Interviewer: You mentioned bioavailability, and explain that a little bit in an articulated materials more bioavailable has that had been proven then getting them through other sources.
Dr. Bortz: So the bioavailability is a sort of a first question that most people want to know about with any ingredients and iron is no exception. Let's begin by talking about what is known about bioavailability of conventional ferrous salts, things like ferrous sulfate, ferrous fumarate, even some of the polysaccharide irons. Typically, the bioavailability with the amount that is absorbed is somewhere between the range about 5% to 30%. So there is tremendous variability. It's interpersonal and intrapersonal variability. If somebody is very iron deficient they will absorb within the first several days much more than if they were not iron deficient.
So that's a sort of a moving target, that's number one. Number two is that, well, if we look at this range that typically accepted understanding of ferrous salt bioavailable, and it's about 14%, 15%. Let's use that as useful number. Several studies have demonstrated you know, in early 2000 era that the bioavailability of chelates, ferrous bisglycinate has been the most studied iron chelate. That's somewhere in the range of about 40%. Some of them had been little higher, some little lower, but again in the range, in the 30% to 50% range.
That's been done with radioisotope you know, double labeling studies, various ways of lot of that. And in fact there is a study that's also looked at hemoglobin regeneration taking anemic patients seeing what their hemoglobin was after a period of time, four week, six weeks whatever and seeing what the hemoglobin response has been, from there we know that each gram of hemoglobin requires a 150 mg of irons. So you can back calculate how much iron was absorbed.
That's a very nice sort of clinical way of determining this more or less 40% figure. But you have something important Scot and that is that most of the bioavailability studies of the salts in most irons have been single dosing studies, which means that bring in subjects, take blood, give them one tablet or whatever dose or a solution that have an amount of iron and then they measure the amount of iron that appears in their blood over the course of the next 24 hours. And from that they would then calculate what the bioavailability is.
So single dose study, it turns out that that there was some very interesting work that was done by Swedish scientist called Hellberg in the late '50s or early '60s. What he showed was that when you dose every single day has happened to be ferrous sulfate, after about three weeks there was a dramatic reduction in bioavailability. In other words, it following the correctly, in his studies the average bioavailability on day one was about 13.9%, let's say 14%. By the time he got to day 21 it was about 6%. So what's that all about? Well, first of all it actually challenges this concept of bioavailability is not a simple subject here, but it challenges the conventional wisdom that ferrous sulfate, or ferrous fumarate is 15% or 20% you know, bioavailable.
Well, if we look at the end of a month it's you know, 15% or 20% of that. Why is that? Because the body, as I mentioned earlier, the body has to be protected and doesn't want there to be an excess of iron. So there is a shut down. That's something called a mucosal block, used to be some old term, whereby this is the way the body lands up protecting from over absorption. So when doctors are giving a ferrous salt take this daily or twice a day whatever it is, what they don't realize is that in the second month there is a markedly diminished bioavailability if the patient is still taking it, because side effects will end up usually kicking in within a week or two.
The patient will come back, hemoglobin gets usually, the folks are put on because of anemia, hemoglobin gets checked. The response isn't that great. So what do they do? They ramp up the dose. So the dose goes up, the bioavailability hasn't changed, it's now still low. But side effects go up. So other patient says, I'm not going to take this. They usually don't call the doctor and say I'm not going to take it. Some do, most don't. Come back three months later hemoglobin still low the dose gets bumped up or the doctor say oral iron is useless. Okay, and you know, let's you know, just sometimes, you know give a dose of intramuscular or intravenous, I mean it happens.
So in a sense, there is this misunderstanding of what the true bioavailability is of a ferrous salt. I think it leads to really misapplication of you know, oral iron therapy. Chelates, it is there is one very small clinical study, which has show also a drop of after 21 or 30 days, but not nearly to the same extent of the chelate and part of it maybe because the iron is part of it may be absorbed intact. I'm not sure I have mentioned this before, but with ferrous salts you need a very low pH in order to get the iron into solution.
Iron cannot be absorbed if it's [inaudible 00:06:43]. And the area in which the pH is below three, which is what's needed in order to keep ferrous iron solution is only the first probably three or four inches of the duodenum. After that with a pancreatic duct starts pumping in high alkaline you know, pancreatic juice bicarb, pH rockets. Ferrous iron crystallizes can't be absorbed. So it's a very short segment of upper GI tract that can actually absorb ferrous iron.
The Chelate may not be so pH dependent. Because it is complexed you know, with the amount of acid and as a result may also will end up being absorbed over a large absorb to surface. Now, that maybe one of the reasons why in the field people, who use chelates get much fewer side effects, because it's been postulated that a lot of the irritation of the GI tract is because you are absorbing in a very narrow area that with several inches of the duodenum.
That's long been thought to be one of the benefits of chelated minerals such as iron. Dr. Jonathan Bortz discusses the bioavailability of chelated iron. He also goes into some study results and shares some different ways of looking at bioavailability, especially when it comes to iron supplements.
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