Vitamin D

Summary

In this educational video, Dr. Mike explores the importance of Vitamin D, a fat-soluble nutrient essential for growth and development. He explains how UV exposure from sunlight is the primary source of Vitamin D, which is then converted into its active form, calcitriol, in the liver and kidneys. This active form is crucial for calcium and phosphate regulation, impacting bone health. Dr. Mike also discusses the consequences of Vitamin D deficiency, such as rickets in children and osteomalacia in adults, and the risks of over-supplementation, including kidney stones and nervous system depression.

Takeaways

• 🌞 Vitamin D is a fat-soluble vitamin, one of the four (D, E, K, A), and is essential for normal growth and development.
• 💧 Our primary source of Vitamin D is UV exposure or sunlight, which triggers the conversion of 7-dehydrocholesterol in the skin to cholecalciferol (Vitamin D3).
• 🥩 We can also obtain Vitamin D from certain foods, such as fish and liver (animal products) and UV-activated mushrooms (plant products), but in smaller amounts.
• 🔄 The liver plays a crucial role in the synthesis of Vitamin D by converting cholecalciferol into 25-hydroxycalciferol (calcidiol) through the action of 25-hydroxylase enzyme.
• 🔎 The kidneys further metabolize calcidiol into the active form of Vitamin D, calcitriol (1,25-dihydroxycalciferol), facilitated by the 1-alpha hydroxylase enzyme.
• 🔑 Vitamin D's active form, calcitriol, is vital for increasing calcium and phosphate levels in the blood, which are crucial for bone health.
• 🚫 Vitamin D deficiency is widespread, affecting about 50% of the world's population, often due to inadequate sunlight exposure and can lead to rickets in children and osteomalacia in adults.
• 💡 The parathyroid gland releases parathyroid hormone (PTH) in response to low calcium levels, which in turn stimulates the kidneys to activate more Vitamin D and increase calcium absorption.
• ⚠️ Both Vitamin D deficiency and excess can have serious health implications, with the latter potentially leading to hypercalcemia, kidney stones, and nervous system depression.
• 💊 Supplementation is a common way to address Vitamin D deficiency, but it's important to monitor intake to avoid the risks associated with over-supplementation.

Q & A

What are the four fat-soluble vitamins?

The four fat-soluble vitamins are D, E, K, and A.

How does vitamin D differ from water-soluble vitamins?

Vitamin D, being fat-soluble, can be stored in the body's fatty layers, whereas water-soluble vitamins are often excreted more quickly.

What is the primary source of vitamin D for humans?

The primary source of vitamin D is through UV exposure or sunlight.

What happens in the skin when it's exposed to UV light?

UV light triggers the conversion of 7-dehydrocholesterol into cholecalciferol (vitamin D3).

How does the liver process cholecalciferol?

In the liver, cholecalciferol is converted to 25-hydroxycholecalciferol (calcifediol) by the enzyme 25-hydroxylase.

What is the role of kidneys in the activation of vitamin D?

The kidneys convert calcifediol into calcitriol (1,25-dihydroxycholecalciferol) using the enzyme 1-alpha hydroxylase.

Why is the enzyme 1-alpha hydroxylase significant?

1-alpha hydroxylase is significant because it's activated by low calcium and phosphate levels, and it's responsible for converting calcifediol into the active form of vitamin D, calcitriol.

What does active vitamin D (calcitriol) do in the body?

Active vitamin D increases calcium and phosphate levels in the blood by enhancing absorption in the gastrointestinal tract, reabsorption in the kidneys, and bone resorption.

How does vitamin D deficiency affect bone health?

Deficiency in vitamin D can lead to rickets in children, characterized by bendy bones, and osteomalacia in adults, resulting in brittle bones.

What are the recommended daily intakes of vitamin D for different age groups?

For someone under one year, it's about 400 international units, for those between 1 to 70 years it's 600 international units, and for those above 70 years, it's 800 international units.

What are the symptoms of vitamin D overdose?

Overdosing on vitamin D can lead to kidney stones, bone pain, abdominal pain due to muscle contractions, and nervous system depression.

