Number One Risk

Hello and welcome to Nutrition Facts – the podcast that brings you the latest in evidence-based nutrition research.  I’m your host Dr. Michael Greger.

I’m often asked what my opinion is about one food or another.  I know what people are asking but, you know, I’m not interested in opinions.  I’m not interested in beliefs.  I’m interested in the science.  What does the best available balance of evidence published in the peer-reviewed medical literature show right now?  That’s why I wrote my book, “How Not to Die”, and why I created my nonprofit site NutritionFacts.org and, now, this podcast.

Today, we’re going to talk about high blood pressure, also known as hypertension, a condition that can lead to grave health problems.

High blood pressure is the #1 risk factor for death in the world, affecting nearly 78 million Americans–that’s one in three adults, and, as we age, our pressures get higher and higher, such that by age 60, it strikes more than half.  Well, if it affects most of us when we get older, maybe it’s less a disease and more just an inevitable consequence of aging. No.  We’ve known since the 1920s that high blood pressure need not occur.

Researchers measured the blood pressures of a thousand people in rural Kenya who ate a diet centered around whole plant foods—whole grains, beans, vegetables, fruit, and dark green leafies.  Our pressures go up as we age; their pressures actually go down. 

And, the lower the better.  The whole 140 over 90 cut-off is arbitrary.  Even people who start out with blood pressures under 120 over 80 appear to benefit from blood pressure reduction.  If you went to your doctor with a blood pressure of 120 over 80, you’d get a gold star.

But the ideal blood pressure, the no-benefit-from-reducing-it-further blood pressure, may actually be 110 over 70.  110 over 70?  Is it even possible to get blood pressures down that low?  It’s not just possible, it’s normal for those eating healthy enough diets.

Over two years, at a rural Kenyan hospital, 1,800 patients were admitted.  How many cases of high blood pressure did they find?  Zero.  Wow!  They must have had low rates of heart disease?  No. They had no rates of heart disease; not a single case of arteriosclerosis, our #1 killer, was found.

Rural China, too; about 110 over 70 their entire lives; 70-year-olds with the same average blood pressure as 16-year-olds.  Now, Africa, China, vastly different diets, but what they shared in common is that they were plant-based day-to-day, with meat only eaten on special occasions.

Now, why do we think it’s the plant-based nature of their diets that was so protective?  Because in the Western world, as the American Heart Association has pointed out, the only folks really getting it down that low were those eating strictly plant-based diets, coming in at about 110 over 65.

This is the largest study of those eating plant-based diets to date:  89,000 Californians, comparing non-vegetarians to so-called semi-vegetarians or flexitarians (eating meat more on a weekly basis than a daily basis); compared to those who eat no meat, except fish; compared to those who eat no meat at all; compared to those who eat no meat, eggs, or dairy.

Now, this was an Adventist study, so, even the non-vegetarians didn’t eat a lot of meat and they tended to eat lots of fruits and vegetables, and exercised, and, you know, not smoke.  So, even compared to a group of relatively healthy meat-eaters, there appeared to be a stepwise drop in hypertension rates as people ate more and more plant-based.  Same thing with diabetes and obesity.

So, yes, we can wipe out most of our risk eating strictly plant-based, but it’s not all-or-nothing; it’s not black-or-white. Any movement along the spectrum towards eating healthier can accrue significant health benefits.  You can show this experimentally.  You take vegetarians, you give them meat (and pay them enough to eat it); and their blood pressures go up; or, you remove meat from people’s diets and blood pressures go down in just seven days and this is after the vast majority reduced or stopped their blood pressure medications completely.  They had to stop their medications.

Once you treat the cause, once you eliminate the disease, you can’t be on blood pressure pills with normal blood pressure.  You can drop your pressures too low, get dizzy, fall over, or hurt yourself.  So, your doctor has to pull you off the pills.  Lower pressures on fewer drugs; that’s the power of plants.

