WASHINGTON – Two reports offering conflicting advice have spiced up the debate over sodium guidelines at the beginning of 2017. One report issued in January by the Competitive Enterprise Institute (CEI) questions daily sodium limits, but a study appearing online Jan. 10 in the BMJ argues that government strategy to reduce sodium intake could be cost-effective worldwide.
The CEI report questions maximum sodium consumption guidelines, sodium’s impact on hypertension and federal attempts to regulate sodium.
|Michelle Minton, a CEI fellow|
“When it comes to the salt in our food, regulators and health activists are wrong to push a one-size-fits-all sodium-restriction plan on everyone,” said Michelle Minton, a CEI fellow and author of the report titled “Shaking up the Conventional Wisdom on Salt; What Science Really Says About Sodium and Hypertension.” “There’s no evidence that a severe cutback in sodium will lead to overall public health gains as regulators, activists and media reports often claim. In fact, it may actually hurt certain groups of people. Instead, what the science shows is the best way to help prevent or treat hypertension is healthy lifestyle choices, like a diet rich in fruit and vegetables, and recommendations tailored to each person’s unique needs.”
The contrasting study appearing in the BMJ, an international peer-reviewed journal formerly known as the British Medical Journal, examined 183 countries. It found reasons for a government “soft regulation” policy that combines targeted industry agreements, government monitoring and public education to reduce sodium intake. Based on costs and a 10 percent reduction in salt over 10 years, such a “soft regulation” policy in those 183 countries globally could save nearly 6 million life-years currently lost to cardiovascular disease each year at an average cost of $204 per life-year saved.
|Dariush Mozaffarian, MD, dean of the Friedman School of Nutrition Science and Policy at Tufts University|
“We know that excess dietary salt causes hundreds of thousands of cardiovascular deaths each year,” said Dariush Mozaffarian, MD, dean of the Friedman School of Nutrition Science and Policy at Tufts Univ. in Boston and senior and corresponding author of the study. “The trillion-dollar question has been how to start to bring salt down and how much an effort would cost.”
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Americans on average consume about 3,400 mg of sodium per day, according to the CEI report. The US Dept. of Health and Human Services, the US Dept. of Agriculture and the Centers for Disease Control and Prevention all recommend adults consume less than 2,300 mg of sodium per day.
“This limit originated not from a process of scientific consultation but from government fiat, prompted by politicians, bureaucrats and industry,” the CEI report said.
The Washington-based Competitive Enterprise Institute uses analysis, advocacy, coalition-building and litigation in its efforts to remove government-created barriers that may impede “economic freedom, innovation and prosperity.” The 54-page CEI report includes 196 footnotes referring to scientific studies.
Minton, the study’s author, specializes in gambling laws, alcohol regulation, and issues related to food and public health. She received a bachelor’s of arts degree from Johns Hopkins Univ. in Baltimore and is working toward a master’s of science degree in applied nutrition at the Univ. of New England.
The CEI report said scientific evidence is inconsistent regarding the health benefits of moderate sodium restriction for people who are not hypertensive. Other dietary factors, such as weight loss and increasing potassium intake, are as effective as sodium reduction in reducing blood pressure. Government should refocus efforts on lowering hypertension rates by recommending people lose weight and increase potassium in their diet by eating more fruits and vegetables, according to the report.
“Compared with a salt-centric approach, this strategy would have a firmer grounding in science, be less likely to cause unintended harm and may even have health benefits in addition to lowering blood pressure,” the CEI report said.
Many factors, and not a single genetic or lifestyle factor, lead to people developing high blood pressure, the report said. Sodium reduction may be advisable for some but ineffective or counterproductive for others. The best way to prevent or treat hypertension is to create individual plans that account for a person’s unique genetic makeup and lifestyle, according to the CEI report.
“For some people, such as older hypertensives consuming very high levels of salt, this plan might include sodium restriction,” the report said. “However, based on current evidence, sodium restriction is not effective for blood pressure reduction in the majority of people and does not impart health improvements.”
The report cited 23 observational studies up to 2012 that examined health outcomes with lower sodium. Six studies found a direct and significant association between higher sodium and poor health outcomes. Seven found an inverse association, which meant they showed higher sodium intakes associated with better health outcomes. Two studies found a J-shaped or U-shaped curve with poor outcomes associated with very low or very high sodium intake. Eight studies found no associations or mixed results.
The CEI report also cited several meta-analyses published since 2012 that produced conflicting results.
Worldwide government attempts to lower population sodium intake below the recommended limit have failed over the past four decades, according to the report.
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Cost effective considerations
Researchers in the study in the BMJ developed a statistical model for 183 countries using data from 2010 to analyze sodium intake, blood pressure levels, the effects of sodium on blood pressure, the effects of blood pressure on cardiovascular disease, and cardiovascular disease rates.
To measure cost-effectiveness, the researchers used international dollars (the equivalent of the country specific purchase power of US dollars) per DALY (disability adjusted life-years) saved over 10 years. The overall cost-effectiveness of the intervention was based on efforts in the United Kingdom and Turkey, which showed a government-supported program could reduce salt consumption by at least 10 percent over 10 years.
The study found that worldwide, a 10 percent reduction in sodium consumption over 10 years within each country was projected to average 5.8 million DALYs a year related to cardiovascular disease, at a population mean cost of $1.13 in international dollars per capita over the 10-year period.
One analysis in the United States estimated that an 11 percent sodium reduction, or about 0.4 gram per person per day, over 10 years would save from $4 billion to $7 billion in health care costs.
“Our novel results, together with prior studies in selected countries, provide evidence that a national policy for reduction in sodium intake is highly cost-effective and substantially more so than even highly cost-effective medical prevention strategies,” the study said. “This advantage likely arises from several factors. This policy is relatively inexpensive to implement, utilizing system-wide ‘soft regulation’ rather than provision of individual level medical care. It also decreases cardiovascular risk at a population level, such that even small changes in distributions of risk factors translate into large clinical benefits, as compared with more intensive strategies delivered only to a subset of people.”
Mozaffarian demonstrated the cost-effectiveness of this strategy by pointing out statin drugs have an estimated cost-effectiveness of about $37,000 per DALY in the United States while the “soft reduction” government policy would have a cost-effectiveness of about $332 per DALY in the United States.
The study involved researchers from Stanford Univ. in Stanford, California; the Harvard T.H. Chan School of Public Health in Boston; the Tufts Friedman School of Nutrition Science and Policy in Boston, and the Cambridge Institute of Public Health in Cambridge, United Kingdom.
Awards from the National Heart, Lung, and Blood Institute and National Institute of Diabetes and Digestive and Kidney Diseases supported the research. Both institutes are part of the National Institutes of Health.
Both the study in the BMJ and the CEI report recognized the worldwide heart health problem. An estimated 1,648,000 annual deaths from cardiovascular disease were attributable to excess dietary sodium in 2010, according to the study in the BMJ. Elevated blood pressure affects about 40 percent of the world’s adult population, according to the CEI report.