There's a good chance you're not getting enough vitamin D. And if you're over fifty, this matters more than you might think. This humble nutrient—technically a hormone your body produces when sunlight hits your skin—quietly influences everything from how steady you feel on your feet to how well you fight off winter colds.

The challenge is that our ability to make vitamin D naturally declines as we age. At the same time, many of us spend more hours indoors. It's a double shift in the wrong direction. The good news? Understanding how vitamin D works gives you practical options to maintain healthy levels without obsessing over every sunny day.

You probably know vitamin D helps build strong bones. That's true—it's essential for absorbing calcium from your food. Without adequate vitamin D, your body can only absorb about 10 to 15 percent of dietary calcium. With healthy levels, that jumps to 30 to 40 percent. This matters enormously for preventing the bone thinning that leads to fractures.

But vitamin D's resume extends well beyond your skeleton. Research shows it plays a significant role in muscle function. Low levels are associated with muscle weakness and increased fall risk—a serious concern when falls are a leading cause of injury in older adults. Some studies suggest maintaining adequate vitamin D can reduce fall risk by up to 20 percent.

Your immune system also depends on this vitamin. Vitamin D receptors exist on most immune cells, helping regulate your body's defense responses. This may explain why respiratory infections often spike in winter months when vitamin D levels typically drop. While it's not a magic shield, adequate vitamin D supports the immune system you already have.

Takeaway

Vitamin D isn't just about bones—it's a foundational nutrient that supports the interconnected systems keeping you upright, mobile, and resilient.

Your skin can produce vitamin D when exposed to UVB rays, but the efficiency drops significantly with age. A seventy-year-old makes about 25 percent of the vitamin D that a twenty-year-old produces from the same sun exposure. Add sunscreen (necessary for skin cancer prevention), darker skin tones, or living at northern latitudes, and the equation gets trickier.

Food sources help but rarely provide enough on their own. Fatty fish like salmon and mackerel are excellent sources. Egg yolks, fortified milk, and some mushrooms contribute smaller amounts. Most people eating a typical diet get only 100 to 200 IU daily from food—well below the 600 to 800 IU recommended for older adults, and many experts suggest even higher amounts.

This is where supplementation often makes sense. Vitamin D3 (cholecalciferol) is generally preferred over D2 because your body uses it more efficiently. Taking it with a meal containing some fat improves absorption. Most healthy adults can safely take 1,000 to 2,000 IU daily, though your ideal dose depends on your starting levels and individual factors.

Takeaway

Think of vitamin D sources as a portfolio—some sun when practical, dietary sources where possible, and supplementation to fill the gap most of us have.

A simple blood test measuring 25-hydroxyvitamin D tells you exactly where you stand. Most labs consider 30 to 100 ng/mL the normal range, though some researchers argue that levels above 40 ng/mL offer optimal benefits. Below 20 ng/mL is considered deficient, and between 20 and 30 ng/mL is insufficient.

Not everyone needs routine testing, but it's particularly worthwhile if you're over sixty-five, spend most time indoors, have darker skin, or have conditions affecting nutrient absorption. If you're starting supplementation, testing before and after a few months helps you understand how your body responds and whether your dose needs adjustment.

Keep in mind that more isn't always better. While vitamin D toxicity is rare and usually only occurs with very high supplement doses over time, there's no benefit to pushing levels excessively high. The goal is adequacy, not maximum levels. Work with your healthcare provider to interpret results and determine what's right for your situation.

Takeaway

Testing removes the guesswork—knowing your actual vitamin D level lets you make informed decisions rather than assuming supplements are or aren't necessary.

Vitamin D deserves attention precisely because it's so easy to overlook. You can't feel a deficiency developing, and symptoms often get attributed to "just getting older." But adequate levels support the bone strength, muscle function, and immune resilience that make active aging possible.

The practical path forward is straightforward: get tested if you haven't recently, aim for sensible sun exposure when possible, and consider supplementation to bridge the gap. Small, consistent attention to this one nutrient can quietly support your vitality for years to come.