After many years of study, researchers now say that sodium may influence the blood pressure and heart health of some people more than others. Meanwhile, research has raised questions about how sodium consumption may affect two other serious health concerns: stomach cancer and osteoporosis.
Increases in sodium consumption tend to raise blood pressure directly without an apparent "threshold," according to a report of the 2005 Dietary Guidelines Advisory Committee. These experts recommended we limit dietary sodium to no more than 2,300 milligrams (mg) a day. However, they also noted that some people seem to be much more sensitive to sodiumís effect on blood-pressure. People with hypertension, blacks, and middle-aged and older adults are encouraged to limit sodium to 1,500 mg or less per day.
Many Americans need to make dietary changes in their sodium intake. Using data from 2001-2002, the National Health and Nutrition Examination Survey found that Americans on average consumed approximately 3,300 mg of sodium daily. Virtually everyone (97 percent of the population) consumed more than 1,500 mg daily. Cooking and table salt account for only 5 to 10 percent of the average Americanís sodium consumption. In order to bring most of us to target levels, we need to reduce the sodium from processed foods, either choosing low-sodium versions or using less processed food.
The questions of how much to reduce sodium to control or prevent high blood pressure relates to the level of potassium in our diets. In general, researchers agree that high potassium intake lowers the risk of high blood pressure. In studies of the DASH diet (Dietary Alternatives to Stop Hypertension), for example, when people raised potassium consumption (along with other healthful plant compounds) by including 7 to 10 servings of fruits and vegetables every day and a serving of nuts, seeds or legumes most days, blood pressure was much less affected by sodium intake. The potassium goals set in the DASH diet, 4,700 mg per day, is the current recommendations for adults. Only 10 percent of men and 1 percent of women meet this goal.
Some researchers suggest that recommendations to limit sodium should focus on people that it affects most strongly, with the emphasis for most people on increasing potassium. Research also suggests that reaching and maintaining a healthy weight may be at least as important to blood pressure control as sodium intake.
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Will limiting sodium reduce risk of stomach cancer? Population studies around the world clearly link stomach cancer with high sodium consumption, usually associated with salt-preserved meats and fish. In recent years, studies have identified the bacteria Helicobacter pylori as a likely cause of many cases of stomach cancer. If limiting sodium does reduce stomach cancer risk, some suggest that moderate reduction might be enough.
Researchers are also looking at sodiumís possible association with osteoporosis, bone-thinning that dramatically raises risk of fractures. Studies have found that high sodium consumption increases calcium excretion in urine, which may cause blood levels of calcium to drop. Among other functions, calcium forms and maintains bone strength. If calcium levels become too low the body may pull the mineral from bones to maintain a safe calcium blood level. However, research suggests that urinary calcium loss could also be related to how little potassium we consume. When diets contain the recommended level of potassium, sodium reportedly has less impact on urinary calcium loss.
The bottom line: a plant-based diet high in fruits and vegetables and low in high-sodium processed foods may reduce risk of high blood pressure, osteoporosis and stomach cancer, whether due to reduced sodium or other influences. Add weight control and youíve got a picture of good nutrition.