February 26, 2024 • 31 mins
In Season 8, Episode 1, Marc shares clips from Dr. Daniel Owens, PhD, lecturer at Liverpool John Moore's University recent 60-minute lecture at the APN Speaker Series all about Vitamin D & Athletes.
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
In the winter, we simply do not get enough sunlight, particularly at northerly latitude.
Ideally, we would want to test the athlete to see whether that's even necessary.
And if it is necessary, we'd recommend it as a weekly, as a daily dose,
not a weekly or monthly bolus.
Music.
Welcome to the Performance Nutrition Podcast, giving you the latest evidence-based
(00:22):
research and cutting edge insights for elite mental and physical performance.
He's connecting you directly with the world's leading experts and coaches.
Here's your host, Dr. Bubbs.
Welcome back or welcome to the Performance Nutrition Podcast.
I'm Dr. Mark Bubbs, performance nutritionist, and this is season number eight.
(00:44):
This season, we'll be taking a deeper dive on specific topics with the latest
up-to-date evidence-based insights from a broad range of experts as part of our new speaker series,
where you can attend live lectures from experts in the field.
In today's episode, I'll be sharing highlights from our first speaker series live talk with Dr.
(01:05):
Daniel Owens, PhD from Liverpool, John Moores, all on vitamin D in athletes,
health, performance, and testing.
The speaker series live events are free to attend.
And if you missed it, you can access the talk by signing up for our new members
area called the locker room.
For just $9 per month, you can join the locker room members area and stay up
(01:26):
to date on all the latest in performance nutrition from top experts across the
world working in elite and pro sport.
Head over to DrBubz.com forward slash subscribe to register to join the locker
room and keep leveling up your nutrition game.
You can save 20% off with our annual subscription.
All right, let's get the ball rolling. Vitamin D in athletes,
(01:47):
health, performance, and testing.
To kick things off in this episode, let's zoom out to 30,000 feet.
The prevalence of vitamin D deficiency is increasing worldwide,
and the rate at which it's increasing is pretty alarming, to the point where as far back as 2016.
The American Journal of Clinical Nutrition made the case that it could even
(02:10):
be considered a pandemic.
More on that in a minute. The percentage of adults in America with vitamin D
deficiency ranges from 36% to 57%.
So that's about one-third to half the population, or to really appreciate it,
approximately 100 to 150 million Americans.
What about in Europe? A recent 2016 review suggests vitamin D deficiency is
(02:35):
also widespread across Europe.
A European sampling of children, teenagers, adults, and older adults,
over 50,000 people ranging from southern to mid to northern European member
states, found that 13% had vitamin D deficiency,
which in this study was defined as 30 nanomoles per liter in international units
(02:56):
or 12 nanograms per mil in American units.
This prevalence rate actually meets the criteria for a pandemic,
defined as an epidemic occurring worldwide or over a very wide area,
crossing international boundaries, and usually affecting a large number of people.
So vitamin D deficiency is a major, major problem worldwide in the general population,
(03:20):
and that doesn't even take into account insufficiency, let alone the arguments
or debates around what the ideal levels might be for athletes.
Adding to the complexity is there's no universally accepted definition of vitamin D deficiency.
That said, most major organizations use a 25-OHD level of less than 50 nanomoles
(03:41):
per liter, or 20 nanograms per mil in the USA,
as the definition of vitamin D deficiency and therefore the primary treatment goal.
Severe vitamin D deficiency is defined as less than 30 nanomoles per liter,
or 12 nanograms per mil in the USA.
And this is when we see dramatic increases in mortality, infections,
(04:03):
and for athletes, things like injury risk.
Now, before we dive into the levels of athletes and what we see in the research
in the NBA, the NFL, NHL, EPL, and the like, I'm going to share with you a clip from Dr.
Daniel Owens and his recent speaker series, Live Talk in January 2024.
24, all about vitamin D physiology.
Let's revisit the fundamentals so we're all on the same page with how vitamin D works in the body.
(04:28):
So as I said, I'll give a brief overview of the vitamin D system,
more so to try and touch on a few points that I think are important for later
in the talk as it relates to the type of metabolites that we should test,
why we should test them, but also also some of the functional consequences of
having low vitamin D levels as well.
(04:50):
I'm sure most people on the call regard vitamin D as the sunlight vitamin.
I'd be surprised if anyone didn't know that the majority of our vitamin D comes
from sunlight exposure.
It's estimated around 80 to 90% of that comes from ultraviolet B exposure from
the sun, and the rest of that we can get from the diet.
(05:12):
So there's only a modest contribution from the diet of around 10 to 20% of our vitamin D.
There are two main forms of vitamin D that we would get from these different
sources, being vitamin D2 and vitamin D3.
And it's notable that all of the vitamin D that you'll produce in exposure to
(05:32):
sunlight would be vitamin D3.
It's also notable that the main contributor from the diet will also be vitamin D3.
Vitamin D2 plays a much smaller role in our overall vitamin D status.
So we tend to focus our attention around maximizing our intake of vitamin D3.
(05:53):
So regardless of where that vitamin D3 has come from, whether it's been synthesized
in the skin, following exposure to the sun, or whether that comes from the diet.
It has to undergo a couple of steps before it's actually active.
And again, the only reason I'm mentioning this is because it makes sense a little
bit later in the talk when we start to think about how we test vitamin D.
(06:16):
So the first step to activating this vitamin D3 occurs in the liver.
So under the action of an enzyme called 25-hydroxylase. And we end up with this
metabolite, which is often shortened to 25-OHD.
It's 25-hydroxyvitamin D.
And as you'll see later in the talk, it's this metabolite that we measure as
(06:40):
the marker of vitamin D status.
For a number of reasons, which I'll come to after.
That metabolite isn't biologically active as far as we know.
