Still Another A-Salt On Science

      62 Comments on Still Another A-Salt On Science

When I returned from the Ancestral Health Symposium, I mentioned that one of the other speakers pooh-poohed a point I made in my speech about how sodium intake has little effect on blood pressure, then argued his point using bad science – which I found amusing, since my speech was about how to tell good science from bad science.

Here’s his speech. If you skip ahead to about the 9:00 mark, you’ll hear how Dr. O’Keefe “proves” that sodium does indeed cause hypertension.

Well, there you have it. The Yanomami Indians in South America have a low sodium intake compared to ours, and by gosh, you can’t find a single case of hypertension among ‘em. We’ve clearly established a link between A and B, so A must cause B. Case closed. See you next post.

No, wait … hang on a second … I hear some critical-thinking questions banging around in my head. Such as:

Q. Did the researchers control their variables?

You can’t see his slides in the video, but while Dr. O’Keefe was explaining how little sodium the Yanomami Indians consume, he was showing the audience pictures similar to these:

Hmmm … I wonder if sodium intake is the only difference between the lifestyle of the average American and lifestyle of the average Yanomami Indian? Based on these pictures, I’m guessing probably not. In fact, based on these pictures, I’m proposing a new hypothesis about hypertension:

Hypertension is caused by wearing pants.

If makes sense if you think about it. Your body is a bit like a big water balloon, and everyone knows if you squeeze a balloon, you increase the pressure inside. Now add in the fact that many Americans insist on wearing the same size clothes even as they get older and fatter, and you have a good explanation for why blood pressure tends to increase after middle age. I hereby propose we start prescribing nakedness as a cure for hypertension. (This will have the added benefit of speeding up security checks at airports.)

Pictures of the Yanomami have also inspired me to propose a second hypothesis:

You can prevent hypertension by poking holes in your skin and inserting bones.

I think this one is self-explanatory. If you think about that water-balloon example again, you’d have to agree that even if you increase the internal pressure by squeezing the balloon, you could offset the entire effect by poking a hole in the balloon’s skin.

The fact that these people consume less salt than we do and also have lower blood pressure than we do proves absolutely nothing. The lower blood pressure could be due to any number of factors.

Dr. Richard Johnson has presented some compelling evidence that hypertension is largely the result of consuming too much fructose, as I recounted in a previous post. Now, I must admit I’ve never visited the Yanomami tribes in person, but I’m willing to bet Dr. O’Keefe a thousand dollars that in addition to consuming far less sodium than we do, hunter-gatherers living in the Amazon jungle also consume far less fructose … unless they somehow manage to venture into the jungle and gather Krispy Kreme donuts, Frosted Mini-Wheats, Little Debbie Snack Cakes, Chunky Monkey ice cream, Heinz ketchup, fruit rollups, half-gallon jugs of Mott’s apple juice, and 44-ounce Coca-Cola Big Gulps.

Q. If we’re told A is linked to B, do we see that correlation consistently, or are there glaring exceptions in other populations?

A recent article published in Scientific American titled It’s Time to End the War on Salt reported on a meta-analysis of salt-restriction studies by the Cochrane Collaboration. Here’s what they found:

Intersalt, a large study published in 1988, compared sodium intake with blood pressure in subjects from 52 international research centers and found no relationship between sodium intake and the prevalence of hypertension. In fact, the population that ate the most salt, about 14 grams a day, had a lower median blood pressure than the population that ate the least, about 7.2 grams a day.

Well, but, uh, you see … there’s this one tribe in South America that consumes very little salt, and they have low blood pressure, so that must prove salt causes hypertension. We’ll just forget about all those contradictions we find in other populations ….

Q. Is this an observational study or a clinical study?

Dr. O’Keefe’s observation is just that – an observation. So what do the clinical trials tell us about salt intake and blood pressure?

Hypertension is defined as blood pressure that’s more than 20 points above normal. If salt causes hypertension, then drastically restricting salt intake – all by itself – should produce a drop in blood pressure of 20 points or so. But that simply isn’t the case. In the section of my speech that Dr. O’Keefe didn’t like, I recounted the results of a large clinical study in which researchers had the study subjects reduce their salt intake by 75%. That led to a whopping three-point drop in blood pressure on average.

Other clinical studies have produced similar (or even less-impressive) results. Here’s more from the Scientific American article:

Over the long-term, low-salt diets, compared to normal diets, decreased systolic blood pressure (the top number in the blood pressure ratio) in healthy people by 1.1 millimeters of mercury (mmHg) and diastolic blood pressure (the bottom number) by 0.6 mmHg. That is like going from 120/80 to 119/79. The review concluded that “intensive interventions, unsuited to primary care or population prevention programs, provide only minimal reductions in blood pressure during long-term trials.” A 2003 Cochrane review of 57 shorter-term trials similarly concluded that “there is little evidence for long-term benefit from reducing salt intake.”

Since my blood pressure has always been normal or a little on the low side, I believe I’ll keep putting salt on my food, Dr. O’Keefe. But if it makes you feel any better, I’ll spend more time not wearing any pants.


62 thoughts on “Still Another A-Salt On Science

  1. Robinowitz

    I put salt on just about everything and have always maintained a BP around 120/60…even throughout my pregnancy. My doc was always so pleased about that and probably thought I ate a low-salt diet. Whenever someone says that some meal is better because it’s low in salt I always tell them about how much salt I use and my BP and they never know what to say. I’m sure they just think I’m genetically gifted in the BP department but I seriously doubt that’s the case. I love salt and love buying all the different varieties–Himilayan rose salt is one of my favorites, though I usually use celtic sea salt.

