Salt increases heart attack and stroke risk, even if blood pressure is normal

Excess dietary salt is notorious for increasing blood pressure – blood volume increases, placing more stress on blood vessel walls. This forces the heart to pump harder against the pressure, and also structural changes that harden the vessel wall (this hardening is called stenosis) occur in response to these high pressures.

About one-third of all American adults and over 50% of those over the age of 55 have hypertension, and hypertension carries significant risks. Elevated blood pressure accounts for 62% of strokes and 49% of coronary heart disease. [1] Notably, the risk for heart attack and stroke begins climbing with systolic pressures (first number in the blood pressure reading) above 115 mm Hg – considered “normal” by most standards.[2] Also, dietary salt is not only dangerous to the cardiovascular system, but also contributes to kidney disease, osteoporosis , ulcers, and stomach cancer. [3]

There is new evidence that excess dietary sodium intake promotes atherosclerotic plaque development and heart disease, even in those without elevated blood pressure.

In the 1990s, it was found that the relationship between salt intake and stroke mortality was stronger than the relationship between blood pressure and stroke mortality; this suggested that salt may have deleterious effects on the cardiovascular system that are not related to blood pressure.[4] Excess sodium in the diet affects sodium concentrations in the blood, which affects the cells of the blood vessel wall and blood volume, even if blood pressure itself does not change. The eventual results are long-term changes in vessel wall structure, including thickening of the vessel wall and arterial stiffening. Excess dietary sodium prompts changes in hormonal systems and also gene expression in endothelial cells (the cells that make up the inner lining of blood vessels). These changes in turn promote excessive growth of vascular smooth muscle cells, which contributes to thickening of vessel wall, and altered production of structural proteins, such as collagen, elastin, and fibronectin, which contributes to arterial stiffening. Dietary salt has also been associated with endothelial dysfunction (the inability of endothelial cells to properly regulate blood pressure), which is one of the initiating events of atherosclerotic plaque formation. [5-8]

The study population consisted of overweight and obese individuals withoutelevated blood pressure., Their sodium intake was evaluated by measuring the amount of sodium excreted in the urine. The authors found that higher urinary sodium (indicating higher sodium intake) was associated with greater carotid artery intima-media thickness – a predictor of future cardiovascular events. Intima-media thickness (IMT) is an indicator of atherosclerotic plaque development and is established in the medical literature as an accurate predictor of future cardiovascular risk. IMT testing is a non-invasive ultrasound technique for imaging any abnormal thickening in the intima (inner lining) and media (smooth muscle layer) layers of the carotid artery. Thickening indicates atherosclerotic plaque formation, and therefore increased risk of heart attack or stroke. [9] I use this test to assess cardiovascular risk and track patients’ progress in my medical practice.

Reducing dietary salt is not only important for those who already have elevated blood pressure – limiting added salt is essential for all of us to keep our cardiovascular systems in proper working order. On top of consuming the vast majority of our calories from phytochemical-rich, unrefined plant foods, salt avoidance adds another layer of protection against heart attack and stroke. It is also important to remember that a low fat, flexitarian or vegan diet plus a low cholesterol level does not protect you from developing high blood pressure later in life from years of using too much salt; it also does not protect you against the risk of later life hemorrhagic stroke, as long as you overly salt your food.

 

 

References:

