Introduction: Why Vitamin D3 Matters More Than Ever

Have you ever wondered why you feel so good after a day in the sunshine? The answer might be simpler than you think: Vitamin D3. This powerful nutrient isn't just another supplement on the shelf—it's a crucial hormone that impacts virtually every system in your body.

In today's world of indoor living and screen time, many of us aren't getting enough of this vital nutrient. Recent studies suggest that up to 42% of Americans are deficient in Vitamin D3, with even higher percentages in northern regions and among people with darker skin tones.

This comprehensive guide will explore everything you need to know about the "sunshine vitamin" and why it might be the missing piece in your health puzzle. Let's shed some light on this essential nutrient!

The Science Behind Vitamin D3: More Than Just a Vitamin

When sunlight hits your skin, something magical happens. Your body transforms UVB rays into vitamin D3 (cholecalciferol) through a complex biological process. Unlike most vitamins, D3 is technically a prohormone—it converts to a hormone in your body.

This distinction matters. While most vitamins serve as cofactors for enzymes, vitamin D3 influences gene expression. It can actually turn genes on and off throughout your body!

Your liver first converts D3 to calcidiol, then your kidneys transform it to calcitriol—the active form that works its magic throughout your systems. This final form is so powerful it affects over 2,000 genes in your body!  Huh? What does this mean in “english”?  Think of vitamin D3 as a construction manager directing how your cells grow and repair themselves.  

Vitamin D3 vs. D2: Understanding the Critical Difference

Not all vitamin D is created equal. The two major forms are D2 (ergocalciferol) and D3 (cholecalciferol). While they might sound similar, their effects in your body differ significantly.

Vitamin D2 comes from plant sources and fungi. It's less effective at raising blood levels and doesn't bind as well to vitamin D receptors in your body.

Vitamin D3, however, is the form naturally produced in human skin and found in animal products. Research consistently shows it's more potent and effective at improving vitamin D status. One study found D3 to be 87% more effective than D2 at raising blood levels!

When choosing supplements, look specifically for D3. The difference could significantly impact your health outcomes.

The Physical Powerhouse: How D3 Strengthens Your Body

Bone Health: Beyond Basic Calcium Absorption

Most people know vitamin D helps with calcium absorption, but its role goes much deeper. Vitamin D3 actively regulates the balance between bone formation and resorption.

Without adequate D3, your body can't properly mineralize bone tissue. This leads to rickets in children and osteomalacia in adults—conditions where bones become soft and weak.

Even more concerning, low vitamin D levels accelerate bone loss with age. In a landmark study following 36,282 postmenopausal women, those maintaining higher vitamin D levels showed 31% reduced risk of hip fractures.

Vitamin D3 also enhances the activity of osteoblasts (bone-building cells) while regulating osteoclasts (cells that break down bone). This delicate balance keeps your skeletal system strong throughout life.

Muscle Power: The Secret to Strength and Recovery

Your muscles are packed with vitamin D receptors. When active D3 binds to these receptors, it triggers protein synthesis and improves muscle contraction ability.

Athletes with optimal D3 levels show improved:

• Power output
• Recovery time
• Muscle protein synthesis
• Testosterone levels
• Overall physical performance

A meta-analysis of 23 studies found that vitamin D supplementation increased muscle strength, particularly in people who were deficient. Even more impressive, proper D3 levels can reduce fall risk in older adults by improving neuromuscular function.

Want to maximize your workout results? Checking your vitamin D status might be as important as your protein intake!

Heart Health: Protecting Your Cardiovascular System

Your heart loves vitamin D3. Research shows this nutrient helps regulate blood pressure, reduce inflammation, and improve overall cardiac function.

Vitamin D helps relax blood vessels by increasing nitric oxide production. This improves blood flow and reduces hypertension risk. It also helps prevent calcium deposits in arteries—a major factor in heart disease.

The Framingham Heart Study found people with low vitamin D levels had a 62% higher risk of heart attacks compared to those with sufficient levels. Multiple studies show inverse relationships between vitamin D status and coronary artery disease.

