Lowering Your Blood Pressure with a DASH of Salt

by Leah Frankel, MS, RD | frankel@myhousecallmd.com

With increasing numbers of Americans diagnosed with high blood pressure (also known as hypertension), it’s likely you or someone in your family is battling this disease (probably with a smattering of medications). While most people diagnosed with high blood pressure end up taking medications at some point, this can be prevented with a few minor dietary changes. You probably know a few of these tricks, for instance that a high salt intake is bad for hypertension, but that’s just the tip of the iceberg!  We’ll explore hypertension as well as what you can do to manage your high blood pressure while concurrently enjoying the food you eat.

What is hypertension?

Hypertension is defined as persistently elevated blood pressure, with a systolic blood pressure of 140 mm Hg or higher and/or a diastolic blood pressure of 90 mm Hg or higher. You’ve probably been told that your blood pressure is “something over something”; the first “something” is the systolic pressure and the second “something” is the diastolic pressure.  What the heck does that mean?  Systolic blood pressure is our blood pressure when the heart is contracting and diastolic blood pressure is the pressure when our heart is relaxed. The most common type of hypertension is known as essential (also called “primary”) hypertension.  Essential hypertension is diagnosed when the cause of the high blood pressure is unknown (yes, doctors came up with a fancy term to say, “Your blood pressure is high but we don’t know why.”); as opposed to secondary hypertension which is caused by another disease, such as chronic renal failure, endocrine disorders or certain medications.  While high blood pressure usually doesn’t present with any symptoms, uncontrolled blood pressure can lead to death or other diseases including congestive heart failure and stroke.

What’s actually happening in your body when you have high blood pressure?

Blood pressure depends on two factors, the amount of blood being pushed out of the heart and the resistance the blood feels as it moves through the blood vessels. When the diameter of the blood vessel narrows, there is more resistance and blood pressure rises. Think of it this way: your body is trying to push all this blood around but you made the opening smaller, so it has to push harder (the increased blood pressure) to get as much blood to circulate through the body. Some medications work by dilating the vessels so there is less resistance to flow and your blood pressure is lowered. There are also a few systems in the body that help regulate blood pressure: the sympathetic nervous system and the kidneys. The sympathetic nervous system regulates blood pressure in the short term by secreting norepinephrine, a stress hormone, which constricts the arteries leading to increased blood pressure (this is why your blood pressure goes up when you’re under stress). The kidneys have two mechanisms to maintain blood pressure: they control the volume of fluid in the blood (with less volume you don’t need to push as hard, therefore lowering blood pressure) and by activating the renin-angiotensin system which affects 1) how much salt or water is retained and 2) the constriction of blood vessels.  When any of these systems aren’t doing their job correctly, hypertension develops.

How diet changes can help

When most people think of dietary interventions to control high blood pressure the first thing that comes to mind is sodium intake. However, not everyone’s blood pressure is affected by salt intake. Only about 30-50% of people with hypertension are salt sensitive meaning that their blood pressure is affected the amount of salt they consume. We know what you’re thinking, “If I’m not sensitive to sodium then I’m destined to end up on medication.” Luckily, reducing your salt intake is only one approach to controlling high blood pressure.

The most common intervention for controlling hypertension is the DASH (Dietary Approaches to Stop Hypertension) diet. The DASH diet suggests consuming:

  • 7-8 servings of grains a day, primarily whole grains

  • 4-5 servings of vegetables each day

  • 4-5 servings of fruit a day

  • 2-3 servings of dairy, with an emphasis on low-fat or fat free food

  • 2 servings of meat a day, but sticking with only lean meats

  • 4-5 servings of nuts or beans a week

  • 2-3 servings of fat/oil per day with an emphasis on polyunsaturated and monounsaturated oils, and limiting sweets

So how does the DASH diet differ from a standard well balanced diet? It’s actually quite similar. The DASH diet simply puts more emphasis on lean proteins, healthy fats, a reduction in processed foods and an increase in fruits and vegetables (you can see the full DASH Diet Pyramid at the end of the article).  Studies investigating the DASH diet have proven that following the DASH guidelines can lead to significantly lower blood pressure, even when sodium intake isn’t reduced (1). However, study participants who followed the DASH diet and reduced their salt intake had an even better outcome.


Sodium in your food

If you’re already following a well-balanced diet like to the DASH diet but want to know how to reduce your sodium intake, it’s important to know what foods to look out for.  Everyone has different sodium needs/restrictions based on medical conditions including congestive heart failure and chronic kidney disease.  That being said, a typical low sodium diet should contain no more than 2 g (2000 mg) sodium per day. In order to follow a low sodium diet, you want to limit or avoid: canned foods, cured meats, salted snacks, soups, and dairy products; the more processed a food is, the more likely its high in sodium.

Sodium content in various foods (some of the numbers may surprise you):

  • 8 oz milk: 120 mg

  • 1 oz cheese: 200 mg

  • ½ cup fresh or frozen vegetables: 10 mg

  • ½ cup canned vegetables: 230 mg

  • ½ cup fresh or frozen fruit: 2 mg

  • 1 slice bread: 150 mg

  • 1 tsp salted butter or margarine: 50 mg

  • 1 tsp unsalted butter or margarine: 1 mg

  • 1 tbsp salad dressing: 350 mg

  • 1 cup soup: 900 mg

  • 1 cup low sodium soup: 25 mg

  • 1 tsp salt: 2300 mg (that’s more than your whole day’s worth!)

Check the labels on the foods you buy.  We guarantee that you’ll be surprised to discover how much sodium is in the food you eat each day.  Be especially careful when eating out.  New laws require restaurants to include nutritional information so you’ll be able to monitor how much salt you’re actually eating.   If you’re cooking at home, an easy trick is to substitute salt with spices that are sodium free.

Let’s not forget about exercise

As we know, exercise provides a number of benefits including 1) decreased risk of developing many diseases including diabetes and cardiovascular disease, 2) help with weight loss and/or maintenance and 3) improved energy level and mood. Numerous studies have shown that physical activity can also help improve hypertension. A meta-analysis (a study that compares the results of multiple other studies) by Kelley et al. showed that walking decreased blood pressure by an average of 2% (2).  Time to put on your walking shoes!

So when do I start?

Following the DASH diet, decreasing sodium intake and exercising can be beneficial for people with or without hypertension.  Yes, following these guidelines has been shown to reduce blood pressure even in people without high blood pressure (1). So whether you’re recently diagnosed with hypertension, have been on medications for your high blood pressure for years or would like to prevent hypertension in the future, these small changes can make a big difference.  We say you start today.

Questions? E-mail the Author: frankel@myhousecallmd.com

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References:

  1. Appel LJ, Moore TJ, Obarzanek E, et al. The effect of dietary patterns on blood pressure: results from the Dietary Approaches to Stop Hypertension trial. New England Journal of Medicine 1997;336:1117-24.

  2. Kelley GA, et al. Walking and resting blood pressure in adults: a meta-analysis. Preventative Medicine 2001; 33:120-127.

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06 2010

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