Vitamin D: What You Need to Know

Often called the “sunshine vitamin,” vitamin D is essential for your health but frequently overlooked. Unlike most vitamins, your body can produce vitamin D when your skin is exposed to sunlight. Yet despite this, vitamin D deficiency is surprisingly common, affecting an estimated 1 billion people worldwide.

Why Vitamin D Matters

Vitamin D plays crucial roles throughout your body:

Bone Health

Vitamin D helps your body absorb calcium, which is essential for building and maintaining strong bones. Without adequate vitamin D:

• Bones can become thin, brittle, or misshapen
• Risk of osteoporosis increases
• Fractures become more likely, especially as you age

Immune Function

Your immune cells have vitamin D receptors, and research shows vitamin D:

• Helps activate immune defenses
• May reduce the risk of respiratory infections
• Plays a role in regulating immune responses

Muscle Function

Vitamin D supports muscle strength and function:

• Deficiency is linked to muscle weakness
• Adequate levels may improve physical performance
• Important for balance and fall prevention in older adults

Mood and Mental Health

Emerging research connects vitamin D to mental well-being:

• Low levels are associated with increased risk of depression
• May play a role in seasonal affective disorder (SAD)
• Some studies show mood improvement with supplementation

Signs of Deficiency

Vitamin D deficiency can be subtle. Common signs include:

• Fatigue and tiredness: Feeling tired despite adequate sleep
• Bone pain: Particularly in the lower back, hips, and legs
• Muscle weakness: Difficulty with physical tasks
• Mood changes: Depression or feelings of sadness
• Frequent illness: Getting sick often, especially respiratory infections
• Slow wound healing: Cuts and bruises taking longer to heal
• Hair loss: Particularly in women
• Bone loss: Reduced bone mineral density

Many people with deficiency have no obvious symptoms, which is why testing can be valuable.

How to Get Vitamin D

There are three main sources of vitamin D:

1. Sunlight

Your skin produces vitamin D when exposed to UVB rays:

• How much: 10-30 minutes of midday sun, several times per week
• Factors that affect production: Skin tone (darker skin needs more time), latitude, season, time of day, age, sunscreen use
• The balance: Get enough sun for vitamin D while protecting against skin damage
• Reality check: Many people don’t get adequate sun exposure, especially in winter months or northern climates

2. Food Sources

Few foods naturally contain vitamin D, but some good sources include:

Natural sources:

• Fatty fish (salmon, mackerel, sardines, tuna)
• Fish liver oils
• Egg yolks
• Beef liver
• Cheese

Fortified foods:

• Milk and dairy products
• Orange juice
• Breakfast cereals
• Plant-based milk alternatives

Amounts in perspective:

• 3 oz wild-caught salmon: ~600-1000 IU
• 3 oz canned tuna: ~150 IU
• 1 cup fortified milk: ~100-120 IU
• 1 egg yolk: ~40 IU

3. Supplements

For many people, supplements are the most reliable way to maintain adequate levels:

Types of vitamin D:

• Vitamin D3 (cholecalciferol): The form your skin produces; generally preferred
• Vitamin D2 (ergocalciferol): Plant-derived; less effective at raising blood levels

General recommendations:

• Adults: 600-800 IU daily (higher doses may be recommended based on blood levels)
• Upper limit: 4,000 IU daily for most adults (higher doses should be supervised by a healthcare provider)
• Best absorbed: When taken with a meal containing fat

Getting Tested

A simple blood test can measure your vitamin D levels:

The Test

The 25-hydroxyvitamin D test (also called 25(OH)D) is the best indicator of vitamin D status.

Understanding Your Results

Level (ng/mL)	Status
Less than 12	Deficient
12-20	Insufficient
20-50	Adequate for most people
Above 50	Potentially too high

Who Should Get Tested?

Consider testing if you:

• Have limited sun exposure
• Have dark skin
• Are over age 65
• Have conditions affecting fat absorption
• Are obese
• Take medications that affect vitamin D metabolism
• Experience symptoms of deficiency
• Have osteoporosis or a history of fractures

What to Do with Your Results

Work with your healthcare provider to:

• Interpret your specific results
• Determine the right supplementation dose if needed
• Schedule follow-up testing to monitor levels
• Address any underlying causes of deficiency

Key Takeaways

1. Vitamin D is essential for bones, immunity, muscles, and mood
2. Deficiency is common and often goes unnoticed
3. Sun, food, and supplements are your three sources
4. Testing is the only way to know your true vitamin D status
5. Most people benefit from supplementation, especially in winter months