This Is How Much Fish You Have To Eat To Get Enough Vitamin D

In a world of nutrition science and advice that seems riddled with conflicting opinions and open-ended questions, there's one fact you can hang your hat on: Vitamin D is important for a whole slew of body functions*—and almost none of us are getting enough. (An alarming 41% of American adults1 are clinically insufficient, meaning they're in the danger zone for straight-up deficiency—and the health consequences that come with it*.)

And though you might think your healthy eating habits excuse you from thinking too much about whether you're low in the sunshine vitamin, well, we've got a bit of a reality check for you: They don't.

You see, when it comes to vitamin D, the whole "food first" concept fails, says mbg director of scientific affairs Ashley Jordan Ferira, Ph.D., RDN. If we rely on natural food sources of vitamin D alone, 100% of Americans2 over the age of 2 fail to consume just 400 I.U. of vitamin D per day.

Just how much of a problem is that, really? A pretty big one. A little simple math based on landmark pharmacokinetic research3 reveals that we actually need a minimum of 3,000 I.U. per day to avoid vitamin D deficiency.* So, even if we all ate 400 I.U. of vitamin D per day, we'd still be less than 15% of the way there.

In case you're still not sold on the fact that you're likely (OK, almost definitely) not getting enough vitamin D through food alone, allow us to paint a fishy picture for you.

Compared to your next best vitamin D food sources—UV-exposed mushrooms (366 I.U. per serving; but that's vitamin D2, which is way less effective than D3) and fortified 2% milk (100 to 120 I.U. per serving)—fish really does seem impressive.

Unfortunately, though, it only gets you so far. Even if you just aim for that minimum of 3,000 I.U. per day, a serving of cod liver oil makes the most impact, packing 45% of that daily need. However, trout only gets you about 22% of the way there—and salmon just 19%.

Since relying on food alone for vitamin D is an exercise in futility (sorry, the truth hurts!), a daily vitamin D supplement really is necessary.* For that supplement to actually do its job for most normal-weight adults, it needs to check a couple of important boxes. Namely, it needs to provide vitamin D3 instead of vitamin D2 (again, D2 is less effective) and pack 5,000 I.U. of it.