Hypertension (high blood pressure) results from narrowing of the blood vessels. Visualize a blood vessel as a flexible hose. When any liquid flows through the hose, the pressure within the hose can be increased by narrowing its inside diameter while forcing the same amount of liquid through it. The amount of blood within our system is relatively constant. Hence, if our arteries narrow either by contracting their muscular walls or as a result of some disease process, the blood pressure increases.
Our blood pressure is expressed in two values. The higher one is the systolic pressure and the lower one is the diastolic pressure. The normal value is around 120/80 millimeters (mm) of mercury (Hg) when measured in the arm. Blood pressure is high when the systolic pressure reaches a level of 140 or above, or when the diastolic reaches 90 or more.
As it circulates throughout the body, the blood generates pressure within the arteries and veins. The heart initiates this pressure by forcing the blood out of its chambers, into the aorta (the main artery), and through its branches into the various tissues in the body. Blood pressure oscillates between a high and a low value, depending on whether the heart is contracting or relaxing. Contraction forces the blood into the arteries at maximum pressure. This is the systolic pressure. During the period of relaxation, while the heart is refilling with blood, the pressure within the arteries drops to a lower level. This is the diastolic pressure. Since contractions last for a short period, the arteries are exposed to the lower pressure most of the time. Thus, a high diastolic pressure is more dangerous than a high systolic pressure.
High blood pressure favors the deposition of cholesterol from the blood into the arterial wall. Hence, it is a primary cause of atherosclerosis (hardening of the arteries). In addition, high blood pressure can cause a ballooning (called an aneurysm) and a rupture of a blood vessel. This often happens in one of the smaller vessels leading to the brain, causing a cerebral hemorrhage or stroke. Finally, prolonged hypertension can damage small vessels in the kidney, causing scarring in that organ—leading to kidney failure. Strain on the heart muscle can bring on heart failure, and damage to the small blood vessels in the back of the eye can cause other serious consequences.
There is no doubt that hypertension is a genetic disease. It is much more common in African-Americans than in whites, and it runs in families in both races. But genetics is only one part of the story. In the United States, blood pressure rises with age. Until recently, this rise was interpreted as a normal process of aging. The older a person was, the higher his blood pressure could be and still be considered normal. In other countries, particularly among certain primitive societies, such as Greenland Eskimos, Australian Aborigines, Polynesians, African Bushmen, and Native Americans, there is no rise in blood pressure with age. Moreover, high blood pressure is virtually nonexistent within these cultures. By contrast, the incidence of hypertension may be as high as 30 percent in the United States. In China and Japan it is even higher.
While there are many cultural differences between the primitive societies mentioned above and the United States, China or Japan, the distinction that causes high blood pressure is in the diet. There are, likewise, contrasting differences between the diets of the United States, China and Japan. The one similarity relating to hypertension is that they are all high in salt.
A study involving a group of Samburu from northern Kenya illustrates the role of salt. Traditionally, these nomads consume a diet of meat and milk, which is low in sodium. The study followed a group of men drafted into the Kenyan army, where the diet raised their sodium intake five-fold. During the second year of service, their blood pressure began to increase and continued to increase throughout their six years of service.
Knowledge of this relationship between high sodium intake and hypertension is not new. Before the advent of modern drug therapy, the only way to control high blood pressure was with a very low-salt diet. This approach is obsolete because of the restrictive nature of such a diet. Drugs to control hypertension are now safe and effective. Many of these drugs work by causing the body to eliminate more sodium through the kidneys, thus reducing the amount within the tissues and body fluids. Although the extremely low salt diet necessary to treat hypertension is not practical in preventing the disease, moderate reduction may be an effective preventive measure in susceptible populations.
Sodium is essential for life. It is present in all cells and in all body fluids. The body must regulate the amount of sodium it contains. This regulation takes place primarily through the kidneys. When too little sodium is available, the kidney efficiently re-absorbs it, reducing the amount excreted. When too much sodium is available, the kidney filters it from the blood and passes it into the urine. Blood is filtered in the kidney through a small complex of arteries called the glomerulus. The higher the pressure in these arteries, the more efficient the filtration.
