Vitamin D3 in Fall and Winter: Why Your Levels Drop — and How to Support Them
Compartir
By Dr. Julian Cano, ND, LAc™
Every fall in Connecticut, the same thing happens in my practice: energy dips, colds start circulating, and patients ask why they feel "off" heading into winter. One of the first things I look at is vitamin D — because from late fall through early spring, our bodies simply can't make enough of it.
Why vitamin D drops in fall and winter
Vitamin D is called the "sunshine vitamin" because your skin makes it when sunlight hits it. But that only works when the sun is high enough in the sky. At Connecticut's latitude, from roughly November through March, the sun's angle is too low for your skin to produce meaningful vitamin D — no matter how much time you spend outside.
Add shorter days, more time indoors, and clothing that covers most of your skin, and levels steadily slide through the season. Studies consistently find that vitamin D insufficiency is most common at the end of winter, when stores built up over summer are depleted.
What vitamin D supports
Vitamin D plays a role in several systems that matter most in winter:
- Immune health — vitamin D supports the normal function of the immune system, your first line of defense during cold season.
- Bone health — it helps your body absorb calcium and supports strong bones.
- Muscle function — adequate vitamin D supports normal muscle strength and function, which matters for staying active (and steady on your feet) all winter.
- Mood and energy — vitamin D receptors are found throughout the brain, and the nutrient supports a balanced mood during the darker months.
How do you know if your levels are low?
Fatigue, low mood, and getting sick often can have many causes, and low vitamin D doesn't always cause obvious symptoms. The only reliable way to know is a simple blood test — 25-hydroxyvitamin D. I recommend testing rather than guessing, especially before starting or changing a supplement routine. If you're local, that's something we can review together at my North Haven clinic.
Getting vitamin D in winter: what actually works
Food helps, but only a little. Fatty fish like salmon and sardines, egg yolks, and fortified foods contain vitamin D, yet diet alone rarely keeps levels up through a New England winter.
Sunlight is unreliable here until spring — sunscreen, glass, and the low sun angle all block production.
Supplementation is the dependable option in winter, and form matters. Vitamin D3 (cholecalciferol) is the same form your body makes from sunlight, and it's the form used in quality practitioner formulas. Vitamin D also works with complementary nutrient cofactors — nutrients that support how the body uses it — which is why a well-built formula is more than D3 alone. Vitamin D is fat-soluble, so taking it with a meal that contains some fat supports absorption.
The formula I recommend to my patients
I formulated Synergy D3x for exactly this season: a vitamin D3 capsule that includes complementary nutrient cofactors to support how your body uses vitamin D. It's a simple routine — one capsule daily, 60 capsules per bottle.
The bottom line
You can't change a Connecticut winter, but you don't have to head into it running on empty. Supporting your vitamin D levels is one of the simplest foundations for immune health, strong bones, and steady energy through the darker months — and a quick blood test takes the guesswork out of it.
Questions about your levels or what's right for you? Visit us at Dr Julian Cano LLC in North Haven, CT, or reach out through drcano.net.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Consult your healthcare provider before beginning any supplement regimen.