What Happens to Your Body When You Take Vitamin D Every Day

If you’ve been spending a lot more time indoors and covered up (either because it’s cold outside or you work from home), you may wonder if you have sufficient levels of vitamin D, which your skin synthesizes when exposed to the sun’s ultraviolet rays.

Vitamin D is an essential nutrient and hormone associated with healthy bones, muscle function and supporting your immune system, among many other benefits. While it offers an array of impressive benefits, how much vitamin D is really needed? Should you take a vitamin D supplement daily? What happens when you do? Here we’ll discuss what vitamin D is, the types of supplements available, what happens when you take vitamin D supplements daily and how to pick the right one for you.

Vitamin D is a fat-soluble vitamin naturally present in food, and a hormone produced in the skin in response to sun or UV exposure. According to the National Institutes of Health, vitamin D promotes calcium absorption in the gut and helps regulate the concentration of calcium and phosphorus in the blood, which supports building and maintaining healthy, strong bones and helps regulate skeletal and neuromuscular function. Aside from supporting your bones, muscles and nerves, vitamin D plays many roles in the rest of the body. More and more research shows that vitamin D reduces inflammation, regulates many cellular processes and metabolism and promotes immunity.

Insufficient amounts of vitamin D can greatly impact your bone health and other functions of your body. Given vitamin D’s role in absorbing calcium and building bone, vitamin D deficiency can cause rickets in children and osteomalacia in adults, per StatPearls. Long-term vitamin D deficiency is associated with reduced immune function and an increased risk of some conditions, such as cardiovascular disease, migraines, depression and certain types of cancer, per a 2019 review published in Pediatrics and Neonatology. However, more research is needed to determine the exact mechanisms.

Very few foods naturally contain vitamin D, and most are animal-based; that’s why vitamin D supplements are pretty popular. If you shop for vitamin D supplements, you may notice different types, including vitamin D2 and vitamin D3. Vitamin D2 (ergocalciferol) and D3 (cholecalciferol) differ in chemical structure and sources. Both are absorbed in the small intestine, although some studies suggest that D3 increases vitamin D in serum levels for longer than D2, per a 2021 review published in Nutrients. While there’s some debate, some experts believe that D3 is the body’s preferred form of vitamin D since the body naturally produces the D3 form when exposed to UV light.

The right amount of vitamin D can support blood serum levels of vitamin D to maintain your bone health. Supplementing with a low daily dose of vitamin D can help reduce your risk of soft or brittle bones, especially for aging adults or adults with digestive or malabsorption problems. For older adults, taking enough vitamin D combined with calcium can decrease the risk of hip and spine fractures, per a 2019 review published in JAMA Network Open.

Vitamin D plays an essential role in immunity, as research shows that long-term deficiency can result in adverse health effects. A deficiency in vitamin D decreases the body’s ability to fight disease. Additionally, it has been linked to autoimmune diseases like rheumatoid arthritis and inflammatory bowel disease and increased risk of multiple sclerosis, per a 2018 article published in Neurology and Therapy.

According to a 2020 meta-analysis published in Depression and Anxiety, some studies have suggested that vitamin D may play a critical role in regulating your mood and improving symptoms of depression.

Many people aren’t aware of possible toxicity when it comes to vitamins and minerals, and toxicity from vitamin D is possible. However, vitamin D toxicity often occurs from supplementation rather than from food or sun exposure. Taking supplements providing more than 4,000 IU daily is not recommended unless under a health care provider’s supervision, though, according to MedlinePlus, most toxicity occurs with doses above 10,000 IU daily. Symptoms of vitamin D toxicity mostly include digestive, muscular and neurological ones:

• Nausea
• Vomiting
• Muscle weakness
• Loss of appetite
• Constipation
• Confusion
• Disorientation
• Involuntary weight loss
• Irregular heartbeat
• Damage to blood vessels which can damage the heart and kidneys

Additionally, extremely high levels of vitamin D can affect kidney function and result in symptoms such as dehydration, excessive urination and thirst, kidney stones and even kidney failure.

