Should You Take a Vitamin D Supplement?

Updated July 2026

The short version: for most people with normal levels, a vitamin D pill does surprisingly little, but there's a real exception, and it's worth understanding where the line falls.

Do vitamin D supplements actually strengthen bones?

For people who aren't deficient, no. For years the assumption was that vitamin D supplements protect against osteoporosis by helping the body absorb calcium. Then a large 2018 analysis found that vitamin D supplements did not improve bone mineral density at all. That study mostly involved people who already had normal vitamin D levels, which is the key caveat — topping up a level that's already adequate doesn't do anything for your bones.

What does help bone density is food and movement. A separate trial found that people with osteoporosis who ate a Mediterranean-style diet — rich in fruits, vegetables, nuts, whole grains, olive oil, and fish — actually saw bone density increase within 12 months, while those on a control diet kept losing bone. Given how slowly bone forms, seeing measurable improvement in a year is striking.

Does low vitamin D affect your heart?

It may. Vitamin D is usually filed under bone health, but the story is broader. Researchers analyzing data from the UK Biobank found that people with the lowest vitamin D levels had about an 11% higher risk of heart disease than those with higher levels, and also tended to have higher blood pressure. Low vitamin D has been linked to depression as well. So while a supplement isn't a heart drug, being genuinely deficient isn't something to ignore.

And deficiency is common. Almost 6% of Americans are severely deficient, and about 24% don't have enough. For once, we can't pin it on the American diet — vitamin D comes mostly from sunlight, not food, which is why it's called the sunshine vitamin.

How much vitamin D do you need, and where should it come from?

The recommended amount is about 600 IU a day for most adults, and 800 IU after age 70. Getting that from food alone is genuinely hard: three ounces of salmon gives you around 370 IU and three ounces of sardines about 160, and the list of good food sources is short. The most efficient source is the one that's free — 10 to 30 minutes of midday sun a few times a week, without sunscreen, is usually enough for your body to make what it needs.

That last point comes with an obvious tension, because dermatologists rightly push sunscreen to prevent skin cancer. This is exactly the situation where a supplement earns its place.

So who should actually take vitamin D?

People who are deficient — full stop. If a blood test shows you're low, taking vitamin D until your level returns to normal is sound. But if your level is already normal, there's little benefit to taking more, and more is not better — at high doses from supplements it can even cause harm. The rule of thumb is simple: test, correct a real deficiency, then ease off once your stores are back to normal.

That's the whole philosophy of supplements in one nutrient. They're for filling a documented gap, not for insurance. For everything else, food and a bit of sunshine do more than a pill ever will. For the bigger picture on which supplements are actually worth taking, see Do supplements actually work?

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