In order to filter properly, the kidney has a mechanism to raise and lower blood pressure. This involves the secretion of certain hormones, which cause the arterial walls to contract, thus increasing the pressure of the blood circulating through them. Presumably, a moderate increase in salt intake will invoke this mechanism in susceptible people. Once the arteries have been contracted for a long time, they become more fixed in that condition and will not relax as easily when salt intake is lowered. Thus, by how well the kidney regulates sodium through the hormonal response, our genes determine whether we are prone to hypertension. In some people, even mild increases in dietary sodium will evoke this response. Such people are susceptible to high blood pressure. In other people, even large amounts of dietary sodium can be handled by the kidney without any increase in blood pressures. Such people are resistant to hypertension. As the kidney gets older, its ability to filter becomes less efficient; therefore, it has to raise the blood pressure at lower and lower salt intakes. In a society such as ours, which consumes high quantities of sodium, blood pressure rises with age. By contrast, in societies where people consume small amounts of sodium, kidneys filter more efficiently, even in older people, without raising blood pressure.
A second dietary variable related to hypertension is the consistent consumption of too many calories, leading to obesity. The more overweight we are, the greater our chances for high blood pressure. This increased risk in overweight people is independent of the amount of sodium in their diet. Thus, at any given sodium intake, an obese person is more prone to hypertension than a lean individual. If you are susceptible to hypertension, stay lean if you are already thin. Lose weight if you are too heavy. The principles for losing weight or maintaining your ideal weight are discussed in Chapter 4.
Animal studies have suggested that hypertension may involve low calcium intake. The American diet tends to be low in calcium; and our high-fat diet adversely affects absorption of calcium. There is already ample evidence that increasing the amount of dietary calcium may be beneficial. Prevention of hypertension may be one more important reason to improve our calcium intake. Low potassium intake, or loss of potassium due to diuretics such as excessive caffeine, is another factor in hypertension that should be considered. In some cases, particularly borderline hypertension, merely increasing the consumption of potassium rich fruits and vegetables may prevent high blood pressure. (See Table 7 for foods rich in potassium.)
Table 7. Potassium Content of Common Foods
Food Size of mgs per
Almonds 1/3 cup 345
Apple 1 medium 165
Apple juice 1 cup 250
Applesauce ½ cup 78
Artichoke 1 medium 307
Asparagus 2/3 cup 183
Avocado ½ lg. 200
Banana 1 medium 550
Beans, green ½ cup 355
Beans, lima 5/8 cup 422
Beans, baked ½ cup 416
Beef, hamburger ¼ lb. 382
Beef, liver ¼ lb. 431
Beef, steak or roast ¼ 1b. 309
Beer 12 oz 69
Blackberries ½ cup 173
Bread, white 1 slice 20
Bread, corn 1 serving 71
Bread, whole wheat 1 slice 63
Bread, rye 1 slice 33
Broccoli, cooked 2/3 cup 390
Food Size of mgs per
Buttermilk 1 cup 388
Cabbage, coleslaw ½ cup 116
Cabbage, cooked 3/5 cup 163
Cake 1 slice 32
Cantaloupe ¼ medium 368
Carrots, raw 1 large 341
Cashews ½ cup 232
Celery, raw 1 med. stalk 170
Chard, cooked 3/5 cup 321
Cheese, ched. or amer. 1 slice 23
Cheese, cottage ½ cup 72
Chicken ¼ bird 242
Clams, steamed ¼ 1b. 540
Coffee 1 cup 82
Collards, cooked ½ cup 234
Cookies 2 med. 26
Corn, whole ½ cup 80
Cucumber, raw 1 medium 80
Dates 10 medium 648
Egg 1 medium 70
Figs 2 large 194
Fish, freshwater 1/3 lb. 384
Fish, saltwater 1/3 lb. 587
Grape juice 1 cup 250
Grapefruit juice 1 cup 310
Hot dog 1 average 110
Kale, cooked ¼ cup 221
Lamb ¼ 1b. 246
Lettuce 3½ oz 264
Macaroni ½ cup 110
Milk, skimmed 1 cup 336
Nuts, mixed ½ cup 280
Oatmeal ½ cup 130
Orange 1 medium 300
Oysters 6 average 203
Food Size of mgs per
Pancakes, wheat 1 medium 45
Peach 1 medium 202
Peanut butter 3 tbs. 369
Pear 1 medium 260
Peas, green 2/3 cup 196
Pie, fruit 1 piece 210
Pineapple 1 slice 123
Plums 2 medium 299
Pork, ham ¼ lb. 260
Pork, roast ¼ lb. 298
Potato, baked 1 medium 755
Potato, mash. ½ cup 250
Prunes 4 medium 329
Raisins ¼ cup 271
Rice, white 1 cup 42
Rice, brown 1 cup 105
Salmon, canned 3½ oz. 361
Sardines, canned 3½ oz. 560
Soybeans, cooked ½ cup 440
Squash, cooked ½ cup 341
Strawberries ½ cup 123
Sunflower kernels ½ cup 460
Tomato juice 1 cup 556
Turkey ¼ lb. 320
Watermelon 1 wedge 600
Wine 3½ oz 145
Yogurt 1 cup 336
How do you know if you are at risk for high blood pressure?
