Vitamin D is a unique nutrient. Part hormone, part fat-soluble vitamin, your body needs it for balance in many key systems. Researchers are still learning just how vital it is. Since there’s no easy way to get all the nutrients you need from food, vitamin D supplements are a wellness staple for many. If you have to minimize sun exposure, or you don’t live near enough to the equator to get year-round UVB rays, a vitamin D supplement may be your key to adequate intake. Yet choosing a vitamin D supplement can feel complicated. In this guide, we’ll cover the basics of vitamin D and what you need to know to pick the best nutritional support for your needs.
Vitamin D has several benefits, many of which overlap or contribute to multiple body systems, organs, tissues, and cells. Here’s an overview of what this fat-soluble vitamin does:
Vitamin D is also being studied for its effects on the nervous system and neurological health, the microbiome, and more.
Vitamin D deficiency is not something that medical providers routinely screen for. Certain groups of people are more at risk than others. When vitamin D levels are too low, it may have effects on other health factors.
Factors correlated with vitamin D deficiency risk include:
Vitamin D serum levels can be checked with a simple blood test. There are different standards for assessing the results of vitamin D testing. That said, typical lab ranges are as follows:
Many medical providers take it one step farther and look for an “optimal” level, which typically falls within 40–60 ng/mL. Only your medical provider can determine the best range for you based on your health factors and needs.
Unless you live near the sunny equator, it’s not possible to get year-round vitamin D from the sun alone. Even during the months where you can get direct UVB exposure from the sun at more northern or southern latitudes, there are many reasons why it may be impossible to use the sun as your sole source of vitamin D.
Dietary supplements can fill a gap that make reliance on sunlight less crucial for vitamin D balance.
Only your medical provider can decide if vitamin D supplements are necessary for you. However, if you’re concerned about adequate vitamin D intake or exposure, supplements may be a reliable method of support. There are few dietary sources of vitamin D that lead to a consistently optimal intake.
Vitamin D as a nutritional supplement comes in two forms: vitamin D2 and vitamin D3. There are a few key differences.
Vitamin D2, also known as ergocalciferol, is produced from exposing plant-based or fungi organisms to the same type of UV radiation that triggers vitamin D formation in humans.
Vitamin D2 is a vegan form of the nutrient, since no animals are utilized in the process.
Food sources of vitamin D2 include fortified foods like breakfast cereals, orange juice, milk, and other dairy products. Mushrooms can also be a source, but the amount can vary depending on how much time they spent in sunlight.
Vitamin D2 supplements are available as a standalone supplement or can be found in bone health formulas, multivitamins, and prenatal vitamins.
Vitamin D3, known as cholecalciferol, is the form naturally produced in humans and animals after UV sun exposure.
The supplement form of D3 is typically derived from lanolin that comes from sheep’s wool. While it does come from animals, it is a byproduct of wool shearing, and does not subject the sheep to additional procedures. For this reason, vitamin D3 from lanolin is vegetarian-friendly and for many vegans, is still a viable option.
Food sources of vitamin D3 include cod liver oil, trout, salmon, tuna, sardines, egg yolks, and red meat.
Vitamin D3 is available as a standalone supplement, and is also found in bone support formulas, multivitamins, and prenatal vitamins.
When it comes to looking for the right vitamin D supplement for you, there are several options. You’ll need to consider bioavailability, dosage, ingredients, and brand quality.
While both vitamin D2 and D3 are converted into the same compound via a 2-step process in the liver and kidneys, vitamin D3 is considered to be more biologically active and able to more effectively increase serum vitamin D levels.
Vitamin D supplements are available in a wide range of dosages. Your medical provider should guide you on a safe daily or weekly intake.
The recommended dietary allowance (RDA) for vitamin D is fairly consistent for all ages and genders, but requirements increase as part of aging:
The Endocrine Society recommends that adults of all ages should consume between 37.5–50 mcg per day (or 1,500–2,000 IU).
The tolerable upper intake level for vitamin D is 100 mcg or 4,000 IU. This means that consuming up to this amount is unlikely to lead to toxicity. However, that does not mean that this level is safe for everyone. Vitamin D can interact with medications and conditions. Individual factors can alter how vitamin D is metabolized, especially if liver or kidney conditions are present, since they activate supplemental vitamin D in the body.
You can get too much vitamin D, which can cause problems. Your healthcare provider should guide you on finding a balanced intake and serum level that serves your health needs.
All dietary supplements have the main ingredients – in this case, vitamin D – along with additional ingredients. These additional items, which are typically listed below the “supplement facts” panel, can include the capsule, antioxidants, preservatives, sweeteners, flavorings, and more. The presence of additional ingredients does not automatically mean a supplement is bad. They help to deliver the nutrients to your body.
If you have food allergies or sensitivities, dietary concerns like gluten-free or vegan, or other sustainability concerns like non-GMO, you need to carefully read labels to ensure the product aligns with your health needs and values.
Dietary supplements are produced by a wide range of manufacturers and companies. While the U.S. Food and Drug Administration provides a baseline set of requirements for quality, the manufacturers are responsible for maintaining them. Brands may also elect to have higher standards for quality, sustainability, allergy-friendly ingredients, and more.
When you choose a supplement, consider the brand and how that aligns with your needs. Some considerations include:
Vitamin D supplements are generally well tolerated if you take them as directed and don’t exceed the recommended intakes. Unless you are sensitive to other ingredients in the supplement, most don’t lead to any side effects.
If you take too much vitamin D, side effects can include nausea, vomiting, unintended weight loss, constipation, muscle weakness, and kidney issues. That’s why it’s important to take vitamin D supplements as directed, and to follow up with your doctor when they want to check your serum levels.
Vitamin D can be taken at any time of the day. It’s best absorbed if you take it with a meal that contains some fat, since vitamin D is a fat-soluble vitamin.
Yes, vitamin D can be taken with other supplements, unless your medical provider says otherwise. Vitamin D doesn’t interact with other nutrients, although it can interact with medications. Make sure that your doctor and pharmacist know everything that you take, including all supplements and over-the-counter medicines.
Yes, unless your healthcare provider says otherwise, vitamin D supplements can be taken daily.
Vitamin D2 is a vegan form of the nutrient because it is typically sourced from fungi. Vitamin D3 is often derived from lanolin that comes from sheep’s wool. While it is animal-derived, shearing sheep’s wool produces the byproduct of lanolin, so the animals are not subjected to additional procedures to extract the vitamin D. For this reason, vegans and vegetarians may choose to consume vitamin D3, although vitamin D2 is also an option.
Your body can get vitamin D from sun exposure or from oral intake. While many vitamins have ample food sources, vitamin D is harder to get from diet alone, unless you consume cod liver oil. (Cod liver oil has higher vitamin A content, however, which may not be recommended for other reasons.)
If you want to increase your vitamin D without supplements, you’d need to get regular sun exposure, or check the vitamin D content of foods to see how much you’re getting. The RDA for adults is 600 IU (15 mcg). Here’s what you could expect from some common foods:
Constipation is associated with excessive intake of vitamin D or serum levels that are too high. If you take vitamin D supplements as directed, they’re unlikely to be associated with constipation.
Your healthcare provider can determine whether vitamin D supplements are safe for you. Generally, when taken as directed, they are safe and effective for supporting healthy vitamin D levels. Always check with your healthcare provider before starting any new supplements.