What we do know is there needs to be another hydroxylation or activation step,
which happens in the kidneys under the action of a second enzyme called 1-alpha-hydroxylase.
And then we end up with this 1-alpha-25-OHD.
(07:02):
And it's this, which is the biologically active form of vitamin D.
In terms of the function of this active active metabolite, there are probably
two ways of thinking about this.
The sort of classical action of vitamin D, which is to regulate our calcium levels.
And it does that by increasing intestinal calcium absorption.
(07:24):
So if you've got enough vitamin D coming through the diet, enough calcium coming
through the diet, vitamin D is going to help you to get that out of the the
intestine and into systemic circulation.
But I would say in the past 15, probably 20 years now, we've started to understand
that vitamin D has several other roles in many different tissues throughout the body.
(07:48):
And that is owed to the fact that it can regulate thousands of genes by interacting
with the vitamin D receptor.
It's probably a good time to mention here that.
Unlike other vitamins, vitamin D is probably more similar to a steroid hormone,
hence why it has a receptor which it has to interact with in order to exert its effect.
(08:14):
So that, including the fact that it's also mostly synthesized from the sun,
make it quite unique when we think about it as a vitamin.
Most of our other vitamins are going to come from dietary sources,
and they're certainly not structurally similar to a steroid.
Just to touch on the regulation of
calcium to give you an understanding of how vitamin d
(08:36):
can affect bone and to give
you a scenario basically if you had athletes or
clients who who are going to have or might present with low
vitamin d levels we've already seen the
pathway of vitamin d3 through to the active form
if we have low exposure to sunlight for a long enough period of time or if we
(08:57):
don't get enough of it in the diet as well we'll subsequently have a reduction
in our 25 OHD levels and then over a short period of time we'll have a reduction in our 125 OHD levels.
Now as a consequence of that
we start to get a lack of calcium absorption
(09:17):
from the intestine and very
transiently that will reduce the amount of calcium that
is in our circulation and many of you might already know
that calcium is one of the most tightly regulated
nutrients that we have in the
body such that if blood concentrations deviate
(09:37):
a little bit the body will respond quickly to try and correct that and that's
exactly what happens here if these blood calcium concentrations drop we get
some signaling to our parathyroid gland and as a result we get an increase in
parathyroid hormone being released.
The consequence of that is, firstly, we will increase our levels of 125-OHD.
(10:02):
And in a way, this isn't reflective of the amount of vitamin D3 that we're getting.
So you might have twigged on already that this is one of the reasons we don't
measure as the main marker of vitamin D status,
125-OHD, because you could be seeing an okay level of 125-OHD when,
in fact, your 25-OHD is low.
(10:24):
And this could be having some serious consequences.
The reason that this 125-OHD gets upregulated is partly because it then needs
to have an effect on trying to get calcium from somewhere else in order to maintain
our blood calcium levels.
And the main reservoir of that is going to be in our bone. So if we get this
(10:45):
increase in 125-OHD above normal levels, then what we start to see is is this
calcium being resorbed from our bone, increases blood calcium concentration.
But of course, over time, what that means is the bone mineral density is going to decrease.
So this is typically why in children, you'll see the manifestation of rickets.
(11:07):
In adults, you'll see osteomalacia if they have prolonged severe vitamin D deficiency
and an absence of a strong strong osteogenic stimulus okay so weight lifting
or you know weight bearing activity for example.
Now, what about athletes? The prevalence of vitamin D deficiency in athletes
(11:29):
worldwide follows the prevalence of non-athletic populations,
which is a big concern as it relates not only to athlete health,
but athlete performance, recovery, and injury risk.
In the NBA, low vitamin D is very common.
In fact, a recent study at the NBA Combine found 73.5% of players were affected
(11:50):
insufficiency or deficiency,
insufficiency being defined as less than 75 nanomoles per liter,
or 30 nanograms per mil in the U.S.
Nearly one-third of those players were found to have deficient levels of vitamin D.
This is in line with data from the NFL Combine, who looked at vitamin D insufficiency
(12:11):
in a recent cohort of NFL athletes.
68.8% of players had insufficient vitamin D levels, and 26.3% were deficient.
Interestingly, more than two-thirds of the black athletes had a vitamin D level
that was either deficient or insufficient, while only 23.1% of white NFL players
(12:32):
had a vitamin D level that was insufficient.
And no white athletes were deficient in vitamin D.
The average level of vitamin D in that NFL study was 27.4 nanograms per mil,
which is much lower than what we see in
the nhl a recent study of 105 nhl players
found an average level of 45 nanograms per
(12:53):
mil and most of the nhl players were found to have
sufficient levels of vitamin d interesting to note in the nhl players younger
players in the nhl were more likely to be insufficient compared to players who
are on average three years older this may come back to athlete compliance as
more veteran Veteran players tend to be more compliant with things like supplementation or guidelines.
(13:16):
Now, in this cohort of NHL players, 96.2% were white and only 3.8% were black,
compared to 84% of athletes in the NFL study.
We know that dark skin pigmentation is a known risk factor for vitamin D insufficiency.
The increased melanin found in the skin of darkly pigmented individuals can
actually increase the amount of time to synthesize and make vitamin D up to
(13:40):
tenfold, meaning you need to
get out in the sun a heck of a lot longer the darker your skin complexion.
Now what about the English Premier League?
A high-skill sport like basketball but played outside.
The prevalence of vitamin D deficiency in the English Premier League was approximately
36%, so about one-third of players.
This does not include insufficiency. If we look at popular indoor sports in Europe like handball.
(14:07):
We also see a high prevalence of insufficiency at 44%, even in the summer months
when you'd expect peak blood levels.
So if we zoom out to 30,000 feet, where does this leave us amongst elite and
professional athletes?
