Salt May Restrict Blood Flow to Heart

Jan. 22, 2009 -- Reducing the salt in your diet can help lower your blood pressure, but it may also lower your risk for having a heart attack or stroke in another important way.

Results from a new study suggest that eating a low-sodium diet can also help keep blood vessels working properly.

The study measured the impact of salt restriction on the endothelium, the thin layer of cells that line the interior of the blood vessels and help regulate blood flow.

Overweight and obese study participants with normal blood pressure who restricted the sodium in their diets showed evidence of improved endothelial function compared to participants who did not restrict salt.

The improvement appeared to be unrelated to the impact on blood pressure, suggesting that salt restriction is independently protective of blood vessel function.

"We found that if we reduced the salt in the diet, we saw a direct, positive impact on blood vessels," nutrition researcher and study co-author Jennifer B. Keogh, PhD, tells WebMD.

Salt and the Blood Vessels

It is generally recommended that healthy people eat no more than 2,400 milligrams of sodium a day -- about the amount found in one teaspoon (6 grams) of table salt.

But the average American eats more than twice that, even if they rarely pick up a salt shaker, says Mayo Clinic cardiologist Gerald Fletcher, MD, who is a spokesman for the American Heart Association.

"Processed foods are often loaded with salt, even those that don't taste all that salty," Fletcher tells WebMD. "That is why it is so important to read labels."

The newly published study included 29 overweight and obese men and women who ate either 3 1/2 grams of salt a day (low salt) or 7 1/2 grams a day (normal salt) for two weeks. Then they switched to the other diet for two weeks.

None of the participants had high blood pressure when they entered the study.

While on the salt-restricted diet, but not the normal diet, the study participants showed improvements in endothelial function in tests designed to measure blood vessel dilation and blood flow.

The low-salt diet also led to small reductions in systolic (top number) blood pressure but not diastolic (bottom number).

The findings appear in the latest issue of the American Journal of Clinical Nutrition.

"This study suggests, but does not prove, that salt in the diet has an independent impact on blood vessel function," Keogh says.

She and Fletcher agree that larger studies are needed to confirm the findings.

"This tells us that lowering blood pressure may not be the only benefit of eating a lower-sodium diet," Fletcher says. "I would think this is certainly something that should be explored."

Tips to Lower Salt Intake

The American Heart Association (AHA) offers the following tips:

• Read labels. The FDA has established guidelines for processed foods that can help you choose wisely. A product labeled "very low sodium" must have less than 35 milligrams of sodium in a serving, and "low-sodium" foods must have less than 140 milligrams of sodium. A food labeled "reduced sodium" must contain 25% less sodium than the original product.
• Watch those seasonings. Soy sauce, steak sauce, bouillon cubes, Worcestershire sauce, and even cooking sherry are all loaded with sodium. Good, low-sodium choices include lemon juice, vinegar, and herbs.
• Choose fresh or frozen fruits and vegetables over their canned counterparts. Drain and rinse canned foods before preparing them or choose low-salt or no-salt canned items.
• Know the names. In addition to sodium chloride, sodium in foods may be labeled sodium alginate, sodium sulfite, sodium caseinate, disodium phosphate, sodium benzoate, sodium hydroxide, monosodium glutamate or MSG, or sodium citrate.