The protective mechanisms include:

• Reduced arterial stiffness
• Improved endothelial function
• Lower inflammation markers
• Better cholesterol ratios
• Decreased platelet aggregation

Immune System Supercharger: Your Body's Defense Team

The Infection Fighter: How D3 Battles Pathogens

Vitamin D3 serves as a critical regulator of your immune system's response to invaders. When infection strikes, vitamin D helps your immune cells produce potent antimicrobial peptides like cathelicidin.

These natural antibiotics can destroy bacteria, viruses, and fungi. Research shows people with higher vitamin D levels experience fewer respiratory infections and recover faster when illness strikes.

A 2017 global study analyzing data from 11,321 participants found vitamin D supplementation reduced respiratory infection risk by 42% in deficient individuals. These protective effects appear especially strong against influenza, tuberculosis, and upper respiratory infections.

Dr. Michael Holick, a leading vitamin D researcher, explains: "Vitamin D helps regulate the immune system in ways we're only beginning to understand. It appears to be crucial for proper immune response."

Autoimmunity Protection: Balancing Immune Response

Autoimmune conditions develop when your immune system mistakenly attacks your own tissues. Vitamin D3 plays a crucial role in preventing these conditions by teaching your immune system what not to attack.

Vitamin D helps your body distinguish between foreign invaders and your own cells. It modulates T-cell activity and promotes regulatory T-cells that prevent autoimmune reactions.

Population studies show striking correlations between vitamin D deficiency and autoimmune conditions including:

• Multiple sclerosis
• Rheumatoid arthritis
• Type 1 diabetes
• Inflammatory bowel disease
• Psoriasis

One Finnish study following 10,366 children found those receiving vitamin D supplements had a 78% lower risk of developing type 1 diabetes compared to those who didn't supplement.

Cancer Prevention: The Evidence Grows

The relationship between vitamin D and cancer prevention continues to strengthen. Research shows vitamin D can:

• Slow abnormal cell growth
• Cause cancer cell death (apoptosis)
• Reduce tumor blood vessel formation
• Limit cancer cell migration

A landmark study published in PLOS ONE analyzing data from 422,822 participants found that higher vitamin D levels were associated with significantly lower risk of colorectal, breast, prostate, and many other cancers.

The most profound effects appear in colorectal cancer, where individuals with highest vitamin D levels show up to 60% reduced risk compared to those with lowest levels.

Mental and Emotional Wellbeing: The Sunshine Vitamin's Hidden Powers

Depression and Mood: The D3 Connection

Have you noticed feeling down during winter months? There's a biological reason. Seasonal affective disorder (SAD) correlates strongly with reduced sunlight exposure and vitamin D production.

The relationship between vitamin D and mood extends beyond seasonal patterns. Vitamin D receptors appear throughout mood-regulating regions of your brain. When activated, these receptors influence neurotransmitter production and function.

A meta-analysis examining 14 studies with 31,424 participants found those with lowest vitamin D levels had significantly higher rates of depression compared to those with adequate levels.

Vitamin D seems to influence mood by:

• Regulating serotonin production
• Supporting dopamine system function
• Protecting against oxidative stress in brain tissue
• Reducing inflammation in neural pathways
• Promoting neuroplasticity

Cognitive Function: Protecting Your Brain

Your brain relies on vitamin D for optimal function and protection. Vitamin D receptors appear throughout the central nervous system, particularly in areas associated with learning and memory.

Research shows vitamin D helps clear amyloid plaques—protein clusters associated with Alzheimer's disease. It also supports neuron growth and connection while reducing inflammation in brain tissue.

A 25-year study tracking 1,658 adults found those maintaining higher vitamin D levels showed better cognitive performance and slower mental decline with age. Even more striking, severe vitamin D deficiency is associated with twice the risk of Alzheimer's disease.

The protective effects appear strongest for executive function, information processing speed, and memory—the cognitive domains most affected by aging.

