Dr Ula: The overlooked power of vitamin D
- Dr Ula Heywood
- Aug 4
- 4 min read
Why most people are missing this foundational driver.
You’ve probably heard of vitamin D. You might even take a supplement in winter. But for many, it’s still thought of as “the sunshine vitamin”—something nice to have if you’re feeling a bit flat.
Here’s the truth: vitamin D is not just “nice to have.” It’s essential.
And it goes far beyond strong bones and sunlight.
At Autonomy, we see that over 80% of new clients arrive with suboptimal vitamin D levels at this time of year. These aren’t just people who avoid the sun or forget their multivitamins. They’re driven, active professionals. Parents juggling it all. People doing their best for their health—yet missing a foundational piece that influences everything from mood to immunity, muscle strength to metabolic function.
So why is something so critical so often overlooked?
The hidden deficiency
We live in New Zealand—surrounded by beaches, blue skies, and wide open spaces.
So how is it possible that so many people are still deficient?
1. Sunscreen and sun safety
Essential for skin cancer prevention, but even SPF 15 can reduce vitamin D production by over 90%.
2. Modern indoor lifestyles
We spend daylight hours at desks, in meetings, or commuting. Most people miss the key synthesis window (10 am–2 pm).
3. Skin tone and ageing
Darker skin produces less vitamin D from sunlight. As we age, our skin’s ability to convert sunlight declines significantly.
4. Gut and liver function
Vitamin D requires proper gut absorption and conversion in the liver and kidneys. Any digestive or metabolic issues can interfere with this.
5. Seasonal changes and latitude
From May to August, the UVB intensity in New Zealand is too low to make meaningful vitamin D, even if you’re outside.
6. Body fat and vitamin D storage
Vitamin D is fat-soluble, meaning it gets stored in body fat rather than staying readily available in the bloodstream. Higher levels of body fat can reduce the bioavailability of vitamin D, even if total stores are technically sufficient. This helps explain why people with higher body fat percentages often show lower circulating vitamin D levels and may require higher or more carefully adjusted supplementation.
What vitamin D really does
Vitamin D isn’t technically a vitamin; it acts more like a hormone, affecting hundreds of genes throughout the body. It plays a central role in:
Immune regulation
Bone health and calcium absorption
Muscle strength and physical performance
Mood, cognition, and brain health
Metabolic and cardiovascular function
Inflammation control and insulin sensitivity
When vitamin D is low, resilience drops. You might not notice it overnight—but gradually:
You get sick more often.
Recovery takes longer.
You feel flat, foggy, or unusually tired.
Your mood dips for no obvious reason.
You might experience joint aches, cramps, or poor workout recovery.
Sound familiar?
This is exactly why we take vitamin D so seriously.
The “normal range” trap
You might think: “My vitamin D was in the normal range.”
But most lab reference ranges are designed to prevent severe deficiency diseases, like rickets—not to support optimal energy, mood, immunity, or performance.
At Autonomy, we aim for 100–120 nmol/L, higher than the typical lower cut-off of 50 nmol/L. This target is supported by emerging research and our clinical outcomes.
When we optimise levels, clients often report:
More stable energy
Fewer infections and faster recovery
Less joint or muscle pain
Better mood and mental clarity
Improved sleep
More stable blood sugar and metabolic markers
It’s one of the simplest, most cost-effective interventions—and one of the most impactful.
Why we don’t guess
Vitamin D metabolism is complex. That’s why we don’t guess—we test.
We look at baseline levels, body weight, inflammation, gut health, and lifestyle to determine the right dose. Some people need only small daily support, while others require higher correction doses.
We also consider important cofactors—like magnesium, vitamin K2, and omega-3 fatty acids—which help your body use vitamin D safely and effectively.
This isn’t about taking pills randomly. It’s about precision and supporting your whole system.
Vitamin D and the bigger picture
Think of vitamin D as a master switch. It doesn’t do everything on its own—but without it, your other systems can’t run at full capacity.
In our clients, low vitamin D is rarely the only issue, but it’s almost always a critical part of the picture—whether we’re working on fatigue, brain fog, hormonal health, weight struggles, or long COVID recovery.
Correcting it often unlocks the foundation for deeper repair.
Because the symptoms can be vague—low energy, poor recovery, general “offness”—many people ignore it or blame age or stress. But once they feel the shift, they don’t look back.
Your next move
Vitamin D deficiency doesn’t announce itself clearly. It builds quietly. You adapt, compensate, and forget what “good” really felt like.
But when you restore it—when your cells start working properly again—it can feel like the lights are back on.
If you’ve been chasing answers for fatigue, low mood, poor sleep, frequent infections, or unexplained inflammation—vitamin D might be the missing piece.
We’re not here to just keep you out of disease. We’re here to help you thrive.
Book a Discovery Consultation at Autonomy. We’ll help you uncover the missing pieces of your health picture to help you thrive.
Dr. Ula Co-Founder and Lead Physician, Autonomy
