In the ABCs of vitamins, D is one of the most important. The body needs vitamin D to build healthy bones, absorb calcium and maintain immune function.
Vitamin D has anti-inflammatory and antioxidant properties, and it’s essential for early childhood development.
Also known as the “sunshine vitamin,” the body can make its own vitamin D when the skin is exposed to sunlight. It’s also found in fatty fish, added to foods, such as milk, and sold as a supplement.
Vitamin D is one of the most popular dietary supplements in the United States, according to the U.S. Centers for Disease Control.
When is the best time to take vitamin D supplements? Should you take it with food and is it better to take it during certain times of the day or year? Here’s what to know about taking vitamin D.
What is vitamin D?
Vitamin D, also known as calciferol, is a fat-soluble vitamin that the body needs to absorb calcium from the intestines.
“Vitamin D has two main responsibilities: helping calcium reach your bones, which keeps them strong, and supporting your immune system so it can fight off infections,” Julia Zumpano, a registered dietitian at the Cleveland Clinic Center for Human Nutrition, tells TODAY.com.
There are two forms, vitamin D3 and vitamin D2. Vitamin D3 is produced when the skin is exposed to sunlight and found in animal-based foods. Vitamin D2 is found in some plant sources, or human-made and added to foods, according to the National Institutes of Health’s Office of Dietary Supplements.
These inactive forms of vitamin D get stored in fat cells until they are converted by the liver and kidneys into the active form of vitamin D.
Vitamin D benefits
“Vitamin D is very important in the body because it contributes to the bone health, musculoskeletal health, immune function and many functions,” Dr. Julia Adamian, an internist at NYU Langone Health, tells TODAY.com.
Additionally, vitamin D can protect heart and brain health and fight inflammation. It may also help regulate cell growth and glucose metabolism, per the NIH.
During childhood, vitamin D is crucial to prevent rickets, or softening of the bones, per the Mayo Clinic.
In adults, vitamin D, together with calcium, can help prevent osteoporosis, which causes bones to become weak and brittle, increasing the risk of fractures, TODAY.com previously reported.
How much vitamin D do you need per day?
The recommended daily intake of vitamin D for healthy people varies by age, per the NIH.
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Children (1–18 years): 15 mcg or 600 IU
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Adults (18–70 years): 15 mcg or 600 IU
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Older adults (over 70 years): 20 mcg or 800 IU
Sources of vitamin D
Vitamin D can be obtained from several sources.
Sunlight
Humans get a lot of their vitamin D from exposure to ultraviolet (UV) light from the sun. “The production of the vitamin D is activated in the skin through contact with UVB rays,” says Adamian. The body produces vitamin D3, which is converted into active vitamin D.
Getting five to 30 minutes of UV exposure midday at least a few times a week is thought to be enough to maintain sufficient vitamin D levels, per the NIH.
Sunscreen does protect against UVB rays, which can also damage and age the skin, says Adamian. However, research shows people who wear sunscreen can still synthesize vitamin D from exposure to sunlight.
Food sources of vitamin D
Few foods are naturally rich in vitamin D. These include cod liver oil, trout, salmon, sardines and tuna, per the NIH. Raw mushrooms that are exposed to UV light are a good source of vitamin D2. Eggs, beef liver and cheese contain small amounts of vitamin D3.
Vitamin D is also added to foods. Vitamin D-fortified foods provide most of the vitamin D in American diets, per the NIH. These include fortified cow’s milk, plant-based milk (soy, almond or oat), orange juice and cereals.
Vitamin D supplements
Vitamin D dietary supplements contain vitamin D3 or vitamin D2. Research shows that both forms are well-absorbed, but vitamin D3 supplements may elevate blood levels of vitamin D to a greater extent, according to the NIH.
Most multivitamins contain vitamin D but usually a lower amount than pure vitamin D supplements.
Healthy adults typically get enough vitamin D from sunlight, foods and multivitamins with vitamin D. “It is tough to get enough from diet alone, so it’s usually a combination of all these,” says Adamian.
However, some people need a little help to meet their intake.
Who should take a vitamin D supplement?