First—Do you know what your blood pressure is? You should record it every year, preferably every six months. You don’t need to see a physician for this. There are automated blood pressure instruments in many public places; and many clinics will measure your blood pressure as a free service. Also, some of them sponsor annual “health fairs” where they offer free blood pressure screening tests. If your blood pressure is 120/80 or lower, it is normal. If the systolic pressure is over 140, or the diastolic pressure is over 90, you have high blood pressure and should seek medical advice. If your systolic reading is consistently between 120 and 140, or if your diastolic reading is between 85 and 90, you are at risk. Preventive measures are suggested.
Second—Are you overweight? If you are 10 percent overweight, your risk for hypertension is increased. Weight loss is suggested.
Third—Is there a family history of hypertension or a clear familial tendency toward higher blood pressure? Trace back as far as you can. Ask your relatives what they can remember. Did anyone in your family die of a stroke? If so, hypertension was probably the cause. How about heart attacks? Again, hypertension may have been involved. With this general information, a pattern may emerge. If this pattern strongly suggests that many members of your family have suffered from hypertension, you are at increased risk. If you are African-American, the pattern does not have to be a strong one. Because of the high prevalence of hypertension among African-Americans, having one or two family members with high blood pressure is enough to consider yourself at increased risk.
Fourth—What type of diet do you consume now? Are you a “salt-aholic”? Do you habitually add salt when cooking? Do you use the salt shaker immediately before eating a meal? If this is your pattern, you are at increased risk even if none of the other risk aspects are evident.
Fifth—Do you live under excessive hostility and tension either at home or at work? Stress is known to raise blood pressure. The normal response to stress or fear or alarm in all animals is a rapid rise in blood pressure. When stress is constant, the blood pressure may stay elevated.
The major risk patterns for hypertension can be summarized as follows:
A blood pressure that is creeping up
A family history of hypertension or a tendency to high blood pressure
A heavy salt habit
A Type A personality and excessive hostility and tension at home or at work
By assigning a point value to each of these risk patterns, you can calculate your “hypertension score.”
If your blood pressure is between 130 and 140 systolic and between 85 and 90 diastolic, score 5. If you are 10 percent above ideal weight, score 3; 20 percent or more, score 5. If you have a strong family history of hypertension, score 5; sporadic family history, score 3. If you are African-American, add three points. If you have a Type A personality that precipitates strong emotional responses, score 5; if you are unsure, score 1 to 4, depending on the likelihood (similar to the procedure you used for atherosclerosis). Finally, if you are an obvious salt-aholic, score 3.
If your score is below 5, you are probably not susceptible to hypertension. However, you must remain alert to the possibility. Maintain your best body weight, continue using only moderate amounts of salt, and check your blood pressure regularly. If your score is 5 or above, you should initiate preventive measures. These measures involve changing your diet to reduce either your calories or your salt intake, or both. If you are at high risk for developing hypertension, you should reduce your sodium intake. Since salt is by far the most abundant dietary source of sodium, you must begin by restricting your use of salt.
Keep the following principles in mind:
Don’t add salt at the table.
Don’t use extra salt in cooking.
Don’t eat smoked or pickled foods.
Use processed (canned) foods with the least added salt.
Avoid foods that are already high in salt.
You may not be able to accomplish these changes all at once. Some people may have acquired their taste for salt over many years. It may take months to reverse this habit. If you are at risk for hypertension, you should begin as soon as possible.
How much salt reduction is enough? Let’s consider three levels of salt reduction: mild, moderate, and strict. Table 8 outlines the steps to be taken on each of these diets.
Table 8. Foods to Omit on a Sodium Restricted Diet
Food Level of Restriction
Mild Moderate Strict
Fruits All forms are permitted (including fresh,
frozen, canned, and dried).*
Vegetables, Omit pickled and dehydrated forms*.
soups and vegetable Limit canned to 2
juices servings daily.
