Should I Worry About Salt Intake?

Should I Worry About Salt Intake?The Salt Institute claims that, "evidence now shows clearly that only a small minority of the population really benefits from restricting salt." Most people and many clinicians subscribe to this position and assume the only way too much salt can harm the body is by causing hypertension in sodium sensitive individuals. They assume as long as your blood pressure (BP) is "normal" there's no evidence to reduce salt intake. There are three problems with this theory if you are really interested in long-term health and avoiding hypertension.First, the risk of dying from an increase in BP begins long before the diagnosis of HTN (BP greater than 140/90 mmHg). Figure 1 shows that people are more likely to die the higher their BP goes and that this increased death rate begins with a diastolic BP well below 90 mmHg. It is estimated that one third of cardiovascular disease resulting from increased BP occurs within the "normal" range of BP. Ideally your BP should be less than 110/70.A second reason to limit your salt intake if your BP is "normal" is that damage to your blood vessels begins early in life. Offspring from pregnant rats fed a higher salt diet have a higher blood pressure than those from mothers fed a low-salt diet. A study of newborn human infants showed BP responds to the amount of salt in the diet. Half the infants were fed a formula diet containing the amount of sodium found in cow's milk while the other half were fed the same formula except with a lower amount of sodium like that present in human breast milk. After 6 months, the infants fed the higher sodium formula had significantly higher BP than those fed the lower sodium formula.A third reason to be concerned about excessive dietary salt, even in if your BP is "normal," is that too much salt causes serious biochemical and physiological harm to your body and HTN may only be a symptom of that harm.Rats, like people, vary in their susceptibility to develop HTN in response to a high-salt diet. Indeed, rats have been bred to be salt sensitive. Other strains of rats, like some people, are more resistant to the BP raising effects of a high salt diet. One study, published in Circulation, compared the effects of moderate and high salt diets in genetically salt sensitive rats and rats that were not salt sensitive. On the high salt diet, the normal rats showed widespread damage to their hearts, kidneys and blood vessels compared to the salt sensitive rats fed the moderate salt diet even though the BP of the salt resistant rats was much lower.The authors of this study suggested that excessive salt intake may be an important direct pathogenic factor for cardiovascular disease. Simply put, excessive salt intake promotes the overgrowth of scar-like tissue in the blood vessels and other tissues. This damage gradually makes the blood vessels increasingly stiff and more resistant to the flow of blood. In salt resistant individuals, this damage must become more severe before their BP shoots up. So it takes many years for excessive dietary salt to do its damage. By the time HTN has been diagnosed this damage may be only partially reversible and/or may take many years on a very low-salt diet to reverse.It is prudent to follow a lowfat, high-fiber eating plan with a minimum of added salt. This includes eating plenty of fruits, vegetables, whole grains, legumes and some nonfat dairy products along with a little lean fish or chicken.? Pay attention to labels. People often get confused because many high-salt foods do not taste particularly salty. For example, bread has about double and corn flakes about triple the salt content of potato chips if you compare them by content of salt per calorie. A good rule of thumb is to limit the use of any foods with more mg of sodium than calories. This makes reading a label easy. If a 1/2 cup of spaghetti sauce contains 120 calories and 540 calories it is relatively high in sodium. There are more tips inside this issue.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 by the American Board of Nutrition.Health professionals interested in the accompanying full text article with scientific references, along with the questionnaire for 8 CPE hours as approved by the ADA, should see the CPE courses at www.foodandhealth.comQ: If I follow the DASH diet do I still need to be concerned about my salt intake?A. Yes. The DASH study found that there are other factors involved, besides salt reduction, to help lower blood pressure. Study participants ate 7-8 daily servings of grain products, 4-5 servings of vegetables, 4-5 servings of fruit, 2 or fewer servings of nonfat dairy foods, 2 or fewer daily servings of meats, poultry and fish, 4-5 weekly servings of nuts, seeds and legumes. Added fats were limited to 2.5 servings a day and sweets were limited to 1 serving per day. Although sodium restriction wasn't tested, the participants consumed around 3000 mg of sodium per day - much lower than the average American's intake of 4000-5000 mg per day.Lowering blood pressure is much like lowering cholesterol. There are many factors which influence cholesterol, such as saturated fat, soluble fiber, exercise and weight control, vegetable protein versus animal protein, the size and number of meals eaten daily, etc. There are many factors involved to lower blood pressure: decrease your sodium intake, control your weight, limit alcohol, and eat a diet much like the participants of the DASH study: a high fiber, lowfat diet that is based on grains, vegetables, and fruits with a few servings of nonfat dairy and lean fish or chicken. Limiting salt intake does more than just prevent high blood pressure; it prevents the systemic damage to your body discussed in the front-page article of this issue.J.K.