Without sodium, you wouldn’t be able to survive. Nerves would fail to fire, muscles would not contract. But experts say most people consume far too much of it, increasing their risk of high blood pressure and heart disease.
The HSE recommends “no more than 6g of salt (2.4g of sodium) a day, but says people in Ireland eat about 10g of salt (about 4g of sodium) – which is “more than the body needs”.
In recent decades, researchers have disagreed about exactly how much sodium is too much. More recent research has clarified some of that murkiness, according to Dr Lawrence Appel, a professor of medicine at the Johns Hopkins University School of Medicine.
How does sodium affect health?
Scientific studies from the past 50 years or so have shown a clear pattern: “The more salt we eat, the higher our blood pressure goes,” says Cheryl Anderson, a professor of public health at the University of California, San Diego.
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In a 2021 review of 85 clinical trials, for example, scientists looked at what happened to people’s blood pressure when they consumed 400-7,600 milligrams of sodium per day. As their consumption increased, the researchers reported, so did their blood pressure. The effect was strongest for people who already had high blood pressure, but the researchers also saw it in people who didn’t.
Managing your blood pressure is one of the most important things you can do to reduce your risk of developing heart disease or having a stroke, says Prof Anderson.
According to the Irish Heart Foundation, more than 50 per cent of men and women in Ireland aged over 45 have high blood pressure. And researchers say that of all of the problems with our diets, sodium is the most harmful to global health – excessive salt consumption causes about two million deaths each year, they estimate, mainly from cardiovascular disease.
[ Consuming slightly less salt can have big health benefitsOpens in new window ]
How much sodium is too much?
The recommendation in Ireland is 2.4g of sodium per day – equivalent to about 1 teaspoon of table salt. According to the US dietary guidelines, adults should have no more than 2.3g. The World Health Organisation and International Society of Hypertension have a slightly lower limit at no more than 2g per day.
These guidelines are based on the best available evidence concerning high blood pressure and heart disease, says Dr Frank Hu, a professor of nutrition and epidemiology at the Harvard TH Chan School of Public Health.
But not all experts agree. In several studies published in the past decade or so, for instance, researchers reported that it was only people who consumed much more sodium – of the order of 5g per day – who had a greater risk of heart disease or earlier death. Those findings suggest that the sodium guidelines set by health organisations across the world are too strict, says Dr Martin O’Donnell, a professor of neurovascular medicine at the University of Galway.
This perspective garnered a lot of mainstream attention, says Dr Appel. But other researchers found serious flaws with the contradictory studies; the main issue being that they could not accurately measure how much sodium people consumed, he adds.
Several recent trials have shown that adults with normal blood pressure who cut back on sodium are less likely to develop high blood pressure than those who do not reduce their consumption
In a 2022 analysis, Dr Hu and his colleagues compiled the results from studies that used more rigorous methods. Among 10,700 adults who were followed for nearly nine years, most consumed about 2,250-5,250mg per day. The researchers found that those who consumed the least amount of sodium had the lowest risk of cardiovascular disease. And as sodium consumption increased, so did cardiovascular risk, a finding that supports the guidelines.
The sodium debate illustrates many of the challenges of nutrition research, says Dr Appel. Large nutrition trials are much harder to conduct than large drug trials, he says, especially when looking at long-term health risks such as heart attacks and strokes. Instead, nutrition researchers often rely on study designs that can only show associations between certain eating patterns and health, and conflicting results are common.
But the evidence to support reducing sodium consumption to the recommended levels is “pretty darn strong”, says Dr Appel.
And, Dr Hu adds: “I don’t think we should wait for perfect evidence to take action.”
So, do I need to cut back on sodium?
If you have high blood pressure, reducing your sodium consumption will most likely help lower it, says Dr Deepak Gupta, a cardiologist at Vanderbilt University Medical Center in Nashville, Tennessee. This has been shown in many studies, including a 2023 trial led by Dr Gupta, which suggests that, in most people, low-sodium diets reduce blood pressure about as well as medication does.
But you shouldn’t wait until you have high blood pressure to think about sodium, says Alta Schutte, a professor of cardiovascular medicine at the George Institute for Global Health in Australia. Excess sodium throughout life can gradually damage blood vessels and eventually lead to high blood pressure. “It’s a cumulative effect,” she says.
Several recent trials have shown that adults with normal blood pressure who cut back on sodium are less likely to develop high blood pressure than those who do not reduce their consumption. “Prevention is certainly much better than treatment,” says Dr Hu.
At the same time, these and other studies have shown that getting enough potassium may be just as important as cutting back on sodium, says Prof Schutte. Getting adequate potassium from your diet can reduce your risk of high blood pressure and heart disease, in part because potassium helps your kidneys remove extra sodium from your blood.
[ Is your diet too salty? Bananas and salmon could help reduce its harmful effectsOpens in new window ]
But some people should avoid consuming too much potassium. If you have kidney disease or are taking certain medications such as potassium-sparing diuretics, check with your doctor before increasing your consumption, says Prof Schutte. And those who are prone to low levels of sodium in their blood may not want to adopt a low-sodium diet, she adds.
How will I know if I’m consuming the right amount?
If the average person in Ireland is consuming about 4g of sodium, it can be challenging to cut that nearly in half without making drastic dietary changes. It’s also difficult to know if you’re over the limit in the first place, since no simple test can measure this. But it’s not all or nothing, says Dr Hu. Any reduction in sodium should be helpful for most people.
Vegetables, fruits, beans, nuts and dairy products are all rich sources of potassium, and eating more of these foods can boost your potassium while also probably reducing your sodium, says Dr Hu.
You can experiment with adding flavour to your food by using more herbs and spices and less salt. Research suggests that spicy seasonings such as chilli peppers and acids such as lemon juice and vinegar can enhance the taste of salt, making a little bit go a longer way. And in taste tests of shop-bought tomato soup, people said that a low-sodium version seasoned with garlic, celery, oregano, bay leaves and black pepper was just as tasty as a full-sodium version.
When buying packaged foods, Prof Anderson says a good rule of thumb is to choose products with no more milligrams of sodium per serving than calories. And be aware that certain canned foods, such as beans and vegetables, are often high in sodium; draining and rinsing them can reduce the load.
Keep in mind, says Dr O’Donnell, that your overall eating pattern is more important than any one ingredient.
– This article originally appeared in the New York Times
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