Omit all canned and
frozen if processed
Omit all in column 2.
Meats Omit cold cuts, sausages, cured and pickled products*.
Poultry Limit canned to 2 servings daily.
Omit all canned or frozen with salt.
Bread and Omit salted crackers, pretzels, etc.*
grain Limit ready-to-eat and “quick
products cooking” cereals, commercial breads,
or baked products to 3 servings daily. Omit all prepared
Food Level of Restriction
Mild Moderate Strict
Milk and Omit all cheeses and cheese spreads.*
dairy Limit fluid milk
products to 3
Omit all but low sodium products
Seasonings Omit bouillon, dehydrated soups, and soy sauce*
Limit salt to 1 tsp.
Limit salt to ¼ tsp. daily
Omit all salt, salted
butter or margarine.
Omit catsup, mustard, commercial
salad preparations, and seasoning
(*these items apply to all levels of restriction)
Strict sodium restriction is mainly for people who already have hypertension or some other medical condition requiring a very low-sodium diet. Others who should attempt to reach this kind of control are people with a hypertension score of 20 or more who are at further risk because they smoke or have high levels of serum lipids. Although there is no definitive evidence that such people need to reduce their salt intake to such low levels, clinical experience suggests that strict control of dietary sodium intake may be beneficial. If you fall into this category, it is worth a try. If you don’t adhere to the strict diet, the closer you can come, the better.
For people with a score of 5 or more, moderate salt restriction is advisable. While it will require a change in eating habits, this is not as difficult as it might seem. Essentially it entails omitting dehydrated soups, bouillon, cold cuts, sausages and other pickled or cured products, salted crackers, pretzels, cheese and cheese spreads, soy sauce, and seasonings such as catsup, mustard, commercial salad preparations, and seasoning salts. In addition, you should limit the amount of all canned vegetables, soups, and vegetable juices to two servings a week. The same is true for all canned meats, fish, poultry, and eggs. Also limit the amount of ready-to-eat quick-cooking cereals and commercial bread or baked products to three servings a day. Baking powders and sodium bicarbonate contribute a great deal of sodium to corn bread, biscuits and other quick breads. (For home-baked products, you can substitute potassium bicarbonate, which may be obtained from your pharmacist.) Finally, limit the amount of milk and milk products to three servings per day, and use no more than one-fourth teaspoon of salt per day in seasoning all foods.
To begin your moderate salt restriction, take careful stock of what you are eating. It is helpful to record everything you eat for a week. Examine your record. Where does it differ from the desired pattern of moderate salt restriction? Are you adding more than one-fourth teaspoon of salt to your food? If so, cut back, even if you have to do it gradually. Are you eating too many canned goods? This is a common source of excessive sodium intake. Many food processors add large amounts of salt to their products. A few years ago your only alternative was to avoid eating canned goods by using frozen or fresh produce. Today another alternative is becoming more and more practical—the use of canned products that contain no added salt. Read the label! When given a choice of two brands of vegetables or soup, choose the one without added salt. Manufacturers are becoming more aware of the high salt content of our food and are learning that it is good business to have a low-salt alternative. By choosing wisely, we can maintain our usual food pattern and still gain considerable protection against high blood pressure.
Besides the precautions noted above, it is useful to know which foods are naturally high or low in sodium. Table 9 lists vegetables that are high in sodium, and Table 10 lists foods permitted at any level of restriction.
