The report is published in the March 27 issue of the CDC's Morbidity and Mortality Weekly Report.
A main reason for the report is that although guidelines for daily sodium intake were published in the US 4 years ago, the percentage of the population that should be following the lower limit has never been reported.
The 2005 guidelines recommend a maximum daily sodium intake of 2,300 mg (equivalent to 1 teaspoon of table salt) and a lower limit of 1,500 mg for adults with high blood pressure, the over 40s, and all African-American adults.
The main source of sodium in the diet is table salt (Sodium Chloride or NaCl), which comprises 40 per cent sodium by weight.
Using data from the National Health and Nutrition Examination Survey (NHANES) in 2005 and 2006, the CDC researchers estimated the number of Americans aged 20 and over with one of the three risk factors: hypertension, being aged 40 or over, and being black, and found it came to 145 million, or 70 per cent of the adult population of the US.
Previous NHANES results have shown that average daily sodium consumption among Americans aged 2 and over went up from 3,329 mg in 2001-2002 to 3,436 mg in 2005-2006. Both these figures are above the higher 2,300 mg per day limit recommended in 2005.
If the recommended lower sodium limit had been in effect for 8 years instead of 4, the percentage of people it would apply to would have seen a rise from 64.4 per cent in 1999-2000 to 69.2 per cent in 2005-2006, suggesting that the percentage of the population who should be on a lower salt diet is going up as more of them fall under one of the three risk factors.
Hypertension or high blood pressure increases the risk for heart disease and stroke, the first and third leading causes of death in the US. 29 per cent of US adults had hypertension and a further 28 per cent had prehypertension in 2005-2006 , said the CDC report. Research shows that eating too much sodium increase the risk for hypertension.
Reducing sodium consumption is a key recommendation for people with high blood pressure and in the US the public health strategy to encourage less salt eating includes:
- Reducing salt in processed food.
- Eating more fresh fruit and vegetables as these have low sodium content.
- Giving more relevant information about sodium levels on food labels.
A concern is that the current food labeling in the US tends to follow the old guideline of 2,400 mg a day, and this is likely to mislead most consumers, 7 out of ten of whom should be on the lower limit of 1,500 mg a day anyway.
The report recommends that:
"Consumers and health-care providers should be aware of the lower sodium recommendation, and health-care providers should inform their patients of the evidence linking greater sodium intake to higher blood pressure."
"Application of Lower Sodium Intake Recommendations to Adults --- United States, 1999--2006."
C Ayala, EV Kuklina, J Peralez, NL Keenan, DR Labarthe, Div for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion, CDC.
MMWR, March 27, 2009 / 58 (11);281-283.