Doesn’t it seem like when it comes to nutrition there are more opinions than facts to go around? Every day we hear new theories about diets, and supplements, and the best foods to eat. My role is to take the mystery out of good nutrition, and look at the science. Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger. And I’m here to bring you an evidence-based approach to the best way to live a healthier longer life.
Guess what the number-two killer risk factor is in the world after diet? High blood pressure. But it turns out hypertension can also be treated as a choice and not a life sentence. How, you may ask? The first-line treatment for hypertension is lifestyle modification. In our first story, we explore the dash diet.
The American Heart Association, the American College of Cardiology, and the Centers for Disease Control and Prevention recommend, as the first-line treatment, lifestyle modification. If that doesn’t work, you start the patient on a thiazide diuretic, or water pill, and then you keep piling on the meds until you get their blood pressure down. Commonly people will end up on three drugs, though researchers are experimenting with four at a time, and some people end up on five.
Why not just jump straight to the drugs? Well, they don’t treat the underlying cause, and they can cause side effects. Less than half of patients stick with even the first-line drugs, perhaps due to the adverse effects such as erectile dysfunction, fatigue, and muscle cramps. So, what are these recommended lifestyle changes? They recommend to control one’s weight, salt, and alcohol intake, engage in regular exercise, and adopt a DASH eating plan.
The DASH diet has been described as a lactovegetarian diet, but it’s not. It emphasizes fruits and vegetables and low-fat dairy, but just a reduction in meat. Why not vegetarian? We’ve known for decades that food of animal origin is highly significantly associated with blood pressure. In fact, you can take vegetarians, give them meat, and watch their blood pressures go right up.
I’ve talked about how there are benefits to getting blood pressure down as low as 110 over 70, but who can get that low? Populations eating whole food plant-based diets. Like in rural China, about 110 over 70 their whole lives, with meat eaten only on special occasions. Or rural Africa, where the elderly have perfect blood pressure as opposed to hypertension.
In the Western world, as the American Heart Association has pointed out, the only folks really getting down that low were the strict vegetarians, coming out about 110 over 65. So, when they created the DASH diet, 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 who came up with the DASH diet was Dr. Sacks. In fact, the DASH diet was explicitly designed with the #1 goal of capturing the blood pressure-lowering benefits of a vegetarian diet, yet contain enough animal products to make it palatable to the general public. In fact, Sacks found that the more dairy the lactovegetarians ate, the higher their blood pressures. But they had to make the diet acceptable. Research has since shown that it’s the added plant foods, not the changes in oil, sweets, or dairy that appear to be the critical component, so why not eat plant-based?
A recent meta-analysis showed vegetarian diets are good, but strictly plant-based diets may be better. Vegetarian diets in general confer protection against cardiovascular diseases, some cancers and death, but completely plant-based diets, seem to offer additional protection for obesity, hypertension, type 2 diabetes, and heart disease mortality. Based on a study of 89,000 people, those eating meat-free diets appeared to cut their risk of high blood pressure 55%, but those eating meat-free, egg-free, and dairy-free had 75% lower risk.
If, however, you’re already eating a whole food plant-based diet, no processed foods, no table salt, and you’re still not hitting 110 over 70, there are a few foods recently found to offer additional protection. Ground flaxseeds, a few tablespoons a day, induced one of the most potent antihypertensive effects ever achieved by a dietary intervention, two to three times more powerful than instituting an aerobic endurance exercise program.
Watermelon also appears to have extraordinary, but you’d have to eat like two pounds a day. Sounds like my kind of medicine, but it’s hard to get year-round. Red wine may help, but only if the alcohol has been taken out. Raw vegetables or cooked? And the answer is both, though raw may work better. Beans, split peas, chickpeas, and lentils may help a little. Kiwifruits, though don’t seem to work at all, even though the study was funded by a kiwifruit company. Maybe they should have taken direction from the California Raisin Marketing Board came out with this study showing raisins can reduce blood pressure–but only, apparently, compared to fudge cookies, Cheez-Its, and Chips Ahoy!
In our next story, we explore how eating a diet low-enough in sodium (salt) can prevent the rise in hypertension 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 of 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, they eat a high-fiber, plant-based diet, get 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, but how do we know what exactly is to blame? Ideally, we’d do an interventional trial. Imagine if we 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-the-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 in fat, protein, and 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 in salt.
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; 1,000 unnecessary deaths every day.
Finally today, how do the blood-pressure lowering effects of hibiscus tea compare to the DASH diet, a plant-based diet, and a long-distance endurance exercise? Let’s find out.
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 one and a half 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. 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 cholestrol, 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 and 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?
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. 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 the 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 a 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, 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 25mg 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 is more like 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 told to cut down on meat, but are still eating meat every day, so would qualify as nonvegetarians 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 step-wise drop in diabetes rates as one’s diet gets 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 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 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.
So maybe the only reason those eating 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 a 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 it appears if you run an average of about a thousand miles every year you can rival some couch potato vegans. Doesn’t mean you can’t do both, but it may be easier to just eat plants.
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