Table 9. Vegetables Naturally High in Sodium
Artichokes Celery flakes Mustard greens
Beet greens Chard Parsley flakes
Carrots Dandelion greens Spinach
Celery Kale Whole hominy
Table 10. Foods with Insignificant Amounts of Sodium
Grains Wheat, oats, rye, rice, barley, and their products (e.g., pasta, yeast breads, flours, uncooked cereals)
Vegetables All those not in Table 8 or canned, frozen salt free
Fruits All fresh canned fruits and juices
Meats All fresh or frozen/canned without salt beef, lamb, pork, veal, poultry, fish, shellfish,
and game meats
Eggs All fresh
Fats All vegetable oils and shortenings, lard, and unsalted butter and margarine
Condiments Vinegar, all spices, mustard powder, flavorings (without added salt)
Sweeteners Sugar, honey, syrup, jellies, molasses
Beverages Alcoholic beverages, coffee, teas, soft drinks
An adult diet balanced in the essential nutrients includes at least the following daily servings:
Dairy foods (milk, yogurt, unsalted cheese) 2
Protein foods (meats, poultry, fish, eggs, beans) 2
Breads, cereals, pastas, and rice 6
With meals prepared at home, limit salt to one-fourth teaspoon per day and select the appropriate
foods in Tables 9 and 10. The following meal suggestions apply to a moderate sodium restriction:
Juice or grapefruit
Egg, egg whites or unsalted cottage cheese
Whole wheat toast
Unsalted butter or margarine
Cooked cereal (prepared without salt)
Milk (whole or skim)
Tea or coffee
A Brown Bag Lunch
Sliced chicken, lettuce, tomato, alfalfa sprouts on whole wheat bread
Raisins and nuts (unsalted)
Canned fruit juice, coffee, tea, or milk
A Short Order Lunch
Hamburger on whole wheat bun with lettuce and tomato
Vinegar and/or oil (not salad dressing)
Soda or flavored milk
A Dieter’s Lunch
Unsalted wafers or sandwich bread
Hearty tossed salad (with everything except diced cheese and assorted canned vegetables such as those served at salad bars)with vinegar and/or oil (as above)
Melon half with unsalted cottage cheese
Fruit juice, coffee, tea, skim milk (limit use of sodium based artificial sweeteners to 2 packets per day)
Broccoli with lemon sauce
Saffron rice (homemade without salt)
Unsalted butter or margarine
Coffee, tea, or milk
Enhance the variety of your menu at home by making your own mayonnaise and salad dressing. For entertaining, try some of the following items:
Using yogurt as a base, stir in curry powder or black pepper, dill and black pepper, onion and garlic powder (not garlic salt).
Cold diced cooked white potatoes
Fresh bean sprouts
Sliced green peppers, sliced carrots, zucchini slices, sliced celery, etc.
Wafers, unsalted crackers, bite-sized sandwich bread, pita bread
Gourmet favorites, such as stuffed mushrooms, pastry puffs, escargots (snails), steamed seafood, meat balls and aspics should be prepared without salt.
Experiment with such spices as coriander, cumin, fennel, ginger, and others you have never tried. For fancy occasions, convert your favorite recipes to salt-free versions.
For dining out, patronize restaurants that cook to order and prepare fresh vegetables. You will have more control over the amount of sodium in your food. Oriental restaurants use soy sauce, monosodium glutamate, and other pickled items. Their meals are inescapably high in sodium. Seafood and steak houses may be good choices if you can ensure that salt is left out during preparation of your food. Salads and baked potatoes, which usually accompany entrees, are safe if you forgo most dressings and sauces. Fast-food chains and other establishments that serve deep-fried foods usually add a lot of salt to their products. Here again, a boiled or broiled version of the same food is a better choice.
A mild sodium-restricted diet simply omits pickled and dehydrated vegetables, cold cuts, sausages, and cured or pickled meat and fish products; salted crackers, pretzels, and other snacks; cheese and cheese spreads; bouillon, dehydrated soups, and soy sauce. It limits any additional salt to one teaspoon. Such a regimen is suggested even if you have only one risk. Thus, anyone with a strong family history of hypertension, or who is obese, should use this diet. In addition, if you have independent risks for atherosclerosis, such as high serum lipids, or if you are a cigarette smoker, you should use this diet even if your hypertension score is below 5.
For those with scores below 5 and no risks for atherosclerosis, the American diet is probably still too high in salt. Although there is no real evidence that any dietary change is necessary for this group, if you are an excessive salt user, you cook with a lot of salt, and salt your food before tasting it, it would be prudent to use the salt shaker more sparingly. Since we do not know all the causes of high blood pressure, you may be prone to this disease even without any of the known risks. A high salt intake can only worsen your chance. Although modifying your diet is very important, if your total hypertension score is too high, you should also pay attention to other life practices that may contribute to your risk.
Personality is very important. If you have a Type A profile, complicated by environmental stress and nagging anger, try to modify your behavior. Rest, meditation, and exercise are valuable tension relievers. People relax in different ways. Find the way that works for you and that can be applied regularly. This is particularly true if you have any of the other risks for high blood pressure. Watching your diet while continuing to live in a pressure cooker isn’t enough. High blood pressure is the silent killer! You don’t feel it. Uncontrolled, it can attack with little warning. For yourself, and in consideration of your family, take all the necessary steps to prevent this disease!