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Salt, health, & BP: Dr. Aju Mathew states 4 recent updates

M3 India Newsdesk Sep 25, 2021

Too little, or too much salt, both have their own kind of effects on the human body, especially for those having a history of cardiovascular risk factors like hypertension. In this article, Dr. Aju Mathew has listed 4 interesting trial findings that will make you take a relook on sodium consumption and restrictions.

“Be the salt of the Earth”, says the bible. Such is the importance of salt in our cuisine. It makes everything taste better and helps preserve food. But too much salt isn’t good as well. As it turns out, too little may also not be good. Let me review some recent updates on salt and health.

We know for some time that patients who have hypertension must curtail their salt intake. There have been plenty of studies about how much is good enough. Several guidelines suggest a safe limit of 1.5 grams to 2.4 grams of sodium per day. One teaspoon of salt equals 2.4 grams of sodium or 6 grams of salt.

PURE cohort study investigates too much vs too little salt

In a major prospective cohort study called the PURE, Dr Salim Yusuf and colleagues showed that too much salt and too little salt may be bad for health.

  1. In a study of 101,000 persons from 17 countries, they assessed fasting urine samples for urine sodium excretion (an indirect correlation for dietary sodium intake).[1] Those persons who had high and low urine sodium had a greater risk for cardiovascular events when compared to those who had moderate urine sodium excretion.
  2. In another study from the PURE cohort, they found that persons with hypertension did worse when they had too much or too little urine sodium excretion.[2] The authors concluded that only those communities with high salt consumption need to have a community-wide implementation of dietary salt restriction. Their results showed the mirror against the WHO and AHA guidelines which state that very low sodium consumption has a preventative role.

They suggest that such low levels of salt consumption may not even be feasible. Interestingly, their work showed that a higher urine potassium excretion (correlated with potassium intake through fruits and vegetables) was associated with better health outcomes. It is in this context that the recently published SSaSS study gains relevance.

Salt Substitute and Stroke Study (SSaSS)

In a very tedious cluster-randomised trial, nearly 21,000 individuals from 600 villages in China, with a history of stroke or high blood pressure were randomised to receiving a salt substitute (replacing 25% of NaCl with KCl by mass) versus consuming 100% NaCl.[3] 72% had a stroke, 88% had high blood pressure.

After 5 years, there was a 14% risk reduction for stroke and a 13% risk reduction for cardiovascular events among persons who consumed salt substitutes. There was no risk for hyperkalemia (serial levels of potassium was not assessed). The authors extrapolated it to population metrics and state that 365,000 strokes and 1.2 million cardiovascular events could be averted every year in China if there is a population-wide implementation of salt substitution in the diet. Astounding!

Salt substitution trial in India

In a trial among 500 persons with high blood pressure in 7 villages in India, 30% NaCl substitution with KCl was compared with 100% NaCl consumption.[4] Change in BP after 3 months was assessed. There was a substantial reduction in systolic and diastolic BP after 3 months of using a salt substitute.

Clearly, there is a role in increasing potassium in diet and reducing sodium. These various studies point to that. It does not appear that the palatability of food alters. But the safety of such an intervention in patients with kidney disease has not been ascertained.

In any case, I think we must stand for any interventions that can reduce the blood pressure among persons with hypertension. But nothing beats adequate screening and counselling and active interventions.

Barbershops and BP

An elegant cluster-randomised trial from barbershops in the USA showed the significant impact of screening, counselling and active treatment in barbershops with trained pharmacists under a doctor’s guidance when compared to just counselling in barbershops.[5] The mean systolic BP fell by 27 mmHg with the active intervention when compared to only 9 mmHg when only counselling was provided.

Let’s devise community-wide strategies to improve screening, counselling and active intervention for BP reduction. And, save lives.

To read Dr. Aju Mathew's previous articles, click here: Dr Aju Mathew picks 3 clinical updates you should not missDr. Aju Mathew lists 4 new updates in diabetes treatmentDr. Aju Mathew presents top 3 updates on antibioticsA hidden side effect of COVID-19 on children: Dr. Aju MathewDr. Aju Mathew reviews 3 crucial studies on liver disease,  New insights on LDL lowering therapies: Dr. Aju Mathew & Dr Aju Mathew lists 2 updates on dengue

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Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

Dr Aju Mathew is a medical oncologist, haematologist, internist and epidemiologist practising in Kochi.

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