Single Salty Meal Impairs Artery Function

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The new US Dietary Guideline level for sodium for all African-Americans, and those with elevated BP and those 51 and older is less than 1500 mg per day. For the rest of the population it is up to 2300 mg.

Most people consume 3000-5000 mg per day so either of these are major cuts in what people are used to. Of course the prudent thing to do is cut as much as you can. Waiting until high blood pressure develops or age 51 to cut back on salt is questionable. We don?t wait until people reach age 51 or develop emphysema to tell them to stop smoking. Telling people with normal blood pressure that added salt is not a problem if you?re younger than 51 can also be questioned because people get accustomed to a higher salt intake early in life, making it more difficult for them to cut back after blood pressure rises or after they reach middle age. It also assumes excess salt intake only harms the body by increasing blood pressure, which is known to be false. Reduced flow mediated dilation (FMD) results from damage to endothelial cells that line the artery?s walls. Damage to endothelial cells is believed to be involved in the development cardiovascular disease. FMD was measured after an overnight fast in subjects who had for the previous two weeks been consuming either a high-salt and low-salt diet (3600 vs. 1475 mg Sodium). The results of this study showed FMD was reduced by 45% on the high-salt diet compared to the low-salt diet.1 Importantly, this study found that the impaired FMD caused by increased salt intake was independent of its short-term impact on blood pressure. The authors conclude, ?These findings suggest additional cardio-protective effects of salt reduction beyond blood pressure reduction.? More recently this same group of research fed another group of subjects with normal blood pressure a single meal of tomato soup after an overnight fast. The soup contained either 1500mg or only 115mg of sodium. In this study FMD was reduced significantly more 30 and 60 minutes after just a single high-salt meal compared to the same meal without added salt.2

Excessive salt intake appears to interfere with normal endothelial function and impair blood flow after each salt rich meal. Just two weeks of eating salty foods already leads to impaired endothelial function in the fasting state and all this happens in younger people before hypertension develops. So salty meals damage the artery wall after each salty meal and after just a few weeks this damage is already lasting beyond the postprandial state. Waiting for hypertension to develop or age 51 to cut back on salt seems ill-advised.

By James J. Kenney, PhD, RD, FACN

References:

1 Am J Clin Nutr 2009;89:485-90

2 Am J Clin Nutr 2011 doi: 10:3045/

ajcn.110.006155

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