Almost everyone today has been told they're vitamin D deficient. The standard recommendation is to take a supplement. But here's what most practitioners don't tell you: vitamin D in pill form is not the same as what your body makes from the sun — and the supplement form may carry risks that are rarely discussed.

Cholecalciferol — sold as vitamin D3 — was registered in 1984 as a rodenticide (rat poison). The same compound that kills rodents via hypercalcemia (toxic calcium overload) is what is in most vitamin D supplements, at far smaller doses. Whether those smaller doses cause cumulative harm over years of daily use is a question that has not been adequately studied.

"In 1984, cholecalciferol (vitamin D3) was registered for use as a rodenticide." — ChemService / Bell Laboratories. Source →

Research has found that supplemental vitamin D does not produce the same cardiovascular benefits as sun-derived vitamin D. A randomized controlled trial found that sunlight exposure improved lipid profiles in vitamin D deficient men significantly better than supplementation.

Patwardhan VG, et al. Randomized Control Trial Assessing Impact of Increased Sunlight Exposure versus Vitamin D Supplementation on Lipid Profile in Indian Vitamin D Deficient Men. Indian J Endocrinol Metab. 2017. View study →

The sun delivers far more than vitamin D. Sunlight triggers a cascade of biological processes — many of which cannot be replicated by a supplement. Research confirms the following benefits of regular, non-burning sun exposure:

Mead MN. Benefits of Sunlight: A Bright Spot for Human Health. Environ Health Perspect. 2008. View study →

Weller RB. Sunlight has beneficial effects on cardiovascular risk factors independently of vitamin D. PubMed →

One of the most remarkable findings in sunlight research: UV light triggers the release of nitric oxide stored in the skin — a vasodilator that directly lowers blood pressure and improves blood flow throughout the cardiovascular system. This effect happens independently of vitamin D production and cannot be replicated by any supplement.

This is part of why countries at higher latitudes — less annual sun — have statistically higher rates of heart disease. It's not just vitamin D levels. It's the full-spectrum benefit of light on the skin.

Weller R. Could the sun be good for your heart? TED Talk — Richard Weller, dermatologist, University of Edinburgh.

The medical community's decades-long fear campaign around sun exposure may itself be causing harm. A Swedish study tracking nearly 30,000 women for 20 years found that those who avoided the sun had a mortality rate two to three times higher than those with the most sun exposure. The risks of sun avoidance were comparable to smoking in terms of overall mortality.

Lindqvist PG, et al. Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort. J Intern Med. 2016. View study →

Additionally, a large review found that low sun exposure was associated with a range of serious conditions including certain cancers, multiple sclerosis, diabetes, cardiovascular disease, autism, and Alzheimer's disease.

Alfredsson L, et al. Insufficient Sun Exposure Has Become a Real Public Health Problem. Int J Environ Res Public Health. 2020. View →

Your skin adapts to sun exposure the way your feet adapt to walking barefoot — through gradual conditioning. The "solar callus" is the term for a skin that is prepared for sun rather than shocked by it. Building it protects against burning while maximizing the biological benefits of light.

Set aside 6 weeks to build your solar callus by following this protocol:

• A Sperti Vitamin D lamp (UV-B specific) provides a sun-comparable signal for vitamin D production through the skin — not a supplement, but a light source that mimics the sun's mechanism
• A trip to a location below latitude 27° for a few weeks can meaningfully build vitamin D stores through the skin
• Whole food dietary sources: wild sardines, mackerel, herring, pasture-raised egg yolks, grass-fed beef liver, and UV-exposed mushrooms — vitamin D in its natural food matrix with co-factors intact
• Minimizing non-native EMF and blue light exposure helps maintain higher baseline vitamin D signaling year-round

One of the most overlooked explanations for weight that does not respond to diet or exercise is this: the body is a light-harvesting system. When photon input drops, the body does what every solar-powered system does — it expands its collection surface.

It gets bigger.

Every mammal that lives through winter understands this cycle. In the autumn, as day length shortens and photon input drops, mammals gain weight. In the spring, as light returns, they lose it. This is not a caloric phenomenon — food intake often stays roughly constant. The signal driving the shift is photonic, not caloric.

The trigger is the change in the light environment — specifically, the ratio of light to dark, the spectrum of available light, and the timing of light exposure relative to the circadian clock.

For wild mammals, summer always comes. They return to the light.

Modern humans have built a light environment that mimics permanent winter:

• Indoors for most daylight hours — light levels 50–500 lux instead of the 10,000–100,000 lux of outdoor daylight
• Screens and artificial lighting dominant — heavy in blue, absent in near-infrared and full-spectrum
• Morning light missed — the critical photobiological signaling window (sunrise through 10am) bypassed
• No skin exposure — clothing, glass, and sunscreen block the photons that drive the biological signal

The body reads this as: the light is gone. Winter is here. Expand the collection surface and wait.

For most modern humans, summer never comes.

T.S. Wiley and Bent Formby's book Lights Out: Sleep, Sugar, and Survival laid out a compelling case decades ago: artificial light extension, disrupted sleep timing, and loss of the dark phase of the circadian cycle are the primary drivers of the modern obesity and metabolic disease epidemic — not calorie excess. The mechanism they described is hormonal and photobiological, not arithmetic.