Well, a recent meta-analysis of over 51 studies And over 5,000 elite athletes
(14:27):
found that approximately 30% of adult athletes had vitamin D levels,
that's 25 OHG, less than 50 nanomoles per liter.
So about one-third of athletes are deficient in vitamin D.
If we look at teens and adolescents, that number jumps to 39%.
And this doesn't even take into account athletes with insufficient levels of
(14:50):
vitamin D, as well as an optimal level of vitamin D, which is again debatable
on the number that you might target with athletes.
Before we dive into who is at increased risk of vitamin D insufficiency and
deficiency, blood testing and target values, I want to circle back to another clip from Dr.
Daniel Owens at our recent speaker series in January to shed some more light
(15:13):
on the direct and indirect performance effects of vitamin D for athletes.
So we'll switch our focus towards the implication of vitamin D in sports performance now.
I'm sure that's what we're all here today to hear about.
I like to think about this and I've started I suppose in the past three or four
(15:33):
years to think about vitamin D's impact on performance,
in this way which is that we think it probably has indirect and direct effects on performance.
And so the indirect effects in my mind would be the effect on athlete availability.
So that would mean changes in immunity, potentially some impact on muscle repair,
(15:55):
and perhaps an influence on injury risk.
If i was to say where vitamin
d might have the greatest effect for the athlete i
actually think it would be in these indirect effects affecting athlete availability
rather than the direct effects those direct effects we would say are related
(16:16):
to muscle function and muscle metabolism so i'll try and give an overview of
these key areas as it relates to the athlete in the coming in slides.
So in terms of vitamin D and muscle, the first one is related to our mitochondria.
This is a big research focus for us at the moment in our lab,
and there's been substantial evidence that's been published over the past few
(16:39):
years, really, that show this link between vitamin D and mitochondrial function.
One of the first papers that came out around this was on vitamin D and phosphocreatine
recovery half-time, as well as ATP recovery half-time as well in humans,
which was the SYNAP paper in 2013,
which really showed evidence that if you have severe vitamin D deficiency,
(17:02):
the ability to recover these high energy phosphates in the muscle is disturbed.
And that's directly related to mitochondrial function.
Since then, we've seen that elements of the the vitamin D system are also really
important for oxidative capacity in vitro and in vivo.
So in our basic biology type research, but also in real life situations as well.
(17:29):
Some of the work I focused on a few years ago was related to vitamin D and its
ability to interact with elements of muscle that control muscle repair.
So we showed in humans that as As vitamin D levels decline below 75 nanomoles
per liter, we start to see decrements in the ability to recover force after
exercise-induced muscle damage.
(17:50):
And we also tried to explore this a little bit more from a basic biology perspective as well.
And we found that the sort of resident stem cells in the muscle,
the satellite cells, have a requirement for vitamin D.
They express the vitamin D receptor and they sort of need vitamin D to function in a way.
As it relates to athletes and perhaps injury or the repair from injury as well,
(18:15):
there was one study published in NFL Players a few years ago indicating an association
between muscle strain incidents when players had 25-0 HD levels that were low.
We'll get into what constitutes low a little bit later.
Now, I'd say here the caveat is that that is an observational type study.
(18:35):
So you can't infer causality in that last point there.
And finally, as it relates to physical performance, some of our colleagues here
at John Moores have looked at vitamin D levels in large cohorts of military
recruits and found that we see decrements in physical performance parameters
as vitamin D levels start to decline.
(18:57):
Now, again, that's more of an observational type piece of work.
It there's no direct cause and effect but it corroborates
some other evidence that we can see from from basic biology studies
an area that i think is really important for the athletes some of the athletes
that i work with that travel a lot this is something that we're highly conscious
(19:19):
of is is their immunity and what can we do to support it vitamin d has been
implicated in with with the immune system for a long time.
Probably one of the early studies on vitamin D was all around the immune system, really,
where we see a seasonal variation in the risk of infection that quite tightly
(19:39):
correlates sunlight exposure and also therefore our vitamin D levels.
In athletes, we also have fairly good evidence for a link between vitamin D and their immunity.
We've seen studies from here in the UK in both athletes and military personnel
and L, which show this negative association between the amount of vitamin D
that you've got and the frequency of upper respiratory tract infections.
(20:05):
We also know that whilst the frequency of infection,
the likelihood of you getting an infection increases as your vitamin D goes down,
the severity of that infection will also
increase as your vitamin D status goes down
as well so that means you have more days
with symptoms and the symptoms themselves are
(20:27):
typically rated as being more severe in those
that have low vitamin d levels so if
we're trying to keep athletes healthy for as long as we can throughout the year
minimize their risk of losing days to train and this is something that we need
to think about so what athletes are at highest risk of of vitamin D deficiency
(20:47):
or vitamin D insufficiency.
If you have athletes that train early in the morning or training late at night,
you're at increased risk.
If your athletes wear uniforms or sports gear that covers their limbs and protects
against the ultraviolet B light, that is also increasing risk of insufficiency or deficiency.
(21:08):
If you play an indoor sport, obviously that also increases risks as well.
Even in the summer months, due to modern lifestyles, if you live in a hot area,
you're probably indoors more. and the consistent use of sunscreen when you're
even outside is protecting against that UVB radiation.
And if you're not getting it on the skin, then you won't be able to convert it into vitamin D.
(21:29):
Now, obviously, you need to be sensible and ensure you don't burn and increase
that risk for things like skin cancer.
Now, how do we get enough vitamin D?
Exposure to natural sunlight is the most effective way to increase 250H vitamin D levels.
Obviously, in winter months at northern latitudes, the intensity of the sun
is not going to be sufficient to be able to uptake enough UVB rays.
(21:55):
Can you just eat more vitamin D-rich foods in your diet?