Outlines

00:00

🌞 Understanding Vitamin D Synthesis and Storage

Dr. Mike discusses the basics of Vitamin D, one of the four fat-soluble vitamins, which are essential for growth and development. Vitamin D is unique because it can be stored in the body's fatty layers. The primary source of Vitamin D is UV exposure from sunlight, which triggers the conversion of 7-dehydrocholesterol in the skin into cholecalciferol (Vitamin D3). This compound then circulates in the bloodstream and reaches the liver, where it is converted into 25-hydroxycholecalciferol (calcidiol) by the enzyme 25-hydroxylase. Ingested Vitamin D from animal sources, mainly fish and liver, enters the bloodstream directly as cholecalciferol, while plant sources like UV-activated mushrooms provide ergocalciferol (Vitamin D2), which follows the same liver conversion process. The video emphasizes the difference between fat-soluble and water-soluble vitamins, with the former being easily stored and the latter quickly excreted.

05:01

🩸 The Role of Vitamin D in Calcium and Phosphate Regulation

The video explains the activation of Vitamin D in the kidneys by the enzyme 1-alpha hydroxylase, which converts calcidiol into calcitriol (1,25-dihydroxycholecalciferol), the active form of Vitamin D. This activation is stimulated by low levels of calcium and phosphate in the blood. The active Vitamin D increases calcium and phosphate levels by enhancing their absorption in the gastrointestinal tract, reabsorption in the kidneys, and release from bones. This process is crucial for maintaining strong bones. The video also discusses the importance of blood tests that measure 25-hydroxycholecalciferol as an indicator of baseline Vitamin D levels. It highlights the role of parathyroid hormone, which is released in response to low calcium levels and stimulates 1-alpha hydroxylase, thereby increasing active Vitamin D levels. The summary also touches on the consequences of Vitamin D deficiency and excess, with the former leading to rickets in children and osteomalacia in adults, and the latter causing issues like kidney stones and nervous system depression.

10:02

🌡️ Factors Affecting Vitamin D Production and Deficiency

Dr. Mike explores the factors that influence Vitamin D production, including sunlight exposure, skin color, and geographical location. Lighter skin produces more Vitamin D due to greater UV light absorption. The video addresses the consequences of Vitamin D deficiency, which is prevalent in 50% of the world's population, often due to inadequate sunlight exposure. It also mentions the importance of fat absorption for Vitamin D, as it is a fat-soluble vitamin. Recommended daily allowances for Vitamin D are discussed, with varying levels for different age groups. The video concludes by warning about the potential risks of Vitamin D overdose from supplementation, which can lead to harmful conditions like kidney stones, brittle bones, abdominal pain, and nervous system depression.

15:02

⚠️ Vitamin D: Balancing Intake for Optimal Health

The final paragraph summarizes the key points about Vitamin D: its synthesis, the importance of maintaining proper levels, and the risks associated with both deficiency and excess. It underscores the need for a balanced approach to Vitamin D intake, whether through sunlight exposure or supplementation, to ensure optimal health and avoid the adverse effects of imbalances.

Keywords

💡Vitamin D

Vitamin D is one of the four fat-soluble vitamins, essential for normal growth and development. It is unique because our bodies can produce it through exposure to ultraviolet (UV) light from the sun. The video emphasizes that vitamin D is crucial for bone health and calcium absorption, and it can be obtained from sunlight, food, or supplements. The script discusses the importance of vitamin D in the synthesis process of its active form, calcitriol, which is vital for calcium and phosphate regulation in the body.

💡Fat-soluble vitamins

Fat-soluble vitamins are a group of vitamins that include Vitamins A, D, E, and K. These vitamins are stored in the body's fatty tissues and liver, unlike water-soluble vitamins that are excreted more quickly. The script highlights that because vitamin D is fat-soluble, it can be stored in the body's fatty layers, which is a key factor in its absorption and storage.

💡UV exposure

UV exposure refers to the skin's exposure to ultraviolet light from the sun, which is essential for the body to synthesize vitamin D. The video explains that UV light triggers the conversion of 7-dehydrocholesterol in the skin into cholecalciferol, the precursor to vitamin D. This process is fundamental to understanding how vitamin D is produced naturally in the body.

💡Cholecalciferol

Cholecalciferol, also known as vitamin D3, is the form of vitamin D produced in the skin upon UV exposure. It is the precursor to the active form of vitamin D and is converted into 25-hydroxyvitamin D in the liver. The script uses cholecalciferol to illustrate the first step in the synthesis of active vitamin D.

💡25-Hydroxylase

25-Hydroxylase is an enzyme in the liver that converts cholecalciferol into 25-hydroxyvitamin D, also known as calcifediol. This is an essential step in the activation process of vitamin D, as highlighted in the script, and it is a key indicator of vitamin D status when measured in blood tests.

