Industry efforts to reduce the amount of salt in foods are unlikely to work to reduce salt consumption to levels backed by public health advocates, according to new research that suggests salt intake is regulated by the body’s needs rather than by the food supply.
The Danish and US researchers said that population-wide salt reduction programmes are based on the idea that salt intake is greater than physiological need, and therefore, can be reduced and maintained at a lower level. However, their latest research backs earlier findings that salt intake is regulated in the brain, and has remained stable within a relatively narrow range over the past 50 years, regardless of ethnicity or changes to the food supply.
The World Health Organisation (WHO) recommends a maximum daily salt intake of 5 g – equivalent to about 2,000 mg of sodium – but three-quarters of the world’s population consumes at least twice this amount, according to 2010 data .
Published in the American Journal of Hypertension , this latest study used review data of sodium intake measured by urine analysis from 45 countries, involving more than 69,000 participants over five decades. It found that average sodium intake ranged from about 2,600–4,800 mg a day (6.5 g - 12 g of salt).
“Thus, our analysis indicated that there is a “normal” range of human sodium intake defined by physiology and biological needs and not by the food supply,” the researchers wrote. “…No matter how well intended, public policy simply cannot alter a physiologically set parameter.”
They added: “It is reasonable to conclude that a normal range for human sodium intake exists. If future guidelines are to be effective and feasible, they must be based on that scientific reality.”
‘Limitations of available evidence’
The study’s authors presented their findings to the US Institute of Medicine, which responded with a report titled Sodium Intake in Populations.
It says: “Sodium Intake in Populations recognizes the limitations of the available evidence, and explains that there is no consistent evidence to support an association between sodium intake and either a beneficial or adverse effect on most direct health outcomes other than some CVD outcomes (including stroke and CVD mortality) and all-cause mortality.”
The IOM committee said it was not its role to define the normal range of human sodium intake. Therefore the report did not define ‘excessive’ or ‘inadequate’ intake.
The study’s authors claim that these latest findings, combined with those of an earlier 2009 study , support the idea that the brain controls human appetite for sodium, as has been demonstrated in other vertebrates that tend to regulate sodium intake within a narrow range.
However, they acknowledge that patients with high blood pressure may indeed benefit from “moving from the higher end of this normal intake range to the lower end”, although they added that clinical trials would be needed to assess effectiveness.
Source: American Journal of Hypertension
Published online ahead of print doi: 10.1093/ajh/hpt139
“Normal Range of Human Dietary Sodium Intake: A Perspective Based on 24-Hour Urinary Sodium Excretion Worldwide”
Authors: David A. McCarron, Alexandra G. Kazaks, Joel C. Geerling, Judith S. Stern and Niels A. Graudal