I’m often asked my opinion about a diet or a disease is. Who cares what my or anyone else’s opinion is? All we should care about is what the science says. What does the best available balance of evidence published in the peer-reviewed medical literature have to say right now?
Welcome to the NutritionFacts Podcast – I’m your host Dr. Michael Greger.
Today, we examine the need for less sodium and more potassium-rich foods.
Did you know that – a staggering 99.99 percent of Americans fail to meet the minimum recommended potassium or the maximum recommended sodium? Here’s the story.
Worldwide, physical inactivity accounted for more than 10 million years of healthy life lost, but what we eat accounts for nearly 20 times that. Unhealthy diets shave hundreds of millions of disability-free years off of people’s lives every year. What are the worst aspects of our diets? Four out of the five of the deadliest dietary traps involve not eating enough of certain foods. Not eating enough whole grains, not eating enough fruits, not eating enough nuts and seeds, and not eating enough vegetables. But our most fatal flaw is too much salt. On the order of 15 times deadlier than diets too high in soda, for example, just to help put things in perspective. “There remains no single more effective public health action related to nutrition than the reduction of sodium in the diet.” This is why national and international health organizations have called for warning labels on salt packets and salt shakers, with messages like “too much sodium in the diet causes high blood pressure and increases risk of stomach cancer, stroke, heart disease, and kidney disease. Limit your use.” Salt also increases inflammation. For example, sodium intake is associated with increased disease activity in multiple sclerosis, an inflammatory autoimmune nerve condition––about three to four times the exacerbation rate in those with medium or high sodium intakes compared to those getting less than a teaspoon (less than 6 grams) of salt total in a day. Just as you can see higher sodium levels in the tissues of those who suffer from lupus, another serious inflammatory autoimmune disease, you can correlate high sodium levels in the spinal cord of MS patients with the disease, and decreased structural integrity. Where’s sodium found though? Really crappy foods. So, it’s hard to know if increased salt intake is just a marker for a bad diet overall. But what we do know is that salt and high blood pressure are cause-and-effect. How? Because we have more than a hundred randomized controlled trials demonstrating that if you cut down on added salt, your blood pressures fall, and the more you cut down the better. Part of the mechanism may actually be the damage salt may do to your microbiome, the friendly flora in your gut. And no wonder. Our bodies evolved only to handle about 750mg a day. The American Heart Association says we should stay under at least twice that about, but we’re eating more than four times what’s natural. And it’s only getting worse, increasing over the last decade. Anyone care to guess what percentage of Americans exceed the 1,500mg upper limit recommendation? 98.8 percent. And that’s more than a decade ago! The vast majority of U.S. adults consume too much sodium and, at the same time, too little potassium, a mineral that lowers blood pressure. Less than 2 percent of U.S. adults consumed the recommended daily minimum intake of potassium. So, more than 98 percent of Americans eat potassium deficient diets. This deﬁciency is even more striking when comparing our current intake with that of our ancestors, who consumed large amounts of dietary potassium. We evolved probably getting more than 10,000mg a day. The recommendation is to get around at least like around half that, yet most of us don’t come anywhere close. Put the two guidelines together, and sodium and potassium goals are currently met by less than 0.015 percent of the U.S. population. So, we’re talkin’ close to 99.99 percent noncompliance. As in only 1 in 6,000 Americans even hits the recommended guidelines. What about using potassium-based salt substitutes? Instead of using sodium chloride—salt, why not shake on some potassium chloride? Seems a little too good to be true. Same salty taste, but you’re reducing sodium while at the same time increasing your potassium intake? Is there a catch? Are potassium-based salt substitutes safe? Effective? We’ll find out, next.
