Sun, Light, and Nutrient Metabolism

Your pediatrician prescribes vitamin D drops. This is treating a symptom while ignoring the cause.

Humans evolved outdoors. Our biochemistry expects sunlight. When we raise babies indoors under artificial light, we create deficiencies that supplements only partially address.

Vitamin D: The Obvious Connection

Vitamin D is synthesized in the skin when UVB rays hit cholesterol precursors. This is the mechanism everyone knows. What's less appreciated:

Sunlight produces more than just vitamin D3. UV exposure creates multiple photoproducts, including vitamin D metabolites and other compounds. Oral vitamin D supplements provide one molecule; sunlight provides a complex of related compounds.

The vitamin D system is dose-regulated by sun exposure. You cannot overdose on vitamin D from sunlight—the skin has feedback mechanisms. Supplements lack this regulation.

Vitamin D needs cofactors. Vitamins A and K2 work together with D. Traditional sun-exposed populations also ate vitamin A-rich foods (liver, egg yolk) and K2-rich foods (fermented foods, grass-fed animal fats). The nutrients were balanced. Supplementing D alone without A and K2 creates imbalances.

Practical Vitamin D Guidance

Sunlight first:
• Brief daily sun exposure on face and arms
• Time depends on latitude, season, and skin tone
• Morning sun is gentler and still stimulates vitamin D
• 10-20 minutes for fair skin; more for darker skin
• Avoid burning—never let baby's skin redden

When supplements are appropriate:
• Winter at high latitudes (above 35 degrees N)
• Dark-skinned babies with limited sun exposure
• Premature infants
• Situations where outdoor time is truly impossible

If supplementing:
• Choose D3 (not D2)
• Consider formulations with K2
• Don't supplement in isolation—ensure vitamin A intake (egg yolk, liver)
• Typical infant dose: 400 IU daily if needed

Beyond Vitamin D: Light and Circadian Rhythm

Here's what's less commonly discussed: light exposure affects far more than vitamin D.

Circadian rhythm and metabolism: Every cell in the body has a circadian clock. These clocks regulate:
• Hormone production
• Nutrient metabolism
• Immune function
• Growth and repair

Light is the primary signal that synchronizes these clocks. Morning light exposure tells the body "it's daytime"—triggering cascades of metabolic activity.

For babies, this means:
• Morning outdoor time helps establish healthy sleep patterns
• Bright days and dark nights support hormonal development
• Artificial light at night disrupts melatonin and growth hormone

The Indoor Problem

Modern babies often experience:
• Low light levels during the day (indoor lighting is 100-500 lux; outdoor shade is 10,000+ lux)
• Blue light from screens at night
• Irregular light patterns

This isn't just about sleep. Circadian disruption affects:
• Glucose metabolism
• Immune function
• Neurodevelopment
• Appetite regulation

Simple intervention: Morning outdoor time, even in shade, provides light exposure thousands of times brighter than indoor environments. This sets circadian rhythm more powerfully than any sleep training technique.

Infrared Light and Mitochondria

Beyond the visible spectrum, near-infrared light (from sunlight, not artificial sources) directly affects cellular energy production.

The mechanism: Near-infrared light is absorbed by cytochrome c oxidase in mitochondria, enhancing ATP production. This is why sunlight feels energizing in ways that don't reduce to vitamin D alone.

For developing babies:
• Mitochondria are being established in these early years
• Energy production capacity affects everything
• Outdoor time supports cellular energy systems

This isn't mysticism—it's photobiomodulation, a field with substantial research backing.

Red Light, Melatonin, and Evening

The other end of the light spectrum matters at night.

