Scientifically Speaking | We are eating too much salt and it is killing us

New research conducted in India and in China shows that by using substitutes for table salt, health risks associated with high sodium intake can be lowered

Over the past few decades, a strong link between the rising incidence of high blood pressure, stroke, and heart disease and high sodium-intake (mainly through table salt) has been shown. Humans can’t live without sodium, but we only need small amounts of it. Today, the problem isn’t getting enough sodium, but that we are eating far more of it than we need. Millions of people die each year from conditions linked to excess sodium.

Some people who have normal blood-pressure do not have to worry about how much salt they consume (Shutterstock)

The World Health Organization (WHO) set a limit of 2,000 milligrams of sodium per day. Our Paleolithic ancestors probably consumed around 800 milligrams of sodium a day. Today, the average American consumes around 3,400 milligrams a day, while in India, the average salt consumption is nearly double the WHO limit.

High blood-pressure is easy to detect and there are cheap and effective drugs to treat it. But the problem is that many of us do not know we are suffering from it until it is too late. It is estimated that one in four Indian adults has high blood-pressure. Over 200 million people are at risk from a silent killer.

New research conducted in India and in China shows that by using substitutes for table salt, health risks associated with high sodium intake can be lowered. This should pave the way for a broader dialogue, more clinical studies, and adoption of salt substitutes.

Most of dietary sodium comes from table salt. Other sodium products such as baking soda, baking powder, monosodium glutamate, and sodium ascorbate contribute the balance. Of course, reducing consumption of salt is the best way to control sodium intake. To an extent, limiting salt in diets is possible. After all, what might seem salty to someone might not seem salty to someone else. Reducing salt in diets is achievable. But over 70 years of research has found that salt is extremely addictive.

There’s a reason we eat so much salt. It tastes good. In Salt Wars: The Battle Over the Biggest Killer in the American Diet, Michael Jacobson offers an evolutionary perspective. Our ancestors evolved in the salt-poor African continent. Our tastebuds craved salt when it was scarce, and now that it is abundant, we can’t keep our love of salty food under control. Food manufacturers know this, and they use massive amounts of salt in processed food. Salt can also mask unpleasant flavours in cheap ingredients.

Some people who have normal blood-pressure do not have to worry about how much salt they consume. Genetics plays a part, but we do not know exactly why they are resistant to the detrimental effects of increased sodium consumption. The problem is that those of us who have borderline high-blood pressure or very high-blood pressure are at risk of adverse effects of ingesting too much salt.

The two recent studies in India and China focused on people with high blood-pressure. These twin studies provided participants with a salt substitute with 70-75% sodium chloride (the same compound found in table salt) and 25-30% potassium chloride. This proportion was chosen carefully, and participants did not complain about the taste of the potassium chloride in the substitute.

I know the problem with including too much potassium chloride in a salt substitute firsthand. I have used a salt substitute with 50% sodium chloride and 50% potassium chloride while cooking. It has a slightly bitter aftertaste that makes it unsuitable for most people to use regularly.

Researchers published findings of a clinical trial conducted in rural Telangana in the July 2021 issue of the American Journal of Clinical Nutrition. Half the 500 participants were randomly assigned to receive regular table salt, while the other half received the sodium chloride/potassium chloride salt substitute. Just three months of salt substitute use reduced average systolic blood pressure by around 4.6 units compared to the blood pressure in those who used table salt. The researchers say this is significant because it is similar to the reduction achieved by using some blood-pressure medicines. Participants didn’t change their cooking habits and they didn’t report any issues with the taste of the salt substitute either.

Results of a landmark study involving 21,000 elderly individuals in rural China who were at heightened risk of strokes, heart attacks, and death was published in in the New England Journal of Medicine on September 16. The trial was randomised with half using the salt substitute and half using table salt. After five years, there was a lower rate of strokes, heart attacks, and death in the salt substitute group compared to the table salt group.

This was an elegantly designed study because it tracked health outcomes in a large population over a long period of time. In rural China, a large amount of processed food is not consumed, so the predominant source of dietary sodium is from salt or its substitute used at home.

The key assumption from both studies is that the same amount or less of a sodium-containing substitute will be used in place of table salt. If a substitute tastes less salty people may be compelled to use more of it to satisfy a salt craving. But this did not seem to be a problem in these two cases.

There are a few caveats to these two studies that should be mentioned. Dietary changes should only be made on the recommendation of a qualified health professional. Although adverse effects of consuming more potassium chloride were not reported, the health of patients will need to be tracked for a longer period of time. Excess potassium in the blood will be something to look out for; among those with chronic kidney disease, it can lead to irregular heartbeats.

But the importance of these studies is unmistakable, and on balance, the benefits seem to outweigh possible risks. Both studies show replacement of table salt with a salt substitute has the potential to save lives. This is a cheap and easy intervention that warrants further investigation.

Anirban Mahapatra, a microbiologist by training, is the author of COVID-19: Separating Fact From Fiction

The views expressed are personal