Leah:
Hello and welcome to the Ideal Nutrition Podcast. I am Leah Higl and I am here with my co-host Aidan Muir, and today we will be discussing vitamin D. So when people think about vitamin D, I think the main thing that does come to mind usually is bone health. Well, that and the sun, I feel like people always think about the sun, but usually bone health, which is a super important one from a nutrition point of view. But vitamin D plays a lot of factors in a lot of different things in the body and we will go through these today. But first starting with a little bit of background stuff, just on what is a good vitamin D level and what would deficiency clinically be defined as? So around 30% of people in Australia are vitamin D deficient. Some places such as in the ACT have even higher deficiency rates at nearer that 50% mark, which is a lot of the population, literally half of the population. And deficiency is defined as less than 50 nanomoles per liter of vitamin D on a blood test.
A healthy range would be anywhere between 50 to 150 nanamoles per liter, although there’s a pretty strong argument to be made that that range maybe should be starting from 80 rather than 50 and 80 is going to be better than 50 nanamoles per liter. And that’s where I tend to aim for with my clients. If they have a blood test and it’s not coming up as clinically deficient by those standards, but they’re still on that lower end of the range, I would still deem that as suboptimal and would want to supplement accordingly. So that also means that whilst 30% of the population is deficient, it’s probably another 25, 30% of people that have at least suboptimal levels. So now we’re talking about a good majority of the population perhaps that have either a deficiency or suboptimal levels.
Aidan:
Sometimes I feel like I talk about vitamin D too much, but that statistic there is exactly why I do it. This is one of the easiest things we can overcome and I’ll talk about that and how you would address having low levels. It’s one of the easiest wins we can get in the nutrition world, and it’s relevant for probably more than half the population. It’s something I just think is super important, super easy to fix. And even if it’s boring going through it all the time, I think it’s important.
Starting with the easy, the obvious one that is the most strongly linked with low vitamin D is bone health. So very clearly low vitamin D linked with low bone mineral density. That’s a very clear observation that’s been happening for a long time. Even historically, conditions such as rickets, which is involving softening and malformation of bones, particularly in infancy or youth and stuff like that, that’s clearly linked with vitamin D deficiency. If people have very, very low levels of vitamin D, rickets is a common outcome.
Alternatively, more common in the average person is low vitamin D levels can contribute to osteoporosis and osteopenia, which are basically low bone mineral density. And vitamin D, the reason why it does this is because it is required for the absorption of calcium and phosphorus. So even if you had really good intakes of calcium and phosphorus, but you had low vitamin D, you wouldn’t be absorbing them well and that’s part of why bones get weaker when we have low vitamin D levels.
From a research perspective, even just supplementing vitamin D at a population level without measuring levels at all has been shown to improve bone mineral density on average at a population level. That’s pretty exciting because once again, that’s another easy win. This is why certain countries such as the UK have in their public health guidelines, they just recommend everyone to supplement vitamin D.
Leah:
Yeah, which I don’t think that is a particularly bad recommendation.
Aidan:
Yeah, particularly at the dosages, if they’re recommending a moderate dosage of 1,000 international units, which is a pretty standard dosage, it’s not going to harm anyone and has potential to help. If these are numbers over here, I assume the UK’s a little bit worse, has potential to help more than half the population.
Leah:
At worst case scenario, it probably just does nothing for those that already have decent levels.
Aidan:
And another common theme that we’re probably going to talk about is I just said that was without measuring levels, very clearly, people who are deficient get a lot more benefit from supplementing vitamin D than those who have high levels. I’m of the opinion that in almost all cases, people who already have very good levels, well above that 80 number you were talking about, they likely don’t get much additional benefit, particularly above the 100, whereas people who are at the lower you get, the more benefit you’re likely to get out of addressing it.
