Getting enough vitamin D in a Southern Hemisphere winter (a herbalist's honest guide)

Ok so this is something buzzy that no one really tells you - being in New Zealand or Australia, you can live here with it's reputation for sunshine and still be vitamin D deficient for four to five months of the year.

In winter, the sun in most of the Southern Hemisphere sits too low in the sky for its UVB rays to actually reach your skin at a useful angle. Below about 37 degrees latitude (which includes most of New Zealand and southern Australia), the winter sun simply doesn't have enough UVB intensity to trigger vitamin D synthesis in your skin - even on clear days.

That means from roughly May to August, you are not making vitamin D from sun exposure in any meaningful way. And because vitamin D is fat-soluble and stored slowly, most people enter winter already depleted from the tail end of summer.

 

Why this matters more than you've been told

Vitamin D isn't just a bone mineral. Its receptors are found in almost every tissue in the body, including the brain. Low vitamin D is strongly associated with:

• Low mood and seasonal depression (your brain uses it to regulate serotonin)
• Fatigue and physical exhaustion
• Immune dysfunction - which is exactly why winter illness is so common
• Poor sleep quality
• Increased inflammation

For ADHD brains specifically, there's emerging research linking low vitamin D to worsened executive function and mood dysregulation. It's one of the first things I look at when someone comes to me with winter brain fog.

The problem is that deficiency is slow and subtle. It doesn't announce itself. It just makes everything feel slightly harder.

 

How much sun do you actually need?

In summer, most lighter-skinned adults can synthesise adequate vitamin D in about 10–15 minutes of midday sun exposure on arms and legs. And yep, if you have an outdoorsy lifestyle and prioritise sunlight during Spring and Summer, you can store a decent amount. 

There's no one-size-fits-all answer, but if you're choosing to supplement or utilise food to support your D intake, read on.

D3, not D2 - this matters

If you're buying a supplement, look for vitamin D3 (cholecalciferol), not D2 (ergocalciferol). D3 is the form your body produces naturally from sunlight and raises blood levels significantly more effectively than D2. Most quality supplements now use D3, but it's worth checking the label.

Pair it with K2 (specifically MK-7 form) if you're supplementing long-term - K2 helps direct the calcium that D3 mobilises toward your bones rather than your arteries. This pairing matters at higher doses.

Standard maintenance dose for adults: 1000–2000 IU daily through winter. If you suspect you're significantly deficient, get a blood test (25-OH vitamin D) —-it's the only way to know your actual levels.

Food sources that genuinely contribute

Food alone won't get you there in winter, but these make a real difference as part of the picture:

• Oily fish (salmon, sardines, mackerel) - by far the best food source
• Egg yolks - modest but meaningful, especially from pasture-raised eggs
• Mushrooms exposed to sunlight - UV-treated mushrooms contain D2; place regular mushrooms gills-up in direct sun for 20 minutes before eating to boost their D content significantly (genuinely works)
• Fortified foods - some milks and cereals, though the amounts are usually low

 

A warming winter recipe: golden turmeric broth

This isn't a miracle D3 source - but it combines several ingredients that support immune function and warmth through winter, and it makes you feel genuinely cared for on a cold evening.

Ingredients:

• 500ml good-quality bone broth or vegetable stock
• 1 tsp ground turmeric
• ½ tsp ground ginger
• Pinch of black pepper (activates the curcumin in turmeric significantly)
• 1 tsp coconut oil or ghee
• Small handful of dried shiitake mushrooms, rehydrated (modest D2 source + immune support)
• Sea salt to taste
• Optional: a soft-boiled egg stirred in at the end (D3 + protein)

Method: Warm broth gently, whisk in spices and fat, add rehydrated mushrooms, simmer 5 minutes. Drink from a mug. PS this is what herbal medicine looks like as a daily practice - not all witchy and dramatic like you might think lol.

 

How Wake Up AM supports you this winter

Our Wake Up AM formula includes methylated B vitamins and botanical adaptogens - because low vitamin D and low B vitamins create almost identical fatigue and mood symptoms, and they often occur together in winter.

If you're waking up exhausted and dragging through your mornings from May onwards, this is where I'd start.

See what's inside Wake Up AM →

 

Winter doesn't have to mean five months of low-grade depletion. A little attention to D levels makes a quiet but significant difference to how you feel, think, and stay well.

Disclaimer: This content is educational and does not constitute medical advice. If you have a health condition, are pregnant, or take medication, please consult your healthcare provider before supplementing.