High blood pressure has proven to be a major risk factor for cardiovascular diseases such as stroke and heart disease. A study on sodium intake published in 2010 used typical outpatient subjects to simulate an otherwise healthy patient on antihypertensive medication. They studied the effect of increased salt intake on arterial vascular tone and found that a high-salt diet stiffened arterial walls and increased blood pressure (Todd et. al, 2010).

The Kidney Foundation of Canada stresses that high blood pressure can cause or exacerbate kidney disease, and vice versa. In a 2009 study on the effect of a high sodium diet on renal function, it was found that a high salt intake promotes inflammation of the kidneys, causing and/or worsening hypertension, as well as causing general oxidative stress and kidney damage. Oxidative stress tends to cause the kidney to retain sodium, which requires higher blood pressure to excrete excess sodium via urination. Since the kidneys filter waste products from the blood, any damage caused by prolonged high blood pressure may eventually lead to kidney failure, resulting in the need for dialysis or transplants (Rodriguez-Iturbe et. al, 2010).

The Canadian Cancer Foundation has found that consuming a salt-laden diet may increase the risk for stomach cancer. In a 2010 meta-analysis of 17 studies that looked at associations between dietary salt intake and precancerous/cancerous tumors in the gut (intestinal metaplasia), it was found that there is a general positive association between salt intake and intestinal metaplasia. The analysis did note that salted foods such as processed meat contained other carcinogenic substances that may have contributed to such an association, such as high nitrite content. The role of salt (in high concentrations) as a carcinogen has been thoroughly studied, but there is currently no firm conclusion (Dias-Neto et. al, 2010).

Risk factors for high blood pressure include being overweight or obese, not exercising regularly, smoking, consuming excess alcohol, older age, a family history of high blood pressure, and/or being of African descent. For diabetics, high blood glucose (sugar) levels are one of the risk factors for high blood pressure, and if prolonged, can lead to hardening of the arteries, potentially contributing to cardiovascular disease.

 
Recommended eating habits

Most of the salt in North American diets can be found in processed foods. The Heart and Stroke Foundation recommends consumption of no more than one teaspoon of salt a day, which equates to the 2300 mg recommended by the Dietary Reference Intakes (DRI’s). It recommends looking for foods that have a daily value (DV%) of sodium 10% or less, as those products are considered low in salt.

The Heart and Stroke Foundation also suggests looking for products with the Health Check™ symbol, which implies that food has been tested by the Heart and Stroke Association to comply with their nutrient standards. However, this has been met with controversy as typically “unhealthy” foods, such as slushies and pizza, have been found to carry the Health Check. 

Health Canada advises consumers to

·         read the nutrition label available on all packaged foods and avoid consuming foods that have high sodium content.  

·         not add salt when preparing or eating meals. Children’s meals should have no additional sodium.

·         use seasonings such as herbs, as a way to reduce sodium intake.

·         eat meals high in sodium less often.

·         buy unprocessed food to prepare at home, instead of purchasing pre-packaged or processed foods. This gives more control over the amount of sodium being consumed.

·         eat fruits and vegetables which are high in potassium and reduce the risk of high blood pressure. This also ensures the intake of vitamins and minerals needed for bodily function.

The DASH diet (Dietary Approaches to Stop Hypertension) has been proven to manage high blood pressure effectively. It limits salt intake to less than 2300 mg per day (preferably around the 1500 mg level, which is less than half a teaspoon), which is initially very difficult to achieve. The DASH diet consists of whole grains, vegetables, fruits, low-fat dairy products, lean meats, and food generally low in saturated or trans fats. For more information about this diet, click here.

References 

Britton KA, Gaziano JM, Sesso HD, Djousse L. (2009). Relation of alcohol consumption and coronary heart disease in hypertensive male physicians. Am J Cardiol, 104:932-935.

Dias-Neto M, Pintalhao M, Ferreira M, Lunet N. (2010). Salt Intake and Risk of Gastric Intestinal Metaplasia: Systematic Review and Meta-Analysis. Nutr Cancer, 62(2), 133–147.

http://www.cancer.ca/Ontario/Prevention/Eat%20well/Salt%20and%20sugar.aspx?sc_lang=en

http://www.diabetes.ca/documents/about-diabetes/CDA_HighBP_Sep09_Eng.pdf

http://www.hc-sc.gc.ca/hl-vs/alt_formats/pacrb-dgapcr/pdf/iyh-vsv/food-aliment/sodium_eng.pdf

http://www.heartandstroke.on.ca/site/c.pvI3IeNWJwE/b.3581951/k.6E17/Healthy_Living__Salt.htm

http://www.canada.com/ottawacitizen/news/story.html?id=9a6e4c69-eb94-4b53-b37f-a06b80b9bb25&k=20008

Todd AS, Macginley RJ, Schollum JB, Johnson RJ, Williams SM, Sutherland WH, Mann JI, Walker RJ.(2010). Dietary salt loading impairs arterial vascular reactivity. Am J Clin Nutr, Mar;91(3):557-64.

http://www.cmaj.ca/cgi/content/full/178/4/386

Document information

Author:  Grace Cheung

Last modified:  Posted May 2010

Last reviewed:  Posted May 2010

History:  Posted May 2010

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