Hold the Salt Gramps!

Drugs

Let food be thy medicine and medicine be thy foodHippocrates

Hippocrates’ famous advice still holds true 2,500 years later as Tennessee, USA researchers confirm that lowering salt intake reduces blood pressure in older adults.

Lower Salt, Lower Blood Pressure

In a recent JAMA Network report1, a team of US researchers challenged the claim that lowering sodium intake is only recommended for people with resistant hypertension2,3. You could say, we should take those claims with a pinch of salt, rather than a shake. People with normal blood pressure, high blood pressure and even those taking medication for hypertension, all saw a drop in blood pressure after switching to a low-sodium diet.

The study involved 213 participants aged 50 to 75, including individuals with both normal blood pressure (normotension) and hypertension, even those currently on medications. The findings showed that, after only one week of following a low-sodium diet, participants’ blood pressure decreased significantly. Indeed, they showed an average decrease of 6 mm Hg—a level comparable to the common antihypertensive medicine hydrochlorothiazide1.

How High is Too High?

Blood pressure readings are expressed as two numbers, a reading might look like “120/80 mmHg”. The first number (systolic pressure) represents the pressure in the arteries when the heart beats. The second number (diastolic pressure) represents the pressure in the arteries when the heart is at rest between beats.

Doctors define normal blood pressure as less than 120 mmHg for systolic and less than 80 mmHg for diastolic. A reading of more than 130 mmHg for the systolic, or 80 mmHg for the diastolic, means that your blood pressure is too high. 



Several factors affect blood pressure, these can be divided into two main categories. Permanent factors like age, sex, ethnicity, and genetics. Then there are factors linked to lifestyle, such as excessive alcohol or caffeine intake, insufficient exercise, smoking, and of course, eating unhealthily4.

Switching up Salt

While the effect of salt on blood pressure is well known5, this study added a little seasoning to the usual approach. First, it involved people with hypertension who were taking antihypertensive medications. Second, they thought up a clever method to measure measured a person’s individual response to salt. The participants alternated between high sodium (2,200 mg added daily) and low-sodium (500 mg total daily) diets for one week each.

Before the study began, the researchers measured participants’ blood pressure. At the end of each diet week, they took new measurements. The researchers collected urine samples to check that participants were sticking to their diet. Urinary sodium levels reflect dietary sodium intake. By crossing over and switching diets, researchers could study the salt sensitivity of each participant’s blood pressure.

Pressure Drop

The results showed several key findings:
—Mean arterial pressure decreased in 73.4% of participants while on the low-sodium diet compared to the high-sodium diet. Similar results were observed for systolic and diastolic blood pressure, as well as pulse pressure.
—After the first week of the switch, participants experienced an average systolic blood pressure difference of 8 mm Hg between the low-sodium and high-sodium diet groups regardless of their baseline blood pressure levels.
—The researchers found that salt sensitivity was independent of antihypertensive drug classes.
—A small minority of participants (5%) exhibited inverse salt sensitivity. These participants experienced an increase in blood pressure while on a low-sodium diet.

Diet Doctors

While this study highlights the promising benefits of reducing salt intake, regardless of blood pressure status, it does have limitations.

The short duration of the study, lasting only one week, means that long-term benefits were not assessed. Although no serious adverse events were reported, a small number of participants experienced inverse salt sensitivity. This means an increase in blood pressure when they reduced salt intake. If you have high blood pressure or diabetes, check in with your doctor before making big dietary changes.

For the rest of us though, the universal guideline to keep an eye on our salt intake still holds true. This research demonstrates that in adults between 50 and 75, lowering dietary salt leads to lower blood pressure.

If you are among the lucky majority, adopting the DASH diet, consisting of nutritious options such as oatmeal, yogurt, fruits, chicken breast, lentils, salad, rice, or pasta, is an easy way to keep your heart healthy.

References

1.Gupta DK, Lewis CE, Varady KA, et al. Effect of Dietary Sodium on Blood Pressure: A Crossover Trial. JAMA. 2023;330(23):2258-2266. doi:10.1001/jama.2023.23651

2. Cohen JB, Juraschek SP. Making Sense of Individual Responses to Sodium Reduction. JAMA. 2023;330(23):2251-2252. doi:10.1001/jama.2023.23650

3.DiNicolantonio JJ, Niazi AK, Sadaf R, Keefe JHO, Lucan SC, Lavie CJ. Dietary Sodium Restriction: Take It with a Grain of Salt. The American Journal of Medicine. 2013;126(11):951-955. doi:10.1016/j.amjmed.2013.05.020

4. High Blood Pressure – Causes and Risk Factors | NHLBI, NIH. Accessed February 15, 2024. https://www.nhlbi.nih.gov/health/high-blood-pressure/causes

5. Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on Blood Pressure of Reduced Dietary Sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet. New England Journal of Medicine. 2001;344(1):3-10. doi:10.1056/NEJM200101043440101

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