Leah:
Next topic we are going to discuss is immune function. So this is a lesser known one when it comes to vitamin D, although it has been more of a hot button issue since COVID, which I will get into. But first we’ll go over a little bit of general research. So a 2017 meta analysis, which included 25 studies, found that vitamin D supplementation reduced the rate of respiratory tract infections. So that’s really promising. Supplementation showed significantly more benefit the lower the starting the vitamin D levels were. So for example, those be below the 25 nanomole per liter amount in their blood had very significant improvements from supplementation, where we would expect people with already decent vitamin D levels would benefit a lot less.
Now getting onto the COVID stuff, I found is so interesting when this came out and everyone started taking vitamin D pretty much. So a 2021 meta analysis on COVID and vitamin D status found that those with vitamin D deficiency were 80% more likely to get COVID than those without. So that’s a pretty huge statistic, 80%. So I don’t know about you, but I started recommending vitamin D for most people that asked about COVID prevention or preventing catching it. So vitamin D does seem to be a pretty big player in immune function. So if you have low vitamin D levels, perhaps it is affecting your immune function and you could benefit from supplementation.
Aidan:
People were quick to recommend vitamin D with the COVID thing. I remember-
Leah:
It’s also no harm, right?
Aidan:
Yeah, yeah. I remember hearing it in 2019. I was like, eh, makes sense. We see it in upper respiratory tract infections, helping in everything like that. But it’s cool to see the meta analysis data from 2021 after we had a good amount of data being like, yeah, it’s a thing.
The next one is depression. So I’m aware of five different meta analyses on vitamin D supplementation and depression. And it’s pretty rare, pretty much any topic to have five meta analysis, because the entire purpose of these is to summarize all the research. Why do we need five different things summarizing all the research? The only reason this really exists is because there’s contradictory findings. I’m going to go through my interpretation of the research and then say why there’s contradictory findings. So my interpretation is vitamin D likely can help improve depression symptoms a bit on average. In some cases it might help and in other cases it might not help. The effect likely isn’t huge.
And as with other areas, the effect is likely bigger in cases where people have quite low vitamin D levels and one meta analysis, so I’m using their words not my own, but I do agree with this. They concluded that one reason that the other meta analysis that had been done didn’t find a difference was because in some of these other ones, the levels of depression included in the studies were quite low at the baseline and vitamin D status was quite high at the baseline as well.
If the symptoms of depression weren’t large to start off with, it’s harder to measure huge improvements or anything like that if there’s not really this large amount of improvement to be had and the vitamin D status, that’s the kind of thing we’re talking about. We don’t really care what happens to people supplementing vitamin D when their vitamin D’s already good. As I’ve said, I assumed that’s not going to do anything.
But if people have low vitamin D and they address it, that’s what we care about particularly because it’s a large percentage of the population. And going back to the bone mineral density thing, when they did it without context and they just did it without measuring, there was improvements. That’s because there’s a pretty strong link between bone mineral density and vitamin D. I think for depression it’s a relatively weak link. I do think it helps a little bit, can be skewed by other variables, which I’m probably going to touch on at the end, but I think that explains why there’s a bit of a lack of finding, but I still see it as something that could potentially help and is worth addressing if it is low.
Leah:
Somewhere else where vitamin D might be a factor or at least play a role is balance and strength. So there’s pretty strong research supporting improvements in balance and strength in people that are over the age of 60. This translates into a reduction in falls which further reduces fracture risk beyond just having stronger bones. So it can even play that role in, you’ve got old people falling less, which is less likely to fracture a bone, but also it has that really strong link in bone health as well.
But when we look at the research in younger people, there seems to be a much less pronounced effect. Athletes who address a vitamin D deficiency do tend to get a little bit stronger on average. According to a 2017 systematic review on the topic, but it doesn’t seem to be this huge difference. It is worth noting that it isn’t anywhere near as much research on that topic as there is in those older populations looking at falls and things like that. But there is a little bit there. And there are certain athletes who are more likely to be vitamin D deficient where maybe looking at vitamin D levels and supplementing maybe more appropriate or be more beneficial. So athletes who play a lot indoors, so things like basketball players for example, when we know these athletes in general because of their training don’t get a lot of sun, they might in fact benefit from this kind of supplementation or at least having some focus on vitamin D.
