THE TEST: We soaked three 12-pound turkeys in a brining solution that contained ½ cup of kosher salt (that's about 46,000mg sodium!) for 12, 18, and 24 hours. For comparison, we also analyzed an unbrined bird.
THE RESULTS: (per 4 ounces roasted turkey) No brine: white meat, 55mg; dark meat, 90mg; 12-hour brine: white meat, 151mg; dark meat, 235mg; 18-hour brine: white meat, 186mg; dark meat, 254mg; 24-hour brine: white meat, 223mg; dark meat, 260mg
The largest sodium increase happens in the first 12 hours. It then tapers off, but the tenderizing continues. Only about 1% of the total sodium from the brine is absorbed. Bottom line: If you like a longer brine (we prefer 24 hours), the added sodium isn't that significant. Brine for texture reasons, and put away sodium fears.
Kosher turkeys may have 200mg per 4 ounces due to the processing method. Frozen turkeys may have been washed in salt water to speed the freezing, adding 200 to 350mg per 4 ounces. And some birds are enhanced with up to 15% broth, which adds 330 to 440mg per 4 ounces. Check your labels.