💡Calcitriol

Calcitriol, or 1,25-dihydroxyvitamin D, is the active form of vitamin D. The video explains that it is produced in the kidneys and is responsible for increasing calcium and phosphate levels in the blood, which are critical for bone health. The script emphasizes the importance of calcitriol in the regulation of calcium and phosphate metabolism.

💡Parathyroid hormone (PTH)

Parathyroid hormone is produced by the parathyroid glands and plays a crucial role in calcium homeostasis. The video script explains that low calcium levels trigger the release of PTH, which in turn stimulates the production of active vitamin D (calcitriol). This process is vital for maintaining proper calcium levels in the blood.

💡Rickets

Rickets is a disease caused by vitamin D deficiency in children, leading to soft and weak bones. The video script uses rickets as an example of the consequences of vitamin D deficiency in children, where the bones do not harden properly due to a lack of mineralization.

💡Osteomalacia

Osteomalacia is a condition resulting from vitamin D deficiency in adults, causing bones to become soft and brittle. The script contrasts osteomalacia with rickets, explaining that while rickets affects children's bones that are not yet fully mineralized, osteomalacia affects adults by causing demineralization of already hardened bones.

💡Vitamin D toxicity

Vitamin D toxicity occurs when too much vitamin D is ingested, leading to high levels of calcium in the blood, which can cause kidney stones, bone pain, and neurological issues. The video script warns about the dangers of over-supplementation with vitamin D, emphasizing the importance of maintaining a balance to avoid such toxicity.

Highlights

Vitamin D is one of the four fat-soluble vitamins, which can be stored in the body due to its solubility in fat.

The primary source of vitamin D is UV exposure or sunlight, which triggers the conversion of 7-dehydrocholesterol in the skin to cholecalciferol.

Cholecalciferol, also known as vitamin D3, is inactive and requires further conversion in the liver by the enzyme 25-hydroxylase to become 25-hydroxycholecalciferol.

Vitamin D from animal sources, such as fish and liver, enters the bloodstream as cholecalciferol and follows the same liver conversion pathway.

Plant sources like UV-activated mushrooms provide ergocalciferol, or vitamin D2, which also undergoes hydroxylation in the liver.

The kidneys play a crucial role in activating vitamin D through the enzyme 1-alpha hydroxylase, which converts 25-hydroxycholecalciferol to the active form, calcitriol.

Calcitriol, the active form of vitamin D, increases calcium and phosphate levels in the blood, which are essential for bone health.

Low calcium and phosphate levels stimulate the production of parathyroid hormone, which in turn activates the enzyme 1-alpha hydroxylase to produce active vitamin D.

Active vitamin D enhances the absorption of calcium and phosphate in the gastrointestinal tract and their reabsorption in the kidneys.

Vitamin D also increases bone resorption, which releases calcium and phosphate into the bloodstream to be deposited into the bone, strengthening it.

A deficiency in vitamin D can lead to rickets in children and osteomalacia in adults, both conditions affecting bone mineralization.

Vitamin D deficiency is widespread, affecting 50% of the world's population, often due to insufficient sunlight exposure.

Skin color affects vitamin D production, with lighter skin producing more vitamin D upon UV exposure compared to darker skin.

The recommended daily allowance of vitamin D varies by age, with higher amounts suggested for older adults.

Supplementation is a common method to address vitamin D deficiency, but it comes with the risk of overdose, which can lead to serious health issues.

Overdosing on vitamin D can cause an increase in blood calcium levels, leading to conditions like kidney stones and nervous system depression.

The video provides a comprehensive overview of vitamin D's synthesis, functions, deficiency, and toxicity, emphasizing the importance of maintaining a balanced level.

Transcripts

hi everybody dr mike here in this video

i want to take a look at vitamin d

[Music]

