Low-sodium diets not always worth their salt, McMaster study finds

Contrary to popular thought, maintaining a low-sodium diet may not be beneficial to one's health. According to a recently published study, cutting down your daily salt intake could actually be harmful to your body.

Dangers include increased risk of heart attack and stroke, researchers say

New research suggests it's time for Canada to update its guidelines around salt intake. (CBC)

Contrary to popular thought, maintaining a low-sodium diet may not be beneficial to one's health. According to a recently published study, cutting down your daily salt intake could actually be harmful to your body.

A recent global study conducted by researchers of the Population Health Research Institute of McMaster University and Hamilton Health Sciences found low-sodium diets actually increase the risk of cardiovascular disease and death compared to diets with average sodium consumption.

The new study was published in The Lancet medical journal on Friday.

Everything in moderation

For years, Canadians have been told to avoid consuming too much sodium. While that still stands to be true, lead author Andrew Mente said there's also another message that isn't usually heard: make sure you get enough sodium. 

Salt is an essential nutrient and is needed by the body, said Mente, a principal investigator of the Population Health Research Institute and an associate professor of clinical epidemiology and biostatistics at McMaster's Michael G. DeGroote School of Medicine in Hamilton.

McMaster researcher Andrew Mente was the lead author of the study.

If the body doesn't get enough of it, a variety of health problems could result, including an increased risk of heart attack and stroke. 

Maintaining a moderate intake of sodium each day is the healthiest choice for everyone, he said, including those who suffer from high blood pressure. 

What does a moderate intake of sodium look like? 

"Just follow an overall healthy diet, and don't be concerned about sodium," he said, adding the majority of Canadians are eating the right amount of sodium.

If you eat your fruits and vegetables, exercise, minimize processed foods and don't smoke, "you'll be fine, you don't even have to think about sodium," he said.

Dangers of low-sodium diets

The study is very important for those who have high blood pressure, Mente said. The data highlights the importance for people with high blood pressure to reduce their salt intake, but also shows the dangers of going on a low-sodium diet.

According to the study, a high-sodium diet is only linked to an increased risk of cardiovascular disease in populations of people with high blood pressure. For people with a normal blood pressure, the study found a high-sodium diet was not associated with cardiovascular disease. 

The study involved more than 130,000 people from 49 countries. It looked specifically at how the relationship between sodium intake and heart disease, stroke and death differed in people with high blood pressure as compared to those with normal blood pressure.

'The current guidelines need to be updated'

Mente said previous research that favoured low-sodium diets was based on assumptions about the relationship between blood pressure and sodium levels. 

"Given that lower sodium is related to lower blood pressure, they assume that that's going to translate into lower cardiovascular disease," he said, speaking of past researchers. "It turns out these assumptions are wrong."

Mente said that over the past five years numerous studies have revealed the dangers of low-sodium diets. This newest study at McMaster just confirms what the latest research has shown, he said.

"It appears that low sodium truly is harmful and we need to be cautious before recommending low levels for the entire population," he said.

The current guidelines from Health Canada call for people to cut their salt intake to less than 2.3 grams per day, but Mente said these levels are too low.

"The current guidelines need to be updated to reflect contemporary research," he said.

Continuing debate

Between 2007 and 2010, Health Canada tasked a Sodium Working Group with developing a population health strategy to help reduce sodium content in the diets of Canadians. The final report recommended Canadians aim for an intake level of 2.3 grams of sodium daily. At the time, the average daily sodium intake for Canadians was around 3.4 grams. 

Mente said that currently the majority of individuals in Canada and in most other countries are consuming the right amount of salt — between three and six grams daily.

The debate stems from how researchers measure the overall health of a population. Some scientists think blood pressure is an infallible measure of predicting health effects, Mente said. They rely on the clinical trials of blood pressure measurements and then extrapolate that data.

Others rely on measuring actual health events like heart attacks, strokes and deaths. This is the process Mente and his team went through for their study.

To settle this debate, Mente said there would likely need to be a randomized controlled trial that would have to run for years, holding participants strictly to a low-sodium diet. These types of trials are very difficult to run, he said, added that he hopes to take part in organizing one in the future.


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