So, does the American Heart Association recommend a no-meat diet?  No.  They recommend a low-meat diet, the so-called DASH diet.  Why not completely plant-based?  When the DASH diet was being created, were they just not aware of this landmark research, done by Harvard’s Frank Sacks? No.  They were aware.  The chair of the design committee that came up with the DASH diet was Frank Sacks.

See, the DASH diet was explicitly designed with the #1 goal of capturing the blood pressure-lowering benefits of a vegetarian diet, yet contained enough animal products to make it palatable to the general population.  They didn’t think the public could handle the truth.

Now, in their defense, you can see what they were thinking. Just like drugs never work unless you actually take them, diets never work unless you actually eat them.  So, they’re like, look, no one is going to eat strictly plant-based. So, if they soft-pedaled the message and came up with some kind of compromise diet, then maybe, on a population scale, they’d do more good.

Okay, tell that to the thousand American families a day that lose a loved one to high blood pressure.  Maybe, it’s time to start telling the American public the truth.

Here’s a fun fact.  Did you know that eating a diet low enough in sodium may prevent the rise of high blood pressure risk as we age? 

For the first 90% of our evolution, we ate diets containing less than a quarter teaspoon of salt a day, because for the first 90% of our evolution, we ate mostly plants.  We went millions of years without salt shakers and so our bodies evolved into salt-conserving machines, which served us well until we discovered salt could be used to preserve foods. Without refrigeration, this was a big boon to human civilization.  Of course, this may have led to a general rise in blood pressure, but who cares if the alternative is starving to death because all your food rotted away?  But where does that leave us now, when we no longer have to live off pickles and jerky?  We are genetically programmed to eat ten times less salt than we do now.  Even many low-salt diets can be considered high-salt diets. That’s why it’s critical to understand what the concept of “normal” is when it comes to salt.

Having a “normal” salt intake can lead to a “normal” blood pressure, which can help us die from all the “normal” causes, like heart attacks and strokes.

Doctors used to be taught that a “normal” systolic blood pressure is approximately 100 plus age (systolic blood pressure means the top number) and, indeed, that’s about what we’re born with.  Babies start out with a blood pressure around like 95 over 60, but then as we age, that 95 can go to 120 by our 20s, then 140 by our 40s (the official cut-off for high blood pressure) and keep climbing as we age.  That was considered normal, since everyone’s blood pressure creeps up as we get older and, if that’s normal, then heart attacks and strokes are normal too, since risk starts rising once we start getting above the 100 we had as a baby.

But if blood pressures over 100 are associated with disease, maybe they should be considered abnormal, perhaps caused by our abnormally high salt intake–ten times more than what our bodies were designed to handle.  Maybe if we just ate a natural amount of salt, our blood pressures naturally would not go up with age, and we’d be protected. Of course, to test that theory, you’d have to find a population in modern times that doesn’t use salt, or eat processed food, or go out to eat.  For that, you’d have to go deep into the Amazon rainforest.  

Meet the Yanomamo people, a no-salt culture.  Lowest salt intake ever reported, which is to say a normal-for-our-species salt intake and, so, what happens to their blood pressure?  They start out with a blood pressure of about 100 over 60 and end up with a blood pressure of about 100 over 60.  Though theirs is described as a salt–deficient diet.  That’s like saying they have a diet deficient in Twinkies. They’re the ones, it seems, eating normal salt intakes, apparently leading to truly normal blood pressures.  Those in their 50s have the blood pressure of a 20-year-old.  The percentage of the population tested that had high blood pressure—zero!  Whereas elsewhere in Brazil, up to 38% of the population may be affected.  The Yanomamos probably represent the ultimate human example of the importance of salt on blood pressure.