Well, we've seen a couple papers highlighting that dietary vitamin D intake
through natural food sources often cannot compensate for insufficient sun exposure
due to low vitamin D amounts in the typical Western diet. it.
We also see from the Journal of Clinical Nutrition, even an increased intake
(22:16):
of fatty fish, which contains some of the highest amounts of vitamin D in food
sources, was not able to increase 25-OHD levels substantially.
So supplementing then in the winter months becomes the main strategy.
Now, what about vitamin D dosing? In this next clip, you'll hear from Dr.
Michael Gleason, PhD, exercise immunologist from Lefborough University in the
(22:39):
UK, from our conversation in Season 6,
Episode 1 of the Performance Nutrition Podcast about a general vitamin D dosing
strategy and what the upper ends of the range to target might be.
Yeah, well, vitamin D status is usually measured by taking a blood sample and
measuring the concentration of 25-hydroxyvitamin D in the blood serum.
(23:05):
Serum that's derived that's derived from what's being produced
in in the liver where that first hydroxylation of the vitamin d precursor molecule
takes takes place and that seems to give us a good measure the concentration
of that in nanomoles per liter gives us a good measure of vitamin d status you
have different classifications of it so it's less than 30.
(23:27):
That's deficient if it's less than 50 it's considered inadequate and somewhere
above 50 and up to about 150 is the desirable range to be in.
For bones, certainly 50 is considered the,
the adequate value for immune
function it seems it's probably somewhat higher so probably
(23:49):
in excess of 100 would be desirable and
at least 75 nothing below that really
and studies have actually measured various markers of
immune function in athletes some of which we did
ourselves and i was working at loughborough in
the labs there we we found that the the best
protection for the athlete against picking up infections
(24:10):
and against getting you know more
severe longer lasting symptoms when they did get infected was
with above 120 animal
per liter you don't want to go too high
you can only achieve that with your regular exposure to sunlight or by taking
vitamin d supplementation there is a limit that's suggested to be 4 000 international
(24:33):
international units per day is the maximum you should take to avoid going above
150 nanomoles per litre, which could potentially be harmful.
And I mean, probably 2000 international units per day is what we recommend for
an athlete that will ensure that they have levels that are in excess of at least
(24:54):
75 nanomoles per litre of that metabolite. So that's good.
I think going to the training camp is just sort of
a perhaps a psychological boost you know a change
of scene a bit of nice warm sunshine making the
players or the the athletes feel good and
the observations that have been made on
people who don't take supplements but who are living in sunny environments you
(25:20):
know your your vitamin d concentration the 25 hydroxy vitamin d in the blood
never goes above above 150 because we regulate it and we stop producing vitamin
D in the body when we get to that level.
So that's more or less telling you the body doesn't want to go above about 150,
so don't do it with supplements.
(25:42):
In this final clip, you'll hear another excerpt from Dr. Daniel Owens of what
practitioners are currently doing.
Music.
When it comes to what practitioners are currently doing, and again,
(26:03):
this is data from the article we haven't published yet, most practitioners are
using vitamin D3, which was a relief for me to see.
Some are getting that in the form of a multivitamin. I don't see any problem
with that at all, as long as it's the right dose. dose.
Most get it from oral capsules. I know there are different products on the market
now, such as liquid drops, oral sprays, and chews.
(26:25):
There's not much evidence to suggest
there's any difference really in the bioavailability of these products.
So I think if you've got any of these, they're probably doing the job.
In terms of the dosing, I was quite surprised to see quite a bit of heterogeneity here.
Most people land around the right mark of 1,000 to 2,000 international units,
(26:47):
but we're still seeing people use upwards of 5,000 international units per day
or a case by case approach.
And at the moment, I don't really know what evidence there is for a case by case approach. Okay.
If we look at how often people are given their vitamin D, most are given it
(27:08):
daily, but we're still seeing some weekly and some bi-weekly and some monthly as well.
So, as I said before, how do we achieve levels that are considered to be sufficient?
In my mind, this is probably the best paper that has combined two different
approaches to show how we can achieve sufficiency.
(27:29):
This was done in military recruits by my colleagues here at John Moores University. Okay.
They took an approach where they either provided simulated sunlight exposure,
so a low dose of ultraviolet B.
This is 1.3 standard erythemal dose. That means that you are not burning the skin.
(27:49):
It's like a minimal dose, just about see a little bit of rosiness in the skin,
but it does not burn the skin. Okay, so it's safe sun exposure.
They did that three times a week for four weeks and them once a week or they
provided a thousand international units a day for four weeks and then 400 international
units a day for the following eight weeks.
(28:10):
And you can see that in both cases this takes people from inadequacy to a normal level of vitamin D.
I would say that you could probably just land at a thousand or two thousand
a day and keep people on that through the winter and that would be effective.
What it also does show is that during the summer months seeking safe sun exposure
is a way that we can maintain vitamin D through the summer that will help us
(28:35):
through the winter as well.
That wraps things up for episode one of season number eight.
I hope you enjoyed the episode. If you'd like to take a deeper dive and watch
the full 60-minute talk from Dr.
Daniel Owens, then head over to drbubbs.com forward slash APN.
That's drbubbs.com forward slash APN. and you can register for the new members
(29:00):
area called the Locker Room for only $9 a month and access this talk and more.
Or register for the annual subscription and save 20% off.
Again, that's drbubbs.com forward slash APN.
Our next live speaker series talk is Monday, February 26th at 3 p.m.
(29:21):
Eastern, 12 p.m. Pacific.
You can register free by visiting drbubbs.com forward slash APN and join us
for this live talk and Q&A session.
All right, that's it for this week. Appreciate you listening.
Please subscribe and leave a review on iTunes or Spotify.
If you enjoyed the content, it's a very big help to the show. See everyone next time.
(29:44):
The Dr. Bubz Performance Podcast
endeavors to provide accurate and helpful information to listeners.