So overall, even though the evidence for performance isn’t super strong, I still think it’s worth addressing. And we’ve said it before because we talk about vitamin D so much, but I think it’s worth seeing where your levels are at and regardless of whether there is a strong link between performance, strength, et cetera, balance, I think it’s worth addressing for my athletes. Even if we’re just looking outside of this particular context for vitamin D, I think there’s still a role that it plays somewhat.
Aidan:
Yeah. I’m not a hundred percent sure on this, but one of my clients recently went to get a blood test for vitamin D and they were told that it is no longer covered by Medicare, they have to pay for it now, which is-
Leah:
Really? I’ve not heard that at all.
Aidan:
Disappointing if true, but I still think it’s worth, even if you had to pay a little bit out of pocket, that- I still think it’s worth it. Yeah. But yeah, it’s good before if that is true, it’s good in Australia that it was free. It’s like, well, there’s no downside.
Leah:
Maybe that doctor just didn’t want to give them the test.
Because I think a lot of people have started asking for vitamin D. I tell my clients to ask for vitamin D and I know there are some doctors who are like, “Well, it’s not clinically relevant, I don’t have enough reason.” So perhaps they just, who knows?
Aidan:
An area that I’m interested in. So another area is IBS symptoms. We’ve talked about this previously on podcasts specific to IBS, but I’m still going to cover it briefly now just in case somebody’s just listening to this one or in case I would in a different way that resonates with somebody. So there are plenty examples of research linking vitamin D and IBS. One example came from Saudi Arabia that founded 82% of participants with IBS were deficient in vitamin D while only 30% of people without IBS had low vitamin D. That sounds extremely compelling. That’s one of the most promising things I’ve ever seen in this area. But that doesn’t necessarily mean addressing the deficiency helps. It could be that whole correlation, not causation kind of situation. What we really need is let’s get a bunch of people with vitamin D deficient supplement, see what happens. And I’ll talk about that more as to why I think that.
But as of right now, in 2023, there are only four randomized control trials looking at vitamin D supplementation and IBS and the results are mixed. It’s nowhere near as promising as you would conclude from that Saudi Arabia study, but it looks mildly promising. So once again, it’s another area where people who are quite low at baseline are more likely to get more benefit. And very briefly touching on the things I’m alluding to in relation to depression, IBS, all of these things to that correlation versus causation kind of thing is we get vitamin D from the sun. And if you get more sunshine, does that change anything about you? Does being out in the sun, does that affect your mood at all? Is that going to affect depression at all? Is the kind of person who gets out in the sun more a different person to somebody who doesn’t get out in the sun more and vice versa? What if somebody has really bad IBS and they don’t want to leave the house and suddenly they’re not getting as much sun and that’s why the vitamin D is low?
That’s why I talk about this whole thing being we can’t just look at percentages of the people who are deficient and then use that as being this is why we need to address it. We actually need to look at does addressing the deficiency improve the symptoms?
Leah:
Yeah, absolutely. And then in terms of addressing vitamin D deficiency, or at least where you get vitamin D from, there are three main areas that we can get vitamin D. So supplements, food, and like you said, the sun, which is probably the most well known one. Everyone’s like, yeah, get out in the sun, get your vitamin D. So you can focus on any of these in order to get adequate vitamin D. But usually my preference is to either supplement or sun rather than food and we’ll go through why.
But sunlight is definitely the preferred approach if you’re not wanting to supplement because vitamin D in food is not, especially if you’re plant-based, which is the area I work in, it’s just not relevant to me. We’re just not going to get a whole lot of vitamin D usually in our food. But obviously with the sun factor, particularly living in Australia and particularly us living in Brisbane, Queensland, we do have to balance that with the risk of skin cancer. So you want to get enough sun to get enough vitamin D, but not so much sun where there is that increased risk of skin cancer.