Stress Response: Calming Your System

Modern life bombards us with stressors. Fortunately, vitamin D helps regulate our stress response systems in profound ways.

Vitamin D modulates cortisol—your primary stress hormone. Proper D3 levels help prevent cortisol overproduction while supporting proper adrenal function. This translates to better stress resilience and recovery.

Research confirms this connection. A Dutch study examining 2,809 adults found those with lowest vitamin D levels showed highest perceived stress and anxiety levels. When supplemented, many reported significant improvements in stress tolerance.

Vitamin D appears to influence stress response through:

• Regulation of the HPA axis (your body's stress control center)
• GABA receptor function (calming neurotransmitter system)
• Reduction of inflammation (which amplifies stress responses)
• Improved sleep quality (crucial for stress recovery)
• Enhanced parasympathetic nervous system activation (rest and digest mode)

The Dosage Debate: How Much D3 Do You Actually Need?

RDA vs. Optimal Levels: Understanding the Controversy

The official Recommended Dietary Allowance (RDA) for vitamin D seems surprisingly low to many health experts. Current guidelines suggest:

• 400 IU for infants
• 600 IU for children and adults up to age 70
• 800 IU for adults over 70

These recommendations aim to prevent deficiency diseases like rickets. But many researchers argue they don't promote optimal health or immune function.

The RDA levels were established primarily for bone health—not immune function, mood regulation, or disease prevention. This narrow focus explains why many doctors now recommend higher intake.

Dr. Michael Holick, professor at Boston University Medical Center, suggests: "The RDA is the minimum needed to prevent disease, not the optimal amount for health promotion."

The 10,000 IU Perspective: Why Some Doctors Recommend More

Dr. Eric Berg and other health practitioners often recommend significantly higher vitamin D3 intake—around 10,000 IU daily for many adults. This recommendation stems from several key observations.

First, our ancestral exposure far exceeded modern levels. Humans evolved spending days outdoors, producing an estimated 10,000-20,000 IU through skin synthesis. Our biology expects this input.

Second, research shows blood levels associated with optimal health require higher intake. To maintain blood levels between 40-60 ng/ml (considered optimal by many experts), most adults need 5,000-10,000 IU daily.

Third, vitamin D toxicity appears exceedingly rare below 50,000 IU daily. The safety margin far exceeds most vitamins, making conservative recommendations less necessary.

Dr. Berg explains: "We're seeing patients achieve remarkable health improvements at these higher intake levels, particularly with immune function and inflammatory conditions."

Finding Your Personal Sweet Spot: Testing and Customization

Everyone's vitamin D requirements differ based on:

• Skin pigmentation (darker skin produces less D3)
• Age (production decreases with age)
• Geography (northern latitudes receive less UVB)
• Season (winter months limit production)
• Weight (D3 stores in fat tissue)
• Genetic factors affecting metabolism

The only reliable way to determine your needs is through blood testing. The 25(OH)D test measures calcidiol—the storage form of vitamin D in your blood.

Most conventional labs consider 30 ng/ml sufficient. However, integrative practitioners typically recommend 40-80 ng/ml as the optimal range for disease prevention and immune function.

Regular testing allows personalized supplementation. Starting with 5,000 IU daily, then testing after 3 months, provides a baseline for adjustment. Many find they need 8,000-10,000 IU during winter months and less during summer.

Beyond Supplements: Natural Sources of Vitamin D3

Sunlight Exposure: Nature's D3 Factory

Your skin creates vitamin D3 when exposed to UVB rays. This natural production remains the most bioavailable source. However, several factors influence production:

Midday sun (10am-3pm) provides most UVB exposure. Morning and evening sunlight contains primarily UVA—which doesn't produce vitamin D.

For light-skinned individuals, 15-30 minutes of midday sun exposure to arms and legs can generate 10,000-20,000 IU. Darker skin may require 3-5 times longer exposure for equivalent production.

Latitude matters tremendously. Above 37° latitude (approximately Boston or Rome), winter sun doesn't provide sufficient UVB for vitamin D production between November and February.