1. He, F.J. and G.A. MacGregor, A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens, 2009. 23(6): p. 363-84.
2. Lewington, S., et al., Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet, 2002. 360(9349): p. 1903-13.
3. Tsugane, S. and S. Sasazuki, Diet and the risk of gastric cancer: review of epidemiological evidence. Gastric Cancer, 2007. 10(2): p. 75-83.
4. Perry, I.J. and D.G. Beevers, Salt intake and stroke: a possible direct effect. J Hum Hypertens, 1992. 6(1): p. 23-5.
5. Simon, G., Experimental evidence for blood pressure-independent vascular effects of high sodium diet. Am J Hypertens, 2003. 16(12): p. 1074-8.
6. Sanders, P.W., Vascular consequences of dietary salt intake. Am J Physiol Renal Physiol, 2009. 297(2): p. F237-43.
7. Safar, M.E., et al., Pressure-independent contribution of sodium to large artery structure and function in hypertension. Cardiovasc Res, 2000. 46(2): p. 269-76.
8. Dickinson, K.M., J.B. Keogh, and P.M. Clifton, Effects of a low-salt diet on flow-mediated dilatation in humans. Am J Clin Nutr, 2009. 89(2): p. 485-90.
9. Lorenz, M.W., et al., Prediction of clinical cardiovascular events with carotid intima-media thickness: a systematic review and meta-analysis. Circulation, 2007. 115(4): p. 459-67.

 

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Comments (8) Read through and enter the discussion with the form at the end
Ginger - February 7, 2011 12:00 PM

I've never been one to use much salt in cooking and never at the table. However, until I began ETL, I had no idea how much added salt is in processed or restaurant foods. One favorite salad had 1200 mg, no kidding! On becoming aware of this fact, we don't eat out anymore. It was getting harder and harder as a nutritarian anyway. My once salt addicted spouse doesn't use the shaker anymore either. I wonder why this information is not taught to the public?

wendy (healthy girls kitchen) - February 7, 2011 2:35 PM

I have been a Nutritarian for over a year but salt is something that I still struggle with.

For example, if I make a big pot of soup, I find it very, very hard to put no salt in it at all. I certainly am much more careful than I was in the past. I have never been a salt shaker at the table kinda gal nor have I ever liked salty chips and snacks (sugar was my drug of choice). I am paying greater attention to the salt in the canned goods that I do use in my home cooking. But for some reason, I am still struggling with letting go of the little bit of salt to bring out the flavors in my homemade food.

Thoughts anyone?

Fat Fudge - February 7, 2011 5:10 PM

Unfortunately, there are irresponsible articles like this one that discounts the dangers of salt:

http://www.bonappetit.com/magazine/2009/05/the_saline_solution

Stephanie - February 8, 2011 6:22 PM

Wendy,
If you still need a little saltiness but want to minimize the amount, you may find that you can use far less salt but still get the taste of it by adding a little to the surface of your food (i.e., after you've served up a bowl of soup, sprinkle a little on top) rather than salting the whole pot as it cooks. This is what I have found--much less salt is needed if it's on the surface than if it's incorporated in the food when it was cooked.

Miko Aguillera - February 11, 2011 12:06 AM

Thank you for sharing this it has a very informative content.. I hope more of this comes.. More power!!

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Glenda - February 13, 2011 10:28 PM

I think it's OK to add a little bit of salt to your homemade soup-if most of your food is as close to nature as possible you won't get overdosed on sodium. I also think some things are really really bland without a bit, but I find it doesn't take much to liven up a large pot full of beans or soup.

Nevada Smith - April 13, 2011 8:32 AM

I have to wonder who the participants were and from what source all their sodium came from.

Without those details how do we know whether or not it makes a difference as to the source of the sodium?

Most people get their sodium from refined packaged foods, restaurant food and refined table salt. How about the folks in the study did they get theirs from those same sources? Most likely would be my guess. Is there a difference? Without knowing the source we won't ever know conclusively if the minute amounts of other minerals in unrefined salt make a difference or not will we [&/or the absence of anti-caking additives]?

Babbler - February 27, 2012 2:11 PM

I had what they call a TIA about seven years ago and just spent one night in the hospital. Five months ago I had a major stroke that affected my left side. Though it is expected for me to recover pretty much to normal, there is minor things that will remain. I have always had low blood pressure and am not over weight. But I have abused salt since I was a teenager. I have been trying to figure out what caused this stroke. I am not a health nut but also not a couch potatoe. I am convinced that my salt intake is the culprit. I am sure now that stroke is what will be my final demise. I will now limit my salt intake. Thank you for this article.

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