There are plenty of zinc supplements out there, and while many are acceptable, I don’t recommend using zinc oxide or zinc picolinate. People are often surprised that I recommend against picolinate. So, in this episode, I explain why.
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Read the Transcript
This is why you shouldn’t use zinc picolinate as your zinc supplement.
Hi, I’m Dr. Chris Masterjohn of chrismasterjohnphd.com, and this is Chris Masterjohn Lite, where the name of the game is “Details? Shmeetails. Just tell me what works!”
And today we’re going to talk about zinc picolinate. I get a lot of questions about why I don’t recommend zinc picolinate because other people do recommend zinc picolinate. And so today I want to show you why.
Shown on the screen is a study where 15 students were given four different zinc supplements in a double-blind crossover trial. Each zinc supplement contained 50 milligrams of elemental zinc. And you can see at the top that the zinc picolinate is in the green diamonds, the zinc citrate is in the yellow circles, the placebo is in the blue stars, and the zinc gluconate is in the pink triangles.
And you can see in these graphs that in the upper left, we have the zinc that wound up in the hair. In the upper right, we have the urine. In the lower left, we have red blood cells, and in the lower right, we have serum. Now, notice that two episodes ago, I said that to measure zinc status, you want the plasma zinc. The reason you want the plasma zinc is because in plasma is where we have what we call the exchangeable zinc pool, which is the small portion of zinc that is fully liberated that is moving in between the different tissues and is moving back and forth between the tissues and the diet.
In other words, in order to become usable, zinc that you supplement with or that you eat in your diet must enter the plasma zinc pool. And we do not have the plasma zinc pool measured here at all, so we don’t actually know which of these best improved the one metric that we care most about for zinc status. But one thing that we can see if we just look at the green lines is that zinc picolinate did look best in hair. Zinc picolinate did look, I wouldn’t say best, but it did cause the most zinc to wind up in the urine. It did cause the most zinc to wind up in the red blood cells, but none of these improved serum zinc. And one of the things that we want to see if we know that there was a change is we want to see these lines move from close together to farther apart.
Now, an optimistic interpretation of this is to say, “Look, although none of these things made a difference in the serum zinc, and although we don’t have plasma zinc, the measurement that we would want, the zinc picolinate did increase red blood cell zinc more than the others.” And that’s a good thing. And maybe it’s a good thing that it increased hair zinc more thanthe others. But it also increased urine zinc more than the others, which means that you’re peeing out the zinc picolinate. One pessimistic way of looking at this data is to say maybe the reason that more wound up in the urine is because picolinate binds so tightly to zinc that the zinc never gets liberated to enter the plasma zinc pool and instead just accumulates as zinc picolinate in all these tissues.
So you have zinc as zinc picolinate just being stuffed into the hair, the zinc gets into the red blood cells, but it’s as zinc picolinate, and it just accumulates there without being able to fulfill any of the functions of zinc because it never gets released from the picolinate, and then a lot just winds up in the urine again as zinc picolinate.
So to look at this a little further, we’re going look at one more study. In this case, we’re looking at a study where rats were given diets with or without picolinic acid, and the researchers looked at what happened to the zinc in their diet. So in this case, we’re not looking at zinc picolinate supplementation. We’re just saying what happens to zinc when you add the picolinate to the diet of the animal. As you go across the graphs on the screen, you see fecal zinc, urinary zinc, total zinc excretion, net zinc absorption, and zinc retention.
You can see that fecal zinc was decreased a little bit by the picolinic acid, but it wasn’t statistically significant. You can also see that net zinc absorption was increased a little bit by the picolinic acid, but again, it wasn’t statistically significant. On the other hand, let’s look at the loss of zinc through the urine and how it impacted the net retention of zinc.
Adding picolinic acid to the diets of the animals increased the urinary zinc by about eightfold. So just adding the picolinic acid to the diet of the animals with everything else being the same causes them to spill eight times as much zinc into their urine. As a consequence of this, the total zinc excretion was increased, and the net zinc retention was negative both with and without the picolinic acid.
But it was fairly close to zero without the picolinic acid, which means that the incoming zinc and outgoing zinc is in balance, and it was significantly negative when the picolinic acid was added. So when we look at the rat study, it looks like just adding picolinic acid to the animal makes the picolinic acid bind to the zinc and carry it into the urine.
When we take that information and we look at the human study, the human study where zinc picolinate caused a better increase in red blood cell zinc, hair zinc, and urine zinc, then it looks like the zinc picolinate, when you feed it to the human as zinc picolinate, carries the picolinate, carries the zinc into various tissues, where it probably never gets freed to act as zinc, and it carries zinc right into the urine.
So with these and with the absence of tests showing even equivalence let alone superiority at increasing plasma zinc, and with the known track record of the forms that I recommended in the last episode, in on the ground curing zinc deficiency, something that’s extremely well-studied because the World Health Organization lists zinc deficiency as something that impacts half the world’s population, so this is something very well studied, with a known track record of cheap forms of zinc, like zinc sulfate, curing zinc deficiency, I cannot recommend zinc picolinate.
The available data indicate that the forms that I’ve recommended in the last episode are adequate and the adequacy of zinc picolinate is at best questionable.