THE SUNSHINE VITAMIN FOR BONES, IMMUNITY & MOOD
30-day supply
Key Benefits
Supports calcium absorption and bone building
Promotes muscle strength and function
Supports immune health and cell-to-cell communication
Supports mood regulation and cognitive function
Wellness Goals
Recommended Dose
5,000 IU (125mcg)
Take one capsule daily with a fat-containing meal. Vitamin D is fat-soluble and requires dietary fat for absorption. For those with known deficiency, a healthcare provider may recommend higher doses initially. Getting your blood levels tested (25-hydroxyvitamin D) helps determine the right dose for you.
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The Details
Vitamin D is less of a vitamin and more of a hormone — and it influences the expression of over 1,000 genes in your body. Despite its critical importance, an estimated 42% of American adults are deficient, with rates even higher in people with darker skin tones, those who live in northern latitudes, and anyone who spends most of their time indoors.
The consequences of deficiency are far-reaching. Beyond its well-known role in calcium absorption and bone health, vitamin D is a key regulator of immune function. It activates your innate immune system's first responders (including antimicrobial peptides like cathelicidin) and helps modulate the adaptive immune response to prevent overreaction. Low vitamin D is consistently associated with increased susceptibility to respiratory infections.
Vitamin D also supports muscle strength (deficiency is linked to increased fall risk in older adults), mood regulation (low levels correlate with seasonal depression), and cardiovascular health. We use D3 (cholecalciferol), the same form your skin produces from sunlight, at 5,000 IU — a dose supported by research for achieving and maintaining optimal blood levels of 40-60 ng/mL.
Research
Key studies supporting Vitamin D3, from peer-reviewed journals.
Association between vitamin D supplementation and mortality: systematic review and meta-analysis — 2019
The effect of vitamin D supplementation on depression: a systematic review and dose-response meta-analysis — 2024
Study titles are simplified for readability. Provided for informational purposes — not medical advice.
Transparency
Every batch is independently tested by ISO-17025 accredited labs for purity, potency, and contaminants.
Designed by healthcare professionals using evidence-based research and clinical expertise.
Manufactured in cGMP & UL certified, FDA-registered facilities with a flawless inspection record.
Important Information
Contraindications
Those with hypercalcemia, sarcoidosis, or granulomatous diseases should consult their healthcare provider before use. Have your vitamin D levels monitored if supplementing long-term at 5,000 IU.
As with any natural health product, consult your healthcare practitioner. Store in a cool, dry place. Keep out of reach of children. Discontinue use immediately if you experience an adverse event.
What people say
Really good supplement brand. The daily pack format is so convenient and I've been 100% consistent because of it. The quiz was genuinely thorough. Knocked one star off because I'd love the option to add or remove individual supplements as I learn more about my body.
I've tried so many supplements and honestly nothing has worked like this. The quiz is actually thorough and the results show it. Energy is UP, recovery is UP, sleep is SO much better. Can't believe it took me this long to find this brand.
Three weeks in and I already feel the difference. My morning energy is COMPLETELY different. No more dragging myself out of bed. The personalization through the quiz is what makes it work — it's not just a generic multivitamin. Stack actually thought about what MY body needs.
I've been on a health optimization journey for about three years and have tried what feels like every supplement brand on the market. Most of them are either generic multivitamins dressed up in pretty packaging, or they're so specific that you need to be a nutritionist to understand what you're actually taking. Stack sits in a completely different category. The quiz is the first thing that impressed me. It asks genuinely intelligent questions — not just 'how old are you and what's your gender' but questions about your diet, your sleep patterns, your stress levels, your exercise frequency. It felt like a real consultation rather than a data collection exercise. The pack that arrived was clearly personalized to my answers. After six weeks, the improvements have been consistent and measurable: better sleep quality, more stable energy throughout the day, and noticeably faster recovery after my runs. My partner commented that I seemed more 'on' in the evenings rather than crashing after dinner. The daily pack format is brilliant for compliance — I've been 100% consistent because the habit is so frictionless. One pack, done, every morning. No bottles, no measuring, no forgetting half of them. Genuinely one of the best health investments I've made.
My focus at work has been sharper and I'm waking up without that groggy feeling I used to have every morning. Told two friends about Stack already. Customer support was also really helpful when I had a question about one of the ingredients.
honestly wasn't sure about it at first but three weeks in and i'm so glad i tried it. energy is way better, i'm sleeping properly for the first time in months. the quiz was really detailed which gave me confidence it was actually personalized. would 100% recommend.
Personalized for you
Take our 2-minute Health Assessment and let our AI build your personalized stack — every supplement chosen for your specific goals.
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