Conflicting views on sodium and mortality

by Jeff Gelski
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Two studies published five days apart reported different findings on the association between sodium intake and the risk of death. According to a study published July 11 in the Archives of Internal Medicine, Americans who eat a diet high in sodium and low in potassium have a 50% increased risk of death from any cause and about twice the risk of death from heart attacks. The publication came after a review published July 6 in the American Journal of Hypertension said reducing the amount of salt in the diet has no clear benefits in terms of likelihood of dying or experiencing cardio-vascular disease.

Researchers from the Atlanta-based Centers for Disease Control and Prevention, Atlanta-based Emory University and the Harvard School of Public Health in Boston examined the joint effects of dietary sodium and potassium intake. They used the third National Health and Nutrition Examination Survey Linked Mortality File (1988-2006), a prospective cohort study of a nationally representative sample of 12,267 U.S. adults, and studied all-cause, cardiovascular and ischemic heart diseases mortality.

Researchers documented 2,270 deaths, including 825 cardiovascular deaths and 443 ischemic heart disease deaths, during a mean follow-up period of 14.8 years. Higher sodium intake was associated with increased all-cause mortality while higher potassium intake was associated with lower mortality risk. Sodium intake was not statistically associated with cardiovascular disease or ischemic heart diseases mortality.

Higher sodium-potassium ratio was significantly associated with the risk of cardiovascular disease and ischemic heart diseases mortality. The study found usual daily sodium intake of 4,323 mg per man and 2,918 mg per woman and usual daily potassium intake of 3,373 mg per man and 2,483 mg per woman. The sodium:potassium ratios were 1.31 for men and 1.23 for women.

“The study’s findings are particularly troubling because U.S. adults consume an average 3,300 mg of sodium per day, more than twice the current recommended limit for most Americans,” said Elena Kuklina, an investigator involved with the study and a nutritional epidemiologist with the C.D.C.’s Division for Heart Disease and Stroke Prevention. “This study provides further evidence to support current public health recommendations to reduce sodium levels in processed foods, given that nearly 80% of people’s sodium intake comes from packaged and restaurant foods. Increasing potassium intake may have additional health benefits.”

The other study involved researchers from Florida Atlantic University in Boca Raton, Fla., and researchers in the United Kingdom from the University of Exeter, the University of East Anglia and the London School of Hygiene and Tropical Medicine. They searched for randomized controlled trials with follow-up of at least six months that compared dietary salt restriction to control/no intervention in adults, and reported mortality or cardiovascular disease morbidity. They identified seven studies.

“Despite collating more event data than previous systematic reviews of randomized con-trolled trials (665 deaths in some 6,250 participants), there is still insufficient power to exclude clinically important effects of reduced dietary salt on mortality or cardiovascular morbidity in `normotensive’ or hypertensive populations,” the researchers concluded.

The researchers added further evidence from randomized controlled trials is needed to confirm whether restriction of sodium is harmful for people with heart failure.

“The scientific evidence is overwhelming,” said Lori Roman, president of the Salt Institute, Alexandria, Va., on July 6. “A study by the world-renowned Cochrane Collaboration, published today in the American Journal of Hypertension, proves beyond any reasonable doubt that population-wide sodium reduction efforts provide no measurable benefits and may increase the risk of disease and death. In light of this, and other recent research, it is time for the government to cease its costly and wasteful efforts to reduce salt consumption until it can conclusively prove a tangible benefit for all consumers. This can only be done through a large-scale clinical trial on the impact of dietary salt reduction on health outcomes.” 

Potassium chloride comes with taste issues

Replacing sodium with potassium may give a product a healthier profile, judging by a study published July 11 in the Archives of Internal Medicine (see story on Page 27). Yet replacing sodium chloride, or salt, with potassium chloride may give a product an undesired taste.

“Most salt replacers or salt substitutes contain potassium chloride as the primary means to lower the sodium content in the finished product,” said John Reidy, market development manager, Health & Nutrition, for Jungbunzlauer, Inc., Newton Centre, Mass. “Potassium chloride is known for its metallic, bitter off-notes that companies try very hard to mask with flavoring agents (e.g. flavors, herbs, spices and acids).

“In some applications that contain high levels of these flavoring agents, companies are overcoming these hurdles with potassium chloride. Jungbunzlauer’s sub4salt also contains sodium chloride, potassium chloride and sodium gluconate. The key is sodium gluconate, which masks the undesirable characteristic of potassium chloride. Tasted straight, sub4salt exhibits the same taste profile people expect from salt, without any off-notes.”

Other ingredient companies have their own sodium reduction systems that address potassium chloride taste issues. Symrise, Teterboro, N.J., offers the ingredient brand SymLife Salt and flavors that mask potassium chloride’s taste.

Minneapolis-based Cargill sampled a sliced ham featuring its Premier potassium chloride system at the American Meat Institute Expo in April in Chicago. The system may deliver up to 50% sodium reduction without compromising taste, texture or shelf stability, according to Cargill.

Potassium chloride has functional benefits in sodium reduction efforts. For example, when reducing the salt level in certain food products, companies must be aware of potential preservative and food safety issues, said Janice Johnson, applications technical service leader for Cargill. Companies must maintain microbial management, such as in cheese and sausage production, when using less salt. To achieve the right water activity, they may turn to other molecules such as sugar and potassium chloride, she said.

The Dietary Guidelines for Americans 2010 recommends people reduce daily sodium intake to less than 2,300 mg while people who are 51 and older and those of any age who are African American or have hypertension, diabetes or chronic kidney disease further should reduce daily sodium intake to less than 1,500 mg.

While sodium consumption remains well above the recommendations, potassium consumption remains well below its recommendations, Dr. Johnson said. The Dietary Guidelines for Americans recommends daily potassium consumption of 4,700 mg for people age 14 and over. Children’s daily recommendations range from 3,000 mg to 4,500 mg.

Dr. Johnson said researchers now are focusing on sodium-to-potassium ratios in diets.

“In the next five to 10 years we may understand what is the proper ratio, what is the right ratio,” she said.

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