the given review as either positive or negative.
Query: High levels of Sodium

The ion exchange resin in the filter exchanges the calcium and magnesium ions for sodium ions. Put my blood pressure though the roof. Don't use this type of filter if you are hypertensive or are on a reduced salt intake diet. They sorta forget to mention that in the literature. Plus I had to exchange my first one because the lid wouldn't stay on.