So many different articles have been written over the past decade or two about the connection between nutrition and blood pressure that it's no wonder the ordinary person is probably very confused about what to believe.
For example, based on a few studies some authorities claimed that salt intake is an extremely important cause of high blood pressure; that is, the more salt a person eats, the higher their blood pressure will become. But other more recent studies, however, seem to point to the opposite conclusion.
It now appears that the blood pressure-salt connection is true only for certain "salt sensitive" people or groups.
Could you tell us what is really going on? And how is an individual supposed to know whether or not they need to worry about how much salt they put on their french fries?
The problem with these kinds of studies is that there are so many other differences between the two groups in diet, lifestyle, stress level, medical treatment and other areas that it is nearly impossible to isolate one factor and say that it is responsible for any differences in blood pressure. In other words, one group may have lower blood pressure, but how do we know for sure that the reason is salt, and not how many yams they eat or how often they do the samba — or a combination of all three? Complicating the picture is the fact that studies that have compared people within more homogeneous populations, say different groups of Caucasians living in the United States, have found little or no relationship between salt intake and blood pressure.
In other words, one group may have lower blood pressure, but how do we know for sure that the reason is salt, and not how many yams they eat or how often they do the samba, or a combination of all three?
These contradictory results do not prove that there is no relationship between sodium and blood pressure, just that the relationship may not be as simple as more salt = higher blood pressure. We do know that some individuals and groups are "salt sensitive" — that is, if they increase their salt intake, they will have an increase in blood pressure. The bottom line may be that some people will need to watch their salt intake carefully in order to help control blood pressure, but that most people will not. Unfortunately it is not always easy to tell whether a particular person is salt sensitive or why.
These tests include intravenous saline infusion (a dangerous procedure which is only performed in measuring blood pressure extraordinary circumstances) and taking a person's blood pressure after a period of unusually high or low sodium intake. We also know that there are a number of factors that increase the likelihood that a particular person may be salt sensitive (see Table 1 below).
- Female gender
- Obesity (abdominal obesity)
- African-American origin
- Level of blood pressure
- Isolated systolic hypertension (ISH)
- Low renin hypertension (hypertensive patients with a low plasma renin activity)
- Impaired glucose tolerance
- Renal insufficiency
- Positive family history of hypertension
- (Higher) microalbuminuria
The most important of these is age. With increasing age, salt sensitivity increases. African-Americans also have a much higher prevalence of salt sensitivity than Caucasians. Another important factor is weight. Excess weight and obesity are clearly associated with increased salt sensitivity.
What exactly do you tell people who are at risk for salt sensitivity? How much should they restrict their salt? You brought up age as a risk factor. What is the danger that if you restrict the salt intake of an older person, their food would become so bland that they might eat less and become at risk for malnutrition, which is a common problem among the elderly?
Salt in the diet comes in two forms: discretionary (i.e., added at the table) and non-discretionary (or already present in food). Because as much as 30-50% of the average person's total salt is added at the table, it is clear that significant reductions could be achieved simply by educating people to put down the salt cellar. The next step would be to use less salt while preparing food in the kitchen. A good way to do this is by using salt substitutes such as fresh or dried herbs such as oregano, thyme and rosemary that do a good job of bringing out the flavor of food. You can buy salt substitutes that contain potassium, although these carry health risks for people with high blood pressure and kidney problems, or people taking diuretic medications.
Because as much as 30-50% of the average person's total salt is added at the table, it is clear that significant reductions could be achieved simply by educating people to put down the salt cellar.
Another strategy would be simply to avoid "junk" food, fast food and other processed foods that tend to contain a lot of salt. Those worried about their blood pressure may wish to use the so-called DASH diet.
These are the approaches doctors can offer to those who are at risk for salt sensitivity. The idea is to try to lower blood pressure by following a low salt diet for 3 to 6 months before trying to do the job with drugs. Unfortunately, there are not many patients who are able to stick to a low salt diet for long. For that reason, we advise our patients to drastically reduce the amount of salt they eat for period of only 2-3 weeks. If this leads to a significant drop in blood pressure, the person probably is salt sensitive. We then work with these people to create a workable, life-long dietary program to reduce their salt intake.
View sample menus and tips for getting started on the DASH diet here.
