Healthy kidneys are required for potassium excretion. If you aren’t sure if you’re at risk, ask your doctor about getting your kidney function tested.
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 that used to fill our diets—fruits, vegetables, leafy greens, roots, tubers—with calorie-dense junk heavy with added fats and sugars, and stripped not only of fiber but also potassium.
In a traditional, mostly plant-based diet, potassium intake is high and sodium intake is low. But now, high blood pressure is the second leading risk factor for death worldwide, killing more than 10 million people each year. Only unhealthy diets rank higher among global risk factors for death, as you can see below and at 0:41 in my video Potassium Chloride Salt Substitute Side Effects.
We can improve both by eating more whole, healthy plant foods like greens and beans, which are packed with potassium and help lower blood pressure. But since most of us are getting too much sodium along with too little potassium, what about using salt substitutes? Potassium chloride is the most common salt substitute, 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. Most of the trials involved swapping out regular salt for substitutes with less than 30% potassium chloride, and they still got results. And at less than 30% potassium chloride, most people can’t even tell the difference between regular salt and the potassium salt. So, it can taste the same yet still lower blood pressure? What’s the catch?
Potassium chloride is “generally regarded as safe” (GRAS) by the U.S. Food and Drug Administration. The only major concern for healthy people is that if you go 100% sodium-free and use potassium chloride salt substitutes exclusively, you may find it can taste kind of funny, adding a bitter or metallic taste. I’ve found that it depends on what I’m seasoning. Potassium chloride works perfectly well on some dishes and snacks, but I find it makes other foods inedible. When I learned about the sodium science and threw out my salt shaker for good, within a few weeks, my palate totally changed. Everything tasted fine without salt—except pesto. For some reason, pesto without salt didn’t have the same taste that I loved. 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. I tried it with the potassium salt and almost gagged. The salt substitute is definitely not for everything.
The reason healthy people don’t have to worry about getting too much potassium is that they just pee out the excess, thanks to the kidneys. But that’s with the potassium in food—what about supplements? No adverse effects have been shown with long-term potassium supplementation at doses as high as 3,000 mg a day. In fact, blood levels of potassium are maintained in the normal range by healthy kidneys even when potassium intake is increased to about 15,000 mg a day. That’s no surprise since we evolved eating so many potassium-rich plant foods that the natural intake of potassium for the human species may have been 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 mmol/L; it becomes concerning when it starts creeping up towards 6 mmol/L. But give people potassium supplements—like the salt substitution trials where participants receive an average of about 2,000 daily milligrams—and blood levels only increase by 0.14 mmol/L. So, they might go from 4 to 4.14 mmol/L, not something that would push levels into the danger range.
Now, there is a limit. Someone with a “massive banana eating habit” could bump their potassium from a normal level to above 6 mmol/L, but this specific case was evidently the result of eating little else besides up to 20 bananas a day for years. Eating 10 pounds of carrots every day is also probably not a good idea. That’s like 75 carrots in one day—only really possible with a juicer, which is what one person attempted as part of a quack cancer cure. What about overdoing salt substitutes?
A 1940s report focused on lithium poisoning from the use of salt substitutes. Why? Because lithium chloride was used as a salt substitute. Yikes! But what about potassium chloride, which is what’s used today? There is one case where someone committed suicide by taking 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 smaller amounts of regular salt, if taken all at once, can kill you, too. In fact, ingesting salt water was evidently a traditional suicide method in ancient China.
Having said all that, a small number of the population may run into problems, primarily people 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 potassium, then it can definitely become 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 people 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 those with kidney disease—that using potassium chloride salt substitutes would probably still save more lives despite the risk, as you can see below and at 5:45 in my video.
Traditional dietary recommendations to kidney patients limited the consumption of fruits and vegetables because they were high in potassium. However, this paradigm is changing quickly given the many benefits of a fundamentally plant-based diet. A whole food, plant-based diet may even ameliorate chronic kidney disease. For example, there’s increasing evidence that a whole food, plant-based diet may help slow the progression of chronic kidney disease and delay 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 the progression of chronic kidney disease might in fact lie in the produce aisle.
Doctor’s Note
If you are in crisis, you can call the National Suicide Prevention Lifeline 24 hours a day, seven days a week, at 800-273-8255.
This is the final blog in a three-part series. If you missed the first two, check out The Mineral Intake Recommendations Only 1 in 6,000 U.S. Adults Meet and Are Potassium Chloride Salt Substitutes Worth Trying?.