so remember vitamin d is one of the four

fat-soluble vitamins

d e k and a and a vitamin is a nutrient

that we require in very small amounts

that we cannot produce ourself but we

need it for normal growth and

development

vitamin d being a fat soluble vitamin

what that means

is it can be stored within our body

because the cells of our body are

surrounded by fatty layers

and it allows for the movement of this

vitamin into those cells easily and

therefore

easy to be stored water-soluble vitamins

however

they often get excreted from the body

quite quickly

that's one of the major differences so

when we look at vitamin d

first thing you need to be aware of is

that the main way that we get vitamin d

is through

uv exposure or our exposure to sunlight

so this is going to be the first step

in the synthesis of a precursor vitamin

d

to an active vitamin d we can get some

from the food that we eat from animal

and plant products but it's quite

minimal but i'll get there in a second

so our exposure to uv light

is going to trigger the conversion of a

cholesterol that's present in our skin

in our epidermis

called 7d hydrocholesterol what the uv

light does is it turns 7d

hydrocholesterol

into something called cholecalciferol

so colicalciferol

will now be floating around in our

bloodstream

now when it's floating around in our

bloodstream it's ultimately going to get

to our liver

and in our liver cholecalciferol which

is also known as vitamin d3

still not active yet it's inactive once

it gets to the liver it comes across

an enzyme now this enzyme is called

25

hydroxylase and what it does

is it gives a hydrogen to the 25th

carbon of this cholecalciferol molecule

this cholesterol molecule

and it turns koly kelsey feral into

something called

25

hydroxy coli

kelsey ferrell 25 hydroxycholic

calcifero

which is also known as calcifediol

now interestingly when we ingest vitamin

d so for example

if we ingest it from animal products

what we usually get it from is fish

predominantly

and liver this comes in the form of

cholecalciferol

or vitamin d3 and therefore it's just

going to enter the bloodstream

and go via this particular pathway in

the liver if we ingest it through

plant products one of the main ways is

uv activated mushrooms

we actually get ergo calciferol not coli

calciferol ergo

calciferol and this is actually vitamin

d2

and this will travel to the liver and

undergo this hydroxylation through 25

hydroxylase

and then go via this calcifedial which

means

once this is produced it then moves to

the kidneys

so we've got calciferdil also known as

25 hydroxycalled calciferol

traveling to the kidneys it comes across

another enzyme in the kidneys

which is called one alpha hydroxylase

and what one alpha hydroxylase does is

it gives a hydrogen to the first carbon

of this calcifidel so now we have a

molecule

which is 1 25

hydroxy coli

kelsey which is a mouthful but it's also

known as

calcitriol

now what we have is an active form of

vitamin d

important point these enzymes here

really important because

you're always going to go through this

process

and turn into calcifedeal this 25

hydroxy

coli calciferol we're always going to go

to this point when you're exposed to

sunlight but

that means this enzyme is always going

to be activated in the liver

but this enzyme in the kidneys

specifically it's produced by what's

called the proximal

convoluted tubule cells this one alpha

hydroxylase

that needs to be stimulated to be active

right

so what that means is when you get a

blood test for vitamin d

you are not actually testing often

you're not testing

kelsey triol or 125 hydroxy color kelsey

ferrell you're actually

calcified 25 hydroxycoli calciferol

that's the one you're actually getting

tested for

because you're always going to be

producing that at all times

so that's a good indicator of your

baseline

vitamin d at least precursor if you've

got a problem with

calcium which i'm going to talk about in

a sec then they may test

this one down the track so this gets

activated now the question is what

activates

this well we'll get there in a second

because we need to now talk about

what does the active form of vitamin d

calcitriol do

that will tell us here what it needs to

do

is it needs to increase

calcium in the blood it needs to

increase

phosphate in the blood two really

important points

how does it do this well it's stimulated

if

calcium and phosphate levels are too low

and that means

the thing that stimulates one alpha

hydroxylase

is going to be low calcium low

phosphate now think about like this

what happens is low phosphate

that's going to directly stimulate this

enzyme to activate

all right what indirectly stimulates

this

is calcium low calcium so when calcium

levels are low

it actually travels to the parathyroid

gland

so you've got your trick here and you've

got your thyroid that hugs the front of

your trachea

behind your thyroid you've got the

parathyroid gland

so i'm going to draw the back of your

trick here

so here's the trachea there's the rings

of your tricky this is at the back

the parathyroid glands are these glands

that are embedded

in the larger thyroid gland and what the

parathyroid gland does

is it produces parathyroid hormone

p t h so low calcium

triggered parathyroid hormone to be

released and parathyroid hormone

is going to trigger one alpha

hydroxylase

so that means we've now got active

vitamin d

it's whole job is to increase calcium

because the stimulus was a drop

increased phosphate its stimulus was a

drop how does it do it it does it like

this

it increases absorption

of both calcium and phosphate at the

gastrointestinal tract

it increases reabsorption

of calcium and phosphate at the kidneys

so throws it back

from the tubes of the kidneys back into

the blood really important increased

absorption

and also increases osteo

activity osteo means bone clast means to