These podcasts cannot take into account individual circumstances and are not
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In the winter, we simply do not get enough sunlight, particularly at northerly latitude.
Ideally, we would want to test the athlete to see whether that's even necessary.
And if it is necessary, we'd recommend it as a weekly, as a daily dose,
not a weekly or monthly bolus.
Music.
Welcome to the Performance Nutrition Podcast, giving you the latest evidence-based
(00:22):
research and cutting edge insights for elite mental and physical performance.
He's connecting you directly with the world's leading experts and coaches.
Here's your host, Dr. Bubbs.
Welcome back or welcome to the Performance Nutrition Podcast.
I'm Dr. Mark Bubbs, performance nutritionist, and this is season number eight.
(00:44):
This season, we'll be taking a deeper dive on specific topics with the latest
up-to-date evidence-based insights from a broad range of experts as part of our new speaker series,
where you can attend live lectures from experts in the field.
In today's episode, I'll be sharing highlights from our first speaker series live talk with Dr.
(01:05):
Daniel Owens, PhD from Liverpool, John Moores, all on vitamin D in athletes,
health, performance, and testing.
The speaker series live events are free to attend.
And if you missed it, you can access the talk by signing up for our new members
area called the locker room.
For just $9 per month, you can join the locker room members area and stay up
(01:26):
to date on all the latest in performance nutrition from top experts across the
world working in elite and pro sport.
Head over to DrBubz.com forward slash subscribe to register to join the locker
room and keep leveling up your nutrition game.
You can save 20% off with our annual subscription.
All right, let's get the ball rolling. Vitamin D in athletes,
(01:47):
health, performance, and testing.
To kick things off in this episode, let's zoom out to 30,000 feet.
The prevalence of vitamin D deficiency is increasing worldwide,
and the rate at which it's increasing is pretty alarming, to the point where as far back as 2016.
The American Journal of Clinical Nutrition made the case that it could even
(02:10):
be considered a pandemic.
More on that in a minute. The percentage of adults in America with vitamin D
deficiency ranges from 36% to 57%.
So that's about one-third to half the population, or to really appreciate it,
approximately 100 to 150 million Americans.
What about in Europe? A recent 2016 review suggests vitamin D deficiency is
(02:35):
also widespread across Europe.
A European sampling of children, teenagers, adults, and older adults,
over 50,000 people ranging from southern to mid to northern European member
states, found that 13% had vitamin D deficiency,
which in this study was defined as 30 nanomoles per liter in international units
(02:56):
or 12 nanograms per mil in American units.
This prevalence rate actually meets the criteria for a pandemic,
defined as an epidemic occurring worldwide or over a very wide area,
crossing international boundaries, and usually affecting a large number of people.
So vitamin D deficiency is a major, major problem worldwide in the general population,
(03:20):
and that doesn't even take into account insufficiency, let alone the arguments
or debates around what the ideal levels might be for athletes.
Adding to the complexity is there's no universally accepted definition of vitamin D deficiency.
That said, most major organizations use a 25-OHD level of less than 50 nanomoles
(03:41):
per liter, or 20 nanograms per mil in the USA,
as the definition of vitamin D deficiency and therefore the primary treatment goal.
Severe vitamin D deficiency is defined as less than 30 nanomoles per liter,
or 12 nanograms per mil in the USA.
And this is when we see dramatic increases in mortality, infections,
(04:03):
and for athletes, things like injury risk.
Now, before we dive into the levels of athletes and what we see in the research
in the NBA, the NFL, NHL, EPL, and the like, I'm going to share with you a clip from Dr.
Daniel Owens and his recent speaker series, Live Talk in January 2024.
24, all about vitamin D physiology.
Let's revisit the fundamentals so we're all on the same page with how vitamin D works in the body.
(04:28):
So as I said, I'll give a brief overview of the vitamin D system,
more so to try and touch on a few points that I think are important for later
in the talk as it relates to the type of metabolites that we should test,
why we should test them, but also also some of the functional consequences of
having low vitamin D levels as well.
(04:50):
I'm sure most people on the call regard vitamin D as the sunlight vitamin.
I'd be surprised if anyone didn't know that the majority of our vitamin D comes
from sunlight exposure.
It's estimated around 80 to 90% of that comes from ultraviolet B exposure from
the sun, and the rest of that we can get from the diet.
(05:12):
So there's only a modest contribution from the diet of around 10 to 20% of our vitamin D.
There are two main forms of vitamin D that we would get from these different
sources, being vitamin D2 and vitamin D3.
And it's notable that all of the vitamin D that you'll produce in exposure to
(05:32):
sunlight would be vitamin D3.
It's also notable that the main contributor from the diet will also be vitamin D3.
Vitamin D2 plays a much smaller role in our overall vitamin D status.
So we tend to focus our attention around maximizing our intake of vitamin D3.
(05:53):
So regardless of where that vitamin D3 has come from, whether it's been synthesized
in the skin, following exposure to the sun, or whether that comes from the diet.
It has to undergo a couple of steps before it's actually active.
And again, the only reason I'm mentioning this is because it makes sense a little
bit later in the talk when we start to think about how we test vitamin D.
(06:16):
So the first step to activating this vitamin D3 occurs in the liver.
So under the action of an enzyme called 25-hydroxylase. And we end up with this
metabolite, which is often shortened to 25-OHD.
It's 25-hydroxyvitamin D.
And as you'll see later in the talk, it's this metabolite that we measure as
(06:40):
the marker of vitamin D status.
For a number of reasons, which I'll come to after.
That metabolite isn't biologically active as far as we know.
What we do know is there needs to be another hydroxylation or activation step,
which happens in the kidneys under the action of a second enzyme called 1-alpha-hydroxylase.
And then we end up with this 1-alpha-25-OHD.
