Why Low Vitamin D Is More Common Than You Think

Introduction

Vitamin D is one of the most common nutrient deficiencies I see — even in sunny states. And while it’s best known for bone health, low levels can impact everything from immune function to mood and metabolism. Many patients are surprised to learn they’re low until symptoms (or lab results) reveal the bigger picture. Here’s what you need to know about vitamin D, why it matters, and how to optimize it safely.

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin that acts more like a hormone in the body. It helps regulate calcium, supports immune health, influences mood and brain function, and plays a role in gene expression.

It’s produced by your skin in response to sunlight — but can also be consumed from food or supplements.

Why Are So Many People Deficient?

Several reasons:

• Limited sun exposure (indoor jobs, sunscreen use, long winters)
• Darker skin tones (more melanin = less D production from sun)
• Obesity (vitamin D gets sequestered in fat tissue)
• Gut issues (like celiac or IBD) that impair absorption
• Aging (older adults make less D in the skin)

Even in sunny areas, deficiency is common — especially in winter months.

What Are Signs of Low Vitamin D?

Symptoms can be subtle or nonspecific, including:

• Fatigue
• Depressed mood or seasonal affective disorder
• Frequent illness or slow recovery
• Muscle weakness or bone aches
• Hair thinning

Some patients feel fine — but low levels show up on labs and may contribute to long-term risks.

What’s a Healthy Range?

Optimal levels vary slightly by lab, but here’s a general guide:

• Deficient: Under 30 ng/mL
• Insufficient: 30–50 ng/mL
• Optimal: 50–70 ng/mL

For patients with autoimmune issues or bone concerns, I often aim for the higher end of that range.

Why Does Vitamin D Matter?

Low vitamin D is linked to increased risk of:

• Osteoporosis and fractures
• Autoimmune diseases
• Respiratory infections
• Type 2 diabetes
• Heart disease
• Depression and cognitive decline

Because vitamin D affects hundreds of genes, its impact is widespread.

How Can You Boost Your Levels?

1. Get Some Sun

• 10–30 minutes a few times per week, depending on your skin tone and location
• Expose face, arms, and legs when possible
• Midday sun is most efficient for D production

Note: sunscreen blocks vitamin D synthesis, but I still recommend protecting skin for longer exposures.

2. Eat Vitamin D–Rich Foods

• Fatty fish (salmon, sardines, mackerel)
• Egg yolks
• Cod liver oil
• Mushrooms (especially UV-exposed)
• Fortified foods (milk, plant milks, cereals)

Diet alone is usually not enough — but every bit helps.

3. Supplement Wisely

If your levels are low, I often recommend:

• Vitamin D3: The active form, more bioavailable than D2
• K2: Helps direct calcium to bones instead of arteries (often paired with D)

Dosing depends on labs — a typical maintenance dose is 1000–5000 IU per day, but always test before supplementing long-term.

Can You Get Too Much?

Yes — though it’s rare. Very high doses over time can cause toxicity, leading to calcium buildup in the blood (hypercalcemia), kidney issues, and nausea.

That’s why I recommend testing at least once or twice a year if supplementing consistently.

Final Thoughts

Vitamin D is a foundational piece of your health puzzle — affecting everything from energy to immune function to long-term disease risk. If you haven’t tested your levels recently, ask your provider to include it on your next panel. It’s a simple step that can offer big insights.

And if your levels are low, don’t panic — with sun, smart food choices, and appropriate supplementation, most people can restore healthy levels within a few months.