Why a Low Sodium Diet Might INCREASE your Risk for Hypertension

If you’re on a low sodium diet and peeing too much, your risk for hypertension is high.

Four Words: Renin-Angiotensin-Aldosterone System (RAAS)

When we cut salt, we push our body to maintain sodium levels in the blood using a back-up system. What is this system? The renin-angiotensin-aldosterone system (RAAS). Low sodium in the blood is detected by the kidneys, which releases a compound called renin. Renin leads to the production of another compound, called angiotensin.

Angiotensin directly causes blood vessels to constrict (i.e. increasing pressure) and leads to the production of another compound called aldosterone. Aldosterone’s job is to tell the kidneys to flush out more water and keep sodium. This prevents blood sodium from dropping too low because it’s needed to maintain blood volume. If blood volume drops too low, it can cause blood pressure to drop. Which is why the kidneys have a built-in mechanism to detect sodium levels and pressure.

Individuals with hypertension might have normal sodium levels on their labs, while eating too little salt because of RAAS. Blood sodium levels are directly impacted by our sodium intake. If you don’t eat enough (needs vary person-person), your body will use RAAS to maintain sodium levels. At the expense of your long-term cardiovascular health. Bc chronic exposure to angiotensin and aldosterone = hypertension.

Studies show that excessive angiotensin and aldosterone is a common cause of hypertension. While excessive aldosterone is often due to a tumors, it’s something we can take notes from. Much of conventional medicine is based on acute and extreme situations, which makes sense. But we seldom take the same concepts and assess how they can be applied to other contexts. Whether it’s through a tumor or through an innate mechanism the body has to prevent sodium from dropping too low, too much exposure to aldosterone can cause hypertension. Angiotensin, on the other hand, is known to directly cause blood vessels to constrict and thus, it can definitely increase hypertension.

Why Is this Especially Important for Hypothyroidism?

This is especially important for individuals with hypothyroidism because hypothyroidism causes hyponatremia or low concentrations of sodium in the blood (PMID27484454). Too little sodium activates the RAAS system. Thus, individuals with hypothyroidism, who are not getting enough sodium in their diet, are chronically exposed to angiotensin and aldosterone.

The Data is Inconclusive

Despite what it may seem like, the sodium-hypertension link is actually not solid and there is still a lot of debate on the subject. Below are a few quotes from different studies that show the sodium-hypertension link is still debatable.

“After 16 years of follow‐up, those with the lowest [blood pressure] were those with higher intakes of both sodium and potassium while those with the highest [blood pressure] were those with lower intakes of both. The combined effects of both magnesium and calcium with sodium were very similar to those of potassium. These long‐term data from the Framingham Study provide no support for lowering sodium intakes among healthy adults to below [2300 mg] as recommended. This study does support the finding of a clear inverse association between potassium, magnesium, and calcium and blood pressure change over time.” [Moore et al., 2018] 

“Reducing salt intake has emerged as a leading target, with many guidelines recommending sodium intakes of 2.3 g/day or lower. These guideline thresholds are based largely on clinical trials reporting a reduction in blood pressure with low, compared with moderate, intake. However, no large-scale randomized trials have been conducted to determine the effect of low sodium intake on CV events. Prospective cohort studies evaluating the association between sodium intake and CV outcomes have been inconsistent and a number of recent studies have reported an association between low sodium intake (in the range recommended by current guidelines) and an increased risk of CV death. In the largest of these studies, a J-shaped association between sodium intake and CV death and heart failure was found. In this article, we explore potential reasons for the differing interpretations of existing evidence on the association between sodium intake and CVD. Similar to other areas in prevention, the controversy is likely to remain unresolved until large-scale definitive randomized controlled trials are conducted to determine the effect of low sodium intake (compared to moderate intake) on CVD incidence…The most consistent outcome reported in studies is CV death, and for this outcome, a J-shaped association exists, based on the totality of data.” PMID: 23257945.

“We obtained morning fasting urine samples from 101,945 persons in 17 countries and estimated 24-hour sodium and potassium excretion (used as a surrogate for intake). We examined the association between estimated urinary sodium and potassium excretion and the composite outcome of death and major cardiovascular events. In this study in which sodium intake was estimated on the basis of measured urinary excretion, an estimated sodium intake between 3 g per day and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake. As compared with an estimated potassium excretion that was less than 1.50 g per day, higher potassium excretion was associated with a lower risk of death and cardiovascular events. PMID: 25119607

Remember, the American Heart Association recommends NO MORE than 2,300 mg of sodium a day.

The Most Important Nutrients that Impact Blood Pressure

Now, I’m not saying that you should just eat all the salt you want. Or that salt doesn’t acutely (in the short-term) raise blood pressure. What I am saying is, enough sodium is important for addressing hypertension or reducing risk for it. Magnesium, calcium, and potassium also play a very crucial role in hypertension. You have to hit all four nutrients just right to maintain good blood pressure and prevent the body from using stress-induced mechanisms to sustain itself. Another non-negotiable factor in supporting good blood pressure is getting enough protein in the diet.

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