And then going from a food perspective, there are very few foods that naturally contain vitamin D, which is why it’s not my preferred approach. So there are things like liver, egg yolks, certain types of meat. So again, a lot of your animal products might contain small amounts of vitamin D, but also a fun one is mushrooms that have been exposed to the sun. I have some vegan clients that do sun bake their mushrooms for the specific purpose and they get really into it. But obviously I think that’s not… You just don’t know how much you’re getting, right? Yeah. So I don’t think it’s a super awesome way to go about it, particularly if you’re rectifying a deficiency. So yeah, I’d usually focus on sunlight or supplements.
Which brings us to supplements. I really want to get your opinion on this because we were talking off air about what kind of dosages you’d look at for rectifying a deficiency. We know most of the supplements on the market, the standard amount in a vitamin D supplement would be 1,000 international units. And for someone wanting to maintain their vitamin D levels, they’ve already got decent ones, but maybe they just don’t get a lot of sun. Maybe they also don’t eat animal products. I would just recommend taking that as your daily dose, although it may also be not enough for some people. So an increased dose may be required there.
But to address deficiency quicker, you’ve noted that you sometimes go up to 10,000 IU per day for a few weeks to rectify deficiency. I think I’ve in the past been a lot more conservative with that, just because that’s what I’ve seen other dieticians do and general recommendations from different places. So I never questioned it, but you also said that injections given by doctors, that’s 150,000 international units, so 10,000 international units in comparison, not that crazy. So it’s not going to do any harm.
Aidan:
And adding context to that, if you supplement 1,000 international units per day, we know injections are absorbed quite well, which is why they’re used instead of orally by doctors if they’re looking to address it quickly. But to get the exact same international units, it would take 150 days. So we very much know that it is safe for somebody who’s quite deficient to inject 150,000. Why would 10,000 be unsafe? And then looking further, let’s look around and be like how many people are running into issues from having too high vitamin D levels? I know the range is 50 to 150, but if you look through research, it is a bit of a reach to be like, well what what’s wrong with being 160, 170, 180? There are things that can go wrong and I do not recommend trying to get up to that range.
But the whole point of being like, guys, if we accidentally overshoot, it’s probably not the end of the world. And then what about acute dosages being like, well, how much could we have in a single day? I’ve chosen a number 10,000, but that’s just because that’s a number that I’ve seen people do every single day for over a year with zero consequences. And it just makes sense to me that the 10,000 number to me is a conservative number. If I had seen other people going higher than that, having no issues, everything like that, maybe I’d recommend higher. But that’s the number that I’ve chosen.
And my standard protocol of somebody who is relatively deficient because I think deficient is already well below what would be suboptimal, which is already below what is optimal, there’s quite somewhere to go, is I’d often do 10,000 international units per day for two weeks, then drop to 4,000 for another couple of weeks, then drop to 2,000. And then based on a blood test, whether you drop to 1,000 and whatever it takes to maintain after that time, I’ve just seen no downside in doing it. It will address the deficiency a lot quicker than other options and you get to where you want to be quicker while also doing it quite safely as well.
So wrapping things up, vitamin D is linked with pretty much everything. There’s even a lot of stuff we haven’t touched on that is linked with, but a lot of the links are quite weak. The links with bone health is very strong. The links with immune function is very clearly there. Sometimes it’s relatively weak, sometimes it’s a bit strongly like that COVID thing, the 80% deficiency, that’s a crazy number. But with a lot of the other stuff, it can be hard to tell whether addressing vitamin D fixes it or if it’s due to a lot of other things. But because there’s no downside to addressing it and it’s such a common deficiency, I think it makes sense to look into and address, because even if it doesn’t necessarily address the one thing you’re specifically wanting to address, it’s probably going to help a bunch of other stuff along the way.
Leah:
This has been episode 87 of the Ideal Nutrition Podcast. As always, we’d love a rating or review if you haven’t left one. But otherwise, thanks for tuning in with this episode.