Dietary Salt Restriction
We are evolved from early hominids that lived in a hot, arid climate and ate foods with a very low salt intake. Our current lifestyle with its high salt intake poses a problem for us in preventing the damaging effects of excessive salt intake. All of us eat more salt than we need, and almost all of us eat more than is good for our health and wellbeing. Too high an intake of salt raises the blood pressure in many people, especially those past age 50, African-Americans, and those with kidney disease. A high salt intake accelerates the loss of kidney function in patients with chronic kidney disease, increases the excretion of protein in the urine in those with proteinuria and increases the edema of those who have kidney or heart failure. Population studies have shown that a high salt intake increases the probability of stroke or heart attacks and increases the blood pressure.
Therefore, dietary salt restriction is advised, and indeed required, for most that have high blood pressure and/or chronic kidney disease.
The exceptions to the need for dietary salt restriction are relatively few. Some patients with chronic kidney disease who excrete little protein in the urine have predominantly damage to their tubules rather than to the glomeruli or blood vessels. Some patients with this rather uncommon form of chronic kidney disease do not retain salt and do not have high blood pressure. Therefore, if you are excreting less than 1 gram of protein per 24 hours and have normal or low blood pressure without treatment, you should discuss with your physician whether dietary salt restriction is necessary or advisable. A second, uncommon group of patients are those who have too Iowa blood pressure on standing.
This can often be managed by a change in a medication, but if not, is worsened by salt
How to Assess Salt Intake
You can get a rough idea of your salt intake by reference to the accompanying table of foods that are especially high or low in salt. Nevertheless, this provides only a rough indication. Moreover, salt intake is determined both by the salt of the food and the amount of food consumed. Most obese people have an excessive intake of food calories and of salt. Your physician may suggest, from time to time, that you undertake a 24-hour urine collection (see separate patient instructions for collecting a 24-hour urine). This provides the most accurate assessment of salt intake, since the amount of salt excreted in the urine generally is very close to the amount of salt consumed in the diet. It is important that the 24-hour urine collection is complete and that you have not either started or stopped taking diuretics or altered the dosage of diuretics in the last week. You should insure that your diet has not changed over the time you are collecting the urine so that it provides a valid indication of your normal salt intake.
Goals of Salt Restriction
Most people in America eat food containing 120-300 mmol of sodium each day and excrete a corresponding amount of sodium in their urine. This is equivalent to 2,750 to 7,000 mg or 2 % to 7 grams daily of sodium. A reasonable goal for subjects with pre-hypertension (average systolic BP of 130-139), established hypertension (average systolic BP of 140 mmHg or above), and for most patients with chronic kidney disease (a serum creatinine above normal or an excessive amount of albumin or protein in the urine), is 80-120 mmol of sodium daily. This is equivalent to 1,800 to 2,750 mg daily. This should be achievable. For patients with drug-resistance hypertension, and those with edema, more severe salt restriction is needed. Daily sodium intake should fall within the range of 60-80 mmol or 1,375-1,800 mg. Achieving this goal requires considerable attention to detail.
Salt Intake and Eating Habits
Three-quarters of the salt that we eat currently is already added to the food before it reaches the table. Therefore, banishing table salt is insufficient on its own to achieve a low salt intake, but is one essential step in the right direction. The ideal eating habit is to prepare fresh food in your own home. Those able to eat fresh, home-prepared food regularly should be able to achieve a diet properly-restricted in salt. Unfortunately, fast foods, especially hamburgers, pizzas, Thai, and Mexican foods contain a huge amount of salt already added to the food prior to serving. Therefore, regular consumption of fast foods such as these is invariably associated with excessive salt intake.
Steps to Achieving a Salt-Restricted Diet
These are several steps to achieving a salt-restricted diet. The first is that no salt should be added to the food. Those of us accustomed to a high salt intake often crave salt when it is not added to food. Fortunately, this passes after 1-2 weeks. Most subjects report that after this time their food tastes just as pleasant without salt as it did previously when heavily salted. Providing that you do not have a problem that requires limitation of potassium intake (such as advanced kidney disease or high serum potassium concentrations) a potassium-containing salt substitute can be used for table
salt. Spices can be used in place of salt, although curries and some sauces unfortunately contain a high salt intake and should be used sparingly.
