Which Sippy Cup Reigns Supreme?

Ever since our 2-year-old son, Angus, stopped breast-feeding, my wife and I have served him milk in sippy cups [2]. Now and then, we leave one in the bottom of a bag or the back seat of our car, only to find the receptacle days—or, in several memorable cases, weeks—later, the contents curdled and foul. A run through the dishwasher takes care of the cup, but when there's a leak, we're tempted to declare Angus lactose-intolerant and put him on a strict water diet. (For the record, it's impossible to completely eliminate the odor of rancid milk from car upholstery.)

But I hear calcium is good for the bones. So after an especially nasty cleanup, I quelled the desire to deprive my son of milk from here on out and scoured the marketplace for a truly leakproof cup for kids.

Methodology
Most modern sippy cups consist of three parts: the cup itself, a lid that screws on to the threaded top, and a plastic or rubber valve that fits on the inside of the lid and controls the flow of both the liquid going out and the air coming in. Beyond this basic design, however, there's plenty of variation.

To start, I surveyed a bunch of experts—namely, the parents of young children—to find out what mattered to them most when shopping for sippy cups. By a long shot, leakproofness was the top concern. Second on the list was ease of care and assembly. A close third was ease of use—both for the child and for the adult. Most of the parents also mentioned that the style and appearance of the sippy cup played some role in their decision.

My poll of 22 parents was split down the middle on the issue of bisphenol A, a chemical used in the production of some sippy cups. In certain conditions—say, after multiple runs through the dishwasher—BPA can leach [3] out from the cup and seep into the drink it contains. Some parents were alarmed by a slew [4] of recent [5] studies [6] that have shown the ingestion of BPA to be potentially dangerous. (As the Washington Post reported [7] last year, BPA has been "linked to breast and prostate cancer, behavioral disorders and reproductive health problems in laboratory animals.") Other parents pointed out that BPA has been used in food containers for decades—seemingly without harm. Good point, but I decided to play it safe [8] and test only BPA-free cups.

Read the rest of this article [9] in Slate [10].