There are few foods naturally rich in vitamin D; however, foods fortified with vitamin D are prevalent in the U.S. food supply. Some food sources include:

• Fatty fish like salmon, tuna, herring, swordfish and sardines
• Beef liver
• Cod liver oil
• Egg yolks
• Mushrooms
• Fortified foods and drinks like dairy products such as cow’s milk, cheese and yogurt, soymilk, orange juice and cereals

It’s important to choose a form of vitamin D that works for you. If your recent blood test indicates that supplementation is needed, a health care provider can prescribe you the proper amount and form, which could be important for optimal absorption if you have a medical condition, like inflammatory bowel disease (Crohn’s, celiac disease, ulcerative colitis) or a history of gastric bypass. “Vitamin D comes in capsule, sublingual (under the tongue) or liquid form. A sublingual may be best for those who have issues absorbing vitamin D,” says Gretchen Zimmermann, RD, CDCES, senior director of cardiometabolic care & prescribing at Vida Health. “Starting with the form you are most comfortable taking is ideal.”

Research suggests that D3 is the body’s preferred form of vitamin D and may be more effective at raising serum levels. However, you may want to choose based on your lifestyle choices. “Vitamin D2 is produced naturally in some plant and fungi foods, while D3 is produced in animals,” says Zimmermann, which may make D2 the more appropriate choice if you follow a vegan diet pattern.

Further, you may want to take a close look at the ingredients list for filler ingredients, sugar or artificial coloring. “There are ingredients that FDA approves as generally recognized as safe (GRAS), which may be a good basis to ensure that you are not getting harmful additives and preservatives,” says Catherine Gervacio, RDN, a registered dietitian nutritionist for Living.Fit.

Since supplements are not regulated by the FDA, choosing a supplement with third-party verification can help ensure that the supplement is safe and effective. Some agencies include NSF-certified, ConsumerLab, Labdoor and USP verification. Gervacio advises, “It’s best to get supplements from a reputable manufacturer to ensure quality ingredients.”

Choose a supplement packaged in dark glass or other light-blocking package, which helps protect its efficacy and potency. When you get home, you’ll also want to store your vitamins in a cool, dark place if possible.

One out of 4 people in the United States have vitamin D levels considered too low to support bone and general health. Some people are at higher risk of vitamin D deficiency, including breastfed infants, older adults, people who do not get enough sun exposure, people with darker skin, people with digestive disorders, those who have had bariatric surgery that reduces the amount of fat absorption in the gut, and people who follow a strict vegan diet.

The recommended daily amount of vitamin D is 400 international units (IU) for children up to age 12 months, 600 IU for people ages 1 to 70 years and 800 IU for people over 70 years. However, more important than the amount consumed is the amount of vitamin D in your blood. According to the NIH, levels of 50 nmol/L (20 ng/mL) are adequate for most people to maintain bone health, while levels below 30 nmol/L (12 ng/mL) are too low and could cause your bones to weaken or adversely affect your health.

Vitamin D interacts with some medications and other dietary supplements and should not be consumed by people who take cholesterol-lowering statins or thiazide diuretics. If you already have high serum levels of vitamin D, calcium or phosphate, or existing kidney problems, you should not take a supplement as it can increase your risk for toxicity and kidney stones. Get your blood serum level tested first and discuss the results with your health care provider before taking any new supplements.

The only way to determine vitamin D deficiency is through a blood serum test where a small blood sample will be collected, such as with a finger-prick test. However, even with at-home tests available, you must still mail your blood sample to a lab to measure vitamin D levels.

Vitamin D does not directly increase your energy. However, vitamin D plays a vital role in all your cells’ functions. To that end, a vitamin D deficiency may result in symptoms like fatigue, musculoskeletal pain or weakness, depression and impaired cognitive function. Fatigue is a commonly reported symptom in people with vitamin D deficiency. Some research has shown that people with vitamin D deficiency have lessened fatigue after taking vitamin D supplements.

Many people can experience a vitamin D deficiency, especially during winter when there’s little sun and people are generally indoors and bundled up. While vitamin D is available in the food supply through some natural and fortified sources, you may still want to take a supplement to ensure your vitamin D levels are sufficient to maintain your bone and general health. If you’re thinking of adding a supplement to your diet, speak with your health care provider and get your serum levels tested first before choosing a supplement that’s right for you.