Understanding Sodium Intake and Cardiovascular Risk

A recent review (ME Cogswell et al. NEJM 2016; 375: 580-5) helps sort out some of the confusion regarding sodium intake and cardiovascular disease. In brief, the authors point out the excessive sodium intake is clearly linked to heart disease, stroke and death.  The importance has been questioned by some due to a few studies suggesting that low sodium intake could also increase the risk of cardiovascular disease.

The authors note that these studies have shown only weak associations & were likely a matter of reverse causation due to the low sodium group having increased numbers of participants with numerous health issues (eg diabetes, hypertension, chronic illness and cardiovascular disease).

By looking at these results based on “Hill’s Criteria” to assess whether an association is causal, the authors show that the association of low sodium intake and cardiovascular disease indicates that this association is NOT causal.

Hill’s criteria:

  • Strength -degree which the exposure is associated with the outcome
  • Consistency -is this finding observed by different persons, in different places/times
  • Specificity -is observation limited to the exposure and the outcome
  • Temporality -did observation cause the outcome or did the outcome affect changes that lead to observation
  • Biologic gradient -?dose-response noted
  • Plausibility -is there a physiologic basis
  • Coherence -does this association conflict with other known facts
  • Experiment -is the finding affected by actions to prevent the exposure
  • Analogy -does an exposure with a similar physiologic action cause the outcome

The authors note that population exposure to sodium correlates better than individual exposure, perhaps due to measurement issues. Key points:

  • “There is strong evidence of a linear, dose-response effect of sodium reduction on blood pressure.  In addition, the evidence shows that sodium reduction prevents cardiovascular disease.”
  • “Reducing the average sodium intake by just 400 mg per day could potentially avert as many as 28,000 deaths and save $7 billion in health care costs annually in the United States.”
  • “Yet sodium levels are high before food reaches the kitchen or table, and the sodium density of the U.S. diet has changed little despite consumer education encouraging individual behavior change.”

My take: If we are to take advantage of the science to reduce cardiovascular deaths, we need to convince manufacturers and restaurants to reduce sodium.

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Highline Trail, Glacier Nat'l park

Highline Trail, Glacier Nat’l park

Excess Childhood Salt Intake Associated with Obesity

A recent study (C Grimes et al. 24-h urinary sodium excretion is associated with obesity in a cross-sectional sample of Australian schoolchildren  British Journal of Nutrition  Volume  115 / Issue 06 / March 2016, pp 1071 – 1079) was summarized at AJP.com.au: Childhood salt intake linked to obesity.

An excerpt:

The study also found that in both four-to-seven-year olds and eight-to-12-year-olds, the prevalence of abdominal obesity was also higher in children with a higher intake of salt.

The recent findings published in the British Journal of Nutrition came from the SONIC (Salt and Other Nutrient Intakes in Children) study that measured salt intake in 666 primary schoolchildren aged four to 12 years….

“We found that 70% of Australian children are eating over the maximum amount of salt recommended for good health.

“In this study children were eating on average six grams of salt a day, which is over a teaspoon, and they should be aiming to eat about 4-5 grams a day.

”For every additional gram of salt children ate this was associated with a 23% greater likelihood of being overweight or obese. Such high intakes of salt are setting children up for a lifetime risk of future chronic disease such as high blood pressure and heart disease”

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On the Merits of Moderation: Salt, Cholesterol, and Vitamins

At excellent overview from NY Times that explains that strict reductions in salt and cholesterol may be detrimental and that additional vitamins may be harmful. Here’s the link: Dash of Salt Does No Harm

Here’s an excerpt:

The second New England Journal of Medicine study did just that. In addition to looking at high sodium diets, it also compared the health outcomes of those who had very low sodium diets. What they found was worrisome. When compared with those who consumed 3-6 grams per day, people who consumed less than 3 grams of sodium per day had an even higher risk of death or cardiovascular incidents than those who consumed more than 7 grams per day.

This result would be shocking if we in the medical community hadn’t seen it before. But we have. In 2011, researchers published a study in the Journal of the American Medical Asssociation after following 3,681 people over almost a decade. They, too, found that excessive salt intake was associated with high blood pressure. They also found that a low-sodium diet was associated with higher mortality from cardiovascular causes….

Why experts and organizations feel the need to go from one extreme to the other is unclear. But it’s unfortunately something we do far too often in medicine.

