Published: Jul 2, 2015
By Keith Ayoob EdD, RD
For decades, dietary guidelines recommended about 2,300 mg/day of sodium for most people. Sodium has for years been thought to be linked with hypertension, and it was often present in a lot of foods people didn't need to be eating too often, so the available evidence pointed to the 2,300 mg level.
Enter the 2010 U.S. Dietary Guidelines for Americans (DGA). The available evidence that was reviewed by the DGA Advisory Committee (DGAC) found that if sodium is really restricted, you get a little more bang for your buck. They still recommended 2,300 mg/day in general. But certain groups, particularly people over age 50 and African Americans of any age, are at higher risk for hypertension, and for them a stronger restriction was indicated. They said the evidence indicated you could reduce blood pressure an extra 3 or 4 mmHg if you take in only 1,500 mg/day of sodium. And that's what they recommended.
That's really strict and rough for anyone but the most sodium-phobic person to follow. A standard "low-sodium" hospital diet is often 2,000 mg/day, so this is 25% less than that for tens of millions of people. It's not very realistic for free-living citizens.
This level of sodium restriction is possible, but not palatable for most people. And "possible but not palatable" is never a good approach to changing people's eating styles. A 1,500 mg sodium diet would essentially mean that you've already had your last condiment, that eating out would be a near fantasy, and that most cookbook recipes would need serious altering. Living as I do in New York, the land of Mom's chicken soup, lox, and mile-high pastrami sandwiches, I knew these sodium recommendations were basically D.O.A. for New Yorkers.
Maybe 1,500 mg/day of sodium isn't really that necessary. A recent study looked at not only the influence of dietary sodium but also of potassium on the blood pressure of adolescents, with the objective of shedding some light on risk factors for hypertension and cardiovascular disease later in life. The study has good credibility -- it's part of the National Heart, Lung and Blood Institute's Growth and Health Study that looked prospectively at 2,185 adolescent girls, white and black, starting at ages 9 and 10. The researchers looked at intakes of both sodium and potassium but also at the sodium-to-potassium ratio, not just absolute amounts of each. And, of course, they looked at their systolic and diastolic blood pressures throughout the study, following them for 10 years.
The study found no evidence of adverse effects on blood pressure from sodium intakes above 3,000 mg/day or even above 4,000 mg/day.
Now it gets interesting. Higher potassium intakes were strongly associated with lower systolic and diastolic blood pressure both throughout the adolescent period and at follow-up. A higher potassium to sodium ratio was also linked with lower diastolic pressure, but not as strongly as for total potassium intake.
So, should we be thinking about sodium intake and blood pressure for our patients? Probably, but we ought to be giving equal attention to potassium intake -- think more fruits and vegetables.
Of course, sodium affects more than blood pressure and another recent review looked at the effects of elevated sodium intakes on organ systems. The authors of that review point out evidence that even in the absence of hypertension, higher sodium intakes can negatively impact function of the kidneys, heart, and endothelial issue, leading to arterial stiffness, and even more so in the presence of elevated blood pressure. The authors were responsible in noting that many of the studies have significant weaknesses, but they also made a case for reducing sodium regardless of whether someone is hypertensive or not.
I doubt we've heard the last word on sodium intake and our health, and as a clinician I have to weigh all the evidence and develop some practical solutions that won't send patients running for the hills.
Before even discussing sodium with patients I make every effort to get enough high-potassium foods into their diet as possible, not just for better blood pressure but because these are really nutrient-rich foods anyway. We're speaking about most fruits and vegetables, especially green leafy ones, citrus, berries. But also potatoes (yes -- even white potatoes are loaded with potassium) and even milk, a huge potassium source (on par with bananas). Getting enough of these, especially for snacks, will likely push out some of the salty junk in patients' diets and make a trade-up in quality of diet. If they make these changes, they'll have an easier time hitting that sodium target of 2,300 mg/day.
And if they choose wisely the rest of the day, 2,300 mg of sodium still allows for a bowl of Mom's chicken soup.
Keith Ayoob, EdD, RD, is an associate professor of pediatrics at Albert Einstein College of Medicine in New York City.
Ayoob disclosed relationships with McCormick Spice Institute, Hass Avocados, Calorie Control Council, the Walt Disney Company, Monsanto, and the Milk Processor Education Program.comments powered by Disqus