THERE ARE 13 different vitamins essential to human functioning, but you've probably heard more about vitamin D than others. Your doctor may have brought it up, or you've heard people talking about it during winter. But, did you know that there's a subtype known as vitamin D3?
In fact, there are two types of vitamin D: D2 and D3. Vitamin D2 is largely made in our bodies, whereas most of your D3 comes from external sources. Our bodies utilize sunlight to develop some in our skin, but there are certain foods that contain the nutrient, too.
And, the vitamin really is essential: You need enough D3 to ensure strong bones and proper energy consumption. We tapped experts to figure out exactly what vitamin D3 is, where it comes from, how your body uses it, and how to know if you're deficient in it.
What is vitamin D3?
“Vitamin D3 (cholecalciferol) is a nutrient that’s made in the body when the skin is exposed to sunlight," says Kim Yawitz, R.D., a gym owner in St. Louis, Mo. It can also be found in certain foods. It's mostly known for its importance to our bone health and growth.
While some nutrients have a "recommended dietary allowance" (RDA), there’s no established guideline for vitamin D3, specifically, says Yawitz. That said: “Men should aim for 600 international units (IU) of vitamin D per day, which can come from vitamin D2, vitamin D3, or a combination of both,” she says.
Because D3 is more easily absorbed than D2, and it also remains in the body longer than D2. “And so, you may be able to get a bit more bang for your buck by choosing foods that are naturally high in vitamin D3," says Yawitz.
Before we dive into signs of vitamin D3 deficiencies, the best sources of vitamin D3, and more, there is one more important thing to keep in mind: “Vitamin D3 is fat-soluble, which means that you can enhance its absorption by taking it with foods that have a bit of healthy fat,” says Yawitz. This is especially true for supplements and may also be beneficial for food sources of D3 that are naturally low in fat.
What are the health benefits of vitamin D3?
Vitamin D3 is best known for strengthening your bones, which is done by helping the body absorb calcium and phosphorus from food, Yawitz says. Not only does it help bones grow, but it also helps bone remodeling after injuries.
Vitamin D3 also plays a role in energy production, which is why you often hear complains about low energy in the winter months when most people are generally less exposed to sunshine.
“It also reduces inflammation, boosts the immune system, promotes heart health, and serves other important functions in the body,” Yawitz says.
What are signs of a D3 deficiency?
Vitamin D may be “the sunshine vitamin,” but you can also get it from your diet.
Either way, most Americans are not getting enough of vitamin D. “By some estimates, more than 90 percent of American men don’t get enough vitamin D in their diets. But that doesn’t necessarily mean they’re deficient,” says Yawitz. “Your body makes vitamin D3 when your skin is exposed to sunshine. So even if you don’t eat a lot of foods that are naturally high in D3, your D levels could be fine if you regularly spend even a few minutes in direct sunlight.”
And a true vitamin D3 deficiency can be difficult to identify, simply because there aren’t a lot of easy-to-spot symptoms. “Severe deficiency can lead to osteomalacia—a condition that causes weak and painful bones and sometimes dental issues,” she says.
”One large study also found that people with low vitamin D levels are more likely to experience depression. However, depression alone isn’t a good indicator of low vitamin D3 status.”
What foods are high in vitamin D3?
There’s a host of food sources that are good or excellent sources of vitamin D3.
4 Foods High in Vitamin D3
Rainbow trout
If you don’t eat it already, it’s time to add this nutrient-dense fish to your diet. “Three ounces of rainbow trout provide 645 IU of vitamin D3, plus 17 grams of muscle-building protein,” says Yawitz.
Salmon
“Three ounces of salmon will get you pretty close to your daily D3 quota (570 IU, to be exact) and can also help protect your heart if you have heart disease risk factors,” says Yawtiz, adding that according to a 2021 study, eating 12 ounces of salmon or other fatty fish each week could lower your risk of heart attack and stroke by about 17 percent.
Milk
“One cup of 2% milk provides 120 IU of vitamin D, usually in the form of D3. Adding a glass each morning can help protect your teeth and bones, especially as you age,” says said.
Cod liver oil
“Coming in at 1,360 IU per tablespoon, cod liver oil is the best dietary source of vitamin D3 by far,” says Yawitz. Try adding it into a shot of juice like OJ or tart cherry juice if you don’t want to chase it straight.
Should I take a vitamin D3 supplement?
Vitamin D3 supplements aren’t for everyone, but they may be a good idea for some people.
“A vitamin D3 supplement could be beneficial if you’re vegan or lactose intolerant, if you have dark skin, if you don’t get a lot of sun, or if you have certain medical conditions,” says Yawitz. “That being said, it’s always best to talk with your doctor before starting any supplement.”
As she points out, taking high doses of vitamin D3 can lead to nausea, vomiting, diarrhea, muscle weakness, dehydration, kidney stones, kidney failure, irregular heartbeat, and other health problems. Again, talking to a medical professional can help you determine if a vitamin D3 supplement may be right for you.