But look, it could have been other factors.  They didn’t drink alcohol, ate a high-fiber plant-based diet, lots of exercise, no obesity.  There are a number of plant-based populations eating little salt that experience no rise in blood pressure as they age, so, you know, how do we know what exactly is to blame?  Ideally, we’d do an interventional trial.  I mean, imagine if you took people literally dying from out-of-control high blood pressure, so-called malignant hypertension, where you go blind from bleeding into your eyes, your kidneys shut down, your heart fails, and then you withhold from those people blood pressure medications so their fate is certain death, and then you put them on a Yanomamo level of salt intake, a normal-for-human-species salt intake, and, if instead of dying, they walked away cured of their hypertension, that would pretty much seal the deal!

Enter Dr. Walter Kempner and his rice and fruit diet.  Patients coming in with blood pressures of 210 over 140, dropping down to 80 over 60.  Now, the reason he could ethically withhold all modern blood pressure medications and treat with diet alone, the drugs hadn’t been invented yet.  This was back in the 1940s.  Now, the diet wasn’t just extremely low salt, but strictly plant-based, extremely low fat, protein, calories.  But there is no doubt that Kempner’s rice diet achieved remarkable results, and Kempner is now remembered as the person who demonstrated, beyond any shadow of doubt, that high blood pressure can often be lowered with a low enough salt diet.

Forty years ago, it was acknowledged that the evidence is very good, if not conclusive, that a low enough reduction of salt in the diet would result in the prevention of essential hypertension—that rising of blood pressure as we age—and its disappearance as a major public health problem.  It looks like we knew how to stop this four decades ago.  In that time, how many people have died?  Today, high blood pressure may wipe out 400,000 Americans every year, a thousand unnecessary deaths every day.

So, here’s a question for you.  How do the blood-pressure-lowering effects of hibiscus tea compare to the DASH diet, a strictly plant-based diet, and long distance endurance exercise?  Here’s your answer.

The latest research pitted hibiscus against obesity, giving hibiscus to overweight individuals and showed reduced body weight, but after 12 weeks on hibiscus they only lost like 3 pounds, and really only 1 1/2 pounds over placebo; clearly, no magic fix.

The purported cholesterol-lowering property of hibiscus tea had looked a bit more promising.  Some older studies suggested as much as an 8% reduction drinking two cups a day for a month but, when all the studies are put together, the results were pretty much a wash.  Now, this may be because only about 50% of people respond at all to drinking the equivalent of between 2 to 5 cups a day, though those that do respond may get a respectable 12 or so percent drop in cholesterol, but nothing like the 30% drop one can get within weeks of eating a healthy enough plant-based diet.

High blood pressure is where hibiscus may really shine, a disease affecting a billion people, killing millions.  Up until 2010, there wasn’t sufficient high-quality research out there to support the use of hibiscus tea to treat it, but there are now randomized, double-blind, placebo-controlled studies where hibiscus tea is compared to artificially colored and flavored water that looks and tastes like hibiscus tea and the tea did significantly better.

We’re still not sure why it works, but hibiscus does appear to boost nitric oxide production, which could help our arteries relax and dilate better.  Regardless, an updated review acknowledged that the daily consumption of hibiscus tea may indeed significantly lower blood pressures in people with hypertension, but by how much?  How does this drop in blood pressure compare to other interventions?

Well, the premier clinical trial, when it comes to comprehensive lifestyle modification for blood pressure control, is the PREMIER clinical trial.  Realizing that 9 out of 10 Americans are going to develop hypertension, they randomized 800 men and women with high blood pressure into one of three groups:  One was the control group, the so-called advice only group, where patients were just told to lose weight, cut down on salt, increase exercise and eat healthier, here’s a brochure.  In the two behavioral intervention groups, they got serious, 18 face-to-face sessions, groups meetings, food diaries, monitored physical activity, calorie and sodium intake.  Now, one intervention group just concentrated on exercise and the other one included exercise and diet.  They pushed the DASH diet, high in fruits and vegetables, and low in full-fat dairy products and meat and in six months achieved a 4.3-point drop in systolic blood pressure, compared to control, slightly better than the lifestyle intervention without the diet.  Now, a few points might not sound like a lot, that’s like someone going from a blood pressure of 150 over 90 to a blood pressure of 146 over 90 but, on a population scale, a 5-point drop in the total number could result in 14% fewer stroke deaths, 9% fewer fatal heart attacks, and 7% fewer deaths every year overall.

