Salt intake has become a major health concern in the United States. An array of studies have claimed too much salt in the diet can increase the risk of serious illness, such as heart disease and stroke, prompting recommendations to lower salt intake. But how much is "too much" when it comes to salt consumption?
The Dietary Guidelines for Americans recommend that adults consume less than 2,300 milligrams of sodium each day - the equivalent to around 1 teaspoon of salt - as part of a healthy diet.
A report from the Centers for Disease Control and Prevention (CDC) released earlier this year, however, found that around 90 percent of adults and children in the U.S. consume more than the recommended sodium intake, with most adults consuming more than 3,400 milligrams daily.
CDC Director Dr. Tom Frieden branded the report findings "alarming," noting that more needs to be done in order to reduce the salt intake of Americans and "save lives."
And it seems the U.S. Food and Drug Administration (FDA) agree; earlier this month, the organization issued draft guidelines for the reduction of sodium in processed foods, which account for around 75 percent of all salt consumption.
The aim of these guidelines is to lower salt intake among consumers to the recommended level of 2,300 milligrams daily, in order to reduce the health risks associated with high salt consumption.
However, some researchers suggest that such a level is too low. In fact, some say that consuming salt in such small amounts may even do more harm than good.
Salt intake: The benefits and risks
According to the American Heart Association (AHA), around 90 percent of Americans' sodium intake comes from sodium chloride, found in table salt and often added to processed foods for preservation and flavor.
- A single slice of bread contains anywhere from 80-230 milligrams of sodium
- Some breakfast cereals can contain up to 300 milligrams of sodium before milk is added
- One slice of frozen pizza can contain 370-730 milligrams of sodium.
It is well known that the body needs some salt; it is important for nerve and muscle function, and it helps regulate bodily fluids.
One study, published in the journal Cell Metabolism last year, even suggested that salt consumption can stave off harmful bacteria and reduce the risk of infection.
However, numerous studies have indicated that consuming too much salt can increase the risk of serious health problems, particularly when it comes to cardiovascular health, with research linking high salt intake to hypertension, stroke, and heart disease.
A study published in the Journal of Agricultural and Food Chemistry earlier this year also suggested a high-salt diet may cause liver damage, while another study linked high salt intake to increased risk of multiple sclerosis (MS).
The basis for which high salt intake can cause bodily harm is a feasible one; too much salt can cause the body to retain water, which can put additional strain on the heart and blood vessels, raising blood pressure and increasing the risk of cardiovascular diseases.
But at what point does salt intake stop helping and starting hindering our health? This remains a subject of debate.
Are current salt intake recommendations too low?
While current guidelines recommend consuming less 2,300 milligrams of sodium daily, a study reported by Medical News Today last month suggested that even 3,000 milligrams of sodium daily may be too little and could put health at risk.
Led by researchers from McMaster University in Canada, the study found that adults who consumed less than 3,000 milligrams of salt a day were at greater risk of heart attack, stroke, and premature death than those with an average sodium intake.
What is more, the team questioned the health risks of high salt intake, finding that it was only adults who already had high blood pressure who were at greater risk of heart disease and stroke with high salt intake - defined as 6,000 milligrams daily.
"While our data highlights the importance of reducing high salt intake in people with hypertension, it does not support reducing salt intake to low levels," concluded study leader Andrew Mente, of McMaster's Michael G. DeGroote School of Medicine.
This is not the first study to question the current salt intake guidelines; a 2014 study conducted by Michael H. Alderman, of the Albert Einstein College of Medicine in New York City, found that reducing salt intake to less than 2,500 milligrams a day was not linked to reduced risk of the health conditions associated with high salt consumption.
'The science is clear - reducing salt lowers blood pressure'
Despite such findings, the FDA conclude there is an "overwhelming body of scientific evidence" that reducing daily sodium intake to less than 2,300 milligrams can prevent the health risks of a high-salt diet.
"Experts at the Institute of Medicine have concluded that reducing sodium intake to 2,300 milligrams per day can significantly help Americans reduce their blood pressure and ultimately prevent hundreds of thousands of premature illnesses and deaths," notes Susan Mayne, Ph.D., director of the FDA's Center for Food Safety and Applied Nutrition.
Additionally, the organization points to previous studies that have suggested lowering sodium intake in the U.S. by around 40 percent over the next 10 years can save around 500,000 lives and reduce healthcare costs by around $100 billion.
The CDC echo the FDA's view on reducing salt intake. "The science is clear - reducing salt lowers blood pressure," says Dr. Frieden, "and high blood pressure is a major risk factor for cardiovascular disease."
Speaking to The New York Times earlier this month, Dr. Frieden acknowledged that there are a number of researchers who disagree that reducing salt intake improves health outcomes, but he claims the studies they cite have "fatal flaws."
Explaining what flaws Dr. Frieden is referring to, nutritionist Cheryl Anderson, member of the 2015 Dietary Guidelines Advisory Committee, told The Washington Post that many of the studies citing the negative effects of low-salt diets have only used a small number of urine samples to reach their conclusions, meaning the findings could be misleading.
Additionally, Anderson said some of these studies might be subject to "reverse causality," where instead of low-salt diets causing cardiovascular diseases, it could be that such diseases cause people to consume low-salt diets.
Further investigation into salt consumption is needed
While it seems many health experts are in support of government strategies to reduce salt intake among the general public, others say more research should be conducted on the long-term health effects of low-salt diets before making recommendations.
Additionally, many researchers and organizations - including the Grocery Manufacturers Association (GMA) - believe further research is required to pinpoint the exact salt intake that is most beneficial for health.
"Like others inside and outside of government, we believe additional work is needed to determine the acceptable range of sodium intake for optimal health," says Leon Bruner, chief science officer of the GMA.
"This evaluation should include research that indicates health risks for people who consume too much sodium as well as health risks from consuming too little sodium."
Based on the current evidence, it seems following the current dietary guidelines for salt intake is the best way to reduce the health risks associated with high salt consumption.
Whether such recommendations will ever be proven wrong, however, remains to be seen.