• 05 Oct 2021
  • 19 min 19
  • 05 Oct 2021
  • 19 min 19

Ashlea Broomfield chats with clinical pharmacist Geraldine Moses about the potential adverse effects from some commonly used vitamins and minerals, especially when taken in high doses. Read the full article in Australian Prescriber.


Welcome to the Australian Prescriber Podcast. Australian Prescriber. Independent, peer-reviewed, and free.

Welcome and thank you for joining us on the Australian Prescriber Podcast. My name is Ashlea Broomfield and I'm a GP in New South Wales. So I'm here today with Dr Geraldine Moses who is a Consultant clinical pharmacist at Mater Health Services and an Adjunct associate professor at the School of Pharmacy in the University of Queensland in Brisbane. We've spoken previously on the podcast about complimentary medicines. And I'm really excited to be chatting to you today on the safety of commonly used vitamins and minerals.

Yeah. I think because these are widely seen around the community, people make a giant assumption that they must be safe. And I think a lot of consumers make an assumption of safety of particularly vitamins and minerals because they're derived from food and therefore they judge them as if they were food, but they're not food. They're pharmaceutically prepared products. They're made in a factory by a drug company. And so the same concerns that one might have about any pharmaceutical should be applied to vitamins and minerals as well.

And I really like that you pointed this out, that supplements aren't foods.

That's right, yeah. And so like any other pharmaceutical product, you should be thinking about risk as well as benefit. And in order to make an informed decision about whether you might use them, you have to think of both sides of the equation because people think food’s nothing. And if you were to just eat a food that wasn't very safe, you might, I don't know, feel sick. But with vitamins and supplements, they can be up to 10,000 times more concentrated of the pharmacologically active ingredients that are in them because they've been manufactured in a factory. They've been dried and concentrated and potentised in that manufacturing process. And then ultimately, we grade the amount of the ingredients and then the dose that would be required. So they're nothing like food in the end, and therefore have the potential for overdose and toxicity like any pharmaceutical.

And I think that's something that really struck me when learning about vitamins and supplements is that you can't overdose, you can't get hypervitaminosis from food, but you can from vitamins or minerals when they're in supplement form.

Absolutely. And you might hear this from your patients from time to time, patients will say, "Oh, well, you know, they're water-soluble vitamins and so, the body will just eliminate what I don't need. That doesn't happen. So that's why this article was so important that we could talk about the toxicity associated with even the water-soluble vitamins, that would previously have been thought of being regulated by the body, can have toxicity even at normal doses.

So let's jump in and talk about some of the supplements that we're talking about. Can you give our listeners an overview of the most commonly prescribed vitamin and mineral supplements, and what they're generally clinically indicated for?

Well, we can tell ourselves that we think that people take them for a genuine indication or for management of a disease process. But I think a lot of people just take vitamins and minerals because it makes them feel good, not good like a sense of wellbeing, but better about themselves. So there's a certain amount of their consumption just being based on anxiety and the concern that there might be bits missing from their diet. So it's called nutritional insurance, that by taking these things, it might be filling in the gaps of what they're not consuming in their diet.

And so the commonly used ones are ones that contain all the vitamin Bs and then vitamin C, possibly vitamin D, bit of calcium, bit of magnesium, zinc would be the very common ones. And these also then marketed, not just for nutritional purposes, but also for very commonly occurring symptoms, not actual diagnoses, but symptoms. So things like tiredness and fatigue, insomnia, concern about getting infections, for ‘supporting’ eye health, or ‘supporting’ your immune system.

Yes, I certainly see that in my practice that there's quite a lot of people who take a multivitamin or multiple vitamins in terms of wanting to support the way that their body works. So which ones are of primary concern when we look at ones that people can access over the counter that we need to sort of be mindful of checking dosages and advising of in terms of risk?

Well, they all are a problem. I suppose when I look at a list of ingredients, the ones that leap out at me would be vitamin A, sometimes referred to as retinol, vitamin B6 and selenium, because these are the ones that have well-documented risks associated with cumulative toxicity. So let's just briefly talk about that. I think as an introductory statement, I'll just say that dose is frequently ignored and we make this point in the article that often patients take these things without any regard to the dose, or indeed a therapeutic objective like when they're taking them, as you say for wellbeing, what is that? And how do you know when you get there? And yeah, so it's like, you're just taking them forever for no particular purpose. So it would be good if people could be more specific about why they're taking them. What's the intent? What's the therapeutic objective? And indeed, how much do you have to take to reach that goal?

And what we find is that there's often multiple supplements being taken, and they might have a small amount in each individual product, but it's the accumulation of those doses that might lead to toxicity.

So let's start with vitamin A. This is like grade one pharmacology, isn't it, Ashlea? Everybody learns in pharmacology about the toxicity of vitamin A. It's got a well-known syndrome associated with it called hypervitaminosis. When the vitamin A accumulates, it can accumulate not just from supplement doses, but also from the diet. And so that toxicity could be acute from one great big giant dose all at once or accumulated over time. The toxicity manifests in the skin, in the liver, and in the brain. And you can die from it, can't you? It can be very serious. So that's what we do when patients present to clinical pharmacists in hospitals, and we ask what complimentary medicines they take.