The second step is to become acquainted with the salt content of foods, and to alter your dietary intake accordingly. Foods rich in salt are shown in Table A. Those especially high in salt are marked with an asterisk. You should avoid eating these foods with an asterisk and limit the quantity taken of the other foods. Foods with a relatively low salt intake are listed in Table B. These foods should form the stable part of your diet if you are going to be successful in restricting your dietary salt intake. Notice that the low salt food diet is rich in fruits, vegetables, unsalted nuts and grains, pasta, fresh dairy products, most fresh meat, fish, and shellfish. Note that this diet generally is similar to the NIH-sponsored Dietary Advice to Stop Hypertension (DASH) diet that is described in greater detail in the patient handout "Guide to Choosing a Healthy Diet."
The third step, which is especially important for those who have to eat predominantly processed, canned, frozen and prepared foods and drinks, is to become curious about the salt content of these foods and drinks from information on the label.
The fourth step is to have your dietary salt intake assessed from a 24-hour urine collection. You can discuss this, and its interpretation, with your physician.
For those who need to lose body weight, it is ideal to use low fat or skimmed milk dairy products in place of full cream, milk, yogurt, and ice cream. These foods are useful in achieving a salt restricted intake. Note that some full-cream cheeses have a very high salt intake (Table A).
A reduction in salt intake will only be successful if you are motivated to make a significant change in your choices of foods and in your habits of eating. It is advisable for many to use this opportunity to reduce body weight by a calorie-restricted, carbohydrate-restricted diet and to increase exercise, ideally to 30 minutes of aerobic exercise daily if this is within your capability.
However, this description deals specifically with dietary salt intake rather than dietary means to reduce weight. Please refer to the patient handout on "Weight Reduction" for details.
Table 1: Salt content of common foods
(a) Food that contain a lot of salt
- Constituents of fast food, especially hamburgers*, pizza*, Thaj* and Mexican food*
- Olives in brine*, salted nuts*
- Canned beans*, corn* and peas*
- Potato chips*
- Sauerkraut*, tomato ketchup* or puree*
- Peanut butter
- Corn flakes
- Bread*, crackers*, donuts, muffins, pies, pretzels*, scones*
- Cheese (specially Roquefort*, processed cheese*, camembert*)
- Bacon*, ham, pate*, sausages*, salami*
- Pickled, smoked or canned fish
* a food especially rich in salt.
(b) Foods that contain little salt
- Fruits and fruit juices
- Vegetables and salads
- Unsalted nuts
- Grains and pasta
- Eggs, milk, yogurt, ice cream
- Most fresh meats, fish and shellfish
- Cottage cheese
- Carbonated drinks and alcoholic beverages
The following provide good general advice about a healthy diet:
1. US Department of Health and Human Services, NIH, NHLBI, NIH Publication No. 06 4082,2006. Your Guide to Lowering Your Blood Pressure with DASH.
2. Moore T, Svetkey L, Lin P-H and Karanja N. The DASH dietfor hypertension: Lower your blood pressure in 14 days without drugs. Publ: The Free Press, New York, N.Y., 2001.
3. Willett, W.C. Eat, drink and be healthy: The Harvard Medical School guide to healthy eating. Publ: The Free Press, New York, N.Y., 2001.
4. Ellis, P. The Cleveland Clinic Foundation Creative Cooking for Renal Diets. Publ: Senay Publishing Inc., Chesterland, a.H., 1985.
Copies of the pamphlet, A DASH cookbook, and other materials for healthy diets, are available from the receptionist in the Division of Nephrology and Hypertension. Please feel free to take out one of these books for your use. Please remember to return it within 1-2 weeks so that it can be used by others.
The following are practical guides to how to select and prepare food, with low salt content.
I. Gittleman, AI. Get the Salt Out. Publ: Three Rivers Press, 1996.
2. James, SV and McIndou, H. The Complete Idiot's Guide to Low Sodium Meals. Publ: AlphalPenguin, 2008.
3. Logue, D. 500 Low Sodium Recipes. Publ: Fair Winds Press, 2007.
The following is an excellent reference for the salt content of foods:
I. Documenta Geigy: Scientific Table, Seventh Edition. Publ: Geigy Pharmaceuticals, 1970, pp.499-512
2. Mostyn, B. Pocket Guide to Low Sodium Foods. PubI: InData Group Inc., 2006
For those of you who want a more detailed set ofreferences, the following may be helpful:
I. Mattes RD, Donnelly D. Relative contributions ofdietary sodium sources. J Am Coli Nutr 10: 383-393,1991.
2. Lentner, C. Geigy SCientific Tables (Vol 1 ); Units ofMeasurement, Body Fluids, Composition ofthe Body, Nutrition. PubI: Ciba Geigy, BasIe, Switzerland, p.p. 243-260, 1981.
For those who would like to have a nutritional consultation, you can contact:
Cell phone: (202) 390-8044
To Research for further information, please visit: http://www.cnpp.usda.gov/DGAs2010-policydocument.htm