The sunshine is here and don’t we just love it !! 

You should know by now that vitamin D is essential for strong bones and immune function—but its influence reaches far beyond that.

Emerging research shows that vitamin D plays a key role in regulating serotonin, the “feel-good”  or “happy” neurotransmitter responsible for mood, social behavior, and emotional well-being.

If you’ve ever felt more down during the dark winter months (aka Seasonal affective disorder), vitamin D might be part of the reason why.

Vitamin D is produced when our skin is exposed to ultraviolet B (UVB 3 or above) rays from sunlight.

And in simple patient terms that means your shadow must be shorter than you are. 

In real terms, that means between 11-4 PM, between April and September. 

And no lotion !! 

The number on the front of the sun lotion is how good it is at stopping UVB. 

Factor 30 and above stops 99% of UVB, hence you do not get burnt, but also you do not get vitamin D production. 

So if you are going for natural vitamin D, make sure you get at least 25% skin out, ideally as much as you can, without getting arrested. 

If you, do, aim for 1/3 to 1/2 the time you would need to go pink, and you can make 10,000-20,000 iu of vitamin D – REMEMBER the RDA is 200 iu 🤯

The facts above in relation to sun lotion and the limited time on the day to get >UVB3, are one reason in the UK, in summer we still have 60% of the population under 75 nmol/L.

And remember the three at risk groups, are low all year round and must maintain supplementation year round.

  • Dark skin/higher melanin
  • Obesity
  • Over 65 years old

And if patients cannot go out without lotion on, or let their kids out with factor 50 on, then they must supplement all year. 

The three things patients struggle to understand:

– You cannot wear factor 30 and make vitamin D

– You want to get the sun on your skin when the sun is strongest (aka shadow short, 11PM – 4PM).

– Conversely, you cannot make any vitamin D after 4 PM, when your shadow is longer. 

Remember we want to mimic living in a sunny climate, where you had year round UVB, ie if you lived in Florida. 

Then your levels would naturally be in the 100’s.

So how does vitamin D affect mood? It acts as a powerful gene regulator and boosts our mood via manipulation of neuro-transmitter levels. 

In its active form—1,25-dihydroxyvitamin D3 (calcitriol)—vitamin D can enter cells and influence which genes are turned on or off.

This includes genes involved in neurotransmitter production.

Serotonin is made from an amino acid called tryptophan.

The conversion process relies on an enzyme called tryptophan hydroxylase (TPH) to convert tryptophan to 5HTP, which converts to SEROTONIN.

Note that tryptophan hydroxylase is an IRON DEPENDENT enzyme – this means iron dropping low-er before you get anaemia can affect your mood.

We will talk more about iron once we launch our new IRON supplement.

Interestingly, the body produces two versions of this enzyme:

TPH2 is found in the brain.

TPH1 is found in the gut and other peripheral tissues.

Vitamin D helps increase TPH2 expression, which boosts serotonin production in the brain.

At the same time, it suppresses TPH1, preventing excess serotonin production in the gut.

This balance is important: too much peripheral serotonin can cause inflammation, while low brain serotonin is linked to depression and anxiety.

CLINICAL TIP: Excess serotonin in the gut from 5HTP supplementation can lead to diarrhoea. 

So, part of the way vitamin D makes you feel so good is more serotonin in your brain. 

But vitamin D doesn’t just influence how much serotonin is made—it also affects how it’s used.

Research suggests that vitamin D down regulates the serotonin transporter (SERT) which removes serotonin from the synpatic cleft – anti-depressants like sertaline or citalopram, or fluoxetine block this SERT transporter, hence hence they are known as Selective Serontonin Reuptake Inhibitos (SSRI’s)

Vitamin D may also down regulate the enzyme monoamine oxidase A (MAO-A).

MAO breaks down not only serotonin but also dopamine and noradrenaline. 

By turning them down, vitamin D allows serotonin (and dopamine and noadrenaline) to stay active longer in the brain, potentially improving mood and cognitive function.