106 | Is Fennel Contraindicated for Diabetes?

0:00 Welcome to In the Clinic with Camille. My name is Camille Freeman. I'm an herbalist and nutritionist, and in this podcast, I share little tips and tidbits that might be helpful for other practitioners. Today, I wanted to talk about a pet peeve of mine. This is something that happens a lot when I am researching for a class, a lecture, doing research for a client, etc. I find that I am reading a. Something they just said here is interesting, new to me, it doesn't sound right, I want to know more about it, and so I look at the reference that they have cited in the paper, and I do a little bit of digging around, I track down that reference, and I find, what? What are they talking about? This doesn't have anything to do with or directly contradicts with the statement that I originally read.

0:46 And to me, this is a perfect example of why we cannot always trust AI literature summaries or even review articles or discussion sections or things like that. A lot of people don't know what they're talking about when it comes to herbs. They don't have the full context of interpreting and understanding what they're seeing. And I would say the same is true for supplements, nutrition, etc. And so we wind up with people who are confidently incorrect, and apparently peer reviewers who just don't catch this perhaps are not also experts in this field as well, etc. So let me give you the specific example that has me all in a flurry today.

1:27 I saw that there is a new article that just came out this month. It's only the 3rd of May, and this paper was published in May of 2026. And it is called Assessing Safety of Herbal Medicine Use Among Type 2 Diabetes. It's a systematic review and meta-analysis. I was like, great, I would like to look at this because I have clients that I work with that have type 2 diabetes and I just, you know, always want to stay on top of what we know, etc. So I go to the paper. Thankfully, I always love this. It's open access. It's free-full text. It's published in Complementary Therapies in Medicine. So I go and I look at it and I'm like, oh, yes, you know, it was actually a very interesting paper because it talks about around the world, different herbs that are commonly used for type 2 diabetes.

2:11 And a lot of them are herbs that I don't know a lot about and they're commonly used in different parts of the world. So that's always kind of interesting just to learn more and so forth. But, you know, overall, this was not groundbreaking information for me. Just, you know, lots of summarizing of information, that sort of thing. However, I got to a part in the paper where they started talking about classification of herbs that they identified that people are using for type 2 diabetes. And they have different criteria, and they have one criteria that's called contraindicated. And the description that they use in the paper says, The available evidence shows severe adverse impacts of herbal medicine use on diabetes mellitus patients or toxicity.

2:54 That's how they define contraindicated. I was like, okay, let's hear more about that. Then I go down further in the paper, and I see that they have, of all the different herbs that these people were taking, they decided that eight of them, maybe seven, were contraindicated. And some of them, I'm like, okay, I don't really know anything about these. But there on the list, I see funiculum vulgar, which, in case you are not up to date on neuroscientific names is phenyl. I'm like, wow, that's interesting that phenyl would fit into that previous category that I just mentioned. I would not think about that at all. I work with phenyl quite frequently. And while I don't think it's appropriate in every circumstance, it's certainly not one that I would think would cause severe harm or adverse events for people who are who have type 2 diabetes.

3:44 So I'm like, let me just try to find out what kind of citations they're using. And they said that, You know, in the paper, it goes on and it tells a little bit about where they got that. And it says that they found that phenyl, a couple of these herbs were, let's see, let me read you the exact same. The remaining contraindicated herbs, blah, blah, blah, to include phenyl, showed potential glucose-lowering or insulin-sensitizing effects in animals, but were also linked to serious adverse effects. And then they have three citations in there, 86, 87, and 88.

4:25 So I'm like, let me just go find about that because severe or serious adverse effects is something that I would like to know about. So I go down into the reference section and I look at 86, 87, and 88, and those have nothing to do with any of this. They're all about herb drug interactions. It's like, oh, okay. And I kind of poke around. I'm like, okay, fennel's not in there. And that's not a serious adverse effect. And then I'm like, okay, clearly they've mislabeled their references. So I'm scanning the reference list, looking for anything having to do with fennel. And I come across a paper about fennel. It's reference number 74, by the way. And the paper is called In Vitro Toxicity Evaluation of Estrogol Containing Preparations Derived from Funiculum Vulgare on HEPG2 cells, blah, blah, blah.

5:14 So I'm like, okay, well, this is the only thing in here that has to do with phenyl specifically. Let me find that paper. So I go, I look at that paper, and I'm like, wow, this is a paper that was published in 2018. It is, as the title suggests, it's an in vitro study. It is looking at human cells, but they are not attached to a human any longer. And what they found in this paper is actually the opposite. They found that, I thought it was actually an interesting design, they were looking at fennel seed powder and fennel seed essential oil to assess them for toxicity in this model, which, to be super clear, does not translate into adverse effects in a human. It's just kind of step one as you're assessing safety.

