Claire Collins, University of Newcastle
Salt is the most common form of sodium and is added to foods during manufacturing, cooking at home or at the table to enhance taste or extend shelf life.
Most people have heard the advice to cut back on salt. Indeed, high sodium intakes are associated with high blood pressure, a major risk factor for cardiovascular disease, heart attacks and strokes.
So the recent headline “Food Myths Shattered: Dairy, Salt, and Steak May Be Good for You After All” had to grab some attention.
In the research article on which this title is based, the authors examined whether advice to dramatically reduce sodium intake was supported by strong evidence.
The premise of the article is that the current advice of limiting sodium intake to 2.3 grams per day is unworkable for most people in the long term. And he claims there’s no good-quality evidence to show that lower salt intakes reduce the risk of heart attacks and strokes.
The authors suggest that current global sodium intakes, which range from 3 to 5 grams per day, are associated with the lowest risk of heart attack, stroke, or premature death. And that heart attacks and strokes only increase when sodium intakes are higher or lower.
But there are a number of controversies surrounding these claims, and existing advice for limiting salt intake remains. Let’s take a closer look at some of the problems associated with these claims, as well as some important research the authors missed.
Most of us could afford to cut back on salt
A teaspoon of salt weighs about 5 grams and contains 2 grams of sodium.
Australians consume about 3.6 grams of sodium per day, which is equivalent to 9.2 grams (about 2 teaspoons) of table salt.
This is above the suggested dietary goal of 2 grams of sodium (5 grams of salt) per day and the adequate intake range of 460 to 920 milligrams (1.3 to 2.6 grams of salt) per day.
Read more: Health check: how much salt is okay to eat?
Sodium intakes in Australia are similar to those in the rest of the world. Data from 66 countries, representing three-quarters of the world’s adult population, indicate that the average sodium intake is 3.95 grams per day and ranges from 2.2 to 5.5 grams per day.
Yes, it is possible to reduce the salt
Changing individual behavior over the long term is a challenge. But it is possible.
A 2017 systematic review of dietary salt reduction interventions found that individual dietary counseling could reduce a person’s salt intake by about 2 grams per day (equivalent to 780 mg of sodium), over periods of up to ‘at five years.
Population-wide strategies that include reformulating foods manufactured with lower salt levels, improving labeling, and educating mass media have been even more effective in some regions, reducing consumption. average salt of about 4 grams per day in Finland and Japan.
The authors of the last article point out the lack of studies in the population showing that they have reached dietary sodium intakes of less than 2.3 grams per day.
But that doesn’t recognize the challenges of conducting such a study to test this, or the importance of reducing your sodium intake from what you usually eat.
Cutting back on salt lowers the risk of heart disease
A recently published randomized trial in 600 villages in rural China shows that reducing salt intake can reduce the risk of cardiovascular disease, heart attack and stroke.
The study included more than 20,000 people with high blood pressure who had a history of stroke or were over the age of 60. One group was randomly assigned to use a salt substitute to reduce their sodium intake. The second group continued to use common salt. Both groups were followed for five years.
The intervention resulted in a reduction in sodium excreted in the urine (indicating complacency) and a reduction in blood pressure.
The rate of any major cardiovascular event, including heart attack, was 13% lower in people in the salt replacement group compared to the regular salt group. The stroke rate was 14% lower.
This trial demonstrates the benefit of reducing dietary sodium intake, regardless of a specific daily goal.
Is it risky to have too little salt?
Humans need sodium to maintain essential bodily processes such as fluid volume and cell stability. Sodium levels are balanced through a sensitive system of hormones, chemical processes, and nerves to ensure excess sodium needed is excreted in the urine.
There is conflicting evidence for heart health when you have very low sodium intake. Some researchers have suggested that there is a J-shaped relationship, where low and very high intakes increase the risk of poor outcomes (the end of a “J” shape), while the lowest risk is through a wide midpoint of salt intake. (the curve in the “J”).
The J-shaped curve in some salt and blood pressure studies may be explained by issues such as measurement error, random variation, other differences (age, sex, smoking or socioeconomic status), existing eating habits or other health issues, interactions between a significant reduction in sodium and the body’s physiological pathways that regulate blood pressure.
Or it could be explained by reverse causation, where people recruited into the study report low sodium intakes because they were previously advised to follow a low-salt diet before signing up for the trial.
As we await more research to explain the deviations associated with a J-shaped curve, evidence shows that lower sodium intakes, compared to higher intakes, lead to large reductions in blood pressure.
Clare Collins, Laureate Professor of Nutrition and Dietetics, University of Newcastle
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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