But a cup of hibiscus tea with each meal didn’t just lower blood pressure by 3, 4 or 5 points, but by 7 points, you know, 129 down to 122, and, in fact, tested head-to-head against a leading blood-pressure drug, called captopril, two cups of strong hibiscus tea every morning, using a total of 5 tea bags for those two cups, was as effective in lowering blood pressure as a starting dose of 25 mg of captopril taken twice a day.

So, as good as drugs, without the drug side-effects, and better than diet and exercise?  Well, the lifestyle interventions were pretty wimpy.  As public health experts noted, the PREMIER study was only asking for 30 minutes of exercise a day, whereas the World Health Organization it is more like, you know, an hour a day minimum.

And diet-wise, the lower the animal fat intake, and the more plant sources of protein the PREMIER participants were eating, the better the diet appeared to work, which may explain why vegetarian diets appear to work even better, and the more plant-based the lower the prevalence of hypertension.

On the DASH diet, they were, you know, told to cut down on meat, but were still eating meat every day, so it would qualify as the non-vegetarians here in the Adventist 2 study, which looked at 89,000 Californians and found that those who, instead, only ate meat on more like a weekly basis, had 23% lower rates of high blood pressure.  Cut out all meat (except fish) and the rate is 38% lower.  Cut out all meat period–the vegetarians have less than half the rate and the vegans, cutting out all animal protein and fat, appeared to have thrown three-quarters of their risk for this major killer out the window.

One sees the same kind of stepwise drop in diabetes rates as one’s diet gets, you know, more and more plant-based and a drop in excess body weight such that only those eating completely plant-based diets fell into the ideal weight category, but could that be why those eating plant-based diets have such great blood pressure?  Maybe it’s just because they’re so skinny on average.  I’ve shown previously how those eating plant-based diets have just a fraction of the diabetes risk even at the same weight, even after controlling for BMI, but what about hypertension?

The average American has what’s called prehypertension, which means the top number of your blood pressure is between 120 and 139, not yet hypertension, which starts at 140, but it means we may be well on our way.

Compare that to the blood pressure of those eating whole food plant-based diets, not 3 points lower, 4 points lower, or even 7 points lower, but 28 points lower.  Now, but the group here eating the standard American diet was, on average, overweight with a BMI over 26, still better than most Americans, but while the vegans were a trim 21 over here, then again, that’s 36 pounds lighter.

So, maybe the only reason those eating, you know, meat, eggs, dairy, and processed junk had such higher blood pressure was because they were overweight, maybe the diet per se had nothing to do with it.

To solve that riddle, we would have to find a group still eating the standard American diet but as slim as a vegan.  To find a group that fit and trim, they had to use long-distance endurance athletes, who ate the same crappy American diet but ran an average of 48 miles per week for 21 years.  They ran almost two marathons a week for 20 years; so, if you do that, you know, anyone can be as slim as a vegan, no matter what they eat.  So, where did they fall on this graph?  Both the vegans and the conventional diet group were sedentary, less than an hour of exercise a week.

The endurance runners were here.  So, it appears if you run about a thousand miles every year you can start to rival some couch potato vegans.  Doesn’t mean you can’t do both, but it may be easier to just eat plants.

Thanks for listening to this episode of Nutrition Facts.  To see any graphs, charts, graphics, images, or studies mentioned here, please go to the Nutrition Facts podcast landing page.  There, you’ll find all the videos I highlighted with links to all the sources cited.

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Thanks for listening to Nutrition Facts.  I’m Dr. Michael Greger.