Of all the terrible things about our diets, high dietary sodium intake, high salt intake, is the leading risk, estimated to be causing millions of deaths every year––killing millions mainly through adverse effects on blood pressure and increased risk of stroke, heart attack, and kidney damage. Hypertension—high blood pressure––is still called the “silent and invisible killer” because it rarely causes symptoms, but is one of the most powerful independent predictors of some of our leading causes of death. We evolved consuming a diet very rich in potassium and low in sodium. But today, this pattern has been completely reversed. This flip reﬂects a shift from traditional plant-based diets high in potassium and low in sodium––a shift from fruits and greens, roots, and tubers to salty processed foods stripped of potassium, which is considered a “nutrient of public health concern” because 98 percent of the U.S. population doesn’t even reach the recommended minimum daily intake of potassium, as I mentioned in my last video. And, low potassium intake itself is implicated in high blood pressure and cardiovascular disease. Yet few physicians actually think about proposing their patients eat more foods that are high in potassium, like fruits and vegetables, to better control blood pressure––even though several meta-analyses have now conﬁrmed that high potassium intake appears to reduce the risk of stroke. There’s even a reduction in stroke risk independent of blood pressure effects, consistent with other protective effects of potassium, such as reducing clot formation, reducing hardening of the arteries, reducing the generation of free radicals. Higher sodium intake is associated with a 20 percent increased risk of dying prematurely, where higher potassium intake was associated with a 20 percent reduced risk of dying prematurely. Yeah, but sodium is found in crappy processed foods, while potassium is concentrated in healthy foods like beans and greens. So, having low sodium intake and high potassium intake may just be a marker for a more healthful diet—more plant foods and less crap. How do we know sodium is cause-and-effect bad? Because randomized controlled trials show sodium reduction leads to blood pressure reduction, just like there are randomized controlled trials showing that if you give people extra potassium, you can bring down blood pressures as well. So, what about using potassium chloride to salt your food, rather than sodium chloride? That’s what’s found in these zero sodium salt substitutes. Potassium chloride is a naturally occurring mineral salt, which is obtained the same way we get regular sodium salt. Since we get too much sodium and not enough potassium, this would seem to make potassium chloride a win-win solution. Now, whole healthy plant foods would be the best way to increase potassium intake. Fruits and vegetables have all sorts of other good things in them besides potassium, but we have 10 studies now, randomized controlled trials, showing that just swapping in some potassium chloride for regular salt can lead to significant reductions in blood pressure in people with hypertension––suggesting that salt substitutes may even help prevent hypertension as well. We know that salt substitutes can lower blood pressure, but does it actually decrease the incidence of hypertension, and more importantly, disease endpoints like stroke and mortality? You don’t know, until you put it to the test. In a randomized controlled trial, households had their salt replaced with just a quarter potassium chloride. At that level, most people either can’t tell the difference, or even prefer the salt with the potassium mixed in. Okay, but did it actually do any good? The use of even the quarter salt substitute was associated with cutting the risk of developing hypertension in half. Okay, but what about actually following people out to see if there’s any change in the risk of dying from cardiovascular disease? Five kitchens in a veterans’ retirement home were randomized into two groups for about two and a half years, salting meals with regular salt or, unbeknownst to the cooks and the diners, a 50/50 blend of potassium chloride. Those in the half-potassium group cut their risk of dying from cardiovascular disease by about 40 percent, and lived up to nearly a year longer. The life expectancy difference at age 70 was equivalent to that which would have naturally occurred in 14 years––meaning that just switching to half potassium salt appeared to effectively make people more than a decade younger when it came to risk of death. As we speak, there is a massive randomized controlled trial wrapping up in China, involving 600 villages and more than 20,000 people, that will give us an idea of just how low we can drop stroke risk with this strategy. China is perfect, because up to 75 percent of their sodium intake comes from salt they add in the home kitchen or dining room, whereas most sodium in the American diet comes prepackaged in the meat and processed foods we buy––though certainly the food companies could switch over themselves. Why haven’t they? And why haven’t more people embraced these salt substitutes, if they work well and can taste just as good? We could be “Achieving the Beneﬁts of a High-Potassium Paleolithic Diet—Without the Toxicity.” So, “Is salt substitution ready for prime time or what?” What about safety? Yes, there are convincing arguments about the benefits, but what about the risks, like you know, the quote-unquote “inclusion of potentially fatal salt substitutes in the food supply.” Wait, what? We’ll talk about the potential downsides, next.
