Vitamin D: Why We Probably Need More of It

Vitamin D is one of those nutrients everyone has heard about… but few people truly understand. And yet — vitamin D deficiency is incredibly common in both adults and children.

If you’ve ever been told your levels are low and thought, “But I go outside?” or “My kid drinks milk — how could they be low?”

You’re not wrong to be confused. Let’s clear it up.

What Is Vitamin D, and Why Does It Matter?

Vitamin D is essential for:

• Strong bones and teeth

• Mood 

• Hormone production 

• Calcium absorption

• Immune function

• Muscle strength

• Growth and development in children

In kids, low vitamin D can affect bone development. In adults, it’s linked to bone loss, fractures, muscle weakness, fatigue, and immune issues. Vitamin D doesn’t just support health — it helps maintain it.

Why So Many Adults and Children Aren’t Getting Enough Vitamin D

Despite its importance, vitamin D is one of the most commonly deficient nutrients worldwide. Here’s why:

☀️ 1. We Don’t Get Enough Sunlight

Yes, vitamin D is known as the “sunshine vitamin.” But modern life makes sun exposure tricky.

Factors that limit vitamin D production:

• Indoor jobs and school days

• Sunscreen use (important for skin cancer prevention!)

• Living at northern latitudes

• Winter months with low UV exposure

• Early mornings, late afternoons, or cloudy days

You’d need direct midday sun on bare skin, several times per week — which isn’t realistic or recommended for most people.

🥛 2. Very Few Foods Naturally Contain Vitamin D

Vitamin D is not abundant in the food supply.

Foods that contain some vitamin D:

• Fatty fish (salmon, sardines, trout)

• Egg yolks

• Liver (not a crowd favorite)

• Fortified foods (milk, yogurt, cereal, some plant milks)

Even with these foods, most people cannot meet vitamin D needs through diet alone.

🧃 3. Fortified Foods Don’t Always Cover Our Needs

Many parents assume: “My child drinks milk — they must be getting enough vitamin D.”

But:

• Not all kids drink enough milk

• Plant milks aren’t always fortified the same way

• Portion sizes matter

• Some kids avoid dairy entirely

The same goes for adults.

🧬 4. Individual Factors Affect Vitamin D Levels

Some people need more vitamin D than others, including:

• People with darker skin

• Breastfed infants (breast milk is naturally low in vitamin D)

• Older adults

• People with digestive conditions affecting absorption

• Those who carry more body fat (vitamin D gets stored, not used)

Two people can eat the same diet and have very different vitamin D levels.

Signs of Low Vitamin D (Often Subtle)

Low vitamin D doesn’t always scream for attention.

Possible signs include:

• Frequent illness

• Bone or muscle pain

• Fatigue or low energy

• Slow growth in children

• Bone fractures or bone weakness

Many people have no obvious symptoms — which is why deficiency often goes unnoticed.

How Much Vitamin D Do We Need?

General guidelines (may vary by provider):

• Infants: 400 IU/day

• Children & teens: 600–1,000 IU/day

• Adults: 600–2,000 IU/day

Some individuals need more to correct a deficiency — this should always be guided by labs and a healthcare provider.

Should Adults and Kids Take Vitamin D Supplements?

First, we need to make sure we are in fact low in vitamin D before unnecessarily spending money on supplements. If testing isn't available at this time for you or your family, taking the recommended amount in fall and winter months may be the best route. As always, check with your healthcare provider as they will know your situation best. 

Vitamin D supplements are:

• Safe when used appropriately

• Inexpensive

• One of the most effective ways to correct deficiency

Common forms:

• Liquid drops (great for infants and kids)

• Chewables or gummies

• Capsules or tablets for adults

The Bottom Line

Vitamin D deficiency is common in both adults and children, even among people who eat well and spend time outside.

Supporting vitamin D intake through food, safe sun exposure, and supplementation when needed helps protect:

• Bone health

• Immune function

• Growth and development

• Long-term health for the whole family

If you’re unsure whether you or your child are getting enough, a dietitian can help you create a plan that’s simple, safe, and personalized.