What is Vitamin D?
Vitamin D is a fat-soluble vitamin that functions more like a hormone in the body. It exists in two primary forms:
Vitamin D2 (Ergocalciferol): Derived from plant sources and fungi. Created when ergosterol in plants is exposed to UV light. Less potent and shorter-acting than D3.
Vitamin D3 (Cholecalciferol): The natural form produced in human skin when exposed to UVB sunlight. Also found in animal sources. More effective at raising and maintaining blood levels.
How It Works:
Skin synthesis: UVB rays convert 7-dehydrocholesterol to vitamin D3
Liver conversion: Vitamin D becomes 25(OH)D (calcidiol) - the storage form
Kidney activation: 25(OH)D becomes 1,25(OH)2D (calcitriol) - the active hormone
Primary Functions & Benefits
Essential Functions:
Calcium Absorption: Enhances intestinal calcium and phosphorus absorption
Bone Health: Regulates bone mineralization and remodeling
Immune Modulation: Supports both innate and adaptive immune responses
Cell Growth Regulation: Controls cell proliferation and differentiation
Muscle Function: Maintains muscle strength and balance
Gene Expression: Regulates over 1,000 genes
Health Benefits:
Prevents rickets in children and osteomalacia in adults
Reduces risk of osteoporosis and fractures
Supports immune function and reduces autoimmune disease risk
May reduce respiratory infection frequency and severity
Potentially lowers risk of certain cancers (colorectal, breast, prostate)
Supports cardiovascular health
May improve mood and reduce depression risk
Helps regulate blood pressure
Supports muscle strength and reduces fall risk in elderly
Recommended Daily Amounts
Official RDAs (often considered insufficient by many experts):
Infants 0-12 months: 400 IU (10 mcg)
Children 1-18 years: 600 IU (15 mcg)
Adults 19-70 years: 600 IU (15 mcg)
Adults 70+ years: 800 IU (20 mcg)
Pregnancy/Breastfeeding: 600 IU (15 mcg)
Optimal Levels (Based on Current Research):
Maintenance: 1,000-2,000 IU daily for most adults
Deficiency correction: 2,000-5,000 IU daily
Therapeutic: 5,000-10,000 IU daily (under medical supervision)
Target Blood Levels:
25(OH)D: 30-50 ng/mL (75-125 nmol/L) for optimal health
Minimum: >20 ng/mL (50 nmol/L) to prevent deficiency
Optimal range: 40-60 ng/mL (100-150 nmol/L) according to many experts
Food Sources & Sun Exposure
Natural Food Sources (Limited):
Vitamin D3:
Fatty fish: salmon, mackerel, sardines, tuna
Fish liver oils (cod liver oil)
Egg yolks (from pasture-raised chickens)
Beef liver
Cheese (small amounts)
Vitamin D2:
UV-exposed mushrooms (portobello, maitake)
Fortified plant-based foods
Fortified Foods:
Milk and dairy products
Breakfast cereals
Orange juice
Plant-based milk alternatives
Some margarines
Sun Exposure Guidelines:
Fair skin: 10-15 minutes midday sun exposure
Darker skin: 20-30 minutes or longer
Factors affecting synthesis: Latitude, season, time of day, skin color, age, sunscreen use
Optimal time: 10 AM - 3 PM when UVB rays are strongest
Supplementation Guidelines
D2 vs D3 for Supplements:
Vitamin D3 (Cholecalciferol) - PREFERRED:
More effective at raising blood levels
Longer-lasting in the body
Better absorbed and utilized
Natural form for humans
Vitamin D2 (Ergocalciferol):
Less effective than D3
Shorter duration of action
Often used in prescription medications
Suitable for vegans (plant-derived)
Typical Supplement Doses:
Daily maintenance: 1,000-4,000 IU
Weekly dosing: 7,000-28,000 IU once per week
Monthly dosing: 50,000 IU once per month (prescription)
Deficiency treatment: 5,000-10,000 IU daily for 8-12 weeks
Timing & Administration:
Best taken with the largest meal of the day (enhances absorption by 50%)
With dietary fat for optimal absorption
Morning preferred - may interfere with sleep if taken late
Consistent timing helps maintain steady levels
Synergistic Supplements
Essential Cofactors - Take WITH Vitamin D:
Vitamin K2 (MK-7): 100-200 mcg
Directs calcium to bones and away from arteries
Prevents calcium buildup in soft tissues
Essential for bone and cardiovascular health
Magnesium: 300-400 mg
Required for vitamin D metabolism
Activates vitamin D enzymes
Deficiency impairs vitamin D function
Calcium: 1,000-1,200 mg (from food + supplements)
Works synergistically with vitamin D
Better absorbed when vitamin D levels are adequate
Beneficial Combinations:
Vitamin A: Helps prevent vitamin D toxicity
Zinc: Supports immune benefits of vitamin D
Boron: Enhances vitamin D metabolism
Omega-3 fatty acids: Improve vitamin D absorption
Interactions & What NOT to Take
Medications That Reduce Vitamin D:
Corticosteroids: Decrease calcium absorption
Weight-loss drugs (orlistat): Block fat absorption
Cholesterol medications (cholestyramine): Reduce absorption
Anticonvulsants: Increase vitamin D metabolism
Thiazide diuretics: May increase calcium levels dangerously
Supplements That May Interfere:
High-dose magnesium: May reduce absorption if taken simultaneously
Fiber supplements: Take 2+ hours apart
High calcium doses: May reduce vitamin D absorption
Be Cautious With:
Digoxin: Vitamin D increases calcium, which can increase toxicity risk
Calcium channel blockers: Enhanced by increased calcium absorption
Who Should Take Vitamin D
High-Priority Groups:
People with limited sun exposure: Indoor workers, northern latitudes
Older adults: Reduced skin synthesis and dietary intake
Dark-skinned individuals: In northern climates (melanin blocks UVB)
Infants (breastfed): Breast milk is low in vitamin D
