Despite decades of attempts to get people to shake their salt habit, there is little evidence that sodium intake has changed in over 50 years, a new study says.
And, as authors of an editorial published in the November American Journal of Clinical Nutritionpoint out, more regulation of sodium in processed foods isn’t likely to curb intake anytime soon.
Two researchers in the Harvard School of Public Health’s department of nutrition analyzed 38 studies published between 1957 and 2003, reporting the amount of salt passed in urine by 26,000 participants.
The researchers assumed salt intake would have increased over the years due to increased consumption of more processed foods since the late 1950s. Yet, the sodium excretions were found to be unchanged in 50 years, with Americans consistently consuming 3,526 milligrams of sodium per day.
The amount is significantly higher than the recommended intake levels of 2,300 mg per day for adults (1,500 mg per day for those who are at risk or who already have high blood pressure) that health and nutrition authorities have been urging through policy initiatives such as mandatory labelling and pressure on the food industry to lower salt in processed products.
Why haven’t people heeded the health message? And why is average salt intake in the U.S. actually similar to elsewhere in the world?
“One possible explanation… is that human sodium intake is a parameter that even the most well-intentioned public policy cannot modify in most people,” theAJCNeditorial, titled Science Trumps Politics: Urinary Sodium Data Challenge U.S. Dietary Sodium Guideline, asserts.
In other words, humans crave salt, need salt to stay healthy, and have eaten it for millennia. Humans have also long associated salt with foods eaten while hungry, the study asserts.
“Before the introduction of processed foods sodium was added to foods at the time of preservation, cooking or consumption,” writes Dr. David McCarron, lead author of an accompanying journal editorial in theAJCN,adding “sodium has been largely consumed in association with food intake motivated by hunger and appetite.”
Moreover, salt plays a critical role in body fluid regulation, and is important for healthy cellular function across virtually all organ systems.
Recommendations for reducing intakes below 2,760 mg per day “assumes the basic biology of the organism should be ignored,” the editorial states, adding that recommendations for lowered intake also assume that lowered intake isn’t potentially harmful. Other assumptions are that people will desire to make these changes and that the food industry can create lower-salt foods with the same texture, taste and stability that people will still like.
The U.S. government since the early 1980s has urged salt intake reduction to reduce blood pressure and heart disease.
The study also notes that Americans’ rates of high blood pressure and heart disease have increased in the last two decades. Its authors say carrying around too much weight may be the bigger culprit than a rise in salt intake.
TheAJCNeditorial says guidance for salt intake should target specific populations for whom a lower sodium intake is possibly beneficial, including those at risk for high blood pressure and heart disease. About 70 per cent of Americans do fit that target population.
“An appropriate next step is not to lower the sodium guideline further,” it says, “Rather the scientific community should commit to the continued evolution of the science underlying sodium’s role in normal and abnormal human physiology.”