Take cholesterol. Initially, people believed that the evidence was pretty compelling that high cholesterol was bad for you…Eggs were shunned. But later research showed us that egg consumption had no relationship to cardiovascular disease for most people. In fact, a majority of people’s serum cholesterol level has little to do with how much cholesterol is in their diet. Today we use medications to lower our cholesterol levels. Once again, though, our sights keep shifting lower…

We have to learn that when one extreme is detrimental, it doesn’t mean the opposite is our safest course.

“Can you identify the six saltiest foods in American diets?”

From the American Heart Association Twitter Feed: http://bit.ly/SVnguk 

  1. Breads and rolls. We all know breads add carbohydrates and calories, but salt, too? It may not seem like it because a lot of bread doesn’t even taste salty, but one piece can have as much as 230 milligrams of sodium. That’s 15 percent of the recommended amount from only one slice, and it adds up quickly. Have a sandwich and muffin in one day? The bread alone could put you at about 1,000 milligrams of salt – or two-thirds of the American Heart Association’s recommended daily sodium limit of 1,500 milligrams.  Be sure to check the nutrition label as different brands of the same foods may have differing sodium levels.
     
  2. Cold cuts and cured meats. Even foods that would otherwise be considered healthy may have high levels of sodium. Deli or pre-packaged turkey can contain as much as 1,050 milligrams of sodium.  They have so much because most cooked meats would spoil in only a few days without the added sodium solution. Look for lower sodium varieties.
     
  3. Pizza. OK, everybody knows pizza’s not exactly a health food. But you’re probably thinking the big concerns are cholesterol,fat and calories. But pizza’s plenty salty, too. One slice can contain up to 760 milligrams of sodium. It doesn’t take a whole lot of math to realize two or three slices alone can send you way over the daily sodium recommendation. You may want to have fewer slices of pizza topped with vegetables and less cheese.
     
  4. Poultry. Surely chicken can’t be bad for you, right? Well, it depends on how the chicken is prepared. Reasonable portions of lean, skinless grilled chicken are great. But when you start serving up the chicken nuggets or poultry injected with added sodium solutions/marinades, the sodium starts adding up. Just 3 ounces of frozen and breaded nuggets can add nearly 600 milligrams of sodium. (And most kids probably aren’t stopping at 3 ounces.)  Check labels to be sure you are selecting the lower sodium version and that there are no added sodium solutions.
     
  5. Soup. This is another one of those foods that seems perfectly healthy. It can’t be bad if Mom gave it to you for the sniffles, right? But when you take a look at the nutrition label for some products, though, it’s easy to see how too much soup can quickly turn into a sodium overload. One cup of canned chicken noodle soup can have up to 940 milligrams of sodium.  Look for lower sodium options that taste just as great!
     
  6. Sandwiches. This covers everything from grilled cheese to hamburgers. We already know that breads and cured meats are heavy on the sodium. Add them together, and you can pretty easily surpass 1,500 milligrams of sodium in one sitting.   Top sandwiches with plenty of vegetables, such as lettuce, tomato and cucumbers.

Nice graphic: The-Salty-Six-Infographic_UCM_446591_SubHomePage.jsp

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Will salt intake make you fat? | gutsandgrowth

Will salt intake make you fat?

Maybe.  According to a recent study (Pediatrics 2013; 131: 14-20), salt intake is associated with consumption of sugar-sweetened beverages (SSB); hence, it might make you fat.

This cross-sectional study used data (4283 participants, ages 2-16 years) from the 2007 Australian National Children’s Nutrition and Physical Activity Survey.  Calculation of dietary intake (salt, fluid, sugary beverages) was determined by looking at two 24-hour dietary recalls.

Each gram of salt was associated with a 46 gram intake of fluid.  Of those who took SSB (n=2571), salt intake was associated with increased consumption of SSB; each gram of salt was associated with a 17 gram increased intake of SSB.  Participants with SSB intake of more than 1 serving (≥250 g), in turn, were 26% more likely to be overweight/obese (odds ratio 1.26).

Study limitations included the following:

  • 24-hour dietary recalls which likely underrepresented salt intake
  • Salt intake may be clustered with other ‘unhealthy’ dietary habits.  Thus, it may be a marker for undesirable diet rather than a causal factor.

Conclusion: Besides lowering blood pressure and lowering the risk of kidney stones, reducing salt intake may help with obesity prevention.

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