Sunscreen blocks vitamin D production. SPF 15 reduces vitamin D synthesis by approximately 95%. Consider short, unprotected exposure before applying sunscreen for longer periods.

Food Sources: Limited But Important

Few foods naturally contain significant vitamin D3. Top sources include:

• Fatty fish (wild salmon: 988 IU per 3.5 oz serving)
• Cod liver oil (1,360 IU per tablespoon)
• Egg yolks from pasture-raised chickens (up to 120 IU each)
• Beef liver (50 IU per 3.5 oz serving)

Fortified foods provide additional sources:

• Milk (120 IU per cup)
• Orange juice (100 IU per cup)
• Breakfast cereals (varying amounts)

Even with these sources, reaching optimal intake solely through diet proves challenging. Most people require a combination of sunlight and supplementation, especially during winter months.

Synergistic Nutrients: Maximizing D3 Effectiveness

The Vitamin K2 Connection: Critical Cofactor

Vitamin D3 doesn't work alone. It requires partner nutrients—particularly vitamin K2. 

Without sufficient K2, increased calcium absorption can paradoxically contribute to arterial calcification. Think of D3 as the key that unlocks the calcium door, while K2 acts as the traffic director.

Pair your vitamin D3 supplement with K2 to ensure calcium goes to the right places. Good sources of K2 include:

• Natto (fermented soybeans)
• Grass-fed butter
• Egg yolks
• Aged cheese
• Organ meats

Many high-quality D3 supplements now include K2 for this reason. The MK-7 form of K2 shows particularly strong synergistic effects with vitamin D3.

Magnesium: The Essential Enabler

Magnesium activates the enzymes needed for vitamin D conversion and utilization. Without adequate magnesium, vitamin D remains less effective.

Research shows magnesium deficiency can lead to vitamin D resistance—where blood levels remain low despite supplementation. Conversely, correcting magnesium status often normalizes vitamin D levels.

Up to 68% of Americans don't consume adequate magnesium. Good sources include:

• Dark leafy greens
• Almonds and cashews
• Pumpkin seeds
• Dark chocolate
• Avocados
• Black beans

Consider magnesium supplementation if taking higher vitamin D3 doses. Magnesium glycinate and malate forms typically cause less digestive discomfort than oxide forms.

Vitamin A Balance: Maintaining Harmony

Vitamins A and D work together through shared receptors. Proper balance between these fat-soluble vitamins supports immune function and cell differentiation.

Traditional cultures consuming organ meats naturally received balanced ratios of these nutrients. Modern supplementation sometimes disrupts this balance.

If supplementing D3, consider:

• Consuming natural vitamin A sources (liver, egg yolks, butter)
• Using mixed carotenoid supplements rather than isolated beta-carotene
• Maintaining roughly 10:1 ratio of vitamin D to retinol (preformed vitamin A)

Many traditional cod liver oil products provide natural ratios of these nutrients, though modern processing sometimes alters these proportions.

Addressing Common Myths: Alcohol, Sugar, and Vitamin D

Alcohol's Impact: The Vitamin D Disruptor

Despite claims about "healthy" alcohol choices, all alcoholic beverages negatively impact vitamin D status. Here's the truth behind the myths:

Myth: Red wine doesn't affect vitamin D because of its antioxidants. Truth: Alcohol impairs vitamin D activation regardless of type. A study in Alcoholism: Clinical and Experimental Research found chronic alcohol consumption reduces both vitamin D production and activation.

Myth: "Low-sugar" cocktails won't affect vitamin D metabolism. Truth: The alcohol itself, not just the sugar content, disrupts liver function necessary for vitamin D conversion. Even "clean" alcohol options impair 25-hydroxylase—the enzyme converting vitamin D to its active form.

Alcohol also increases urinary excretion of magnesium—critical for vitamin D function. This double-impact makes regular drinking particularly problematic for vitamin D status.

If you consume alcohol, consider additional vitamin D supplementation and increased magnesium intake to partially offset these effects.