Pregnant/breastfeeding women: Increased needs
People with malabsorption: Celiac, Crohn's, cystic fibrosis
Obese individuals: Vitamin D stored in fat tissue, less bioavailable
Individuals with chronic kidney or liver disease: Impaired activation
Specific Conditions That May Benefit:
Osteoporosis or osteopenia
Frequent infections
Autoimmune conditions
Depression or SAD (Seasonal Affective Disorder)
Multiple sclerosis
Type 1 diabetes
Muscle weakness or pain
High blood pressure
Who Should AVOID or Use Caution
Contraindications:
Hypercalcemia: High blood calcium levels
Kidney stones (calcium oxalate): History of kidney stones
Sarcoidosis: Can cause hypercalcemia
Hyperparathyroidism: Already high calcium levels
Severe kidney disease: Impaired vitamin D metabolism
Use Caution:
Atrial fibrillation: High calcium may worsen arrhythmias
Taking digoxin: Monitor calcium levels closely
History of kidney stones: Monitor calcium and consider citrate
Granulomatous diseases: May increase calcium absorption
Deficiency Symptoms
Common Deficiency Signs:
Bone/muscle pain: Especially back, hips, legs
Muscle weakness: Difficulty climbing stairs, getting up from chairs
Frequent infections: Colds, flu, respiratory infections
Fatigue: Despite adequate sleep
Depression/mood changes: Especially seasonal
Hair loss: Particularly in women
Slow wound healing: Impaired immune function
Severe Deficiency:
Children:
Rickets: Soft, weak bones, skeletal deformities
Delayed tooth development
Growth retardation
Increased seizure risk (from low calcium)
Adults:
Osteomalacia: Bone pain, muscle weakness
Increased fracture risk
Severe muscle weakness
Bone deformities in severe cases
At-Risk Populations:
People living in northern latitudes (>37° north)
Those who avoid sun exposure or always use sunscreen
Individuals with dark skin in low-sun environments
Elderly in nursing homes
People following strict vegan diets
Toxicity Symptoms
Hypercalcemia Symptoms (from excess vitamin D):
Early signs:
Nausea and vomiting
Loss of appetite
Excessive thirst and urination
Weakness and fatigue
Nervousness and irritability
Severe toxicity:
Kidney stones and kidney damage
Heart rhythm abnormalities
Confusion and disorientation
High blood pressure
Calcium deposits in soft tissues
Bone pain and muscle weakness
Toxic Levels:
Blood level: >150 ng/mL (375 nmol/L) of 25(OH)D
Daily intake: Generally >10,000 IU daily long-term for adults
Acute toxicity: Rare, requires extremely high doses (>50,000 IU daily for months)
Note: Toxicity from sun exposure is impossible - the body self-regulates production.
Testing & Monitoring
When to Test:
Before starting supplementation
After 3-6 months of supplementation
Annually for maintenance
If symptoms of deficiency or toxicity occur
Test Type:
25(OH)D (calcidiol): Best marker of vitamin D status
NOT 1,25(OH)2D: Can be misleading as it's tightly regulated
Optimal Testing Schedule:
Baseline: Test current level
Follow-up: 3 months after starting supplements
Maintenance: Every 6-12 months once optimal level achieved
Special Considerations
Seasonal Variations:
Levels typically lowest in late winter/early spring
Highest in late summer/early fall
May need higher doses in winter months
Consider "loading doses" before winter
Age-Related Factors:
Infants: Exclusively breastfed babies need supplementation
Children: Especially important during growth spurts
Elderly: Reduced skin synthesis, often need higher doses
Pregnancy: Critical for fetal bone development and maternal health
Geographic Considerations:
Northern latitudes (above 37°N): Limited UVB in winter
Southern latitudes: Year-round synthesis possible
Urban environments: Air pollution reduces UVB penetration
High altitudes: Increased UVB exposure
Absorption Factors:
Enhanced by: Dietary fat, magnesium adequacy, healthy gut
Reduced by: Age, obesity, malabsorption disorders, certain medications
Individual variation: Genetic differences in metabolism
D2 vs D3: The Bottom Line
Choose D3 (Cholecalciferol) unless:
You're strictly vegan (then D2 is acceptable)
Your doctor prescribes D2 specifically
D3 is not available
Why D3 is superior:
3-5 times more effective at raising blood levels
Maintains levels longer
Better recognized by human enzymes
More research supporting benefits
Summary & Key Takeaways
Vitamin D is crucial for bone health, immune function, and overall wellness. Most people need supplementation, especially in northern climates or with limited sun exposure. Vitamin D3 is preferred over D2, and it should be taken with fat and essential cofactors like vitamin K2 and magnesium.
Bottom Line: Test your blood level first, choose D3 over D2, take with your largest meal, include cofactors (especially K2 and magnesium), aim for blood levels of 40-60 ng/mL, and monitor regularly. Start with 2,000-4,000 IU daily for most adults, but adjust based on blood test results.
Hello and welcome to the latest edition of Inner Strength, Outer Glow where we talk about health and wellness from your daily chaotic routine.
As the days grow longer and the world bursts with fresh blooms, spring awakens a natural desire for renewal.
Just like you wouldn't hesitate to declutter your home after a long winter, it's the perfect time to give your health a refresh too!
This newsletter is packed with tips and tricks to help you spring clean your body, mind, and spirit, so you can blossom into your healthiest self this season.