Saturday, 23 January 2010

Sodium Hype- Is it justified?

As predicted, sodium has become a major public health issue. In fact, the New York City Health Department just announced their initiative for restaurants and food manufacturers to voluntary reduce sodium in their food by 25% in the next 5 years.

But is the hype justified?

A recap of what we know

The research is clear. Salt increases blood pressure.


Only about 10-25% of North Americans are salt-sensitive (Another source states that its closer to 50%), meaning that salt will only increase the blood pressure of 10-25% of the population.

The research is also clear: High blood pressure is an important risk factor for heart attacks and strokes.

But wait. Does that mean that salt causes heart attacks and strokes?

That’s the message that’s being thrown out there:

In Ottawa, the Canadian Stroke Network and Blood Pressure Canada teamed up to put ads on buses with the message: Sodium kills 30 Canadians a day.

The Center for Science in the Public Interest (CSPI), a prominent nutrition advocacy group, have been very vocal in associating sodium intake with heart attacks and strokes, stating that a reduction in sodium can save 150,000 lives a year.

Just this week, a study was published in the New England Journal of Medicine stating that reducing salt intake by 1200 mg a day (that’s quite a bit) could prevent up to 66,000 strokes, 120,000 new cases of heart disease, and 92,000 deaths a year.

Sounds good but the thing is, all of these numbers are actually just predictions based on the role of sodium on blood pressure.

Why didn’t they look at the direct role of sodium on heart attacks, stroke or death? Because that data isn't really available.

Review of the research on sodium and heart disease or death

Some fellow students and I decided to do a thorough review of the scientific literature to see if sound research had looked at the role of sodium on death, heart disease or strokes.

What we found was pretty surprising: there are very few studies looking at this direct association; only 4 in the last 10 years, in fact!

And what these 4 studies found wasn’t as clear cut as has been reported:

One study found that the higher the sodium intake, the higher the incidence of heart disease, however, the study had many limitations.

Another study also found that the higher the sodium intake, the higher the incidence of heart disease... but only in overweight people.

Interestingly, two (1,2) studies found that the higher the sodium intake, the lower the incidence of heart disease and death! (so, the lower the sodium intake, the higher the incidence of heart disease and death!)

Clearly, more research needs to be done before directly associating sodium with heart disease.

Update: Turns out that, according to the CSPI, Michael H. Alderman, an author of the aforementioned articles (1,2), is a consultant for the Salt Institute. Click here to read a great piece on the controversy over sodium-and-health papers.

What else do we know?

We know that we’re eating too much salt.

If you’re healthy, you need only 1200-1500mg sodium/day.

The upper tolerable level (the maximum you should eat) is 2300mg/day.

The average North American consumes a whopping 3000-4000mg/day.

80% of this sodium is not coming from the salt-shaker, but is in processed foods.

What does this all mean?

We are, as a population, eating too much salt.

Will a population-wide sodium reduction initiative result in lowering blood pressure? Yes, in some people.

Will a population-wide sodium reduction initiative result in less heart attacks, strokes and death? We really can’t say.

Obviously, it won't harm our health...

But would spending the energy and resources to, instead, focus on initiatives to reduce obesity rates or to make healthy foods more affordable than fast/junk food have a greater, more important, impact on our health?

What do you think?

Sodium-lowering tips

Click Here for some ways you can take matters in your own hands and reduce the sodium in your diet.


Jme said...

Great resources presenting various sides of the story!

Gina said...

Such a fantastic post. Thanks so much for sharing this. Sometimes when people ask me why sodium is so bad, and I say, "well, it raises your blood pressure", I feel bad because I've never seen proof! this post was so perfect, I am marking it down for future reference. Thanks for including the links to all of the studies, that's something I need to go back and read.

I believe I am salt sensitive. I have been watching my intake lately, closely, and feel really good (better than normal)

Have a great night.

Sybil Hebert, RD said...

Thanks Jme and Gina! :)
It's such a hot topic right now... we'll be hearing about sodium for a while! It'll be interesting to see what the effect will be of this voluntary reduction of sodium in processed/restaurant foods... !

Anonymous said...

Excellent post! I always tell my hypertensive patients that lowering sodium intake is, in my opinion, one of the hardest diet changes to make. Sodium is in EVERYTHING! And way too much of it at that! Wonderful post, I appreciate you getting this information out there! Have a great rest of the weekend!