Sugar's Hidden Impact on Vitamin D Function

The relationship between sugar consumption and vitamin D extends beyond empty calories. Research reveals multiple mechanisms through which sugar undermines vitamin D effectiveness:

High sugar intake increases urinary calcium excretion, requiring more vitamin D to maintain calcium balance. This creates functional vitamin D deficiency even with normal intake.

Sugar consumption triggers inflammation that increases vitamin D utilization. Studies show high-glycemic diets can lower serum 25(OH)D levels by increasing metabolic clearance.

Insulin resistance—promoted by excessive sugar—impairs vitamin D receptor function. A 2015 study in the American Journal of Clinical Nutrition found each 10% increase in insulin resistance associated with 1.9% decrease in vitamin D levels.

The myth that "sugar-free" alternatives solve this problem overlooks artificial sweeteners' impact on gut bacteria that influence vitamin D metabolism. Natural stevia appears least problematic among sweetener options.

The Inflammation Connection: Why Modern Diets Deplete D3

Both alcohol and sugar share a common impact—they promote systemic inflammation. This chronic inflammation increases vitamin D requirements while impairing utilization.

Your body uses vitamin D to regulate inflammatory pathways. When inflammation rises from dietary factors, vitamin D gets consumed faster—creating relative deficiency despite adequate intake.

Research from Northwestern University found inflammation can cause vitamin D to be sequestered and stored, making it less available for immune and metabolic functions. This explains why many inflammatory conditions show low vitamin D despite supplementation.

Reducing dietary inflammation through whole foods, omega-3 fats, and anti-inflammatory spices supports vitamin D effectiveness. This strategy proves more effective than simply increasing vitamin D intake while maintaining pro-inflammatory dietary patterns.

Special Populations: Unique Vitamin D Needs

Pregnancy and Breastfeeding: Building Future Health

Vitamin D during pregnancy influences fetal development in profound ways. Research shows maternal vitamin D status affects:

• Fetal bone development
• Brain formation
• Immune system programming
• Future allergy risk
• Birth weight

A landmark study in the Journal of Clinical Endocrinology and Metabolism found pregnant women needed 4,000 IU daily to optimize maternal and neonatal outcomes—far above the standard recommendation of 600 IU.

For breastfeeding mothers, vitamin D needs remain elevated. Breast milk contains relatively little vitamin D unless the mother maintains high blood levels (typically requiring 6,000+ IU daily).

The Cochrane Database analysis concluded: "Women who received vitamin D supplements during pregnancy may have a lower risk of pre-eclampsia, gestational diabetes, low birthweight and severe postpartum hemorrhage."

Children and Adolescents: Building Strong Foundations

Children's vitamin D requirements reflect their rapid growth and development. Beyond bone formation, vitamin D influences:

• Healthy immune development
• Brain growth and cognitive function
• Respiratory health
• Insulin sensitivity

Research from the American Academy of Pediatrics suggests many children require 1,000-2,000 IU daily—particularly during winter months and growth spurts. Deficiency during childhood links to increased asthma, allergies, and autoimmune conditions later in life.

Adolescence represents another critical period. Vitamin D influences pubertal timing, bone mass accumulation, and mood regulation during these transformative years. The rapid bone growth during adolescence creates particularly high vitamin D demands.

Older Adults: Combating Age-Related Decline

After age 70, vitamin D production decreases dramatically. Your skin produces up to 75% less vitamin D from the same sun exposure compared to younger adults.

Simultaneously, vitamin D activation becomes less efficient. Kidney function typically declines with age, reducing conversion to the active form. This double-impact makes older adults particularly vulnerable to deficiency.

Research shows older adults typically need 2,000-4,000 IU daily to maintain optimal blood levels. A meta-analysis of randomized controlled trials found this higher intake associated with:

• 22% reduction in fall risk
• 30% reduction in hip fracture risk
• Improved cognitive performance
• Better mood and emotional wellbeing
• Enhanced immune response to vaccines

Practical Implementation: Building Your D3 Strategy

Testing Protocol: When and What to Measure

Effective vitamin D optimization starts with proper testing. Consider these guidelines:

The 25(OH)D test provides the most accurate assessment of your vitamin D status. This measures both D2 and D3 in their storage form.