Based on how we evolved, the Optimum Dietary Potassium Intake likely greatly exceeds current and even recommended intakes. The problem is we replaced many of the potassium-rich plant foods we used to stuff our faces with, like fruits, leafy greens, and other vegetables, including roots and tubers, with calorie-dense junk stripped not only of fiber but also potassium––such as added fats and sugars. So, in a traditional, largely plant-based diet, potassium content is high and sodium content is low. But now, high blood pressure is the second leading cause of death in the world, killing more than 10 million people a year––second only to unhealthy diets, the #1 killer of humanity. We can improve both by eating more whole healthy plant foods like beans and greens, which are packed with potassium, which lowers blood pressure. But since most of us are getting too much sodium along with too little potassium, what about using salt substitutes? After all, the most commonly-used salt substitute is potassium chloride; so, you’d be swapping out sodium for potassium. And it works. Based on a meta-analysis of more than a dozen randomized controlled trials, replacing sodium chloride with potassium chloride lowers blood pressure, and most of the trials involved just swapping out regular salt for less than 30 percent potassium chloride, and they still got results. And at less than 30 percent, most people can’t even tell the difference between regular salt and the potassium salt. So, it can taste exactly the same and drop your blood pressures? What’s the catch? Potassium chloride is “generally considered as safe” by FDA, with the only major concern for healthy people being that if you go completely 100 percent sodium-free and use straight potassium chloride, it can taste kind of funny, adding a bitter or metallic taste. I’ve found that it depends on what I’m seasoning with it. It works perfectly well on some things, but makes other things completely inedible. When I learned about the sodium science and threw out my salt shaker for good, within a few weeks my palate totally changed, and everything tasted fine without salt—except pesto. For some reason, pesto without salt just never tasted like it used to to me. So, I tried the potassium chloride salt substitute, and it worked perfectly—I couldn’t tell the difference at all. So, I had the best of both worlds. Then, I remembered how as a kid I used to put a tiny sprinkle of salt on watermelon like they do in the South to make it even sweeter. So, I tried it with the potassium salt and almost gagged. So, it’s definitely not for everything. The reason healthy people don’t have to worry about getting too much potassium is that our kidneys just pee out the excess. Okay, but that’s with potassium in food. What about supplements? No adverse effects have been shown for long-term intakes of potassium supplements as high as 3,000 mg a day. And in fact, blood levels of potassium are maintained in the normal range by healthy kidneys, even when potassium intake is increased to approximately 15,000 mg a day––which is no surprise, since we evolved eating so many healthy plant foods, so many fruits and vegetables, that the normal, natural potassium intake for the human species may be on the order of 15,000 mg a day. Basically, the normal range for potassium levels in the blood is between 3.5 and 5.0, and you start to worry when it starts creeping up towards 6. But give people potassium supplements, like all the salt substitution trials that have been giving study subjects an average of about 2,000 mg a day, and blood levels only go up 0.14. So, they might go from 4 to 4.14––not something that would push you into trouble. Now, there is a limit. If you have a “massive banana eating habit,” you could bump your potassium from normal to above 6, but that was evidently from years of not eating much of anything except up to 20 bananas a day. Eating ten pounds of carrots every day is also probably not a good idea. That’s like 75 carrots in one day. What about overdoing salt substitutes? This report from the ‘40s was on lithium poisoning from the use of salt substitutes. Why? Because lithium chloride was used as a salt substitute. But what about potassium chloride, which is what’s used today? There is one fatal case of someone who committed suicide by downing a little more than a tablespoon of a potassium chloride salt substitute. That doesn’t seem like a lot, just a tablespoon? I mean, how can we keep that on the shelves if only a tablespoon will kill you? Well, even less than that of regular salt taken at once can kill you, too. In fact, salt water ingestion was evidently a traditional method of suicide in ancient China, though these days, one may be more likely to die that way from abusive religious practices. Having said all that, there are a small number of the population who may run into problems, primarily those with severely impaired kidney function. That’s why there’s been such a reluctance to push potassium‐based salt substitutes on a population level. If your kidneys can’t regulate your potassium, then you can definitely run into a serious issue. We’re talking about folks with known kidney disease; diabetes, since diabetes can lead to kidney damage; severe heart failure; those on medications that impair potassium excretion; older adults; and individuals with adrenal insufficiency. If you aren’t sure if you’re at risk, ask your doctor about getting your kidney function tested. Ironically, potassium is so good at reducing deaths from high blood pressure, even among even among those with kidney disease, using potassium chloride salt substitutes would probably still save more lives despite the risk. Traditional dietary recommendations to kidney patients limited the intake of fruits and vegetables because of their high potassium content. However, this paradigm is rapidly changing due to the multiple beneﬁts derived from a fundamentally plant-based diet. A whole food plant-based diet may even ameliorate chronic kidney disease. There is increasing evidence that a whole food plant-based diet may oﬀer beneﬁts like slowing the progression of chronic kidney disease, and delaying kidney failure. So, the practice of restricting dietary potassium in kidney patients should really be reserved for patients with documented hyperkalemia––a potassium level of 6 or higher––because the key to halting progression of chronic kidney disease may in fact lie in the produce aisle. 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