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Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH

 
 

Sodium Sensitivity and Hypertension: What’s the Connection?

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Eat better

Thursday, Feb 04, 2016

Hypertension is defined as a resting blood pressure of  >140/90 mm Hg on two or more separate occasions, and is a major risk factor for heart attack, stroke, heart failure, and kidney disease. About 78 million Americans are thought to have hypertension; most of these individuals have no symptoms. In fact, recent data shows that nearly 20% of hypertensive individuals are completely unaware of its presence. It is well-known that rates of hypertension among adults vary greatly with age. For example, you will see in Figure 1 that only about 6% of women and 9% of men ages 20-34 have hypertension, while 72% of men and 80% of women ages 75+ are affected. We will explain why a bit later.

While there are many factors associated with hypertension, diet plays an important role. One dietary factor that you have no doubt heard of is sodium (salt) intake. Actually, dietary sodium is ingested as sodium chloride, which is found in significant amounts in highly processed foods such as canned soups, frozen dinners, condiments, and chips. While sodium chloride is essential for survival, most Americans take in far more than they need. While the average sodium intake among adults is ~3500 mg/day, less than 1000 mg/day is thought to be needed for survival.

This brings us to the issue of sodium sensitivity, which is defined as a characteristic where a high salt intake is followed by an increase in resting blood pressure. Conversely, when dietary salt intake is reduced, a decrease in resting blood pressure follows in sodium sensitive individuals. It is important to emphasize here that some individuals are sodium sensitive while others are not.  For example, a normal healthy 20 year-old woman might have a very high dietary sodium intake with a resting blood pressure of 96/60 mm Hg.  Given this very healthy resting blood pressure value, she is clearly not sodium sensitive. In fact, generally speaking, younger individuals are not as sodium sensitive as older individuals. Here’s why:  During the aging process, the kidneys ability to excrete excess sodium in the urine diminishes. Therefore, more sodium is retained by the blood.  Since water follows salt, more water is retained in the blood as well.  Because the arteries tend to stiffen quite a bit as a result of aging, this extra fluid in the blood causes an increase in blood pressure. Think of it like turning up the water to a garden hose, the pressure in the hose increases as more water flows through it.  

Along with aging, ethnicity has an effect on sodium sensitivity as well.  Approximately 43% of African-American adults are hypertensive, compared to about 30% of Caucasian adults. This is thought to be due partly because of a higher proportion of the African-American population being sodium sensitive than other ethnicities. Gender also seems to be a factor.  You will notice in Figure 1 that at ages 65 and older, a higher percentage of women are hypertensive than men. The thought is that at or beyond age 65, women have a higher proportion of sodium sensitivity than men in the same age group.  Genes for sodium sensitivity have been identified.  While the genes may not express themselves earlier in life, it is pretty much a given that hypertension will rear its’ ugly head sometime later in life when these genes are present.

The bottom line is that people who are sodium sensitive should pay very close attention to dietary sodium intake in order to prevent future hypertension or to improve their current hypertensive state.  Here are some tips to accomplish that goal.

  • Consume more fruits, vegetables, raw nuts, and unprocessed beans.  These foods are generally low in sodium and high in potassium
  • Consume more unprocessed or minimally processed foods.  Heavily processed foods often contain high amounts of sodium in order to increase their shelf life.
  • Never add salt to prepared food
  • Read the Nutrition Facts label when shopping so that you can choose foods that are lower in sodium

It is important to mention other lifestyle changes that can prevent or treat hypertension. In addition to decreasing dietary sodium intake, weight loss, limiting alcohol intake, and regular physical activity are also tried and true strategies for improving resting blood pressure values. In an earlier blog, I wrote about the Dietary Approaches to Stopping Hypertension (DASH) eating plan. That blog contains additional information for managing hypertension (and improving LDL cholesterol levels as a bonus) with dietary changes.

To learn more about nutrition, physical activity, healthy eating and risk of chronic disease, take our Nutrition for Health and Fitness, Weight Loss Strategies, and/or Personal Trainer Education courses. You need not be a health and fitness professional to take these courses; the general public is always welcome to attend any of our courses.

 
Reference
Go, A., et al. (2014). Heart disease and stroke statistics-2014 update: a report from the American Heart Association. Circulation. 127:e6-e245.