Many of the companies that produce and market salty foods and their advocacy organization, the Salt Institute (SI), have long argued that dietary salt has little impact on people with normal blood pressure and only raises blood pressure modestly in those with hypertension who happen to be "salt sensitive". The results from the recent DASH2 (Dietary Approaches to Stop Hypertension) trial have now clearly refuted both claims.1
This study showed that reducing dietary sodium from salt from about 3300 mg to about 1500 mg per day in a typical American diet reduced blood pressure more than adopting the DASH diet without salt restriction. Clearly we now have definitive proof that salt is the #1 cause of hypertension. However, the combination of the DASH diet plus salt restriction to 1500 mg per day was the most effective strategy for lowering blood pressure in people with stage 1 hypertension (systolic blood pressure =140 to 159 mmHg and diastolic blood pressure 90 to 95 mmHg) and those with a "normal" blood pressure of 120/80+.
DASH versus drugs
The DASH-Sodium trial showed that salt restriction, coupled with the DASH diet, reduced blood pressure in those with stage 1 hypertension as much or more than any single anti-hypertension drug.2 Every anti-hypertension drug can cause adverse side effects. Impotence, reduced endurance, weight gain, coughing and adverse changes in blood lipids that may increase the risk of heart disease are the most common side effects. By contrast, reducing salt had no adverse side effects. Indeed, reducing salt reduced the number of headaches that the subjects reported. Reducing salt intake should also help reduce the risk of osteoporosis, kidney stones and stomach cancer.3
The SI has claimed, "we know from the Trials of Hypertension part II study that there is an immediate blood pressure lowering result of sodium restriction which disappears over time." True, there have been clinical trials where the blood pressure lowering impact of salt seems to "wear off" with time. However, this is almost certainly due to waning compliance with salt restriction. In fact most scientific evidence suggests that the longer people with hypertension stay on a low-sodium diet, the greater the drop in blood pressure is likely to be.4 On the DASH low-sodium diet, systolic blood pressure in those with stage 1 hypertension dropped 11.5 mmHg in just 30 days. By contrast, the average rise in systolic blood pressure by age 65 years, in all societies that consume as much salt as Americans or more, is about 40-50 mmHg. After an initial large drop in blood pressure in the first wee or so after adopting a very low sodium DASH diet, blood pressure may continue to drop very slowly for the next 5-7 years. Even greater drops in blood pressure will occur if people who reduce their sodium intake also:
• exercise regularly
• lose excess body fat
• moderate alcohol intake
• replace fatty dairy products with nonfat dairy products
• eat fatty cold-water fish in place of red meats & poultry
Lower sodium is more successful
Despite the now overwhelming evidence that dramatically cutting dietary sodium 1500 mg/day or less has the potential to make essential hyptertension uncommon in America, most private and public organizations continue to preach moderation when it comes to salt. For example, the new American Heart Association guidelines for Americans with and without hyptertension is to reduce dietary salt to 6 g/day or 2400 mg of sodium.5 However, the DASH-Sodium Study showed that the drop in BP was greater in both normotensive and hypertensive subjects when sodium was cut from 2400 to 1500 mg than when it was reduced from 3300 to 2400 mg.
The bottom line:
Cutting dietary salt intake is the single most important step for the prevention and treatment of hypertension. Only 15-25% of American's sodium intake comes from the salt shaker. The rest comes from processed foods and meals eaten away from home. To avoid excess salt from processed foods, people must read food labels and avoid foods that are high in sodium. Increasing the consumption of fruit, vegetables and nonfat dairy products or fortified soy milk ensure an adequate intake of potassium, magnesium and calcium. These foods are plentiful on the DASH diet. Inadequate intake of these minerals increases salt toxicity. For more information on the DASH diet, see http://dash.bwh.harvard.edu/.
For a more comprehensive discussion on salt intake, see Salt: Has it been given a fair shake? Or is it a serial killer? at www.foodandhealth.com (click on CPE Courses). This article has been approved for 3 CPE hours by The American Dietetic Association. The 21st Century Heart Hypertension Kit is now available to help educate your clients how to decrease their sodium intake and control their blood pressure - FMI call 800-462-2352.
1. Sacks FM, Svetkey LP, Vollmer WM, et al. N Engl J Med. 2001;344:3-10
2. Materson BJ, Reda DJ, Cushman WC, et al. N Engl J Med. 1993;328: 914-21
3. Kenney JJ. Salt: Has it been given a fair shake? Or is it a serial killer?
4. Lenfant C. JAMA. 1996;275:1604-6
5. Krauss RM, Eckel RH, Howard B, et al. Circulation 2000;102:2284-99a
Stephanie Ronco has been editing in a professional capacity for the past 10 years. In addition to her work as an editor, Ronco has also served as a ghostwriter and writing tutor. A voracious reader, Ronco loves watching language evolve and change. When she’s not delving into her latest project, Ronco can be found teaching acting classes, performing in community theater, or sailing with her husband.