Blue light (from screens, LEDs) at night:
• Suppresses melatonin
• Disrupts circadian rhythm
• Affects sleep quality

Red/amber light in evening:
• Doesn't suppress melatonin
• Supports natural wind-down
• Traditional firelight was this spectrum

Practical approach:
• Dim lights in the hour before bedtime
• Avoid screens before sleep
• Consider amber/red bulbs for nursery nightlights
• Darkness during sleep (not just "dim")

The Traditional Pattern

Consider how babies lived for most of human history:
• Outside for much of the day
• Exposed to full-spectrum sunlight
• Evening by firelight (red/amber spectrum)
• Total darkness at night
• Circadian rhythm synchronized to the sun

Now consider modern infants:
• Indoors under artificial light
• Low light levels during day
• Blue light from screens until bedtime
• Nightlights and street lights preventing true darkness

We supplement vitamin D because we've eliminated the sun. Perhaps we should also consider what else we've eliminated.

Seasonal Considerations

Summer:
• Vitamin D production is easy with modest exposure
• Morning and late afternoon sun is safest
• Shade still provides beneficial light
• Never let skin burn

Winter (high latitudes):
• UVB insufficient for vitamin D production November-February
• Supplement becomes more important
• Outdoor time still valuable for circadian rhythm and infrared
• Light therapy lamps can help with circadian signaling

The latitude factor:
• Below 35 degrees N (Los Angeles, Atlanta), year-round vitamin D production possible
• Above 35 degrees N, winter supplementation often needed
• Above 50 degrees N (UK, Northern Europe), supplementation essential in winter

The Eye-Light Connection

Bright light entering the eyes (not just hitting the skin) affects:
• Circadian rhythm signaling
• Pupil and eye development
• Mood and alertness

For babies:
• Outdoor time benefits eyes directly
• Don't always shade baby's eyes—they need light exposure
• Avoid direct sun glare, but normal daylight is healthy

Myopia connection: Research increasingly links insufficient outdoor time to increasing rates of childhood myopia. Bright outdoor light appears protective for developing eyes.

Grounding/Earthing

This is more speculative, but worth noting: direct skin contact with the earth may have physiological effects.

The hypothesis: The Earth's surface carries a negative electrical charge. Direct contact (bare feet on grass, hands in dirt) may influence the body's electrical state, with potential effects on inflammation and circadian rhythm.

Research is preliminary but some studies suggest benefits for sleep and inflammation markers.

Practical application: Letting baby play on grass or earth, rather than always on artificial surfaces, has no downside and potential upside.

Integrating Light Into Nutrition Thinking

We think of nutrition as what goes in the mouth. But the body receives inputs through multiple channels:

Mouth: Food, water, supplements Skin: Sunlight, temperature, touch Eyes: Light patterns, intensity, spectrum Lungs: Air quality, oxygen

A "well-nourished" baby needs more than good food. The light environment matters.

Morning routine for light exposure: 1. Wake with natural light when possible 2. Outdoor time within first hour of waking 3. Even 15 minutes in morning light helps 4. Face doesn't need direct sun—ambient outdoor light is sufficient

Evening routine: 1. Dim lights after sunset 2. Avoid screens 1-2 hours before bed 3. Use red/amber light if needed 4. True darkness for sleep

The Supplement Question

Should you give vitamin D drops?

Yes, probably, if:
• Winter at high latitudes
• Limited outdoor time due to weather or circumstances
• Darker skin with low sun exposure
• Pediatrician recommends based on levels

Maybe not if:
• Regular outdoor time in sunny climate
• Fair skin with moderate sun exposure
• Blood levels confirmed adequate

Either way:
• Don't let supplements replace outdoor time
• Ensure vitamin A and K2 intake
• Recognize that sun provides more than vitamin D

Summary

Light is a nutrient. Your baby's body expects:
• Bright light during the day
• Morning sun exposure for circadian setting
• Full-spectrum light including UV and infrared
• Darkness at night

Vitamin D drops are a partial solution to a fundamental mismatch between modern living and human biology. They're useful when needed, but they don't replace what sunlight provides.

Get your baby outside. Morning is ideal. Shade is fine. The light that seems "just normal outdoor light" is actually a complex, full-spectrum signal that drives dozens of biological processes.

Sunshine isn't just pleasant. It's nutritional.