People who do not get enough vitamin D may need a supplement. Over time, inadequate vitamin D intake can lead to a vitamin D deficiency, which can cause bone pain, muscle weakness and fatigue, says Adamian.
A deficiency occurs if a person doesn’t get enough vitamin D from sunlight or food, or if their body can’t synthesize or absorb vitamin D properly due to an underlying condition or medication.
A common risk factor is limited UV exposure, says Adamian, because the skin stops producing vitamin D. This can happen in colder climates or during the winter, when the UVB rays are less strong, there are less hours of sunlight and more skin is covered.
“Vitamin D stores also decline with the age,” says Adamian, adding that she often recommends vitamin D supplements for older adults.
Melanin can also affect vitamin D levels. People with darker skin are less able to produce vitamin D from sunlight and may be at risk of a deficiency, per the NIH.
Certain conditions can affect the body’s ability to synthesize or absorb vitamin D, such as liver disease, kidney disease and inflammatory bowel disease, Adamian adds. Medications that can lower vitamin D levels include laxatives, steroids and cholesterol drugs, per the Cleveland Clinic.
A vitamin D deficiency is diagnosed through a blood test, says Zumpano.
Vitamin D supplement dosage
Always talk to your doctor to find out which supplement dosage is appropriate for your needs. The recommended daily intake for vitamin D is 600 IU for healthy adults. People who are deficient may need to take more.
Most over-the-counter vitamin D supplements are between 1,000 and 5,000 IU, and some are as high as 10,000 IU, says Adamian. “There’s so many different supplements, so it’s very important to consult a health care provider,” Adamian adds.
While vitamin D supplements can fill nutrient gaps, there isn’t much evidence that taking extra has added benefits if you don’t have a deficiency, TODAY.com previously reported.
The Endocrine Society does not recommend vitamin D supplements for healthy adults ages 19 to 74.
When is the best time to take vitamin D supplements?
The best time to take vitamin D supplements depends on the person. It’s optimal to take vitamin D at a time of day that’s easy to remember, says Adamian.
Many people prefer the morning for convenience, Adamian adds, but it’s OK to take vitamin D at any time of day, as long as you stay consistent.
“If you choose one time to take it everyday, then you are more likely to take it on a daily basis,” says Zumpano.
If you take other medications, talk to your doctor about timing. “Vitamin D can interact with statins, steroids and thiazide diuretics,” Zumpano says.
The time of day matters less than whether you take it with food, which affects the absorption of vitamin D, the experts note.
Should you take vitamin D with or without food?
“It’s best to take a vitamin D supplement with food, and at least a source of fat,” says Zumpano.
Vitamin D is fat-soluble, so taking it with a fatty food can help improve the absorption of it in the body, Adamian explains.
The experts suggest taking vitamin D supplements with a food rich in healthy fats, such as nut butter, avocado or whole-fat yogurt. Try to take vitamin D during or after your meal.
When is the best time of year to take vitamin D supplements?
It’s safe to take vitamin D supplements year-round and may be necessary depending on the person. (Always follow your doctor’s guidance.)
However, some people only take vitamin D during the fall and winter, when their body doesn’t produce enough vitamin D due to decreased UV exposure, Adamian notes.
The best months of the year to take vitamin D will depend on your location, the climate and how much time you spend outdoors.
Side effects of vitamin D supplements
When taken in the appropriate dosage as directed by a doctor, vitamin D supplements are generally safe. However, taking too much vitamin D can cause side effects or health issues.
“Vitamin D is a fat-soluble vitamin, therefore it is not excreted in your urine and will accumulate in your body,” says Zumpano.
In rare cases, vitamin D can reach toxic levels. This can increase calcium absorption, leading to abnormally high levels of calcium in the blood, Zumpano notes.
Symptoms of vitamin D toxicity include:
“In extreme cases, vitamin D toxicity can cause kidney failure, cardiac arrhythmias and even death,” says Zumpano.
Vitamin D toxicity is typically caused by taking high doses of the vitamin in supplement form, not from food or sunlight, Zumpano adds.
If you experience side effects, stop taking vitamin D and talk to your doctor.
This article was originally published on TODAY.com
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