(07:02):
And it's this, which is the biologically active form of vitamin D.
In terms of the function of this active active metabolite, there are probably
two ways of thinking about this.
The sort of classical action of vitamin D, which is to regulate our calcium levels.
And it does that by increasing intestinal calcium absorption.
(07:24):
So if you've got enough vitamin D coming through the diet, enough calcium coming
through the diet, vitamin D is going to help you to get that out of the the
intestine and into systemic circulation.
But I would say in the past 15, probably 20 years now, we've started to understand
that vitamin D has several other roles in many different tissues throughout the body.
(07:48):
And that is owed to the fact that it can regulate thousands of genes by interacting
with the vitamin D receptor.
It's probably a good time to mention here that.
Unlike other vitamins, vitamin D is probably more similar to a steroid hormone,
hence why it has a receptor which it has to interact with in order to exert its effect.
(08:14):
So that, including the fact that it's also mostly synthesized from the sun,
make it quite unique when we think about it as a vitamin.
Most of our other vitamins are going to come from dietary sources,
and they're certainly not structurally similar to a steroid.
Just to touch on the regulation of
calcium to give you an understanding of how vitamin d
(08:36):
can affect bone and to give
you a scenario basically if you had athletes or
clients who who are going to have or might present with low
vitamin d levels we've already seen the
pathway of vitamin d3 through to the active form
if we have low exposure to sunlight for a long enough period of time or if we
(08:57):
don't get enough of it in the diet as well we'll subsequently have a reduction
in our 25 OHD levels and then over a short period of time we'll have a reduction in our 125 OHD levels.
Now as a consequence of that
we start to get a lack of calcium absorption
(09:17):
from the intestine and very
transiently that will reduce the amount of calcium that
is in our circulation and many of you might already know
that calcium is one of the most tightly regulated
nutrients that we have in the
body such that if blood concentrations deviate
(09:37):
a little bit the body will respond quickly to try and correct that and that's
exactly what happens here if these blood calcium concentrations drop we get
some signaling to our parathyroid gland and as a result we get an increase in
parathyroid hormone being released.
The consequence of that is, firstly, we will increase our levels of 125-OHD.
(10:02):
And in a way, this isn't reflective of the amount of vitamin D3 that we're getting.
So you might have twigged on already that this is one of the reasons we don't
measure as the main marker of vitamin D status,
125-OHD, because you could be seeing an okay level of 125-OHD when,
in fact, your 25-OHD is low.
(10:24):
And this could be having some serious consequences.
The reason that this 125-OHD gets upregulated is partly because it then needs
to have an effect on trying to get calcium from somewhere else in order to maintain
our blood calcium levels.
And the main reservoir of that is going to be in our bone. So if we get this
(10:45):
increase in 125-OHD above normal levels, then what we start to see is is this
calcium being resorbed from our bone, increases blood calcium concentration.
But of course, over time, what that means is the bone mineral density is going to decrease.
So this is typically why in children, you'll see the manifestation of rickets.
(11:07):
In adults, you'll see osteomalacia if they have prolonged severe vitamin D deficiency
and an absence of a strong strong osteogenic stimulus okay so weight lifting
or you know weight bearing activity for example.
Now, what about athletes? The prevalence of vitamin D deficiency in athletes
(11:29):
worldwide follows the prevalence of non-athletic populations,
which is a big concern as it relates not only to athlete health,
but athlete performance, recovery, and injury risk.
In the NBA, low vitamin D is very common.
In fact, a recent study at the NBA Combine found 73.5% of players were affected
(11:50):
insufficiency or deficiency,
insufficiency being defined as less than 75 nanomoles per liter,
or 30 nanograms per mil in the U.S.
Nearly one-third of those players were found to have deficient levels of vitamin D.
This is in line with data from the NFL Combine, who looked at vitamin D insufficiency
(12:11):
in a recent cohort of NFL athletes.
68.8% of players had insufficient vitamin D levels, and 26.3% were deficient.
Interestingly, more than two-thirds of the black athletes had a vitamin D level
that was either deficient or insufficient, while only 23.1% of white NFL players
(12:32):
had a vitamin D level that was insufficient.
And no white athletes were deficient in vitamin D.
The average level of vitamin D in that NFL study was 27.4 nanograms per mil,
which is much lower than what we see in
the nhl a recent study of 105 nhl players
found an average level of 45 nanograms per
(12:53):
mil and most of the nhl players were found to have
sufficient levels of vitamin d interesting to note in the nhl players younger
players in the nhl were more likely to be insufficient compared to players who
are on average three years older this may come back to athlete compliance as
more veteran Veteran players tend to be more compliant with things like supplementation or guidelines.
(13:16):
Now, in this cohort of NHL players, 96.2% were white and only 3.8% were black,
compared to 84% of athletes in the NFL study.
We know that dark skin pigmentation is a known risk factor for vitamin D insufficiency.
The increased melanin found in the skin of darkly pigmented individuals can
actually increase the amount of time to synthesize and make vitamin D up to
(13:40):
tenfold, meaning you need to
get out in the sun a heck of a lot longer the darker your skin complexion.
Now what about the English Premier League?
A high-skill sport like basketball but played outside.
The prevalence of vitamin D deficiency in the English Premier League was approximately
36%, so about one-third of players.
This does not include insufficiency. If we look at popular indoor sports in Europe like handball.
(14:07):
We also see a high prevalence of insufficiency at 44%, even in the summer months
when you'd expect peak blood levels.
So if we zoom out to 30,000 feet, where does this leave us amongst elite and
professional athletes?
Well, a recent meta-analysis of over 51 studies And over 5,000 elite athletes
(14:27):
found that approximately 30% of adult athletes had vitamin D levels,
that's 25 OHG, less than 50 nanomoles per liter.
