How much vitamin D3 should I take daily?
Why you should add more vitamin D to your diet
Vitamin D can improve your immune function, bone health and even mental health. Here’s how to add more to your diet.
Despite living in an age of abundant food options and supplements, certain vitamin and mineral deficiencies remain surprisingly common – and vitamin D is among the most widespread. Research suggests that a significant portion of the global population is deficient in vitamin D levels, in part because modern life keeps many of us indoors and away from direct sunlight.
This matters because, of vitamin D’s two primary forms, vitamin D3 is the one that requires exposure to sunlight and is considered the most effective at raising and maintaining vitamin D levels in the body. It is also “a nutrient the body needs, along with calcium, to build bones and keep them healthy,” says Caroline Susie, a registered dietitian and national spokesperson for the Academy of Nutrition and Dietetics. “And it supports immune health and helps keep muscles and brain cells working.”
Here’s what vitamin D3 is, why your body needs it and how much you should take if supplementation is necessary.
What is vitamin D3?
Vitamin D3, also known as cholecalciferol, is one of the two main forms of vitamin D. The other is vitamin D2 (ergocalciferol), “which comes from plant sources and fortified foods,” says Susie. But vitamin D3 is the type naturally produced in human skin when it is exposed to sunlight.
It’s considered a fat-soluble vitamin, meaning it dissolves in fat and can be stored in the body’s fatty tissues and liver rather than being quickly flushed out through urine like water-soluble vitamins such as vitamin C. This storage ability helps maintain vitamin D levels over time but also means excessive intake can accumulate in the body.
Although vitamin D2 and D3 “are similar in chemical structure and function,” says Jill Weisenberger, a registered dietitian and author of “Prediabetes: A Complete Guide,” research shows that vitamin D3 is more effective at increasing and sustaining blood concentrations of vitamin D “and keeping the levels elevated longer.”
Sunlight exposure is the most efficient way to increase vitamin D3 levels, says Susie, but factors such as limited sun exposure, regular sunscreen use, age, darker skin pigmentation and geographic location can make it difficult for some people to produce adequate amounts from sunlight alone. In addition, “people who have nutrient absorption problems including Crohn’s disease, celiac disease and cystic fibrosis may also be deficient,” says Weisenberger. “And a body mass index greater than 30 is associated with lower vitamin D levels because fat cells keep vitamin D isolated,” adds Susie.
For many individuals in these groups, supplementation may be recommended. Increasing dietary sources can also help. “Some of the best natural food sources are fatty fish such as trout, salmon, tuna, mackerel and fish liver oils,” says Susie, as well as eggs, beef liver and fortified foods like milk and cereals. “Mushrooms exposed to UV light also provide vitamin D,” adds Weisenberger.
What does vitamin D3 do for the body?
Regardless of its source, vitamin D3 plays a central role in helping the body absorb calcium and phosphorus – “minerals critical for building and maintaining strong bones and teeth,” says Weisenberger. Without sufficient vitamin D, bones can become thin, brittle or misshapen, contributing to conditions such as rickets in children and osteomalacia or osteoporosis in adults.
Vitamin D3 also supports immune function. Weisenberger says it helps regulate the body’s inflammatory response and enhances the ability of immune cells to fight pathogens.
Research also suggests broader potential effects on muscle strength, mood regulation and “protection against infections, including COVID and major diseases like cancer, cardiovascular and respiratory diseases, diabetes and dementia,” says Susie.
How much vitamin D3 should I take daily?
Although vitamin D deficiency is far more common than excessive intake, maintaining the right balance is essential as “too much vitamin D can cause high blood levels of calcium, kidney disease, calcium deposits in soft tissue, heart disease and even death,” says Weisenberger.
For this reason, the National Institutes of Health Office of Dietary Supplements recommends that most children and adults ages 1 to 70 get about 15 micrograms or 600 international units (IU) of vitamin D daily, while adults over 70 typically require about 800 IU.
The NIH also identifies 4,000 IU per day as the maximum upper limit from all sources – including food, beverages and supplements – though individuals should not approach those levels without medical guidance. “Always inform healthcare providers about any vitamin D supplementation,” advises Susie, “especially if taking multiple supplements or medications.”
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