We ask them to bring in all the bottles and containers. And we'll first calculate the accumulated dose of vitamin A. And sometimes it may have even contributed to why they came to hospital. A high dose of vitamin A can cause blindness because of the toxicity in the eye. It can cause raised intracranial pressure in the brain. And that may start as a headache, but actually can cause damage, can't it? And desquamation of the skin, toxicity to the skin, and damage to your liver. Also, we should remind people that it's a proven teratogen. In other words, it's known to cause birth defects. Still, so many people in the general public who don't know that. And the amount that can cause birth defects is very easily attained and it can come from the dual dosing from a supplement, but also from your diet

Vitamin B6 is another one that is thrown into lots of products. But in doses from as little as 50 mg a day, but more frequently from about 200 mg a day, it is associated and well-documented causing damage to the peripheral nerves. That peripheral... Sorry. I was just going to say because of that peripheral neuropathy, this substance is regulated as a prescription drug in different doses around the world, but in Australia, it's from 200 mg and above.

And vitamin B6 in nausea and vomiting of pregnancy is something that is often talked about in terms of helping to reduce the risk of, or help with, hyperemesis in pregnancy or nausea and vomiting in pregnancy. And so what can prescribers be mindful of when thinking that they might recommend vitamin B6 to women who are pregnant?

What is the dose that you prescribe, Ashlea?

25 mg, half in the morning, half in the afternoon, and one at night. So you're actually at that 50 mg dose per day.

As long as you're below that 200 mg a day, you're less likely to cause the peripheral neuropathy. So if you were in the UK, you would have to have prescribed that on a prescription because it's regulated as an S4 from 50 mg a day and above, but in Australia, it's 200 mg. But more importantly, it's that cumulative dose. So I think you've got to also make sure you might have prescribed the pyridoxine just for their nausea and vomiting, but what if they've also got a couple of multivitamins and a green drink that they have every day, that's also got a substantial dose of pyridoxine in there as well, and so inadvertently might then overdose?

Exactly. And I think that's something that I've often been mindful of is like you say, can you bring in all of your vitamins and supplements you're taking? Even in elderly people. And often there's multiple vitamins in lots of the different tablet forms that they're taking, and very much so often an overabundance of the B vitamins, and often C as well.

Yes, that's right. Yeah. And sometimes just because it looks good. An exercise that I do with patients is, especially if their vitamin doses look a bit too low, is to get that list of ingredients and compare it with some commonly found items in their pantry. And they might just find that they're paying all this money for a vitamin supplement where there’s just the same amount in their breakfast cereal or anything else in their pantry or the fridge like sausages often have quite a lot of these very commonly found vitamins. So why spend money on something that looks special, but actually isn't giving you anything more?

And I guess that's where the role of say a primary care provider and working in a multidisciplinary team with an accredited practicing dietician, you might actually find that helping someone optimise their nutritional intake can actually help to sort of have a really nice balanced, nourishing diet that helps them meet all their vitamin and mineral needs.

That's right. And like you say, it is so balanced, but also gives you the dose in a very slow way and in little bits. So that's what we do with calcium these days, isn't it? We'd rather people get their calcium from food than always going for tablets. Tablets make it convenient, but you're getting a whopping great big dose all at once. Not much of it is absorbed, but it can accumulate, especially if most of that dose gets in and calcium is associated with lots of adverse effects because of that.

If you've got something that's calcium fortified like soy milk or almond milk and it has calcium in it, is that the same risk as taking the calcium as a tablet form?

I don't think so. I think the dose is a lot less, it's more like a 100 or 200 mg. I think it's just preferable to try and get it because it's also more slowly absorbed, because calcium and magnesium by the way are absorbed across the gut wall. And so the slower the passage of time across through the intestines and then across the gut wall, the more improved will be the absorption. But if you take a tablet, it all comes in all at once, doesn't it? And it saturates those transporter molecules. And it'll be competing with other minerals that are there at the same time, like magnesium, they do share the same transport pathway. I think it's hilarious when they co-formulate calcium and magnesium because they're just going to fight against each other. If you want to take calcium and magnesium, take them separately, so they both get an opportunity to be absorbed on their own.

And that's interesting, isn't it? When you talk about the complexity of how nutrients are absorbed in the body. And something that we don't know a lot about is when food and the nutrients are broken down, when they're then absorbed into the body, they've probably got a lot more complex mechanisms than we understand that can be achieved by supplementation.

That's right, absolutely. So I just wanted to quickly talk about vitamin B3 or niacin, which is also thrown into lots of things that people take as daily supplements, because it's somehow good for dot, dot, dot, fill in the dotted line. So we all know that if you take a slightly bigger dose of niacin, that it can be useful for managing high lipid levels or high cholesterol levels. And the dose for that does start to get quite high in the grams a day. What's normally in supplements is about 250, maybe a 100 mg. But again, people can bump up the dose. Now people who take, well it's also referred to as nicotinic acid or niacin, might self-medicate with niacin because they read on the internet that's a ‘natural’ remedy you can take for managing your cholesterol.