So about one-third of athletes are deficient in vitamin D.
If we look at teens and adolescents, that number jumps to 39%.
And this doesn't even take into account athletes with insufficient levels of
(14:50):
vitamin D, as well as an optimal level of vitamin D, which is again debatable
on the number that you might target with athletes.
Before we dive into who is at increased risk of vitamin D insufficiency and
deficiency, blood testing and target values, I want to circle back to another clip from Dr.
Daniel Owens at our recent speaker series in January to shed some more light
(15:13):
on the direct and indirect performance effects of vitamin D for athletes.
So we'll switch our focus towards the implication of vitamin D in sports performance now.
I'm sure that's what we're all here today to hear about.
I like to think about this and I've started I suppose in the past three or four
(15:33):
years to think about vitamin D's impact on performance,
in this way which is that we think it probably has indirect and direct effects on performance.
And so the indirect effects in my mind would be the effect on athlete availability.
So that would mean changes in immunity, potentially some impact on muscle repair,
(15:55):
and perhaps an influence on injury risk.
If i was to say where vitamin
d might have the greatest effect for the athlete i
actually think it would be in these indirect effects affecting athlete availability
rather than the direct effects those direct effects we would say are related
(16:16):
to muscle function and muscle metabolism so i'll try and give an overview of
these key areas as it relates to the athlete in the coming in slides.
So in terms of vitamin D and muscle, the first one is related to our mitochondria.
This is a big research focus for us at the moment in our lab,
and there's been substantial evidence that's been published over the past few
(16:39):
years, really, that show this link between vitamin D and mitochondrial function.
One of the first papers that came out around this was on vitamin D and phosphocreatine
recovery half-time, as well as ATP recovery half-time as well in humans,
which was the SYNAP paper in 2013,
which really showed evidence that if you have severe vitamin D deficiency,
(17:02):
the ability to recover these high energy phosphates in the muscle is disturbed.
And that's directly related to mitochondrial function.
Since then, we've seen that elements of the the vitamin D system are also really
important for oxidative capacity in vitro and in vivo.
So in our basic biology type research, but also in real life situations as well.
(17:29):
Some of the work I focused on a few years ago was related to vitamin D and its
ability to interact with elements of muscle that control muscle repair.
So we showed in humans that as As vitamin D levels decline below 75 nanomoles
per liter, we start to see decrements in the ability to recover force after
exercise-induced muscle damage.
(17:50):
And we also tried to explore this a little bit more from a basic biology perspective as well.
And we found that the sort of resident stem cells in the muscle,
the satellite cells, have a requirement for vitamin D.
They express the vitamin D receptor and they sort of need vitamin D to function in a way.
As it relates to athletes and perhaps injury or the repair from injury as well,
(18:15):
there was one study published in NFL Players a few years ago indicating an association
between muscle strain incidents when players had 25-0 HD levels that were low.
We'll get into what constitutes low a little bit later.
Now, I'd say here the caveat is that that is an observational type study.
(18:35):
So you can't infer causality in that last point there.
And finally, as it relates to physical performance, some of our colleagues here
at John Moores have looked at vitamin D levels in large cohorts of military
recruits and found that we see decrements in physical performance parameters
as vitamin D levels start to decline.
(18:57):
Now, again, that's more of an observational type piece of work.
It there's no direct cause and effect but it corroborates
some other evidence that we can see from from basic biology studies
an area that i think is really important for the athletes some of the athletes
that i work with that travel a lot this is something that we're highly conscious
(19:19):
of is is their immunity and what can we do to support it vitamin d has been
implicated in with with the immune system for a long time.
Probably one of the early studies on vitamin D was all around the immune system, really,
where we see a seasonal variation in the risk of infection that quite tightly
(19:39):
correlates sunlight exposure and also therefore our vitamin D levels.
In athletes, we also have fairly good evidence for a link between vitamin D and their immunity.
We've seen studies from here in the UK in both athletes and military personnel
and L, which show this negative association between the amount of vitamin D
that you've got and the frequency of upper respiratory tract infections.
(20:05):
We also know that whilst the frequency of infection,
the likelihood of you getting an infection increases as your vitamin D goes down,
the severity of that infection will also
increase as your vitamin D status goes down
as well so that means you have more days
with symptoms and the symptoms themselves are
(20:27):
typically rated as being more severe in those
that have low vitamin d levels so if
we're trying to keep athletes healthy for as long as we can throughout the year
minimize their risk of losing days to train and this is something that we need
to think about so what athletes are at highest risk of of vitamin D deficiency
(20:47):
or vitamin D insufficiency.
If you have athletes that train early in the morning or training late at night,
you're at increased risk.
If your athletes wear uniforms or sports gear that covers their limbs and protects
against the ultraviolet B light, that is also increasing risk of insufficiency or deficiency.
(21:08):
If you play an indoor sport, obviously that also increases risks as well.
Even in the summer months, due to modern lifestyles, if you live in a hot area,
you're probably indoors more. and the consistent use of sunscreen when you're
even outside is protecting against that UVB radiation.
And if you're not getting it on the skin, then you won't be able to convert it into vitamin D.
(21:29):
Now, obviously, you need to be sensible and ensure you don't burn and increase
that risk for things like skin cancer.
Now, how do we get enough vitamin D?
Exposure to natural sunlight is the most effective way to increase 250H vitamin D levels.
Obviously, in winter months at northern latitudes, the intensity of the sun
is not going to be sufficient to be able to uptake enough UVB rays.
(21:55):
Can you just eat more vitamin D-rich foods in your diet?
Well, we've seen a couple papers highlighting that dietary vitamin D intake
through natural food sources often cannot compensate for insufficient sun exposure
due to low vitamin D amounts in the typical Western diet. it.