Optimal testing frequency varies by situation:

• Baseline test to establish starting point
• Follow-up test 3 months after beginning supplementation
• Twice yearly thereafter (end of summer and end of winter)
• More frequent testing if medical conditions affect vitamin D metabolism

Most commercial labs use 30 ng/ml as the lower acceptable limit. However, research suggests 40-60 ng/ml (100-150 nmol/L) represents the optimal range for disease prevention and immune function.

Consider testing magnesium, calcium, and parathyroid hormone alongside vitamin D for more complete assessment. These markers help evaluate vitamin D metabolism and effectiveness.

Supplementation Strategies: Forms, Timing, and Absorption

Not all vitamin D supplements provide equal benefits. Consider these factors when choosing and using supplements:

D3 (cholecalciferol) shows greater bioavailability than D2 (ergocalciferol). Research demonstrates D3 raises blood levels more effectively and maintains those levels longer.

Oil-based D3 supplements typically show better absorption than dry tablets. Look for D3 in olive oil, MCT oil, or other healthy fat bases.

Taking vitamin D with your largest meal improves absorption by up to 50%. The presence of dietary fat significantly enhances uptake of this fat-soluble vitamin.

Liposomal and microencapsulated forms show promising absorption advantages, particularly for people with digestive issues or malabsorption conditions.

Combination products containing D3 with K2 and magnesium provide synergistic benefits. These combinations better reflect how these nutrients work together in natural food sources.

Lifestyle Integration: Beyond Supplementation

Maximizing vitamin D benefits extends beyond supplementation. Consider these complementary approaches:

Regular outdoor activity during midday hours provides both vitamin D production and its synergistic benefits. Exercise enhances vitamin D utilization while sunlight exposure stimulates natural production.

Stress management supports vitamin D effectiveness. Chronic stress depletes magnesium and increases inflammation—both detrimental to vitamin D function. Meditation, adequate sleep, and stress-reduction techniques complement your vitamin D strategy.

Anti-inflammatory eating patterns enhance vitamin D utilization. Mediterranean and traditional Asian diets provide complementary nutrients while reducing factors that deplete vitamin D.

Sauna use shows interesting connections to vitamin D metabolism. Regular sauna bathing correlates with improved vitamin D receptor sensitivity and reduced inflammation that might otherwise deplete vitamin D.

Recommended Visual Elements to Enhance Understanding

Image Placement Recommendations

1. Header Image: Sunrise/sunset over water showing natural beauty of sunlight (place at top of article)
2. Vitamin D Conversion Infographic: Simple flowchart showing UVB → cholecalciferol → calcidiol → calcitriol pathway (place after "Science Behind Vitamin D3" section)
3. Comparative Map: World map showing vitamin D production potential by latitude and season (place in "Sunlight Exposure" section)
4. Food Sources Photo Array: Visual display of top D3 food sources with IU amounts (place in "Food Sources" section)
5. Synergy Diagram: Visual showing how D3, K2, magnesium, and vitamin A work together (place in "Synergistic Nutrients" section)
6. Before/After Blood Test Results: Anonymous example showing improvement in 25(OH)D levels after supplementation (place in "Testing Protocol" section)
7. Seasonal Variation Graph: Line chart showing typical seasonal fluctuations in vitamin D levels (place between "Dosage Debate" and "Beyond Supplements" sections)
8. Comparison Table: RDA recommendations vs. optimal intake recommendations by age group (place in "RDA vs. Optimal Levels" section)
9. Mechanism Illustration: Simple diagram showing vitamin D receptors in different body systems (place at beginning of physical benefits section)
10. Myth vs. Fact Cards: Visually appealing cards contrasting common myths about alcohol/sugar with scientific facts (place in "Addressing Common Myths" section)

Conclusion: Embracing the Sunshine Vitamin

Vitamin D3 stands as one of nature's most powerful health optimizers. From bone strength to immune function, brain health to emotional wellbeing, few nutrients show such widespread impact.