So the biggish doses we all know can cause vasodilatation. So it causes reddening of the skin, flushing, often a drop in blood pressure because of that. And I have seen people taking these big doses and putting up with those side effects because they go, "But you know, it's natural. It'll be fine." What people need to know also though is that vasodilatation occurs in your eye and both eyes. And as much as you could put up with it on your skin, it's damaging to your eye and can cause macular oedema, and can give you impaired vision and be problematic for just getting around or driving your car. So people need to be aware of all the potential side effects, not just the ones that they think they can put up with.

And I guess that's something that is a theme in your article. Even when you talked about vitamin D, the high doses of vitamin D can then increase risk of fracture.


And it seems as though we need to be really... And we talked about vitamin B6 earlier. It seems that we as clinicians need to be really careful around the particular dosage that we're prescribing and making sure that, if we are recommending a supplement, that we're not actually prescribing super therapeutic doses of something because they're taking something else at home.


In the same way is if you were prescribing a second blood pressure medication, you would want to make sure that you weren't contributing to…

Isn't it funny? Yeah. You'd get very pedantic about dose if it were a prescription drug that you've studied, but somehow with vitamins and minerals, we forget to be concentrated on that particular issue. So thank you for mentioning vitamin D because it does concern me that there's quite a fashion at the moment amongst some prescribers to prescribe mega doses of vitamin D. It's given as an intramuscular injection, and the patient is told your whole vitamin D needs are taken care of for the rest of the year. But it does seem that they're unaware of the recent evidence. And a lot of this research has been presented at conferences in the last one to two years, demonstrating quite clearly that these high doses do increase the risk of fractures, decrease in bone density, and the risk of hypercalcaemia. So it's actually not in the best interest of the patient, even though it's convenient, but also it would hurt. I sort of think it's a bit of elder abuse when it's given to elderly people, this giant intramuscular injection. So people need to be evidence-based and understand that products like this may carry very serious risks.

Mmmmm. And you've definitely highlighted all of the potential adverse risks associated with commonly prescribed vitamins and minerals in the article. And it's a really great read. It's really helpful. And even one of those articles that I can see myself giving out to my patients in the future around the issues that can be associated with commonly prescribed supplements as an educational tool. So I really appreciate that you wrote this article for us.

Geraldine, what are your take home messages around the sort of general things and harms that we need to look out for as prescribers or health clinicians in this area?

Well, Ashlea, I feel like we need to make sure we're focusing on helping consumers make informed decisions. And the only way people can do that is to have information about both the benefits and the risks of complimentary medicines and dietary supplements. In the article, I gave a list of the six potential harms. I've been using this in my practice for some time and I find it very handy to tabulate for patients all the things that could potentially go wrong, but quickly and easily. I use a mnemonic of ABCDIF, if anybody's interested. And if you can document that quickly and easily for patients, they can more readily make an informed decision about their use of supplements.

And so what's your ABCDIF acronym?

It's A for adverse effects. B for burden, so the increased number of medications, the increased risk of medication errors and drug interactions. C is cost, these things aren't free and sometimes they're very expensive. D is delay. Delay in more effective therapy. Sometimes breaks my heart that people are pussyfooting around with supplements and natural remedies because they think somehow that's a good thing and they'll get bonus points for using a thing that is perceived as natural, but in the meantime, some very important disease is being neglected and the time factor in that is being ignored.

I is interactions. And there's so many interactions, we could spend all day talking about them. But remember, even these very boring-looking substances like vitamins and minerals can interact with so many other things, even with each other like calcium and magnesium. So make sure you elaborate on that risk. And then finally, F is for false hope or fraud. We all get false hope trained out of us, don't we, in our academic education, to not give people false hope or make false claims. And yet there's a whole industry that doesn't seem to have any qualms about that. And they're not understanding that when people are subjected to these false claims and the thing doesn't work or it causes harm, that can be very demoralising and sometimes lead to the difference between keeping on trying to manage their disease or giving up.

And I think that's such an important point that you've raised, Geraldine, that we are people that have responsibility to make sure that we're empowering people to make the most optimal decisions for their health and wellbeing. And if we can do that in a kind and caring way and in a supported way, that allows them to feel that they can make an educated decision about what they're going forward with, rather than steering towards false hope, then we can provide a really good role as health professionals in providing that sort of empathetic yet educational and supportive role in relation to this. So-

Yeah, that's right. Yeah. People are generally using these substances, aren't they, to help themselves. So the intention is good, but they don't have enough information to make educated and informed decisions. So yeah, we're not giving the permission to take them or not take them, but as you say, to support them in those decisions.

And therefore, I thank you so much for writing this article because I think it will absolutely help a lot of prescribers out there in having more informed discussions in that sort of supportive way.

You're very welcome. Thank you.


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