We also see from the Journal of Clinical Nutrition, even an increased intake
(22:16):
of fatty fish, which contains some of the highest amounts of vitamin D in food
sources, was not able to increase 25-OHD levels substantially.
So supplementing then in the winter months becomes the main strategy.
Now, what about vitamin D dosing? In this next clip, you'll hear from Dr.
Michael Gleason, PhD, exercise immunologist from Lefborough University in the
(22:39):
UK, from our conversation in Season 6,
Episode 1 of the Performance Nutrition Podcast about a general vitamin D dosing
strategy and what the upper ends of the range to target might be.
Yeah, well, vitamin D status is usually measured by taking a blood sample and
measuring the concentration of 25-hydroxyvitamin D in the blood serum.
(23:05):
Serum that's derived that's derived from what's being produced
in in the liver where that first hydroxylation of the vitamin d precursor molecule
takes takes place and that seems to give us a good measure the concentration
of that in nanomoles per liter gives us a good measure of vitamin d status you
have different classifications of it so it's less than 30.
(23:27):
That's deficient if it's less than 50 it's considered inadequate and somewhere
above 50 and up to about 150 is the desirable range to be in.
For bones, certainly 50 is considered the,
the adequate value for immune
function it seems it's probably somewhat higher so probably
(23:49):
in excess of 100 would be desirable and
at least 75 nothing below that really
and studies have actually measured various markers of
immune function in athletes some of which we did
ourselves and i was working at loughborough in
the labs there we we found that the the best
protection for the athlete against picking up infections
(24:10):
and against getting you know more
severe longer lasting symptoms when they did get infected was
with above 120 animal
per liter you don't want to go too high
you can only achieve that with your regular exposure to sunlight or by taking
vitamin d supplementation there is a limit that's suggested to be 4 000 international
(24:33):
international units per day is the maximum you should take to avoid going above
150 nanomoles per litre, which could potentially be harmful.
And I mean, probably 2000 international units per day is what we recommend for
an athlete that will ensure that they have levels that are in excess of at least
(24:54):
75 nanomoles per litre of that metabolite. So that's good.
I think going to the training camp is just sort of
a perhaps a psychological boost you know a change
of scene a bit of nice warm sunshine making the
players or the the athletes feel good and
the observations that have been made on
people who don't take supplements but who are living in sunny environments you
(25:20):
know your your vitamin d concentration the 25 hydroxy vitamin d in the blood
never goes above above 150 because we regulate it and we stop producing vitamin
D in the body when we get to that level.
So that's more or less telling you the body doesn't want to go above about 150,
so don't do it with supplements.
(25:42):
In this final clip, you'll hear another excerpt from Dr. Daniel Owens of what
practitioners are currently doing.
Music.
When it comes to what practitioners are currently doing, and again,
(26:03):
this is data from the article we haven't published yet, most practitioners are
using vitamin D3, which was a relief for me to see.
Some are getting that in the form of a multivitamin. I don't see any problem
with that at all, as long as it's the right dose. dose.
Most get it from oral capsules. I know there are different products on the market
now, such as liquid drops, oral sprays, and chews.
(26:25):
There's not much evidence to suggest
there's any difference really in the bioavailability of these products.
So I think if you've got any of these, they're probably doing the job.
In terms of the dosing, I was quite surprised to see quite a bit of heterogeneity here.
Most people land around the right mark of 1,000 to 2,000 international units,
(26:47):
but we're still seeing people use upwards of 5,000 international units per day
or a case by case approach.
And at the moment, I don't really know what evidence there is for a case by case approach. Okay.
If we look at how often people are given their vitamin D, most are given it
(27:08):
daily, but we're still seeing some weekly and some bi-weekly and some monthly as well.
So, as I said before, how do we achieve levels that are considered to be sufficient?
In my mind, this is probably the best paper that has combined two different
approaches to show how we can achieve sufficiency.
(27:29):
This was done in military recruits by my colleagues here at John Moores University. Okay.
They took an approach where they either provided simulated sunlight exposure,
so a low dose of ultraviolet B.
This is 1.3 standard erythemal dose. That means that you are not burning the skin.
(27:49):
It's like a minimal dose, just about see a little bit of rosiness in the skin,
but it does not burn the skin. Okay, so it's safe sun exposure.
They did that three times a week for four weeks and them once a week or they
provided a thousand international units a day for four weeks and then 400 international
units a day for the following eight weeks.
(28:10):
And you can see that in both cases this takes people from inadequacy to a normal level of vitamin D.
I would say that you could probably just land at a thousand or two thousand
a day and keep people on that through the winter and that would be effective.
What it also does show is that during the summer months seeking safe sun exposure
is a way that we can maintain vitamin D through the summer that will help us
(28:35):
through the winter as well.
That wraps things up for episode one of season number eight.
I hope you enjoyed the episode. If you'd like to take a deeper dive and watch
the full 60-minute talk from Dr.
Daniel Owens, then head over to drbubbs.com forward slash APN.
That's drbubbs.com forward slash APN. and you can register for the new members
(29:00):
area called the Locker Room for only $9 a month and access this talk and more.
Or register for the annual subscription and save 20% off.
Again, that's drbubbs.com forward slash APN.
Our next live speaker series talk is Monday, February 26th at 3 p.m.
(29:21):
Eastern, 12 p.m. Pacific.
You can register free by visiting drbubbs.com forward slash APN and join us
for this live talk and Q&A session.
All right, that's it for this week. Appreciate you listening.
Please subscribe and leave a review on iTunes or Spotify.
If you enjoyed the content, it's a very big help to the show. See everyone next time.
(29:44):
The Dr. Bubz Performance Podcast
endeavors to provide accurate and helpful information to listeners.
These podcasts cannot take into account individual circumstances and are not
intended to be a substitute for health and medical advice from a qualified health professional.
You should always seek the advice of a qualified health professional before
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