crush

it breaks bone down to release calcium

and phosphate

into the bloodstream now you may be

thinking wait a minute if this is

breaking bone down and releasing calcium

and phosphate into the bloodstream don't

we need vitamin d for strong bones this

seems like the

opposite of what we want all right

important point

if we have vitamin d both

calcium and phosphate will be released

into the bloodstream

calcium and phosphate love to be

together they're partners for life

they love to be together when they're

together they precipitate or mineralize

into the bone so you're going to absorb

it in the git it's going to be in the

blood

you're going to reabsorb it from the

kidneys it's going to be in the blood

some is going to be taken out of the

bone it's going to be in the blood it

gets together and then goes back into

the bone

deposits into the bone strengthens the

bone

that's what we want now important point

if we have

no vitamin d and we only have

parathyroid hormone

something interesting happens calcium

increases in the blood

but phosphate gets peed out that means

this connection this bond of the two is

not present

and bones actually get broken down so

without vitamin d

and only parathyroid hormone bones will

start to become brittle all right

now i want to talk about deficiencies

what happens if we don't have enough

what happens if we have

too much all right let's have a look

deficiencies are important let me tell

you why

firstly because 50 percent of the

world's population

is deficient in vitamin d and that's

because of their lack of exposure to

sunlight

the color of your skin actually changes

how much vitamin d you produce

if you have lighter skin you'll produce

five times more vitamin d

than somebody with darker skin and this

has to do with

where the individual is in the world and

they're exposed to that sunlight so

let's first talk about deficiencies

so a deficiency what can cause it well

lack of sunlight obviously

lack of uv light

it can be caused if you've got a problem

with

fat absorption now why what does this

mean

vitamin d is a fat soluble vitamin it

needs

fat in order to be absorbed from the

intestines into the lymphatic system

then to go from the lymphatic system

into the bloodstream and into the

tissues of the body

if you've got a problem with fat

absorption so what could that be an

issue with your

bile for example or maybe it's a problem

with your intestinal

tract doesn't allow you to absorb

fats this can have a problem and lead to

diminished vitamin d

and maybe you're not getting enough

vitamin d from the diet

now the main issue here with the

deficiency

is going to be the exposure to uv light

so the question then is

how much vitamin d should we be having

so somebody

under one year of age around about 400

international units 600

international units if you're between 1

to 70 years

and 800 international units if you're

above

70 years of age so what happens if you

don't have enough vitamin d

well you can have something called

rickets if you're a child

or you can have something called

osteomalacia

if you're an adult it's basically the

same thing right both are vitamin d

deficiencies that result in issues with

bone now here's the thing if it happens

in a child

their bone has not matured yet so

there's a lot of collagen

and not a lot of the hard stuff the

solidified

mineralized bone tissue from the calcium

of phosphate

so if somebody doesn't have enough

vitamin d and the calcium of phosphate

is leaving it's still

collagenous so it's bendy so somebody

with rickets

gets bendy bones

because they're a child and the bone

hasn't matured somebody with

osteomalacia this is an adult

so ricketts happens in children

osteomalacia as an adult the bone has

mineralized and has hardened

so what's now happening is you're

pulling calcium and phosphate out of

already hardened bones

so it doesn't become bendy it just

becomes brittle and this is what happens

in osteomalacia

brittle bones

all right so the best way

to get vitamin d especially if one of

these disorders

is through supplementation obviously uv

exposure but supplementation as well now

what this also means is anytime you're

exposed or

start to ingest supplements you have the

risk of overdosing

overdosing vitamin d very bad very toxic

it's one of the worst

types of toxicities you can get

from having too much vitamins so let's

have a look at what happens when you

have

too much vitamin d

so overexposure now you're not going to

get overexposure vitamin d from sunlight

you will get overexposure vitamin d from

supplementation

so what happens is this you get

stones bones

abdominal moans

and psychic groans

this is an old-school way of remembering

what happens if you have too much

vitamin d

stones bones abdominal moans and psychic

growns let's have a look

so stones increase the amount of calcium

increases the likelihood of

calcium-based kidney stones

they're the stones bones we spoke about

osteomalacia right

if you're an adult which i assume this

is going to be abdominal hormones

calcium remember you're going to have

too much calcium floating through the

bloodstream this is the problem

with an over amount of overabundance of

vitamin d

abdominal moans calcium we need to tell

muscle to contract

so it contracts the smooth muscle of the

abdomen

contracts the smooth muscle and anytime

you have abdominal pain

it's because the muscle is contracting

over something so

contraction and psychic groans now

what's this referring to

too much calcium blocks your neurons

ability to fire properly

so you get a depression of the nervous

system now not depression

in the classical sense but just a

depression in the firing of the nervous

system

so nervous depression

leading to the psychic groans so

what we've had a look at here is vitamin

d how it's synthesized what happens if

you don't have enough

or if you have too much