Salt: Friend or Foe?

Salt: Friend or Foe?Nutrition researchers have known about the need for salt much longer than most other nutrients. Oddly enough, there is no RDA for sodium although the 10^th edition of the Recommended Dietary Allowances states, "The minimum average requirement for adults is 115 mg of sodium per day. In consideration of the wide variation of patterns of physical activity and climate exposure, a safe minimum intake might be set at 500 mg/day".Although public health agencies and The U.S. Dietary Guidelines call for no more than 2,000-2,400 mg of sodium per day, most Americans consume twice that amount. About 10% of this comes naturally from foods while 15-25% comes from the salt shaker. The other 75% comes from salt added to processed foods and meals eaten away from the home.The Salt Institute (SI) maintains, "Healthy persons with normal blood pressure have no problems with sodium or salt intake." They claim that only about 1/3 to 1/2 of those who already have hypertension (HTN) need to cut back on dietary salt because they are "salt sensitive." They argue that since 75% of the U.S. population does not have HTN, only a small minority of Americans should be concerned about their salt intake. The SI appears to be winning the public relations battle about salt because a recent survey found that only about 10% of Americans are concerned about their salt intake. But they are not winning the scientific debate about the role of excess salt in promoting HTN and other health problems.In 1957, it was shown that increasing dietary salt causes a progressive rise in blood pressure (BP) of rats. Rats fed a diet with only 0.15% salt live significantly longer than rats fed greater amounts of dietary salt. A diet with 0.15% salt would provide a person consuming 2500 calories per day with about 300 mg of sodium per day. The average American's diet is about 2.5% salt on a dry weight basis.A study of chimpanzees found that the progressive addition of salt to their natural diet resulted in a gradual but significant rise in their BP over 20 months. However, within 6 months after their diet returned to normal so did their BP. This evidence from animal studies shows that increasing dietary salt generally causes increased BP.The SI likes to point out that only about 1 in four American adults has HTN; however, BP rises with age and most people will develop HTN in their lifetime while more than half of adult Americans have a BP that is higher than normal. Is this rise in BP with age simply a normal part of growing older?Studies of human populations, which add little or no salt to their food, have found little or no rise in BP with age and a virtual absence of hypertension. See Figure 1. This immunity to rising BP with age was true for Eskimos and Masai whose diets are high in fat and protein and low in carbohydrate. It was also true for the New Guinea Highlanders and Tarahumara Indians whose nearly vegetarian diets were both very high in carbohydrate. Given the wide ranges of climates, genetic diversity and extremely varied diet compositions among these populations, it is hard to imagine what factor other than the lack of added salt could be protecting them from HTN. Clearly, then the rise in BP in all Westernized populations cannot be simply a consequence of normal aging. It appears that excessive dietary salt plays an important role in the development of HTN.Dr. Malcolm Law, who published a comprehensive review article on the link between salt and HTN in the British Journal of Medicine, states, "The effect of universal moderate dietary salt reduction on mortality from stroke and ischaemic heart disease would be substantial, larger, indeed, than could be achieved by fully implementing recommended policy for treating high blood pressure with drugs." He also noted that if salt in processed foods was moderately reduced this could "prevent some 70,000 deaths a year in Britain (or 250,000 in the United States) as well as much disability."A safe bet to avoid HTN later in life or help keep your already elevated blood pressure lower is to try to keep your sodium below 1600 mg if you are on an otherwise optimal diet. See the tips in the side bar.Health professionals interested in the accompanying full text article with scientific references, along with the questionnaire for 3 CPE hours as approved by the ADA, should see the insert to this issue. You can also access it from our website at www.foodandhealth.com/nutritioneducation.htm.Dr. James J. Kenney, PhD, RD, FACN, is the Nutrition Research Specialist for the Pritikin Longevity Centers. He is on the Board of Directors for the National Council Against Health Fraud and is Board Certified as a Specialist in Human Nutrition Sciences by the American Board of Nutrition.5 Steps for Lower Salt Intake:

1. Increase the amount of fresh or frozen fruits and vegetables you eat to at least 7 servings a day. These are naturally low in sodium and contain many beneficial minerals that were shown to lower blood pressure in the DASH study.
2. Eat out less frequently or alter menu items so they are low in added salt. Specify no added salt and ask for sauces and dressings on the side.
3. Get your grain servings from low-sodium, whole grain foods like oatmeal, brown rice, barley and whole wheat pasta. Bread and crackers, along with processed cereal, are responsible for most of the sodium in American's diets.
4. Look for foods such as canned tomatoes, with no added salt or try to keep sodium at 1mg per calorie or less. If a product, such as jarred salsa, contains only 20 calories per serving but 300 mg of sodium, it has a lot of added salt.
5. Limit processed cheese and meat which are high in sodium. Go for fresh baked chicken and fish.