The evidence continues mounting for higher intake than conventional recommendations suggest. Whether through sensible sun exposure, strategic supplementation, or combination approaches, optimizing your vitamin D status represents one of the highest-leverage health strategies available.

The journey to optimal vitamin D status requires personalization. Your genetics, lifestyle, geography, and health goals all influence your ideal approach. Working with knowledgeable healthcare providers who understand both conventional and optimal ranges can help navigate this path.

In a world of complex health challenges, vitamin D3 offers a remarkably simple intervention with profound benefits. As research continues expanding our understanding, the sunshine vitamin's importance only grows brighter.

References and Further Reading

1. Holick, M. F. (2017). The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Reviews in Endocrine and Metabolic Disorders, 18(2), 153-165. https://doi.org/10.1007/s11154-017-9424-1
2. Martineau, A. R., Jolliffe, D. A., Hooper, R. L., Greenberg, L., Aloia, J. F., Bergman, P., ... & Camargo, C. A. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. The BMJ, 356, i6583. https://doi.org/10.1136/bmj.i6583
3. Zittermann, A., & Pilz, S. (2019). Vitamin D and cardiovascular disease: An update. Anticancer Research, 39(9), 4627-4635. https://doi.org/10.21873/anticanres.13643
4. Wimalawansa, S. J. (2018). Non-musculoskeletal benefits of vitamin D. The Journal of Steroid Biochemistry and Molecular Biology, 175, 60-81. https://doi.org/10.1016/j.jsbmb.2016.09.016
5. Hyppönen, E., Läärä, E., Reunanen, A., Järvelin, M. R., & Virtanen, S. M. (2001). Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study. The Lancet, 358(9292), 1500-1503. https://doi.org/10.1016/S0140-6736(01)06580-1
6. Gaksch, M., Jorde, R., Grimnes, G., Joakimsen, R., Schirmer, H., Wilsgaard, T., ... & Pilz, S. (2017). Vitamin D and mortality: Individual participant data meta-analysis of standardized 25-hydroxyvitamin D in 26916 individuals from a European consortium. PLOS ONE, 12(2), e0170791. https://doi.org/10.1371/journal.pone.0170791
7. Hollis, B. W., Johnson, D., Hulsey, T. C., Ebeling, M., & Wagner, C. L. (2011). Vitamin D supplementation during pregnancy: double‐blind, randomized clinical trial of safety and effectiveness. Journal of Bone and Mineral Research, 26(10), 2341-2357. https://doi.org/10.1002/jbmr.463
8. Anglin, R. E., Samaan, Z., Walter, S. D., & McDonald, S. D. (2013). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. The British Journal of Psychiatry, 202(2), 100-107. https://doi.org/10.1192/bjp.bp.111.106666
9. Littlejohns, T. J., Henley, W. E., Lang, I. A., Annweiler, C., Beauchet, O., Chaves, P. H., ... & Llewellyn, D. J. (2014). Vitamin D and the risk of dementia and Alzheimer disease. Neurology, 83(10), 920-928. https://doi.org/10.1212/WNL.0000000000000755
10. Heaney, R. P. (2008). Vitamin D in health and disease. Clinical Journal of the American Society of Nephrology, 3(5), 1535-1541. https://doi.org/10.2215/CJN.01160308
11. Bikle, D. D. (2014). Vitamin D metabolism, mechanism of action, and clinical applications. Chemistry & Biology, 21(3), 319-329. https://doi.org/10.1016/j.chembiol.2013.12.016
12. Cannell, J. J., Vieth, R., Umhau, J. C., Holick, M. F., Grant, W. B., Madronich, S., ... & Giovannucci, E. (2006). Epidemic influenza and vitamin D. Epidemiology & Infection, 134(6), 1129-1140. https://doi.org/10.1017/S0950268806007175