A new study suggests that vitamin D2 supplements may lower blood levels of vitamin D3, the form the body uses more effectively.
Some adults struggle to get enough vitamin D from food sources. Sunlight and supplements are important for keeping your bones, immune system, muscles, and nerves healthy.
What the Study Found
The new systematic review included 1,080 participants from 20 studies. Compared to participants who did not take supplements, those who took vitamin D2 had an 18 nanomoles per liter (nmol/L) drop in blood levels of vitamin D3.
“It’s not necessarily endangering people of deficiency. However, it’s a really significant drop,” Emily Brown, ANutr, lead researcher of the study and a PhD researcher at the University of Surrey, told Verywell.
Vitamin D blood levels below 30 nmol/L may lead to poor health outcomes.
Previous research has also shown that vitamin D3 increases total vitamin D levels more efficiently than D2 and may offer additional benefits for immune health.
"Vitamin D2 in no way is bad. It is still fine to supplement, but D3 seems to be preferential and more useful for the body," Brown said.
Should You Stop Taking Vitamin D2 Supplements?
D2 supplements come from plant sources, while D3 usually comes from animal sources. Because of this, people who follow a vegan or plant-based diet may have limited access to D3.
Still, experts emphasize that people do not need to stop taking D2.
“As a plant-based dietitian, I would say that taking a vitamin D supplement when you need it, after you have spoken to a provider, is the priority. It’s all up to you if you want to take D3 or D2,” said Sue-Ellen Anderson-Haynes, MS, RDN, a registered dietitian at 360Girls&Women and a spokesperson for the Academy of Nutrition and Dietetics.
Mushrooms, fortified soy milk, or salmon can help meet vitamin D needs on a plant-based diet. Vegan vitamin D3 supplements made from lichen, an organism formed from algae and fungus, are also available.
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Best Food Sources of Vitamin D
Dietitians often recommend whole food sources over supplements. However, very few foods naturally contain high amounts of vitamin D, said Ashlee Carnahan, MS, RDN, CLC, manager of Nutrition and Education Services at Henry Ford Hospital in Detroit.
In the United States, dietary vitamin D largely comes from fortified foods, such as:
- Dairy milks
- Plant-based milks
- Cereals
Foods that are naturally rich in vitamin D include:
- Fatty fish such as salmon and trout
- Mushrooms such as shiitake and chanterelle
- Eggs
Supplements are helpful when you can't meet your vitamin D needs through sunlight or food.
How Much Vitamin D Do You Really Need?
You may not need as much vitamin D as you think.
“We need only small-to-moderate amounts of vitamin D for good health because the vitamin’s metabolism is tightly regulated in the body,” JoAnn E. Manson, MD, MPH, DrPH, chief of the division of preventive medicine and a professor of medicine at Harvard Medical School, told Verywell.
Adults need between 600 and 800 International Units (IU) daily. While diet and sunlight can provide some, people with darker skin produce less vitamin D from sun exposure, and many struggle to get enough in the winter.
Supplements can help fill the gap, but too much can be harmful. A recent study found that many U.S. adults take more than 1,000 IU daily, some exceeding the upper limit of 4,000 IU.
Consuming extremely high supplement doses can cause nausea, confusion, dehydration, and kidney stones.