The research since has strengthened this case. Shift workers have dramatically higher rates of metabolic disease, obesity, and cancer — not because they eat differently, but because their light environment is permanently disrupted. Light at night is now classified by the IARC as a probable human carcinogen (Group 2A). The sleep-weight-light connection is not fringe biology. It is documented.

No weight loss drug addresses photon deprivation. No calorie deficit addresses it. The intervention is light itself.

• Morning sunlight on skin and eyes — daily, in the hours when UV index is building; this is the most powerful signal the body receives to reset circadian rhythms and photobiological function
• Bare skin in midday sun during the solar callus building process — the photons must reach the photosensitive tissue; glass, sunscreen, and heavy clothing block the signal
• Block artificial light at night — 550nm+ amber lenses after sunset; eliminate blue and white light sources in the hours before sleep; restore the dark phase of the circadian cycle
• Not vitamin D supplements — an isolated pharmaceutical compound does not replicate the photonic signal. It bypasses the pathway entirely and introduces its own risks.

The person who cannot lose weight despite doing everything right is often correct — the framework being used to explain their body is the problem. The body is not broken. It is responding to its light environment exactly as designed. Change the light environment, and the biology changes with it.

The supplement industry has positioned vitamin D as a simple fix. The long-term picture is more complicated — and the damage can take years to reverse.

Bottom line: sunlight is the source your body was designed to use. Whole foods are the dietary bridge when sunlight is insufficient. Isolated vitamin D supplements are not a neutral intervention — they carry real risk with long-term use.

Here is something almost nobody in conventional medicine talks about: there are two forms of vitamin D circulating in the human body — a fat-soluble form and a water-soluble sulfated form. The standard blood test (25-hydroxyvitamin D) only measures the fat-soluble fraction. The sulfated form is largely invisible to the test and has been quietly documented in research since the 1960s.

Researchers studying human breastmilk found that the water-soluble vitamin D sulfate (25(OH)D3-sulfate) appears in breastmilk at roughly a 3-to-1 ratio compared to the fat-soluble form. A mother's body prioritizes the sulfated form when nourishing an infant — and that sulfated form shows no seasonal variation, unlike fat-soluble vitamin D, which drops in winter. This finding alone is remarkable: the body maintains steady sulfated vitamin D year-round through mechanisms that have nothing to do with sun angle or UV index.

When researchers first discovered this sulfated form in the early 1960s, they labeled it "inert" because it did not mobilize calcium the way fat-soluble vitamin D does. That single functional comparison became the reason an entire class of vitamin D chemistry was set aside. The research on sulfated vitamin D was not pursued — and the supplementation paradigm built entirely around the fat-soluble form moved forward on incomplete data.

What has since emerged: 25(OH)D3-sulfate is a major circulating form of vitamin D in humans — in many individuals, the sulfated fraction exceeds the unconjugated form that everyone is testing and supplementing. The binding protein that carries vitamin D through the body (Vitamin D Binding Protein / GcMAF precursor) preferentially handles the sulfated form. The fat-soluble form that supplements raise is not the primary storage or transport form the body uses.

The entire vitamin D supplementation paradigm — the testing, the diagnosis, the dosing recommendations — was built around one fraction of a two-fraction system. The fraction that supplements can't touch, and that sunlight naturally produces through intact physiological pathways, may be the more biologically significant one.

This is not an argument that vitamin D doesn't matter. It's an argument that the supplement is not what it's been presented to be — and that the test being used to justify it is not measuring what people think it is. Sunlight remains the only intervention that works through the complete system.

Stephenson J Jr. Water-Soluble Vitamin D in Human Breastmilk — the overlooked sulfated fraction and what it means for the supplementation paradigm. Substack — jimstephensonjr.substack.com

The widespread recommendation to apply sunscreen daily — including on children, infants, and during everyday non-beach activity — is presented as purely protective. The ingredients in most commercial sunscreens tell a more complicated story.

The research on whether sunscreen reduces melanoma mortality is surprisingly mixed. Non-melanoma skin cancers (basal cell and squamous cell) are largely benign and highly treatable. Melanoma correlates most strongly with indoor fluorescent light exposure and intermittent burning episodes — not cumulative total sun exposure. The countries with the highest melanoma rates (Australia, New Zealand) are also among the highest sunscreen-using populations.

What to use instead: Shade and clothing during the hottest midday hours. Broad-brimmed hats. Non-nano zinc oxide formulations for genuine high-UV situations (beach, snow, extended outdoor work). EWG's Skin Deep database (ewg.org/skindeep) rates sunscreen ingredients for safety — the contrast between what's on drugstore shelves and what EWG rates as acceptable is significant.

Matta MK, et al. Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients. JAMA. 2019. — Chemical sunscreens absorbed into blood at concentrations exceeding FDA safety threshold after a single application.

FDA Proposed Rule: Sunscreen Drug Products for Over-the-Counter Human Use. 2021. FDA.gov. — Only zinc oxide and titanium dioxide proposed as GRASE; 12 chemical filters lack sufficient evidence of safety.