It's not the salt shakers on our tables that explain why Americans consume way too much sodium. It's the processed foods we buy in grocery stores.

A new analysis from the Centers for Disease Control and Prevention finds that 70 percent of the pizzas, pastas and meat dishes (think frozen entrees) we purchase in chain grocery stores exceed the Food and Drug Administration's "healthy" labeling standards for salt. Americans also get a lot of sodium from soups, cold cuts and bread.

So, who's getting the most salt from packaged foods?

Researchers had a hunch that shoppers in Southern states might be filling their carts with more salty foods. Their reasoning? The prevalence of high-blood pressure (aka hypertension) — which is linked to sodium consumption — is higher in the South. (And, hey, the South has a reputation for foods like fried chicken and salty biscuits.)

For instance, a 2008 study found that high-blood pressure was most pervasive in states including Mississippi, Louisiana, Texas and South Carolina and lowest in states including Minnesota, Vermont, Iowa and Colorado.

In order to evaluate this connection, CDC researchers used Nielsen ScanTrack data, which captured sales of nearly 4,000 packaged food items sold in big, chain grocery stores around the country.

But when they looked for regional differences in the sodium content of purchased foods, their hunch did not hold up.

"No clear pattern emerged," the researchers conclude in their paper, which is published in the journal Preventing Chronic Disease.

"It was surprising," researcher Linda Schieb of the CDC told us. "There was not much variation ... and what we really found is that sodium [consumption] is high everywhere across the U.S."

So it seems there must be factors other than the sodium content of packaged foods that can help explain the regional differences in hypertension.

"We're not really sure what causes this increased level [of hypertension] in the Southeast," Schieb says.

It's possible that restaurant food is saltier in the South. And it's also possible that Southerners add more salt to food when they cook at home.

And, Schieb says, there may be other influences. For instance, the higher prevalence of hypertension tracks with other factors such as "higher levels of tobacco use, low physical activity, higher poverty rates, and less access to [health] care."

But, the big picture here? Regardless of whether you live in the South, Northeast or West Coast, "meeting sodium recommendations may be difficult in the current food environment," the researchers conclude.

Although Americans are supposed to be consuming no more than 2,300 mg of sodium per day — or less — in order to cut the risk of heart disease, on average we actually take in more than 3,300 mg each day.

Some food manufacturers have already started reducing sodium levels in processed foods. And sometimes, stealth reductions — where food manufacturers don't even mention that salt is being cut — can be effective. Studies show that consumers do not notice sodium reductions of up to about 20 percent.

Notes about the study findings: The researchers point to several limitations in their work, including the fact that they tracked purchases of food, not consumption. However, since the two track closely (people eat what they buy), this is unlikely to throw off the findings.

Another shortcoming is that the Nielsen ScanTrack database does not include all grocery sales in the country, though the sales it does capture are likely representative of overall national sales.

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