Every person is different as to how much salt they need for taste. Some people, however, become used to a low salt diet and continue to enjoy eating. Others may have to give up some of the pleasure of eating in order to lower their blood pressure and enjoy better health.
It should be remembered that salt reduction is only one of many weapons in the fight against high blood pressure. A realistic goal for most people is a sodium intake of 6-7 g/d. For most people, getting their salt intake down to that level will lead to a significant drop in blood pressure.
It is true that reducing salt intake is particularly difficult for the elderly. With increasing age, our ability to taste food declines and we develop a greater 'hunger for salt.'
It is true that reducing salt intake is particularly difficult for the elderly. With increasing age, our ability to taste food declines and we develop a greater "hunger for salt." In the elderly, the combination of reduced appetite and extreme sodium restriction may lead to malnutrition and other problems far worse than high blood pressure.
Quitting smoking is also a must. All of these things are important, but it is not realistic to do them at the same time. It is important to carefully select the most promising first step. If you tell someone to eat more fruits and vegetables, lose weight, get more exercise and stop drinking and smoking, all at the same time, the patient will be shellshocked. And, chances are, the doctor will never see them again.
The healthiest way to get more potassium is to eat more fruits and vegetables. Skim milk and milk products are also good sources of potassium. With the exception of processed foods, all potassium rich foods tend to be low in salt as well. This is at the heart of the so-called DASH diet (Dietary Approaches to Stop Hypertension) diet.
Potassium intake should be increased by the consumption of foods rich in potassium and not by supplements. Potassium supplements can lead to serious kidney and other health problems.
In our experience, most of the people we treat for high blood pressure, especially the ones who are difficult to treat, drink a lot of alcohol. This is no surprise...
In a person who never consumes caffeine, blood pressure increases after a cup of coffee or espresso. However, in a person who is used to caffeine consumption, you do not see this effect. In fact, studies have shown that regular coffee drinkers have lower blood pressure than the non-drinkers because of the dehydrating effects of caffeine. Reducing the amount of fluid in the body tends to lower blood pressure. So it is not necessary to advise coffee-drinkers with high blood pressure to cut down their coffee consumption. However, in a difficult to treat patient — after having ruled out all other causes — a reduction in coffee consumption may be worth a try.
It is important to remember that weight loss does not automatically cause a reduction in blood pressure. As with other strategies, there are some who respond and others who do not. Of course, weight loss does lower your risk for a wide range of cardiovascular problems.
We all know how frustrating weight loss is, since most people diet and then regain their body weight within a short time. Accordingly, the most important goal is to stabilize body weight. For most people, weight increases gradually over time. Therefore, any interruption in the normal upward trend should be regarded as a success. After a successful stabilization of body weight, the steps towards weight loss should be small and realistic.
For most people, weight increases gradually over time. Therefore, any interruption in the normal upward trend should be regarded as a success.
The key component in any weight loss and weight maintenance life strategy is exercise. Increased activity takes some of the pressure off reducing calorie intake. In addition, it is associated with many favorable effects on most cardiovascular risk factors, including high blood pressure. We recommend to our patients, whatever their body weight, an individually tailored amount of increased exercise such as daily walking, power walking, jogging and biking sessions, using stairs instead of the elevator or walking to the restaurant at noon time. Usually, we start with advice on integrating physical activity into the daily routine and add sport activities later.
Every person — independent of age, body weight and blood pressure — should pursue at least 30 minutes of daily physical activity that raises the pulse rate. For those with high blood pressure, isometric exercise training, such as weight lifting or rowing, is not recommended, as irregular bouts of heavy physical activity can actually increase blood pressure.
The DASH-I study tested the effect of a diet rich in fruits, vegetables and low fat dairy products on blood pressure. It resulted in a significant reduction of blood pressure. It is important to note that the DASH diet had favorable effects not only on those with high blood pressure but also on those with normal blood pressure. Although we cannot be sure which nutrient was primarily responsible for the reduction in blood pressure, potassium is a likely candidate.
DASH-II used the same dietary intervention except that salt intake was monitored at three different levels The greatest effect of the DASH diet was seen at the lowest level of salt intake.
For a number of reasons, including the difficulty of sticking to a low salt diet, we recommend that most people start with the DASH-I diet. Then, if they are still having trouble with high blood pressure and salt sensitivity is suspected, we attempt to lower salt intake.