Also known as "the sunshine vitamin," vitamin D is an essential nutrient that contributes to many important functions in the body (even though it's perhaps best-known for its ability to assist in calcium and phosphorous absorption and balance in the body, as well as its contribution to bone health).*

And while you might think that the best way to up your vitamin D levels if you're running low is to get more sun, it's not really that simple. While your skin certainly does produce vitamin D when exposed to the sun's rays, just how much you get varies significantly based on factors like where you live, how much skin you expose, your skin tone, and more. (Not to mention that sunbathing sans sunscreen comes with potential risks.)

So, what's at stake here? Well, a lot. Research published in the Journal of Pharmacology & Pharmacotherapeutics has linked vitamin D deficiency to a host of implications for your health, including those related to your bones, immunity, heart health, metabolic health, and more.

The honest truth is that food can only do so much to help most people achieve truly optimal vitamin D status—a serum vitamin D [or 25(OH)D, level of 50 ng/ml or more] which requires 5,000 IU of the vitamin per day.* In fact, 100% of Americans over the age of 2 fail to consume even just 400 IU of vitamin D per day, per research published in The Journal of Nutrition.

You can get some of this all-important micronutrient through your diet. Read on for a breakdown of the best vitamin D foods you can eat (including vegetarian and vegan vitamin D foods), plus what to know about how to best absorb them and the lowdown on supplementing with vitamin D.

When it comes to foods high in vitamin D, fatty fishes lead the pack (or, erm, "lead the school"), offering more of the sunshine vitamin than most other foods out there.

Cod liver oil is one of the most vitamin D-rich food products available for consumption, with one tablespoon offering 1,360 IU (that's about 27% of that 5,000 IU goal). You can spoon the fishy liquid down straight, add it to salad dressings, or find it in softgels.

Three ounces of farmed trout contains 645 IU of vitamin D, which is just shy of 13% of what you'll need to hit 5,000 IU per day (i.e., you'd need around 8 servings of trout). If you needed an excuse to mix up your seafood game, it's a pretty worthwhile one.

One of the most popular picks at the seafood counter (as well as your favorite sushi joint), salmon (specifically sockeye) provides 570 IU per three-ounce serving. That's about 11% of the 5,000 IU you want to hit in a day. Go ahead and order that spicy salmon roll or grill up some salmon at home.

If you don't eat meat or fish, your list of vitamin D food options grows shorter, though you've still got a few sources to pick from.

If milk is a part of your routine, opt for a fortified variety. One cup of fortified 2% milk contains about 100 to 120 IU of vitamin D. That's less than 3% of 5,000 IU, but better than nothing, right? (And milk delivers protein plus an array of essential micronutrients).

Those scrambled eggs you rely on in the morning provide a modest amount of vitamin D, at 44 IU a pop (which, unfortunately, barely moves the needle considering how much we really need each day). But again, a high-quality source of protein, micronutrients, and phytonutrients (carotenoids in the yolk).

Don't eat animal products at all? You've got slim pickin's when it comes to vitamin D foods. Here are your options.

Cool fact of the day: Half a cup of white mushrooms that have been exposed to UV light can pack up to 366 IU of vitamin D, or about 7% of that 5,000 IU daily goal. Cook them up into stir-fries or add raw slices to your next salads.

From soy and oat to almond and cashew, plant-based eaters have plenty of alternative milks to pick from these days. One thing to look for on those labels: whether a given product is fortified with vitamin D. Fortified options typically provide between 100 and 144 IU of vitamin D per one-cup serving. Alas, it's not much; we know.

Many cereal brands are also in on the vitamin D fortification game and provide a measly 80 IU per serving on average. Combine your go-to cereal with a fortified milk alternative to rack up about 200 IU.

Vitamin D is a fat-soluble vitamin, which is just a fancy way of saying its chemical design is such that it dissolves in oils and fats and can be retained in the body for long periods of time. It also means that you need to consume some sort of fat alongside your vitamin D in order to best absorb it (more on that in a minute).

From there, vitamin D undergoes two conversion processes before becoming an active substance in your body, explains the The National Academies. The first step occurs in the liver, where the enzyme 25-hydroxylase forms 25-hydroxyvitamin D, or 25(OH)D. The second step occurs in the kidneys and in target tissues, where 25(OH)D is converted to the hormone calcitriol [1,25(OH)2D].

Serum total 25(OH)D is the form of vitamin D that circulates throughout the body, so it's what your doctor measures when they perform a blood test to check your vitamin D status.

As Ashley Jordan Ferira, Ph.D., R.D.N., mbg's director of scientific affairs, explains: "25(OH)D is a biomarker that represents the totality of your vitamin D inputs from both D3 and D2 forms: from foods, beverages, sunshine, and supplements. It's a number to know."

If you're consuming vitamin D from food sources that happen to already contain some fat (like salmon, eggs, or milk) don't sweat about absorption. However, if that's not the case, you'll want to make sure you're eating a source of healthy fats alongside the nutrient. What fits the bill for healthy fats, though? Plenty of foods, including avocado, olive oil, coconut, and even cheese or yogurt.

According to nationally representative research conducted by The University of Michigan, an alarming 41% of American adults meet the clinical criteria for vitamin D insufficiency: [25(OH)D less than or equal to 30 ng/ml]. That same research also found that 29% of adults in the U.S. are flat-out deficient, which means their levels are less than 20 ng/ml.*

Though vitamin D inadequacy is clearly a widespread problem, there are a few factors that increase your chances of falling way, way short, per 2018 research, including:

Vitamin D deficiency impacts the body in many ways. That being said, if you're critically low in this key nutrient, you might notice red flags such as low mood, less immune resilience, suboptimal bone health, and even brain fog.*

If there's one major takeaway here, it's that even though you can get some vitamin D from food, you'd have to eat a pretty ridiculous diet to get ALL of your vitamin D from food alone. (What, 113 eggs or 62 cups of fortified cereal don't appeal?)

So, in addition to incorporating vitamin D foods into your diet, add a high-quality vitamin D supplement that provides 5,000 IU of vitamin D3 (which is the body's preferred form) to your daily routine, suggests Ferira.*

In fact, mindbodygreen created vitamin D3 potency+ because of this very need. In addition to 5,000 IU of vitamin D3 (sourced from sustainable organic algae), it also provides a unique built-in trio of organic, virgin oils from avocado, flaxseed, and olives.* That way, you can take it any time of the day, with or without a meal, eliminating the need to rely on food altogether.

Sustained levels of vitamin D sufficiency are important to healthy bodily functions and overall health.* While there are some natural food sources of vitamin D out there (as well as fortified food options), supplementing is typically necessary in order to meet your daily needs.*