5:58 However, what they found is that the fennel seed powder, just fennel seeds ground up, didn't have any sign of toxicity in the cell line that they were testing at all, in any way. And in fact, they said that. There was really no cause for concern because it's very, very high doses, relatively speaking, that they're using. They did find that the fennel seed essential oil, while it didn't cause damage to the DNA, there was a little bit of concern when it came to certain aspects of safety in this particular cell line. However, the end, let me just read to you the highlights of this paper, which I will also link in the show notes.

6:42 The highlights are, fennel seed powder did not show any sign of toxicity in human hepatoma cells. Fennel seed essential oil did not cause any primary or fixed DNA damage. Fennel seed essential oil induced cytostasis, apoptosis, and cell cycle arrest. So basically what they said is maybe there's minor cause for concern with fennel seed essential oil, although obviously additional studies would be needed. It's dose dependent, blah, blah, blah. But really there wasn't any cause for concern whatsoever from the fennel seed powder. So contrary to what they said in this article that came out this month, there is not cause. As far as we know, any specific cause for concern for fennel itself.

7:24 Now, they did not distinguish in this study between fennel seed and fennel seed essential oil. And we do not know if the people who are taking this for diabetes are taking it the essential oil, the fennel seed powder, or some other type of fennel. Because again, it's pretty clear to me that some of these folks just don't have perhaps a good understanding of herbal medicine and maybe didn't know to ask that or didn't know to put it in the discussion that like, hey, there's some things about this that we don't understand. So maybe it doesn't make sense to list fennel as contraindicated, one of the few herbs that are contraindicated in type 2 diabetes. Because what now happens is people who are in medical fields that don't have a lot of herbal training, but that are doing their due diligence and researching, they go and they read a paper like this and they're like, oh my goodness, Fennel is in here as a contraindicated for potential safety concerns for toxicity.

8:18 Serious side effects known. That's what they're implying in this paper. And then they're going to tell their clients, hey, you should be staying away from this dangerous, toxic fennel stuff without the nuance of like, yes, you probably shouldn't be ingesting fennel essential oil, especially in large quantities for numerous reasons. But that fennel seed, ground up fennel, there really isn't, as far as I know, a lot of cause for concern in human populations, especially at doses that most people would be normally taking. So anyway, it really drives me up the wall when this happens, and especially that it's not being caught in peer review. I understand that as authors, we can't always know about everything, but my goodness, oh, like there's so much that we can do, so much to work with around fennel, and it breaks my heart.

9:03 And who knows? I'm not familiar with some of the other herbs on this list, so I don't have the nuance to try to do the same type of breakdown for those. But I also wonder, is there some similar misunderstanding? Are we looking at the same plant part? Are we looking at the same dose? Are we looking at the same preparations? Does this actually make sense in the context of somebody applying this to clinical work, to work with patients if you're in the medical field, or whatever it is? So that's me up on my little soapbox for today. I'm going to leave it there for right now. If you want to check out these papers yourself, or if perhaps you know something about this that I don't, maybe I've missed something. I'm always open to being corrected. So if you feel that phenol actually is contraindicated in type 2 diabetes, and you know about a bunch of research to the contrary, I would love to know about it.

9:48 I did a preliminary search just to make sure that I wasn't completely missing a whole aspect of literature. It is Sunday, and I was like, I don't know if I want to do like a multi-hour deep dive, but from my preliminary search, I didn't see anything new that I hadn't seen before. So anyway, let me know if you have something that I should know about. Otherwise, please make sure if you see something that looks weird or off in a paper, make sure to track down the references and really follow that rabbit trail back to figure out where is this coming from? Because it's surprising to me how often the reference that is cited does not actually match up with what is being said in the paper, either because the references got mixed up, the person didn't fully understand the context, they got it from somebody else, you know, lines got crossed, whatever it is.

10:34 But if we want to be safe and effective in doing our best work, we really have to sometimes follow these rabbit holes ourselves and get to the bottom of what's being said. Okay, I hope you have an amazing day. If you want to stay in touch, I would love for you to join my practitioner notes email. It goes out every Thursday. It's just a short little essay followed by some recommendations, things that I thought were interesting that week, and anything that I'm doing that's upcoming in case you want to come to a class, a workshop, or stay connected in other ways. Otherwise, thanks so much for listening, and I will talk to you soon.