An update on salt, sodium, and DASH

High blood pressure (hypertension) affects about one in three adults in the United States and can lead to heart disease, stroke, heart failure, kidney failure, and other health problems. Decades of National Heart, Lung, and Blood Institute (NHLBI) supported research published in peer-reviewed journals have established high sodium intake as an important cause of high blood pressure and have clearly demonstrated that reducing the amount of sodium in one's diet can significantly lower blood pressure and can help safely prevent or control high blood pressure. The Dietary Approaches to Stop Hypertension (DASH) eating plan, combined with reduced sodium intake, may help individuals prevent the development of high blood pressure as well as benefit those with prehypertension and hypertension.

The DASH clinical study
The initial DASH clinical study was funded by the NHLBI and published in 1997. The study involved 459 adults with systolic blood pressures of less than 160 mmHg and diastolic pressures of 80-95 mmHg. About 27% of the participants had high blood pressure; 50% of the participants were women; and 60% were African Americans.

The study compared three eating plans:

• a plan that included foods similar to what many Americans regularly eat
• a plan that included foods similar to what many Americans regularly eat plus more fruits and vegetables
• the DASH eating plan, which emphasizes fruits, vegetables, and low fat dairy foods and is low in saturated fat, total fat, and cholesterol.

All three plans included about 3,000 milligrams of sodium daily. None of the plans were vegetarian or used specialty foods.

Participants who followed both the plan that included more fruits and vegetables and the DASH eating plan had reduced blood pressure. The DASH eating plan had the greatest effect, especially for those with high blood pressure. Furthermore, the blood pressure reductions occurred within 2 weeks of starting the plan.

The DASH-Sodium clinical study
A subsequent study, conducted from 1997 through 1999, looked at the effects of the DASH diet and a reduced dietary sodium intake on blood pressure. The research involved 412 participants, aged 22 and older, with systolic blood pressures of 120-159 mmHg and diastolic blood pressures of 80-95 mmHg. About 41% of the participants had high blood pressure; 57% of the participants were women; and 57% were African Americans.

Participants were randomly assigned to follow either the DASH eating plan or a typical American diet for 3 months. During the study period, each group followed three different intakes of dietary sodium for 1 month each in random order:

• 3,300 milligrams a day (the average level consumed by Americans)
• 2,400 milligrams a day (the upper limit recommended by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure)
• 1,500 milligrams a day

Lower sodium intake resulted in lower blood pressures for those on both the DASH eating plan and the typical American diet. This result applied to men, women, African Americans, whites, and those with and without high blood pressure. At each sodium level, blood pressure was lower on the DASH eating plan than on the typical diet. The greatest blood pressure reductions were for the DASH eating plan at the sodium intake of 1,500 milligrams per day. Those with high blood pressure saw the greatest reductions, but those with prehypertension also had large decreases.

The DASH eating plan
The DASH eating plan provides recommendations, menus, recipes and tips for two levels of daily sodium consumption — 2,300 and 1,500 milligrams per day. The plan:

• Follows heart healthy guidelines to limit saturated fat, cholesterol, and total fat
• emphasizes fruits, vegetables, and fat-free or low-fat milk and milk products
• includes whole grain products, fish, poultry, and nuts
• is reduced in lean red meat, sweets, added sugars, and sugar-containing beverages
• is rich in potassium, magnesium, and calcium, as well as protein and fiber

Learn more about the DASH eating plan.

Reducing sodium in the diet
Following the DASH eating plan and lowering intake of salt and sodium provides the best combination to lower or control high blood pressure. For some patients, lowering the amount of salt in their diet can have the same effect as using medication to control blood pressure. Lower-sodium diets may also help blood pressure medicines work better.

You can advise individuals to reduce sodium in their diet by following these simple, specific steps:

• Choose fresh, frozen, or canned (low-sodium or no-salt-added) vegetables.
• Choose ready-to-eat breakfast cereals that are lower in sodium.
• Cook rice, pasta, and hot cereals without salt. Cut back on instant or flavored rice, pasta, and cereal mixes, which usually have added salt.
• If buying "convenience foods," choose those that are lower in sodium. Cut back on frozen dinners, mixed dishes such as pizza, packaged mixes, canned soups or broths, and salad dressings. These foods often have a lot of sodium.
• Use fresh poultry, fish, and lean meat, rather than canned, smoked, or processed types.
• Limit cured foods (such as bacon and ham), foods packed in brine (such as pickles, pickled vegetables, olives, and sauerkraut), and condiments (such as mustard, horseradish, ketchup, and barbeque sauce).
• Rinse canned foods, such as tuna and canned beans, to remove some of the sodium.
• In cooking and at the table, flavor foods with herbs, spices, wine, lemon, lime, vinegar, or salt-free seasoning blends.

The Institute of Medicine (IOM) Report
The Institute of Medicine (IOM) of the National Academies released a report April 20, 2010 on "Strategies to Reduce Sodium Intake in the United States." The report describes approaches that can be used to reduce sodium intake to levels recommended in the 2005 Dietary Guidelines for Americans published by the U.S. Department of Health and Human Services (HHS) and the U.S. Department of Agriculture.

The U.S. dietary guidelines advise that Americans should eat no more than 2,300 mg of sodium, or about 1 teaspoon of salt, per day. However, according to the IOM report, Americans ages 2 and older average a daily intake of more than 3,400 mg of sodium. Average daily intake is even higher among adult men: more than 4,000 mg.

The report represents the culmination of 19 months of work conducted by a 14-member, multidisciplinary committee appointed by the IOM. The project was initiated by Congress and funded through the Centers for Disease Control and Prevention (CDC) with support from the NHLBI, the Food and Drug Administration (FDA), and the Office of Disease Prevention and Health Promotion, all part of HHS.

The NHLBI will work together with the FDA, CDC, and other components of the HHS, to form an interagency working group on sodium to review options, determine next steps, and promote collaborations among government agencies, professional and consumer organizations, the food industry, and public health partners to lower sodium intake in the United States.

Where can I learn more?

• The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC7)
• Information on clinical practice guidelines for cardiovascular risk reduction that are in development
• NHLBI Diseases and Conditions Index: High Blood Pressure
• NHLBI Tips for Reducing Sodium in the Diet
• Your Guide to Lowering Your Blood Pressure With DASH
• Dietary Guidelines for Americans

Information on the DASH clinical studies:

• A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group. Appel, L.J., et al. New England Journal of Medicine, 336(16):1117-24, 1997.
• Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. Sacks, F. M., et al. New England Journal of Medicine, 344(1):3-10, 2001.
• Effects of diet and sodium Intake on blood pressure: Subgroup analysis of the DASH-Sodium Trial. Vollmer, W. M., et al. Annals of Internal Medicine, 135(12) 1019-1028, 2001.
• A further subgroup analysis of the effects of the DASH diet and three dietary sodium levels on blood pressure: results of the DASH-Sodium Trial. Bray, G. A., et al. American Journal of Cardiology, 94(2):222-7, 2004. 
• The DASH studies were conducted at four medical centers: Brigham and Women's Hospital, Boston, Mass.; Duke Hypertension Center and the Sarah W. Stedman Nutrition and Metabolism Center, Durham, N.C.; Johns Hopkins Medical Institutions, Baltimore, Md.; and Pennington Biomedical Research Center, Baton Rouge, La. The central coordinating center was at Kaiser Permanente Center for Health Research in Portland, Ore.