    P.S. Remember not to feed the trolls or they’ll keep showing up like a bunch of lonely (and hungry) stray cats:)

    Unfortunately, I think they enjoy showing up here and getting smacked around. Either that or they lack the intelligence to recognize when they’re getting smacked around.

  2. Bernardo

    Everybody knows that all modern diseases are caused by speaking English. USA, Canada, Australia, UK, all on top of the list. The rate of incidence of these same diseases have grown in Brazil as people start going to English courses more often. Lately I’ve been trying to stay on a French/Portuguese speaking regime but this post will surely make my pressure skyrocket.

    Si, si, correcto!

  3. C

    Ooh, What Not To Wear is in trou-ble. They always tell people to define a waist and wear decently fitted clothing. THEY MUST BE THE CULPRITS OF HIGH BLOOD PRESSURE IN OUR COMMUNITY!!!!!!

    I’m all for blaming them.

  4. LaurieLM

    Part of ‘Toronoto Sun’ blurb is below. I haven’t looked up the study itself yet, but I’m willing to bet the design of the study didn’t control for sugar and/or wheat consumption in these subjects. Sugar- none required in human diet. Cereal grains- none required in human diet. Salt- required in human diet.
    Here’s absurdum infinitim statement from the report below: “it’s a combination of high salt intake and low physical activity which declined cognitive function”
    I disagree. How about it’s any combination of sugar and wheat in the diet above zero which is a better candidate for what declines cognitive function?. Laurie

    TORONTO – Here’s another reason for couch potatoes to lay off the salt.
    Older adults who lead sedentary lives and consume a lot of salt may be at risk not only for heart disease, but cognitive decline.
    A study — published in the journal Neurobiology of Aging — found evidence that high-salt diets coupled with low physical activity can be detrimental to the mental health of those 65 and older.
    “Our results show it’s a combination of high salt intake and low physical activity which declined cognitive function. The message is if you’re not active, make sure you cut back on your salt intake,” said lead investigator Dr. Alexandra Fiocco, a scientist with Baycrest Hospital’s Kunin-Lunenfeld Applied and Evaluative Research Unit.
    The study followed 1,262 healthy seniors between the ages of 67 and 84, tracking their sodium consumption and physical activity over three years.
    The participants had a daily sodium intake ranging from 2,263 milligrams to 8,098 milligrams.
    Participants were given an exam to measure their cognitive decline. The scores showed those with the lowest salt consumption suffered less of a cognitive decline than participants with the higher sodium intake.
    Health Canada recommends people aged 14 years and older consume no more than 2,300 milligrams of salt each day.”

    Another junk-science observational study.

  5. palo

    You miss the point about salt. You see, less salt, bland food, eat less, lose weight.

    Got it?

    I much prefer losing weight while eating food I enjoy.

  6. Vanessa

    I need to start eating more salt. i keep getting these terrible headaches that I’m pretty sure are caused by sodium deficiency.

    Btw, what do you mean you’re all for blaming What not To Wear? I love that show. 😛

  7. Emma

    I eat salt, I have low blood pressure, but I wear skirts.

    Is skirt wearing a confounding variable?

    Yes, unless it’s a tight skirt.

  8. Peter

    A wonderful book about the Yamamama people is Into the Heart by an anthropologist who lived there for 15 years or so.

  9. S Andrei Ostric

    Tom, you are a funny man. The way you approach everything with humor is really refreshing. Science and medicine should have more guys like you in its ranks. I appreciate what you do, and my patients have learned more from Fathead, through your special gift of humor, than I can teach them. Keep up the great work!

    Thank you.

  10. jay

    i can only speak for myself. since i gave up “processed” food (anything from a box, a bag) and prepare my own meals from fresh vegetables, raw beans and maintain a vegan diet, i lost 70 lbs (i am 6ft 2 inches, from 255 lbs to 185 lbs) in 9 months. i took no weight loss drugs although i totally abstain from any processed food or processed drinks. my cooking ingredients are exclusively natural herbs and spices (no salt, no processed sugar). my snacks are natural salt/sugar free nuts, fresh fruits/berries. due to this lifestyle, my apnea was gone, my joint pain was gone, my back pain was gone, my high blood pressure was gone, my high bad cholesterol was gone. i am a 60 y.o guy and my bio metric, according to my doctor, is like a man in his mid 40s.

  11. Count Iblis

    “Hypertension is defined as blood pressure that’s more than 20 points above normal. If salt causes hypertension, then drastically restricting salt intake – all by itself – should produce a drop in blood pressure of 20 points or so. But that simply isn’t the case.”

    It is the case, but you need to get the salt intake to well below 0.5 grams per day, which isn’t feasible unless you put people on a controlled diet where specially prepared food is served. This can only be done in small studies. One slice of bread will put you over the limit. What then happens is that if you keep on adding salt to your diet, your body will work harder to pump out all that salt, the excess fluids in your blood vessels will only slowly increase and your elastic blood vessels will expand somewhat, so the blood pressure rise will actually be quite limited. But if you drop well below the 0.5 grams per day, then you wont be in that regime in the first place and then your blood pressure will drop a lot more.


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